diff --git a/Cargo.lock b/Cargo.lock
index faca06196737..c62c379f70d7 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -5804,16 +5804,16 @@ checksum = "c62a0a307cb4a311d3a07867860911ca130c3494e8c2719593806c08bc5d0484"
 
 [[package]]
 name = "wasm-component-ld"
-version = "0.5.9"
+version = "0.5.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fde17bc96539700198e12516230c76095cc215c84ef39ad206e1af3f84243e0f"
+checksum = "4d4aa6bd7fbe7cffbed29fe3e236fda74419def1bdef6f80f989ec51137edf44"
 dependencies = [
  "anyhow",
  "clap",
  "lexopt",
  "tempfile",
  "wasi-preview1-component-adapter-provider",
- "wasmparser 0.218.0",
+ "wasmparser 0.219.0",
  "wat",
  "wit-component",
  "wit-parser",
@@ -5837,19 +5837,19 @@ dependencies = [
 
 [[package]]
 name = "wasm-encoder"
-version = "0.218.0"
+version = "0.219.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "22b896fa8ceb71091ace9bcb81e853f54043183a1c9667cf93422c40252ffa0a"
+checksum = "e2b1b95711b3ad655656a341e301cc64e33cbee94de9a99a1c5a2ab88efab79d"
 dependencies = [
  "leb128",
- "wasmparser 0.218.0",
+ "wasmparser 0.219.0",
 ]
 
 [[package]]
 name = "wasm-metadata"
-version = "0.218.0"
+version = "0.219.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "aa5eeb071abe8a2132fdd5565dabffee70775ee8c24fc7e300ac43f51f4a8a91"
+checksum = "96132fe00dd17d092d2be289eeed5a0a68ad3cf30b68e8875bc953b96f55f0be"
 dependencies = [
  "anyhow",
  "indexmap",
@@ -5857,8 +5857,8 @@ dependencies = [
  "serde_derive",
  "serde_json",
  "spdx",
- "wasm-encoder 0.218.0",
- "wasmparser 0.218.0",
+ "wasm-encoder 0.219.0",
+ "wasmparser 0.219.0",
 ]
 
 [[package]]
@@ -5873,9 +5873,9 @@ dependencies = [
 
 [[package]]
 name = "wasmparser"
-version = "0.218.0"
+version = "0.219.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b09e46c7fceceaa72b2dd1a8a137ea7fd8f93dfaa69806010a709918e496c5dc"
+checksum = "324b4e56d24439495b88cd81439dad5e97f3c7b1eedc3c7e10455ed1e045e9a2"
 dependencies = [
  "ahash",
  "bitflags 2.6.0",
@@ -5887,22 +5887,22 @@ dependencies = [
 
 [[package]]
 name = "wast"
-version = "218.0.0"
+version = "219.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8a53cd1f0fa505df97557e36a58bddb8296e2fcdcd089529545ebfdb18a1b9d7"
+checksum = "06880ecb25662bc21db6a83f4fcc27c41f71fbcba4f1980b650c88ada92728e1"
 dependencies = [
  "bumpalo",
  "leb128",
  "memchr",
  "unicode-width",
- "wasm-encoder 0.218.0",
+ "wasm-encoder 0.219.0",
 ]
 
 [[package]]
 name = "wat"
-version = "1.218.0"
+version = "1.219.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4f87f8e14e776762e07927c27c2054d2cf678aab9aae2d431a79b3e31e4dd391"
+checksum = "11e56dbf9fc89111b0d97c91e683d7895b1a6e5633a729f2ccad2303724005b6"
 dependencies = [
  "wast",
 ]
@@ -6179,9 +6179,9 @@ dependencies = [
 
 [[package]]
 name = "wit-component"
-version = "0.218.0"
+version = "0.219.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "aa53aa7e6bf2b3e8ccaffbcc963fbdb672a603dc0af393a481b6cec24c266406"
+checksum = "99a76111c20444a814019de20499d30940ecd219b9512ee296f034a5edb18a2d"
 dependencies = [
  "anyhow",
  "bitflags 2.6.0",
@@ -6190,17 +6190,17 @@ dependencies = [
  "serde",
  "serde_derive",
  "serde_json",
- "wasm-encoder 0.218.0",
+ "wasm-encoder 0.219.0",
  "wasm-metadata",
- "wasmparser 0.218.0",
+ "wasmparser 0.219.0",
  "wit-parser",
 ]
 
 [[package]]
 name = "wit-parser"
-version = "0.218.0"
+version = "0.219.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0d3d1066ab761b115f97fef2b191090faabcb0f37b555b758d3caf42d4ed9e55"
+checksum = "23102e180c0c464f36e293d31a27b524e3ece930d7b5527d2f33f9d2c963de64"
 dependencies = [
  "anyhow",
  "id-arena",
@@ -6211,7 +6211,7 @@ dependencies = [
  "serde_derive",
  "serde_json",
  "unicode-xid",
- "wasmparser 0.218.0",
+ "wasmparser 0.219.0",
 ]
 
 [[package]]
diff --git a/compiler/rustc_lint/src/non_local_def.rs b/compiler/rustc_lint/src/non_local_def.rs
index 56f930ea7f62..6fecddb33194 100644
--- a/compiler/rustc_lint/src/non_local_def.rs
+++ b/compiler/rustc_lint/src/non_local_def.rs
@@ -124,16 +124,6 @@ impl<'tcx> LateLintPass<'tcx> for NonLocalDefinitions {
                 // If that's the case this means that this impl block declaration
                 // is using local items and so we don't lint on it.
 
-                // We also ignore anon-const in item by including the anon-const
-                // parent as well.
-                let parent_parent = if parent_def_kind == DefKind::Const
-                    && parent_opt_item_name == Some(kw::Underscore)
-                {
-                    Some(cx.tcx.parent(parent))
-                } else {
-                    None
-                };
-
                 // 1. We collect all the `hir::Path` from the `Self` type and `Trait` ref
                 // of the `impl` definition
                 let mut collector = PathCollector { paths: Vec::new() };
@@ -148,13 +138,33 @@ impl<'tcx> LateLintPass<'tcx> for NonLocalDefinitions {
                     |p| matches!(p.res, Res::Def(def_kind, _) if def_kind != DefKind::TyParam),
                 );
 
-                // 2. We check if any of path reference a "local" parent and if that the case
-                // we bail out as asked by T-lang, even though this isn't correct from a
-                // type-system point of view, as inference exists and could still leak the impl.
+                // 1.9. We retrieve the parent def id of the impl item, ...
+                //
+                // ... modulo const-anons items, for enhanced compatibility with the ecosystem
+                // as that pattern is common with `serde`, `bevy`, ...
+                //
+                // For this example we want the `DefId` parent of the outermost const-anon items.
+                // ```
+                // const _: () = { // the parent of this const-anon
+                //     const _: () = {
+                //         impl Foo {}
+                //     };
+                // };
+                // ```
+                let outermost_impl_parent = peel_parent_while(cx.tcx, parent, |tcx, did| {
+                    tcx.def_kind(did) == DefKind::Const
+                        && tcx.opt_item_name(did) == Some(kw::Underscore)
+                });
+
+                // 2. We check if any of the paths reference a the `impl`-parent.
+                //
+                // If that the case we bail out, as was asked by T-lang, even though this isn't
+                // correct from a type-system point of view, as inference exists and one-impl-rule
+                // make its so that we could still leak the impl.
                 if collector
                     .paths
                     .iter()
-                    .any(|path| path_has_local_parent(path, cx, parent, parent_parent))
+                    .any(|path| path_has_local_parent(path, cx, parent, outermost_impl_parent))
                 {
                     return;
                 }
@@ -253,8 +263,8 @@ impl<'tcx> Visitor<'tcx> for PathCollector<'tcx> {
     }
 }
 
-/// Given a path and a parent impl def id, this checks if the if parent resolution
-/// def id correspond to the def id of the parent impl definition.
+/// Given a path, this checks if the if the parent resolution def id corresponds to
+/// the def id of the parent impl definition (the direct one and the outermost one).
 ///
 /// Given this path, we will look at the path (and ignore any generic args):
 ///
@@ -267,32 +277,50 @@ fn path_has_local_parent(
     path: &Path<'_>,
     cx: &LateContext<'_>,
     impl_parent: DefId,
-    impl_parent_parent: Option<DefId>,
+    outermost_impl_parent: Option<DefId>,
 ) -> bool {
     path.res
         .opt_def_id()
-        .is_some_and(|did| did_has_local_parent(did, cx.tcx, impl_parent, impl_parent_parent))
+        .is_some_and(|did| did_has_local_parent(did, cx.tcx, impl_parent, outermost_impl_parent))
 }
 
-/// Given a def id and a parent impl def id, this checks if the parent
-/// def id (modulo modules) correspond to the def id of the parent impl definition.
+/// Given a def id this checks if the parent def id (modulo modules) correspond to
+/// the def id of the parent impl definition (the direct one and the outermost one).
 #[inline]
 fn did_has_local_parent(
     did: DefId,
     tcx: TyCtxt<'_>,
     impl_parent: DefId,
-    impl_parent_parent: Option<DefId>,
+    outermost_impl_parent: Option<DefId>,
 ) -> bool {
-    did.is_local()
-        && if let Some(did_parent) = tcx.opt_parent(did) {
-            did_parent == impl_parent
-                || Some(did_parent) == impl_parent_parent
-                || !did_parent.is_crate_root()
-                    && tcx.def_kind(did_parent) == DefKind::Mod
-                    && did_has_local_parent(did_parent, tcx, impl_parent, impl_parent_parent)
-        } else {
-            false
-        }
+    if !did.is_local() {
+        return false;
+    }
+
+    let Some(parent_did) = tcx.opt_parent(did) else {
+        return false;
+    };
+
+    peel_parent_while(tcx, parent_did, |tcx, did| tcx.def_kind(did) == DefKind::Mod)
+        .map(|parent_did| parent_did == impl_parent || Some(parent_did) == outermost_impl_parent)
+        .unwrap_or(false)
+}
+
+/// Given a `DefId` checks if it satisfies `f` if it does check with it's parent and continue
+/// until it doesn't satisfies `f` and return the last `DefId` checked.
+///
+/// In other word this method return the first `DefId` that doesn't satisfies `f`.
+#[inline]
+fn peel_parent_while(
+    tcx: TyCtxt<'_>,
+    mut did: DefId,
+    mut f: impl FnMut(TyCtxt<'_>, DefId) -> bool,
+) -> Option<DefId> {
+    while !did.is_crate_root() && f(tcx, did) {
+        did = tcx.opt_parent(did).filter(|parent_did| parent_did.is_local())?;
+    }
+
+    Some(did)
 }
 
 /// Return for a given `Path` the span until the last args
diff --git a/library/core/src/alloc/layout.rs b/library/core/src/alloc/layout.rs
index 107d82267e57..fca32b9d3c59 100644
--- a/library/core/src/alloc/layout.rs
+++ b/library/core/src/alloc/layout.rs
@@ -540,7 +540,8 @@ impl Layout {
 )]
 pub type LayoutErr = LayoutError;
 
-/// The parameters given to `Layout::from_size_align`
+/// The `LayoutError` is returned when the parameters given
+/// to `Layout::from_size_align`
 /// or some other `Layout` constructor
 /// do not satisfy its documented constraints.
 #[stable(feature = "alloc_layout_error", since = "1.50.0")]
diff --git a/src/rustdoc-json-types/lib.rs b/src/rustdoc-json-types/lib.rs
index b3707cf61571..c8b54728d909 100644
--- a/src/rustdoc-json-types/lib.rs
+++ b/src/rustdoc-json-types/lib.rs
@@ -677,7 +677,7 @@ pub struct FunctionHeader {
 /// on unwinding for more info.
 #[derive(Clone, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
 pub enum Abi {
-    // We only have a concrete listing here for stable ABI's because their are so many
+    // We only have a concrete listing here for stable ABI's because there are so many
     // See rustc_ast_passes::feature_gate::PostExpansionVisitor::check_abi for the list
     /// The default ABI, but that can also be written explicitly with `extern "Rust"`.
     Rust,
diff --git a/src/tools/coverage-dump/src/covfun.rs b/src/tools/coverage-dump/src/covfun.rs
index c779dd0583c4..33fac3edccd1 100644
--- a/src/tools/coverage-dump/src/covfun.rs
+++ b/src/tools/coverage-dump/src/covfun.rs
@@ -56,6 +56,7 @@ pub(crate) fn dump_covfun_mappings(
             expression_resolver.push_operands(lhs, rhs);
         }
 
+        let mut max_counter = None;
         for i in 0..num_files {
             let num_mappings = parser.read_uleb128_u32()?;
             println!("Number of file {i} mappings: {num_mappings}");
@@ -63,6 +64,11 @@ pub(crate) fn dump_covfun_mappings(
             for _ in 0..num_mappings {
                 let (kind, region) = parser.read_mapping_kind_and_region()?;
                 println!("- {kind:?} at {region:?}");
+                kind.for_each_term(|term| {
+                    if let CovTerm::Counter(n) = term {
+                        max_counter = max_counter.max(Some(n));
+                    }
+                });
 
                 match kind {
                     // Also print expression mappings in resolved form.
@@ -83,6 +89,16 @@ pub(crate) fn dump_covfun_mappings(
         }
 
         parser.ensure_empty()?;
+
+        // Printing the highest counter ID seen in the functions mappings makes
+        // it easier to determine whether a change to coverage instrumentation
+        // has increased or decreased the number of physical counters needed.
+        // (It's possible for the generated code to have more counters that
+        // aren't used by any mappings, but that should hopefully be rare.)
+        println!("Highest counter ID seen: {}", match max_counter {
+            Some(id) => format!("c{id}"),
+            None => "(none)".to_owned(),
+        });
         println!();
     }
     Ok(())
@@ -271,6 +287,32 @@ enum MappingKind {
     },
 }
 
+impl MappingKind {
+    fn for_each_term(&self, mut callback: impl FnMut(CovTerm)) {
+        match *self {
+            Self::Code(term) => callback(term),
+            Self::Gap(term) => callback(term),
+            Self::Expansion(_id) => {}
+            Self::Skip => {}
+            Self::Branch { r#true, r#false } => {
+                callback(r#true);
+                callback(r#false);
+            }
+            Self::MCDCBranch {
+                r#true,
+                r#false,
+                condition_id: _,
+                true_next_id: _,
+                false_next_id: _,
+            } => {
+                callback(r#true);
+                callback(r#false);
+            }
+            Self::MCDCDecision { bitmap_idx: _, conditions_num: _ } => {}
+        }
+    }
+}
+
 struct MappingRegion {
     /// Offset of this region's start line, relative to the *start line* of
     /// the *previous mapping* (or 0). Line numbers are 1-based.
diff --git a/src/tools/wasm-component-ld/Cargo.toml b/src/tools/wasm-component-ld/Cargo.toml
index 49f4e59650e7..acdb1aa1ab7d 100644
--- a/src/tools/wasm-component-ld/Cargo.toml
+++ b/src/tools/wasm-component-ld/Cargo.toml
@@ -10,4 +10,4 @@ name = "wasm-component-ld"
 path = "src/main.rs"
 
 [dependencies]
-wasm-component-ld = "0.5.9"
+wasm-component-ld = "0.5.10"
diff --git a/tests/coverage/abort.cov-map b/tests/coverage/abort.cov-map
index 15156ec9811b..06dce43c3cab 100644
--- a/tests/coverage/abort.cov-map
+++ b/tests/coverage/abort.cov-map
@@ -34,6 +34,7 @@ Number of file 0 mappings: 13
 - Code(Expression(9, Add)) at (prev + 1, 9) to (start + 0, 23)
     = (c1 + c2)
 - Code(Counter(3)) at (prev + 2, 5) to (start + 1, 2)
+Highest counter ID seen: c5
 
 Function name: abort::might_abort
 Raw bytes (21): 0x[01, 01, 01, 01, 05, 03, 01, 03, 01, 01, 14, 05, 02, 09, 01, 24, 02, 02, 0c, 03, 02]
@@ -46,4 +47,5 @@ Number of file 0 mappings: 3
 - Code(Counter(1)) at (prev + 2, 9) to (start + 1, 36)
 - Code(Expression(0, Sub)) at (prev + 2, 12) to (start + 3, 2)
     = (c0 - c1)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/assert-ne.cov-map b/tests/coverage/assert-ne.cov-map
index 6d9906fd7f57..906abcd3c2e5 100644
--- a/tests/coverage/assert-ne.cov-map
+++ b/tests/coverage/assert-ne.cov-map
@@ -10,4 +10,5 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 13) to (start + 0, 19)
     = (c0 - c1)
 - Code(Counter(2)) at (prev + 3, 5) to (start + 1, 2)
+Highest counter ID seen: c2
 
diff --git a/tests/coverage/assert.cov-map b/tests/coverage/assert.cov-map
index dd413123de72..018fcc2c3dbb 100644
--- a/tests/coverage/assert.cov-map
+++ b/tests/coverage/assert.cov-map
@@ -25,6 +25,7 @@ Number of file 0 mappings: 9
 - Code(Expression(6, Add)) at (prev + 1, 9) to (start + 0, 23)
     = (c1 + (c2 + c3))
 - Code(Counter(4)) at (prev + 2, 5) to (start + 1, 2)
+Highest counter ID seen: c4
 
 Function name: assert::might_fail_assert
 Raw bytes (21): 0x[01, 01, 01, 01, 05, 03, 01, 04, 01, 02, 0f, 02, 02, 25, 00, 3d, 05, 01, 01, 00, 02]
@@ -37,4 +38,5 @@ Number of file 0 mappings: 3
 - Code(Expression(0, Sub)) at (prev + 2, 37) to (start + 0, 61)
     = (c0 - c1)
 - Code(Counter(1)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/assert_not.cov-map b/tests/coverage/assert_not.cov-map
index 788bc5dbf58f..401dd6450e95 100644
--- a/tests/coverage/assert_not.cov-map
+++ b/tests/coverage/assert_not.cov-map
@@ -13,4 +13,5 @@ Number of file 0 mappings: 5
 - Code(Counter(3)) at (prev + 1, 5) to (start + 0, 22)
 - Code(Expression(1, Sub)) at (prev + 1, 1) to (start + 0, 2)
     = (c3 - Zero)
+Highest counter ID seen: c3
 
diff --git a/tests/coverage/async.cov-map b/tests/coverage/async.cov-map
index 43b497a1d3fe..9a67cefcf985 100644
--- a/tests/coverage/async.cov-map
+++ b/tests/coverage/async.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 12, 1) to (start + 0, 25)
+Highest counter ID seen: c0
 
 Function name: async::c::{closure#0}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 0c, 19, 01, 0e, 05, 02, 09, 00, 0a, 02, 02, 09, 00, 0a, 01, 02, 01, 00, 02]
@@ -18,6 +19,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 9) to (start + 0, 10)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: async::d
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 14, 01, 00, 14]
@@ -26,6 +28,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 20, 1) to (start + 0, 20)
+Highest counter ID seen: c0
 
 Function name: async::d::{closure#0}
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 14, 14, 00, 19]
@@ -34,6 +37,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 20, 20) to (start + 0, 25)
+Highest counter ID seen: c0
 
 Function name: async::e (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 16, 01, 00, 14]
@@ -42,6 +46,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 22, 1) to (start + 0, 20)
+Highest counter ID seen: (none)
 
 Function name: async::e::{closure#0} (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 16, 14, 00, 19]
@@ -50,6 +55,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 22, 20) to (start + 0, 25)
+Highest counter ID seen: (none)
 
 Function name: async::f
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 18, 01, 00, 14]
@@ -58,6 +64,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 24, 1) to (start + 0, 20)
+Highest counter ID seen: c0
 
 Function name: async::f::{closure#0}
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 18, 14, 00, 19]
@@ -66,6 +73,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 24, 20) to (start + 0, 25)
+Highest counter ID seen: c0
 
 Function name: async::foo (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 1a, 01, 00, 1e]
@@ -74,6 +82,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 26, 1) to (start + 0, 30)
+Highest counter ID seen: (none)
 
 Function name: async::foo::{closure#0} (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 1a, 1e, 00, 2d]
@@ -82,6 +91,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 26, 30) to (start + 0, 45)
+Highest counter ID seen: (none)
 
 Function name: async::g
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 1c, 01, 00, 17]
@@ -90,6 +100,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 28, 1) to (start + 0, 23)
+Highest counter ID seen: c0
 
 Function name: async::g::{closure#0} (unused)
 Raw bytes (59): 0x[01, 01, 00, 0b, 00, 1c, 17, 01, 0c, 00, 02, 09, 00, 0a, 00, 00, 0e, 00, 17, 00, 00, 1b, 00, 1c, 00, 00, 20, 00, 22, 00, 01, 09, 00, 0a, 00, 00, 0e, 00, 17, 00, 00, 1b, 00, 1c, 00, 00, 20, 00, 22, 00, 01, 0e, 00, 10, 00, 02, 01, 00, 02]
@@ -108,6 +119,7 @@ Number of file 0 mappings: 11
 - Code(Zero) at (prev + 0, 32) to (start + 0, 34)
 - Code(Zero) at (prev + 1, 14) to (start + 0, 16)
 - Code(Zero) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: (none)
 
 Function name: async::h
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 24, 01, 00, 16]
@@ -116,6 +128,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 36, 1) to (start + 0, 22)
+Highest counter ID seen: c0
 
 Function name: async::h::{closure#0} (unused)
 Raw bytes (39): 0x[01, 01, 00, 07, 00, 24, 16, 03, 0c, 00, 04, 09, 00, 0a, 00, 00, 0e, 00, 19, 00, 00, 1a, 00, 1b, 00, 00, 20, 00, 22, 00, 01, 0e, 00, 10, 00, 02, 01, 00, 02]
@@ -130,6 +143,7 @@ Number of file 0 mappings: 7
 - Code(Zero) at (prev + 0, 32) to (start + 0, 34)
 - Code(Zero) at (prev + 1, 14) to (start + 0, 16)
 - Code(Zero) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: (none)
 
 Function name: async::i
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 2d, 01, 00, 13]
@@ -138,6 +152,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 45, 1) to (start + 0, 19)
+Highest counter ID seen: c0
 
 Function name: async::i::{closure#0}
 Raw bytes (63): 0x[01, 01, 02, 07, 19, 11, 15, 0b, 01, 2d, 13, 04, 0c, 09, 05, 09, 00, 0a, 01, 00, 0e, 00, 18, 05, 00, 1c, 00, 21, 09, 00, 27, 00, 30, 15, 01, 09, 00, 0a, 0d, 00, 0e, 00, 17, 1d, 00, 1b, 00, 20, 15, 00, 24, 00, 26, 19, 01, 0e, 00, 10, 03, 02, 01, 00, 02]
@@ -159,6 +174,7 @@ Number of file 0 mappings: 11
 - Code(Counter(6)) at (prev + 1, 14) to (start + 0, 16)
 - Code(Expression(0, Add)) at (prev + 2, 1) to (start + 0, 2)
     = ((c4 + c5) + c6)
+Highest counter ID seen: c7
 
 Function name: async::j
 Raw bytes (58): 0x[01, 01, 02, 07, 0d, 05, 09, 0a, 01, 38, 01, 00, 0d, 01, 0b, 0b, 00, 0c, 05, 01, 09, 00, 0a, 01, 00, 0e, 00, 1b, 05, 00, 1f, 00, 27, 09, 01, 09, 00, 0a, 11, 00, 0e, 00, 1a, 09, 00, 1e, 00, 20, 0d, 01, 0e, 00, 10, 03, 02, 01, 00, 02]
@@ -179,6 +195,7 @@ Number of file 0 mappings: 10
 - Code(Counter(3)) at (prev + 1, 14) to (start + 0, 16)
 - Code(Expression(0, Add)) at (prev + 2, 1) to (start + 0, 2)
     = ((c1 + c2) + c3)
+Highest counter ID seen: c4
 
 Function name: async::j::c
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 3a, 05, 01, 12, 05, 02, 0d, 00, 0e, 02, 02, 0d, 00, 0e, 01, 02, 05, 00, 06]
@@ -192,6 +209,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 13) to (start + 0, 14)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 2, 5) to (start + 0, 6)
+Highest counter ID seen: c1
 
 Function name: async::j::d
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 41, 05, 00, 17]
@@ -200,6 +218,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 65, 5) to (start + 0, 23)
+Highest counter ID seen: c0
 
 Function name: async::j::f
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 42, 05, 00, 17]
@@ -208,6 +227,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 66, 5) to (start + 0, 23)
+Highest counter ID seen: c0
 
 Function name: async::k (unused)
 Raw bytes (29): 0x[01, 01, 00, 05, 00, 4a, 01, 01, 0c, 00, 02, 0e, 00, 10, 00, 01, 0e, 00, 10, 00, 01, 0e, 00, 10, 00, 02, 01, 00, 02]
@@ -220,6 +240,7 @@ Number of file 0 mappings: 5
 - Code(Zero) at (prev + 1, 14) to (start + 0, 16)
 - Code(Zero) at (prev + 1, 14) to (start + 0, 16)
 - Code(Zero) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: (none)
 
 Function name: async::l
 Raw bytes (37): 0x[01, 01, 04, 01, 07, 05, 09, 0f, 02, 09, 05, 05, 01, 52, 01, 01, 0c, 02, 02, 0e, 00, 10, 05, 01, 0e, 00, 10, 09, 01, 0e, 00, 10, 0b, 02, 01, 00, 02]
@@ -238,6 +259,7 @@ Number of file 0 mappings: 5
 - Code(Counter(2)) at (prev + 1, 14) to (start + 0, 16)
 - Code(Expression(2, Add)) at (prev + 2, 1) to (start + 0, 2)
     = ((c2 + c1) + (c0 - (c1 + c2)))
+Highest counter ID seen: c2
 
 Function name: async::m
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 5a, 01, 00, 19]
@@ -246,6 +268,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 90, 1) to (start + 0, 25)
+Highest counter ID seen: c0
 
 Function name: async::m::{closure#0} (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 5a, 19, 00, 22]
@@ -254,6 +277,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 90, 25) to (start + 0, 34)
+Highest counter ID seen: (none)
 
 Function name: async::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 5c, 01, 08, 02]
@@ -262,4 +286,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 92, 1) to (start + 8, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/async2.cov-map b/tests/coverage/async2.cov-map
index 3816401ac634..ed61e91efc29 100644
--- a/tests/coverage/async2.cov-map
+++ b/tests/coverage/async2.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 16, 1) to (start + 0, 23)
+Highest counter ID seen: c0
 
 Function name: async2::async_func::{closure#0}
 Raw bytes (24): 0x[01, 01, 00, 04, 01, 10, 17, 03, 09, 05, 03, 0a, 02, 06, 00, 02, 06, 00, 07, 01, 01, 01, 00, 02]
@@ -16,6 +17,7 @@ Number of file 0 mappings: 4
 - Code(Counter(1)) at (prev + 3, 10) to (start + 2, 6)
 - Code(Zero) at (prev + 2, 6) to (start + 0, 7)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: async2::async_func_just_println
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 18, 01, 00, 24]
@@ -24,6 +26,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 24, 1) to (start + 0, 36)
+Highest counter ID seen: c0
 
 Function name: async2::async_func_just_println::{closure#0}
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 18, 24, 02, 02]
@@ -32,6 +35,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 24, 36) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: async2::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 1c, 01, 07, 02]
@@ -40,6 +44,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 28, 1) to (start + 7, 2)
+Highest counter ID seen: c0
 
 Function name: async2::non_async_func
 Raw bytes (24): 0x[01, 01, 00, 04, 01, 08, 01, 03, 09, 05, 03, 0a, 02, 06, 00, 02, 06, 00, 07, 01, 01, 01, 00, 02]
@@ -51,4 +56,5 @@ Number of file 0 mappings: 4
 - Code(Counter(1)) at (prev + 3, 10) to (start + 2, 6)
 - Code(Zero) at (prev + 2, 6) to (start + 0, 7)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/async_block.cov-map b/tests/coverage/async_block.cov-map
index 65f3d821f6e4..e3309bd51b40 100644
--- a/tests/coverage/async_block.cov-map
+++ b/tests/coverage/async_block.cov-map
@@ -12,6 +12,7 @@ Number of file 0 mappings: 6
 - Code(Counter(1)) at (prev + 0, 20) to (start + 1, 22)
 - Code(Counter(1)) at (prev + 7, 10) to (start + 2, 6)
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: async_block::main::{closure#0}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 0a, 1c, 01, 17, 05, 01, 18, 02, 0e, 02, 02, 14, 02, 0e, 01, 03, 09, 00, 0a]
@@ -25,4 +26,5 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 20) to (start + 2, 14)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 3, 9) to (start + 0, 10)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/attr/impl.cov-map b/tests/coverage/attr/impl.cov-map
index 9b0deed8b64c..4d068c290f42 100644
--- a/tests/coverage/attr/impl.cov-map
+++ b/tests/coverage/attr/impl.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 14, 5) to (start + 0, 19)
+Highest counter ID seen: (none)
 
 Function name: <impl::MyStruct>::on_inherit (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 16, 05, 00, 17]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 22, 5) to (start + 0, 23)
+Highest counter ID seen: (none)
 
 Function name: <impl::MyStruct>::on_on (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 19, 05, 00, 12]
@@ -21,4 +23,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 25, 5) to (start + 0, 18)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/attr/module.cov-map b/tests/coverage/attr/module.cov-map
index 34898eb4ca81..b318ac85a6c8 100644
--- a/tests/coverage/attr/module.cov-map
+++ b/tests/coverage/attr/module.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 12, 5) to (start + 0, 15)
+Highest counter ID seen: (none)
 
 Function name: module::on::inherit (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 14, 05, 00, 14]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 20, 5) to (start + 0, 20)
+Highest counter ID seen: (none)
 
 Function name: module::on::on (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 17, 05, 00, 0f]
@@ -21,4 +23,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 23, 5) to (start + 0, 15)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/attr/nested.cov-map b/tests/coverage/attr/nested.cov-map
index 466aec8956e0..2bd953253732 100644
--- a/tests/coverage/attr/nested.cov-map
+++ b/tests/coverage/attr/nested.cov-map
@@ -6,6 +6,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 63, 1) to (start + 1, 15)
 - Code(Counter(0)) at (prev + 11, 5) to (start + 1, 2)
+Highest counter ID seen: c0
 
 Function name: nested::closure_tail
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 4e, 01, 01, 0f, 01, 11, 05, 01, 02]
@@ -15,4 +16,5 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 78, 1) to (start + 1, 15)
 - Code(Counter(0)) at (prev + 17, 5) to (start + 1, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/attr/off-on-sandwich.cov-map b/tests/coverage/attr/off-on-sandwich.cov-map
index d5fbac6ebf74..ae5c9bd19a29 100644
--- a/tests/coverage/attr/off-on-sandwich.cov-map
+++ b/tests/coverage/attr/off-on-sandwich.cov-map
@@ -6,6 +6,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 15, 5) to (start + 2, 18)
 - Code(Counter(0)) at (prev + 7, 5) to (start + 0, 6)
+Highest counter ID seen: c0
 
 Function name: off_on_sandwich::sparse_a::sparse_b::sparse_c
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 21, 09, 02, 17, 01, 0b, 09, 00, 0a]
@@ -15,6 +16,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 33, 9) to (start + 2, 23)
 - Code(Counter(0)) at (prev + 11, 9) to (start + 0, 10)
+Highest counter ID seen: c0
 
 Function name: off_on_sandwich::sparse_a::sparse_b::sparse_c::sparse_d
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 24, 0d, 02, 1b, 01, 07, 0d, 00, 0e]
@@ -24,4 +26,5 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 36, 13) to (start + 2, 27)
 - Code(Counter(0)) at (prev + 7, 13) to (start + 0, 14)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/await_ready.cov-map b/tests/coverage/await_ready.cov-map
index 38c2cf7b2d36..95dbf68a191c 100644
--- a/tests/coverage/await_ready.cov-map
+++ b/tests/coverage/await_ready.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 15, 1) to (start + 0, 30)
+Highest counter ID seen: c0
 
 Function name: await_ready::await_ready::{closure#0}
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 0f, 1e, 03, 0f, 05, 04, 01, 00, 02]
@@ -14,4 +15,5 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 15, 30) to (start + 3, 15)
 - Code(Counter(1)) at (prev + 4, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/bad_counter_ids.cov-map b/tests/coverage/bad_counter_ids.cov-map
index 7eff7f5f02f3..2b5399f33bbd 100644
--- a/tests/coverage/bad_counter_ids.cov-map
+++ b/tests/coverage/bad_counter_ids.cov-map
@@ -6,6 +6,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 36, 1) to (start + 2, 31)
 - Code(Zero) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c0
 
 Function name: bad_counter_ids::eq_bad_message
 Raw bytes (21): 0x[01, 01, 01, 01, 00, 03, 01, 29, 01, 02, 0f, 02, 02, 20, 00, 2b, 00, 01, 01, 00, 02]
@@ -18,6 +19,7 @@ Number of file 0 mappings: 3
 - Code(Expression(0, Sub)) at (prev + 2, 32) to (start + 0, 43)
     = (c0 - Zero)
 - Code(Zero) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c0
 
 Function name: bad_counter_ids::eq_good
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 10, 01, 02, 1f, 05, 03, 01, 00, 02]
@@ -27,6 +29,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 16, 1) to (start + 2, 31)
 - Code(Counter(1)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: bad_counter_ids::eq_good_message
 Raw bytes (19): 0x[01, 01, 00, 03, 01, 15, 01, 02, 0f, 00, 02, 20, 00, 2b, 05, 01, 01, 00, 02]
@@ -37,6 +40,7 @@ Number of file 0 mappings: 3
 - Code(Counter(0)) at (prev + 21, 1) to (start + 2, 15)
 - Code(Zero) at (prev + 2, 32) to (start + 0, 43)
 - Code(Counter(1)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: bad_counter_ids::ne_bad
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 2e, 01, 02, 1f, 00, 03, 01, 00, 02]
@@ -46,6 +50,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 46, 1) to (start + 2, 31)
 - Code(Zero) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c0
 
 Function name: bad_counter_ids::ne_bad_message
 Raw bytes (19): 0x[01, 01, 00, 03, 01, 33, 01, 02, 0f, 05, 02, 20, 00, 2b, 00, 01, 01, 00, 02]
@@ -56,6 +61,7 @@ Number of file 0 mappings: 3
 - Code(Counter(0)) at (prev + 51, 1) to (start + 2, 15)
 - Code(Counter(1)) at (prev + 2, 32) to (start + 0, 43)
 - Code(Zero) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: bad_counter_ids::ne_good
 Raw bytes (16): 0x[01, 01, 01, 01, 00, 02, 01, 1a, 01, 02, 1f, 02, 03, 01, 00, 02]
@@ -67,6 +73,7 @@ Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 26, 1) to (start + 2, 31)
 - Code(Expression(0, Sub)) at (prev + 3, 1) to (start + 0, 2)
     = (c0 - Zero)
+Highest counter ID seen: c0
 
 Function name: bad_counter_ids::ne_good_message
 Raw bytes (21): 0x[01, 01, 01, 01, 00, 03, 01, 1f, 01, 02, 0f, 00, 02, 20, 00, 2b, 02, 01, 01, 00, 02]
@@ -79,4 +86,5 @@ Number of file 0 mappings: 3
 - Code(Zero) at (prev + 2, 32) to (start + 0, 43)
 - Code(Expression(0, Sub)) at (prev + 1, 1) to (start + 0, 2)
     = (c0 - Zero)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/bench.cov-map b/tests/coverage/bench.cov-map
index aa702a486818..9ee6510f6904 100644
--- a/tests/coverage/bench.cov-map
+++ b/tests/coverage/bench.cov-map
@@ -5,4 +5,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 8, 1) to (start + 0, 39)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/branch/generics.cov-map b/tests/coverage/branch/generics.cov-map
index 2e5668c8b568..656890634ff4 100644
--- a/tests/coverage/branch/generics.cov-map
+++ b/tests/coverage/branch/generics.cov-map
@@ -13,6 +13,7 @@ Number of file 0 mappings: 5
 - Code(Expression(0, Sub)) at (prev + 2, 12) to (start + 2, 6)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: generics::print_size::<u32>
 Raw bytes (33): 0x[01, 01, 01, 01, 05, 05, 01, 06, 01, 01, 24, 20, 05, 02, 01, 08, 00, 24, 05, 00, 25, 02, 06, 02, 02, 0c, 02, 06, 01, 03, 01, 00, 02]
@@ -29,6 +30,7 @@ Number of file 0 mappings: 5
 - Code(Expression(0, Sub)) at (prev + 2, 12) to (start + 2, 6)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: generics::print_size::<u64>
 Raw bytes (33): 0x[01, 01, 01, 01, 05, 05, 01, 06, 01, 01, 24, 20, 05, 02, 01, 08, 00, 24, 05, 00, 25, 02, 06, 02, 02, 0c, 02, 06, 01, 03, 01, 00, 02]
@@ -45,4 +47,5 @@ Number of file 0 mappings: 5
 - Code(Expression(0, Sub)) at (prev + 2, 12) to (start + 2, 6)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/branch/guard.cov-map b/tests/coverage/branch/guard.cov-map
index d67c3d349a14..0f33ed17a0ac 100644
--- a/tests/coverage/branch/guard.cov-map
+++ b/tests/coverage/branch/guard.cov-map
@@ -29,4 +29,5 @@ Number of file 0 mappings: 13
     = (c1 + c2)
 - Code(Expression(2, Add)) at (prev + 4, 1) to (start + 0, 2)
     = ((((c1 + c2) + c3) + c4) + c5)
+Highest counter ID seen: c7
 
diff --git a/tests/coverage/branch/if-let.cov-map b/tests/coverage/branch/if-let.cov-map
index 0b098bc6497c..380765c7af4b 100644
--- a/tests/coverage/branch/if-let.cov-map
+++ b/tests/coverage/branch/if-let.cov-map
@@ -16,6 +16,7 @@ Number of file 0 mappings: 7
     = (c1 - c2)
 - Code(Counter(2)) at (prev + 2, 12) to (start + 2, 6)
 - Code(Counter(1)) at (prev + 3, 5) to (start + 1, 2)
+Highest counter ID seen: c2
 
 Function name: if_let::if_let_chain
 Raw bytes (66): 0x[01, 01, 04, 01, 05, 05, 09, 0f, 0d, 05, 09, 0a, 01, 17, 01, 00, 33, 20, 02, 05, 01, 0c, 00, 13, 02, 00, 11, 00, 12, 01, 00, 16, 00, 17, 20, 0d, 09, 01, 10, 00, 17, 0d, 00, 15, 00, 16, 02, 00, 1a, 00, 1b, 0d, 01, 05, 03, 06, 0f, 03, 0c, 02, 06, 0b, 03, 05, 01, 02]
@@ -45,4 +46,5 @@ Number of file 0 mappings: 10
     = (c1 + c2)
 - Code(Expression(2, Add)) at (prev + 3, 5) to (start + 1, 2)
     = ((c1 + c2) + c3)
+Highest counter ID seen: c3
 
diff --git a/tests/coverage/branch/if.cov-map b/tests/coverage/branch/if.cov-map
index 7f4ee980e262..4a8cb664dd83 100644
--- a/tests/coverage/branch/if.cov-map
+++ b/tests/coverage/branch/if.cov-map
@@ -22,6 +22,7 @@ Number of file 0 mappings: 8
     = (c3 + (c1 - c2))
 - Code(Expression(2, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c4 + (c3 + (c1 - c2)))
+Highest counter ID seen: c4
 
 Function name: if::branch_not
 Raw bytes (116): 0x[01, 01, 07, 05, 09, 05, 0d, 05, 0d, 05, 11, 05, 11, 05, 15, 05, 15, 12, 01, 0c, 01, 01, 10, 05, 03, 08, 00, 09, 20, 09, 02, 00, 08, 00, 09, 09, 01, 09, 00, 11, 02, 01, 06, 00, 07, 05, 01, 08, 00, 0a, 20, 0a, 0d, 00, 08, 00, 0a, 0a, 00, 0b, 02, 06, 0d, 02, 06, 00, 07, 05, 01, 08, 00, 0b, 20, 11, 12, 00, 08, 00, 0b, 11, 00, 0c, 02, 06, 12, 02, 06, 00, 07, 05, 01, 08, 00, 0c, 20, 1a, 15, 00, 08, 00, 0c, 1a, 00, 0d, 02, 06, 15, 02, 06, 00, 07, 05, 01, 01, 00, 02]
@@ -66,6 +67,7 @@ Number of file 0 mappings: 18
     = (c1 - c5)
 - Code(Counter(5)) at (prev + 2, 6) to (start + 0, 7)
 - Code(Counter(1)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c5
 
 Function name: if::branch_not_as
 Raw bytes (90): 0x[01, 01, 05, 05, 09, 05, 0d, 05, 0d, 05, 11, 05, 11, 0e, 01, 1d, 01, 01, 10, 05, 03, 08, 00, 14, 20, 02, 09, 00, 08, 00, 14, 02, 00, 15, 02, 06, 09, 02, 06, 00, 07, 05, 01, 08, 00, 15, 20, 0d, 0a, 00, 08, 00, 15, 0d, 00, 16, 02, 06, 0a, 02, 06, 00, 07, 05, 01, 08, 00, 16, 20, 12, 11, 00, 08, 00, 16, 12, 00, 17, 02, 06, 11, 02, 06, 00, 07, 05, 01, 01, 00, 02]
@@ -101,6 +103,7 @@ Number of file 0 mappings: 14
     = (c1 - c4)
 - Code(Counter(4)) at (prev + 2, 6) to (start + 0, 7)
 - Code(Counter(1)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c4
 
 Function name: if::branch_or
 Raw bytes (56): 0x[01, 01, 04, 05, 09, 09, 0d, 0f, 11, 09, 0d, 08, 01, 35, 01, 01, 10, 05, 03, 08, 00, 09, 20, 09, 02, 00, 08, 00, 09, 02, 00, 0d, 00, 0e, 20, 0d, 11, 00, 0d, 00, 0e, 0f, 00, 0f, 02, 06, 11, 02, 0c, 02, 06, 0b, 03, 01, 00, 02]
@@ -127,4 +130,5 @@ Number of file 0 mappings: 8
 - Code(Counter(4)) at (prev + 2, 12) to (start + 2, 6)
 - Code(Expression(2, Add)) at (prev + 3, 1) to (start + 0, 2)
     = ((c2 + c3) + c4)
+Highest counter ID seen: c4
 
diff --git a/tests/coverage/branch/lazy-boolean.cov-map b/tests/coverage/branch/lazy-boolean.cov-map
index 09ce91376733..c2b6a5b8df24 100644
--- a/tests/coverage/branch/lazy-boolean.cov-map
+++ b/tests/coverage/branch/lazy-boolean.cov-map
@@ -13,6 +13,7 @@ Number of file 0 mappings: 6
     false = (c1 - c2)
 - Code(Counter(2)) at (prev + 0, 18) to (start + 0, 19)
 - Code(Counter(1)) at (prev + 1, 5) to (start + 1, 2)
+Highest counter ID seen: c2
 
 Function name: lazy_boolean::branch_or
 Raw bytes (38): 0x[01, 01, 01, 05, 09, 06, 01, 1b, 01, 01, 10, 05, 04, 09, 00, 0a, 05, 00, 0d, 00, 0e, 20, 09, 02, 00, 0d, 00, 0e, 02, 00, 12, 00, 13, 05, 01, 05, 01, 02]
@@ -30,6 +31,7 @@ Number of file 0 mappings: 6
 - Code(Expression(0, Sub)) at (prev + 0, 18) to (start + 0, 19)
     = (c1 - c2)
 - Code(Counter(1)) at (prev + 1, 5) to (start + 1, 2)
+Highest counter ID seen: c2
 
 Function name: lazy_boolean::chain
 Raw bytes (149): 0x[01, 01, 13, 11, 07, 0b, 16, 15, 1a, 09, 0d, 05, 09, 05, 09, 09, 0d, 47, 25, 4b, 21, 19, 1d, 03, 19, 03, 19, 3e, 1d, 03, 19, 3e, 1d, 03, 19, 47, 25, 4b, 21, 19, 1d, 13, 01, 24, 01, 01, 10, 03, 04, 09, 00, 0a, 05, 00, 0d, 00, 12, 20, 09, 16, 00, 0d, 00, 12, 09, 00, 16, 00, 1b, 20, 0d, 1a, 00, 16, 00, 1b, 0d, 00, 1f, 00, 24, 20, 11, 15, 00, 1f, 00, 24, 11, 00, 28, 00, 2d, 03, 01, 05, 00, 11, 43, 03, 09, 00, 0a, 03, 00, 0d, 00, 12, 20, 19, 3e, 00, 0d, 00, 12, 3e, 00, 16, 00, 1b, 20, 1d, 3a, 00, 16, 00, 1b, 3a, 00, 1f, 00, 24, 20, 21, 25, 00, 1f, 00, 24, 25, 00, 28, 00, 2d, 43, 01, 05, 01, 02]
@@ -94,6 +96,7 @@ Number of file 0 mappings: 19
 - Code(Counter(9)) at (prev + 0, 40) to (start + 0, 45)
 - Code(Expression(16, Add)) at (prev + 1, 5) to (start + 1, 2)
     = (((c6 + c7) + c8) + c9)
+Highest counter ID seen: c9
 
 Function name: lazy_boolean::nested_mixed
 Raw bytes (155): 0x[01, 01, 16, 33, 1a, 09, 0d, 1e, 0d, 05, 09, 05, 09, 05, 09, 1e, 0d, 05, 09, 09, 0d, 33, 11, 09, 0d, 33, 11, 09, 0d, 19, 57, 1d, 21, 03, 15, 15, 19, 4a, 4e, 15, 19, 03, 15, 19, 57, 1d, 21, 13, 01, 31, 01, 01, 10, 03, 04, 09, 00, 0a, 05, 00, 0e, 00, 13, 20, 09, 1e, 00, 0e, 00, 13, 1e, 00, 17, 00, 1d, 20, 0d, 1a, 00, 17, 00, 1d, 33, 00, 23, 00, 28, 20, 11, 2e, 00, 23, 00, 28, 2e, 00, 2c, 00, 33, 03, 01, 05, 00, 11, 53, 03, 09, 00, 0a, 03, 00, 0e, 00, 13, 20, 15, 4e, 00, 0e, 00, 13, 15, 00, 17, 00, 1c, 20, 19, 4a, 00, 17, 00, 1c, 47, 00, 22, 00, 28, 20, 1d, 21, 00, 22, 00, 28, 1d, 00, 2c, 00, 33, 53, 01, 05, 01, 02]
@@ -163,4 +166,5 @@ Number of file 0 mappings: 19
 - Code(Counter(7)) at (prev + 0, 44) to (start + 0, 51)
 - Code(Expression(20, Add)) at (prev + 1, 5) to (start + 1, 2)
     = (c6 + (c7 + c8))
+Highest counter ID seen: c8
 
diff --git a/tests/coverage/branch/let-else.cov-map b/tests/coverage/branch/let-else.cov-map
index 070799344647..e6bf7ed6a925 100644
--- a/tests/coverage/branch/let-else.cov-map
+++ b/tests/coverage/branch/let-else.cov-map
@@ -16,4 +16,5 @@ Number of file 0 mappings: 7
 - Code(Expression(0, Sub)) at (prev + 4, 5) to (start + 0, 11)
     = (c1 - c2)
 - Code(Counter(1)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c2
 
diff --git a/tests/coverage/branch/match-arms.cov-map b/tests/coverage/branch/match-arms.cov-map
index 1f17f11baaa0..fd0366ee8183 100644
--- a/tests/coverage/branch/match-arms.cov-map
+++ b/tests/coverage/branch/match-arms.cov-map
@@ -34,6 +34,7 @@ Number of file 0 mappings: 12
     = ((((Zero + c2) + c3) + c4) + c5)
 - Code(Expression(4, Add)) at (prev + 3, 5) to (start + 1, 2)
     = ((((((((Zero + c2) + c3) + c4) + c5) + c6) + c7) + c8) + c9)
+Highest counter ID seen: c10
 
 Function name: match_arms::match_arms
 Raw bytes (51): 0x[01, 01, 06, 05, 07, 0b, 11, 09, 0d, 13, 02, 17, 09, 11, 0d, 07, 01, 18, 01, 01, 10, 05, 03, 0b, 00, 10, 11, 01, 11, 00, 21, 0d, 01, 11, 00, 21, 09, 01, 11, 00, 21, 02, 01, 11, 00, 21, 0f, 03, 05, 01, 02]
@@ -56,6 +57,7 @@ Number of file 0 mappings: 7
     = (c1 - ((c2 + c3) + c4))
 - Code(Expression(3, Add)) at (prev + 3, 5) to (start + 1, 2)
     = (((c4 + c3) + c2) + (c1 - ((c2 + c3) + c4)))
+Highest counter ID seen: c4
 
 Function name: match_arms::or_patterns
 Raw bytes (75): 0x[01, 01, 0d, 11, 0d, 05, 2f, 33, 11, 09, 0d, 09, 2a, 05, 2f, 33, 11, 09, 0d, 03, 27, 09, 2a, 05, 2f, 33, 11, 09, 0d, 09, 01, 25, 01, 01, 10, 05, 03, 0b, 00, 10, 11, 01, 11, 00, 12, 0d, 00, 1e, 00, 1f, 03, 00, 24, 00, 2e, 09, 01, 11, 00, 12, 2a, 00, 1e, 00, 1f, 27, 00, 24, 00, 2e, 23, 03, 05, 01, 02]
@@ -89,4 +91,5 @@ Number of file 0 mappings: 9
     = (c2 + (c1 - ((c2 + c3) + c4)))
 - Code(Expression(8, Add)) at (prev + 3, 5) to (start + 1, 2)
     = ((c4 + c3) + (c2 + (c1 - ((c2 + c3) + c4))))
+Highest counter ID seen: c4
 
diff --git a/tests/coverage/branch/match-trivial.cov-map b/tests/coverage/branch/match-trivial.cov-map
index 1136a529b255..6af8ce46f5fa 100644
--- a/tests/coverage/branch/match-trivial.cov-map
+++ b/tests/coverage/branch/match-trivial.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 22, 1) to (start + 1, 16)
+Highest counter ID seen: (none)
 
 Function name: match_trivial::trivial
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 1e, 01, 01, 10, 05, 03, 0b, 05, 02]
@@ -14,4 +15,5 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 30, 1) to (start + 1, 16)
 - Code(Counter(1)) at (prev + 3, 11) to (start + 5, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/branch/no-mir-spans.cov-map b/tests/coverage/branch/no-mir-spans.cov-map
index cb19211913f8..ab12732b1ed3 100644
--- a/tests/coverage/branch/no-mir-spans.cov-map
+++ b/tests/coverage/branch/no-mir-spans.cov-map
@@ -8,6 +8,7 @@ Number of file 0 mappings: 2
 - Branch { true: Counter(1), false: Counter(2) } at (prev + 4, 11) to (start + 0, 16)
     true  = c1
     false = c2
+Highest counter ID seen: c2
 
 Function name: no_mir_spans::while_cond_not
 Raw bytes (16): 0x[01, 01, 00, 02, 01, 19, 01, 00, 15, 20, 09, 05, 04, 0b, 00, 14]
@@ -19,6 +20,7 @@ Number of file 0 mappings: 2
 - Branch { true: Counter(2), false: Counter(1) } at (prev + 4, 11) to (start + 0, 20)
     true  = c2
     false = c1
+Highest counter ID seen: c2
 
 Function name: no_mir_spans::while_op_and
 Raw bytes (25): 0x[01, 01, 01, 09, 0d, 03, 01, 22, 01, 00, 13, 20, 09, 05, 05, 0b, 00, 10, 20, 02, 0d, 00, 14, 00, 19]
@@ -34,6 +36,7 @@ Number of file 0 mappings: 3
 - Branch { true: Expression(0, Sub), false: Counter(3) } at (prev + 0, 20) to (start + 0, 25)
     true  = (c2 - c3)
     false = c3
+Highest counter ID seen: c3
 
 Function name: no_mir_spans::while_op_or
 Raw bytes (25): 0x[01, 01, 01, 09, 0d, 03, 01, 2d, 01, 00, 12, 20, 05, 09, 05, 0b, 00, 10, 20, 0d, 02, 00, 14, 00, 19]
@@ -49,4 +52,5 @@ Number of file 0 mappings: 3
 - Branch { true: Counter(3), false: Expression(0, Sub) } at (prev + 0, 20) to (start + 0, 25)
     true  = c3
     false = (c2 - c3)
+Highest counter ID seen: c3
 
diff --git a/tests/coverage/branch/while.cov-map b/tests/coverage/branch/while.cov-map
index fd05bbb69a55..d5840a2c320b 100644
--- a/tests/coverage/branch/while.cov-map
+++ b/tests/coverage/branch/while.cov-map
@@ -14,6 +14,7 @@ Number of file 0 mappings: 6
     false = c1
 - Code(Counter(2)) at (prev + 0, 17) to (start + 2, 6)
 - Code(Counter(1)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c2
 
 Function name: while::while_cond_not
 Raw bytes (38): 0x[01, 01, 01, 05, 09, 06, 01, 15, 01, 01, 10, 05, 03, 09, 00, 12, 03, 01, 0b, 00, 14, 20, 09, 05, 00, 0b, 00, 14, 09, 00, 15, 02, 06, 05, 03, 01, 00, 02]
@@ -31,6 +32,7 @@ Number of file 0 mappings: 6
     false = c1
 - Code(Counter(2)) at (prev + 0, 21) to (start + 2, 6)
 - Code(Counter(1)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c2
 
 Function name: while::while_op_and
 Raw bytes (56): 0x[01, 01, 04, 05, 09, 03, 0d, 03, 0d, 11, 0d, 08, 01, 1e, 01, 01, 10, 05, 03, 09, 01, 12, 03, 02, 0b, 00, 10, 20, 0a, 0d, 00, 0b, 00, 10, 0a, 00, 14, 00, 19, 20, 09, 11, 00, 14, 00, 19, 09, 00, 1a, 03, 06, 0f, 04, 01, 00, 02]
@@ -57,6 +59,7 @@ Number of file 0 mappings: 8
 - Code(Counter(2)) at (prev + 0, 26) to (start + 3, 6)
 - Code(Expression(3, Add)) at (prev + 4, 1) to (start + 0, 2)
     = (c4 + c3)
+Highest counter ID seen: c4
 
 Function name: while::while_op_or
 Raw bytes (66): 0x[01, 01, 09, 05, 1b, 09, 0d, 03, 09, 03, 09, 22, 0d, 03, 09, 09, 0d, 22, 0d, 03, 09, 08, 01, 29, 01, 01, 10, 05, 03, 09, 01, 12, 03, 02, 0b, 00, 10, 20, 09, 22, 00, 0b, 00, 10, 22, 00, 14, 00, 19, 20, 0d, 1e, 00, 14, 00, 19, 1b, 00, 1a, 03, 06, 1e, 04, 01, 00, 02]
@@ -89,4 +92,5 @@ Number of file 0 mappings: 8
     = (c2 + c3)
 - Code(Expression(7, Sub)) at (prev + 4, 1) to (start + 0, 2)
     = (((c1 + (c2 + c3)) - c2) - c3)
+Highest counter ID seen: c3
 
diff --git a/tests/coverage/closure.cov-map b/tests/coverage/closure.cov-map
index 6edd35921fe9..d50f9f8e7afa 100644
--- a/tests/coverage/closure.cov-map
+++ b/tests/coverage/closure.cov-map
@@ -30,6 +30,7 @@ Number of file 0 mappings: 24
 - Code(Expression(0, Sub)) at (prev + 4, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 5) to (start + 3, 2)
+Highest counter ID seen: c1
 
 Function name: closure::main::{closure#0}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 28, 05, 02, 14, 05, 02, 15, 02, 0a, 02, 02, 0a, 00, 0b, 01, 01, 09, 01, 06]
@@ -43,6 +44,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 10) to (start + 0, 11)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 9) to (start + 1, 6)
+Highest counter ID seen: c1
 
 Function name: closure::main::{closure#10} (unused)
 Raw bytes (10): 0x[01, 01, 00, 01, 00, 9b, 01, 07, 00, 21]
@@ -51,6 +53,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 155, 7) to (start + 0, 33)
+Highest counter ID seen: (none)
 
 Function name: closure::main::{closure#11} (unused)
 Raw bytes (10): 0x[01, 01, 00, 01, 00, 9f, 01, 07, 00, 21]
@@ -59,6 +62,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 159, 7) to (start + 0, 33)
+Highest counter ID seen: (none)
 
 Function name: closure::main::{closure#12} (unused)
 Raw bytes (10): 0x[01, 01, 00, 01, 00, a7, 01, 01, 00, 17]
@@ -67,6 +71,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 167, 1) to (start + 0, 23)
+Highest counter ID seen: (none)
 
 Function name: closure::main::{closure#13} (unused)
 Raw bytes (10): 0x[01, 01, 00, 01, 00, ac, 01, 0d, 02, 0e]
@@ -75,6 +80,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 172, 13) to (start + 2, 14)
+Highest counter ID seen: (none)
 
 Function name: closure::main::{closure#14}
 Raw bytes (27): 0x[01, 01, 01, 01, 05, 04, 01, b3, 01, 0d, 02, 1b, 05, 02, 1e, 00, 25, 02, 00, 2f, 00, 33, 01, 01, 0d, 00, 0e]
@@ -88,6 +94,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 0, 47) to (start + 0, 51)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 13) to (start + 0, 14)
+Highest counter ID seen: c1
 
 Function name: closure::main::{closure#15}
 Raw bytes (37): 0x[01, 01, 01, 01, 05, 06, 01, bb, 01, 09, 00, 0a, 01, 01, 0d, 00, 15, 01, 01, 11, 01, 1b, 05, 01, 1e, 00, 25, 02, 00, 2f, 00, 33, 01, 02, 09, 00, 0a]
@@ -103,6 +110,7 @@ Number of file 0 mappings: 6
 - Code(Expression(0, Sub)) at (prev + 0, 47) to (start + 0, 51)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 2, 9) to (start + 0, 10)
+Highest counter ID seen: c1
 
 Function name: closure::main::{closure#16}
 Raw bytes (27): 0x[01, 01, 01, 01, 05, 04, 01, c5, 01, 0d, 02, 1b, 05, 02, 1e, 00, 25, 02, 00, 2f, 00, 33, 01, 01, 0d, 00, 0e]
@@ -116,6 +124,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 0, 47) to (start + 0, 51)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 13) to (start + 0, 14)
+Highest counter ID seen: c1
 
 Function name: closure::main::{closure#17}
 Raw bytes (37): 0x[01, 01, 01, 01, 05, 06, 01, cd, 01, 09, 00, 0a, 01, 01, 0d, 00, 15, 01, 01, 11, 01, 1b, 05, 01, 1e, 00, 25, 02, 00, 2f, 00, 33, 01, 02, 09, 00, 0a]
@@ -131,6 +140,7 @@ Number of file 0 mappings: 6
 - Code(Expression(0, Sub)) at (prev + 0, 47) to (start + 0, 51)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 2, 9) to (start + 0, 10)
+Highest counter ID seen: c1
 
 Function name: closure::main::{closure#18} (unused)
 Raw bytes (24): 0x[01, 01, 00, 04, 00, 19, 0d, 02, 1c, 00, 02, 1d, 02, 12, 00, 02, 12, 00, 13, 00, 01, 11, 01, 0e]
@@ -142,6 +152,7 @@ Number of file 0 mappings: 4
 - Code(Zero) at (prev + 2, 29) to (start + 2, 18)
 - Code(Zero) at (prev + 2, 18) to (start + 0, 19)
 - Code(Zero) at (prev + 1, 17) to (start + 1, 14)
+Highest counter ID seen: (none)
 
 Function name: closure::main::{closure#19}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 43, 0d, 02, 1c, 05, 02, 1d, 02, 12, 02, 02, 12, 00, 13, 01, 01, 11, 01, 0e]
@@ -155,6 +166,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 18) to (start + 0, 19)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 17) to (start + 1, 14)
+Highest counter ID seen: c1
 
 Function name: closure::main::{closure#1}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 52, 05, 02, 14, 05, 02, 15, 02, 0a, 02, 02, 0a, 00, 0b, 01, 01, 09, 01, 06]
@@ -168,6 +180,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 10) to (start + 0, 11)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 9) to (start + 1, 6)
+Highest counter ID seen: c1
 
 Function name: closure::main::{closure#2}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 68, 05, 02, 14, 05, 02, 15, 02, 0a, 02, 02, 0a, 00, 0b, 01, 01, 09, 01, 06]
@@ -181,6 +194,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 10) to (start + 0, 11)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 9) to (start + 1, 6)
+Highest counter ID seen: c1
 
 Function name: closure::main::{closure#3} (unused)
 Raw bytes (25): 0x[01, 01, 00, 04, 00, 81, 01, 05, 01, 14, 00, 01, 15, 02, 0a, 00, 02, 0a, 00, 0b, 00, 01, 09, 01, 06]
@@ -192,6 +206,7 @@ Number of file 0 mappings: 4
 - Code(Zero) at (prev + 1, 21) to (start + 2, 10)
 - Code(Zero) at (prev + 2, 10) to (start + 0, 11)
 - Code(Zero) at (prev + 1, 9) to (start + 1, 6)
+Highest counter ID seen: (none)
 
 Function name: closure::main::{closure#4} (unused)
 Raw bytes (10): 0x[01, 01, 00, 01, 00, 89, 01, 35, 00, 43]
@@ -200,6 +215,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 137, 53) to (start + 0, 67)
+Highest counter ID seen: (none)
 
 Function name: closure::main::{closure#5}
 Raw bytes (10): 0x[01, 01, 00, 01, 01, 8c, 01, 3d, 00, 4f]
@@ -208,6 +224,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 140, 61) to (start + 0, 79)
+Highest counter ID seen: c0
 
 Function name: closure::main::{closure#6}
 Raw bytes (10): 0x[01, 01, 00, 01, 01, 8d, 01, 41, 00, 57]
@@ -216,6 +233,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 141, 65) to (start + 0, 87)
+Highest counter ID seen: c0
 
 Function name: closure::main::{closure#7} (unused)
 Raw bytes (10): 0x[01, 01, 00, 01, 00, 8e, 01, 3b, 00, 51]
@@ -224,6 +242,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 142, 59) to (start + 0, 81)
+Highest counter ID seen: (none)
 
 Function name: closure::main::{closure#8} (unused)
 Raw bytes (10): 0x[01, 01, 00, 01, 00, 93, 01, 3b, 00, 55]
@@ -232,6 +251,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 147, 59) to (start + 0, 85)
+Highest counter ID seen: (none)
 
 Function name: closure::main::{closure#9} (unused)
 Raw bytes (10): 0x[01, 01, 00, 01, 00, 95, 01, 38, 02, 06]
@@ -240,4 +260,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 149, 56) to (start + 2, 6)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/closure_bug.cov-map b/tests/coverage/closure_bug.cov-map
index 32e8db5fb2f4..96e1e339e569 100644
--- a/tests/coverage/closure_bug.cov-map
+++ b/tests/coverage/closure_bug.cov-map
@@ -29,6 +29,7 @@ Number of file 0 mappings: 17
 - Code(Expression(3, Sub)) at (prev + 0, 23) to (start + 0, 24)
     = (c0 - c4)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c4
 
 Function name: closure_bug::main::{closure#0}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 0e, 09, 00, 12, 05, 00, 15, 00, 19, 02, 00, 23, 00, 28, 01, 00, 29, 00, 2a]
@@ -42,6 +43,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 0, 35) to (start + 0, 40)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 0, 41) to (start + 0, 42)
+Highest counter ID seen: c1
 
 Function name: closure_bug::main::{closure#1}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 17, 09, 00, 12, 05, 00, 15, 00, 19, 02, 00, 23, 00, 28, 01, 00, 29, 00, 2a]
@@ -55,6 +57,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 0, 35) to (start + 0, 40)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 0, 41) to (start + 0, 42)
+Highest counter ID seen: c1
 
 Function name: closure_bug::main::{closure#2}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 20, 09, 00, 12, 05, 00, 15, 00, 19, 02, 00, 23, 00, 28, 01, 00, 29, 00, 2a]
@@ -68,6 +71,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 0, 35) to (start + 0, 40)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 0, 41) to (start + 0, 42)
+Highest counter ID seen: c1
 
 Function name: closure_bug::main::{closure#3}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 29, 09, 00, 12, 05, 00, 15, 00, 19, 02, 00, 23, 00, 28, 01, 00, 29, 00, 2a]
@@ -81,4 +85,5 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 0, 35) to (start + 0, 40)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 0, 41) to (start + 0, 42)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/closure_macro.cov-map b/tests/coverage/closure_macro.cov-map
index fb4a137d4c8e..7c9d3292f988 100644
--- a/tests/coverage/closure_macro.cov-map
+++ b/tests/coverage/closure_macro.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 29, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: closure_macro::main
 Raw bytes (36): 0x[01, 01, 01, 01, 05, 06, 01, 21, 01, 01, 21, 02, 02, 09, 00, 0f, 01, 00, 12, 00, 54, 05, 00, 54, 00, 55, 02, 02, 09, 02, 0b, 01, 03, 01, 00, 02]
@@ -21,6 +22,7 @@ Number of file 0 mappings: 6
 - Code(Expression(0, Sub)) at (prev + 2, 9) to (start + 2, 11)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: closure_macro::main::{closure#0}
 Raw bytes (35): 0x[01, 01, 03, 01, 05, 05, 0b, 09, 0d, 05, 01, 10, 1c, 03, 21, 05, 04, 11, 01, 27, 02, 03, 11, 00, 16, 0d, 00, 17, 00, 1e, 07, 02, 09, 00, 0a]
@@ -38,4 +40,5 @@ Number of file 0 mappings: 5
 - Code(Counter(3)) at (prev + 0, 23) to (start + 0, 30)
 - Code(Expression(1, Add)) at (prev + 2, 9) to (start + 0, 10)
     = (c1 + (c2 + c3))
+Highest counter ID seen: c3
 
diff --git a/tests/coverage/closure_macro_async.cov-map b/tests/coverage/closure_macro_async.cov-map
index 091e87909f90..e2a52e57015c 100644
--- a/tests/coverage/closure_macro_async.cov-map
+++ b/tests/coverage/closure_macro_async.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 34, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: closure_macro_async::test
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 26, 01, 00, 2b]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 38, 1) to (start + 0, 43)
+Highest counter ID seen: c0
 
 Function name: closure_macro_async::test::{closure#0}
 Raw bytes (36): 0x[01, 01, 01, 01, 05, 06, 01, 26, 2b, 01, 21, 02, 02, 09, 00, 0f, 01, 00, 12, 00, 54, 05, 00, 54, 00, 55, 02, 02, 09, 02, 0b, 01, 03, 01, 00, 02]
@@ -29,6 +31,7 @@ Number of file 0 mappings: 6
 - Code(Expression(0, Sub)) at (prev + 2, 9) to (start + 2, 11)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: closure_macro_async::test::{closure#0}::{closure#0}
 Raw bytes (35): 0x[01, 01, 03, 01, 05, 05, 0b, 09, 0d, 05, 01, 15, 1c, 03, 21, 05, 04, 11, 01, 27, 02, 03, 11, 00, 16, 0d, 00, 17, 00, 1e, 07, 02, 09, 00, 0a]
@@ -46,4 +49,5 @@ Number of file 0 mappings: 5
 - Code(Counter(3)) at (prev + 0, 23) to (start + 0, 30)
 - Code(Expression(1, Add)) at (prev + 2, 9) to (start + 0, 10)
     = (c1 + (c2 + c3))
+Highest counter ID seen: c3
 
diff --git a/tests/coverage/closure_unit_return.cov-map b/tests/coverage/closure_unit_return.cov-map
index c97b4a44dd6b..9a66e0b0e772 100644
--- a/tests/coverage/closure_unit_return.cov-map
+++ b/tests/coverage/closure_unit_return.cov-map
@@ -6,6 +6,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 7, 1) to (start + 1, 16)
 - Code(Counter(0)) at (prev + 5, 5) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: closure_unit_return::explicit_unit::{closure#0} (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 08, 16, 02, 06]
@@ -14,6 +15,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 8, 22) to (start + 2, 6)
+Highest counter ID seen: (none)
 
 Function name: closure_unit_return::implicit_unit
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 10, 01, 01, 10, 01, 05, 05, 02, 02]
@@ -23,6 +25,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 16, 1) to (start + 1, 16)
 - Code(Counter(0)) at (prev + 5, 5) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: closure_unit_return::implicit_unit::{closure#0} (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 11, 16, 02, 06]
@@ -31,4 +34,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 17, 22) to (start + 2, 6)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/condition/conditions.cov-map b/tests/coverage/condition/conditions.cov-map
index 74726e269fc6..208d671919cf 100644
--- a/tests/coverage/condition/conditions.cov-map
+++ b/tests/coverage/condition/conditions.cov-map
@@ -29,6 +29,7 @@ Number of file 0 mappings: 9
     false = c4
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 1, 2)
     = ((c2 + c3) + c4)
+Highest counter ID seen: c4
 
 Function name: conditions::assign_3_or_and
 Raw bytes (73): 0x[01, 01, 09, 05, 07, 0b, 11, 09, 0d, 01, 05, 01, 05, 22, 11, 01, 05, 22, 11, 01, 05, 09, 01, 17, 01, 00, 2f, 03, 01, 09, 00, 0a, 01, 00, 0d, 00, 0e, 20, 05, 22, 00, 0d, 00, 0e, 22, 00, 12, 00, 13, 20, 1e, 11, 00, 12, 00, 13, 1e, 00, 17, 00, 18, 20, 09, 0d, 00, 17, 00, 18, 03, 01, 05, 01, 02]
@@ -64,6 +65,7 @@ Number of file 0 mappings: 9
     false = c3
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 1, 2)
     = (c1 + ((c2 + c3) + c4))
+Highest counter ID seen: c4
 
 Function name: conditions::assign_and
 Raw bytes (51): 0x[01, 01, 04, 07, 0e, 09, 0d, 01, 05, 01, 05, 07, 01, 0d, 01, 00, 21, 03, 01, 09, 00, 0a, 01, 00, 0d, 00, 0e, 20, 05, 0e, 00, 0d, 00, 0e, 05, 00, 12, 00, 13, 20, 09, 0d, 00, 12, 00, 13, 03, 01, 05, 01, 02]
@@ -88,6 +90,7 @@ Number of file 0 mappings: 7
     false = c3
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 1, 2)
     = ((c2 + c3) + (c0 - c1))
+Highest counter ID seen: c3
 
 Function name: conditions::assign_or
 Raw bytes (51): 0x[01, 01, 04, 07, 0d, 05, 09, 01, 05, 01, 05, 07, 01, 12, 01, 00, 20, 03, 01, 09, 00, 0a, 01, 00, 0d, 00, 0e, 20, 05, 0e, 00, 0d, 00, 0e, 0e, 00, 12, 00, 13, 20, 09, 0d, 00, 12, 00, 13, 03, 01, 05, 01, 02]
@@ -113,6 +116,7 @@ Number of file 0 mappings: 7
     false = c3
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 1, 2)
     = ((c1 + c2) + c3)
+Highest counter ID seen: c3
 
 Function name: conditions::foo
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 21, 01, 02, 02]
@@ -121,6 +125,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 33, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: conditions::func_call
 Raw bytes (39): 0x[01, 01, 03, 01, 05, 0b, 02, 09, 0d, 05, 01, 25, 01, 01, 0a, 20, 05, 02, 01, 09, 00, 0a, 05, 00, 0e, 00, 0f, 20, 09, 0d, 00, 0e, 00, 0f, 07, 01, 01, 00, 02]
@@ -141,6 +146,7 @@ Number of file 0 mappings: 5
     false = c3
 - Code(Expression(1, Add)) at (prev + 1, 1) to (start + 0, 2)
     = ((c2 + c3) + (c0 - c1))
+Highest counter ID seen: c3
 
 Function name: conditions::simple_assign
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 08, 01, 03, 02]
@@ -149,4 +155,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 8, 1) to (start + 3, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/conditions.cov-map b/tests/coverage/conditions.cov-map
index 17143775b7b4..a392d1b70288 100644
--- a/tests/coverage/conditions.cov-map
+++ b/tests/coverage/conditions.cov-map
@@ -260,4 +260,5 @@ Number of file 0 mappings: 68
 - Code(Counter(9)) at (prev + 2, 9) to (start + 0, 15)
 - Code(Expression(137, Add)) at (prev + 2, 1) to (start + 0, 2)
     = ((c4 + (((c5 + c6) + c7) + c8)) + ((((c9 + c10) + c11) + c12) + ((c0 - c2) - c3)))
+Highest counter ID seen: c35
 
diff --git a/tests/coverage/continue.cov-map b/tests/coverage/continue.cov-map
index 810694d7f662..7781d2d2544c 100644
--- a/tests/coverage/continue.cov-map
+++ b/tests/coverage/continue.cov-map
@@ -76,4 +76,5 @@ Number of file 0 mappings: 30
 - Code(Counter(16)) at (prev + 3, 9) to (start + 0, 14)
 - Code(Expression(27, Add)) at (prev + 2, 13) to (start + 1, 2)
     = (c18 + c17)
+Highest counter ID seen: c18
 
diff --git a/tests/coverage/coroutine.cov-map b/tests/coverage/coroutine.cov-map
index 6ff5ed74a96d..2fdc3220c196 100644
--- a/tests/coverage/coroutine.cov-map
+++ b/tests/coverage/coroutine.cov-map
@@ -10,6 +10,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 9) to (start + 0, 40)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: coroutine::main
 Raw bytes (65): 0x[01, 01, 08, 07, 0d, 05, 09, 11, 15, 1e, 19, 11, 15, 15, 19, 1e, 19, 11, 15, 09, 01, 13, 01, 02, 16, 01, 08, 0b, 00, 2e, 11, 01, 2b, 00, 2d, 03, 01, 0e, 00, 35, 11, 02, 0b, 00, 2e, 1e, 01, 22, 00, 27, 1a, 00, 2c, 00, 2e, 17, 01, 0e, 00, 35, 1a, 02, 01, 00, 02]
@@ -39,6 +40,7 @@ Number of file 0 mappings: 9
     = (c5 + c6)
 - Code(Expression(6, Sub)) at (prev + 2, 1) to (start + 0, 2)
     = ((c4 - c5) - c6)
+Highest counter ID seen: c4
 
 Function name: coroutine::main::{closure#0}
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 16, 08, 01, 1f, 05, 02, 10, 01, 06]
@@ -48,4 +50,5 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 22, 8) to (start + 1, 31)
 - Code(Counter(1)) at (prev + 2, 16) to (start + 1, 6)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/coverage_attr_closure.cov-map b/tests/coverage/coverage_attr_closure.cov-map
index 5d2c6b00b40f..fb861996a0d2 100644
--- a/tests/coverage/coverage_attr_closure.cov-map
+++ b/tests/coverage/coverage_attr_closure.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 6, 15) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: coverage_attr_closure::contains_closures_off::{closure#0} (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 1d, 13, 02, 06]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 29, 19) to (start + 2, 6)
+Highest counter ID seen: (none)
 
 Function name: coverage_attr_closure::contains_closures_on
 Raw bytes (19): 0x[01, 01, 00, 03, 01, 0f, 01, 01, 1a, 01, 05, 09, 00, 1b, 01, 04, 01, 00, 02]
@@ -23,6 +25,7 @@ Number of file 0 mappings: 3
 - Code(Counter(0)) at (prev + 15, 1) to (start + 1, 26)
 - Code(Counter(0)) at (prev + 5, 9) to (start + 0, 27)
 - Code(Counter(0)) at (prev + 4, 1) to (start + 0, 2)
+Highest counter ID seen: c0
 
 Function name: coverage_attr_closure::contains_closures_on::{closure#0} (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 11, 13, 02, 06]
@@ -31,4 +34,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 17, 19) to (start + 2, 6)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/dead_code.cov-map b/tests/coverage/dead_code.cov-map
index 31599d9072c9..b94c6e656abf 100644
--- a/tests/coverage/dead_code.cov-map
+++ b/tests/coverage/dead_code.cov-map
@@ -10,6 +10,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: dead_code::unused_fn (unused)
 Raw bytes (24): 0x[01, 01, 00, 04, 00, 0f, 01, 07, 0f, 00, 07, 10, 02, 06, 00, 02, 06, 00, 07, 00, 01, 01, 00, 02]
@@ -21,6 +22,7 @@ Number of file 0 mappings: 4
 - Code(Zero) at (prev + 7, 16) to (start + 2, 6)
 - Code(Zero) at (prev + 2, 6) to (start + 0, 7)
 - Code(Zero) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: (none)
 
 Function name: dead_code::unused_pub_fn_not_in_library (unused)
 Raw bytes (24): 0x[01, 01, 00, 04, 00, 03, 01, 07, 0f, 00, 07, 10, 02, 06, 00, 02, 06, 00, 07, 00, 01, 01, 00, 02]
@@ -32,4 +34,5 @@ Number of file 0 mappings: 4
 - Code(Zero) at (prev + 7, 16) to (start + 2, 6)
 - Code(Zero) at (prev + 2, 6) to (start + 0, 7)
 - Code(Zero) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/drop_trait.cov-map b/tests/coverage/drop_trait.cov-map
index eb9d7d7acfdf..a97c0f8794c4 100644
--- a/tests/coverage/drop_trait.cov-map
+++ b/tests/coverage/drop_trait.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 9, 5) to (start + 2, 6)
+Highest counter ID seen: c0
 
 Function name: drop_trait::main
 Raw bytes (24): 0x[01, 01, 00, 04, 01, 0e, 01, 05, 0c, 05, 06, 09, 01, 16, 00, 02, 06, 04, 0b, 01, 05, 01, 00, 02]
@@ -16,4 +17,5 @@ Number of file 0 mappings: 4
 - Code(Counter(1)) at (prev + 6, 9) to (start + 1, 22)
 - Code(Zero) at (prev + 2, 6) to (start + 4, 11)
 - Code(Counter(0)) at (prev + 5, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/fn_sig_into_try.cov-map b/tests/coverage/fn_sig_into_try.cov-map
index 49758954831a..374811dba9ef 100644
--- a/tests/coverage/fn_sig_into_try.cov-map
+++ b/tests/coverage/fn_sig_into_try.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 10, 1) to (start + 5, 2)
+Highest counter ID seen: c0
 
 Function name: fn_sig_into_try::b
 Raw bytes (26): 0x[01, 01, 01, 01, 00, 04, 01, 11, 01, 03, 0f, 00, 03, 0f, 00, 10, 02, 01, 05, 00, 0c, 01, 01, 01, 00, 02]
@@ -18,6 +19,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 1, 5) to (start + 0, 12)
     = (c0 - Zero)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c0
 
 Function name: fn_sig_into_try::c
 Raw bytes (26): 0x[01, 01, 01, 01, 00, 04, 01, 18, 01, 03, 17, 00, 03, 17, 00, 18, 02, 01, 05, 00, 0c, 01, 01, 01, 00, 02]
@@ -31,6 +33,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 1, 5) to (start + 0, 12)
     = (c0 - Zero)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c0
 
 Function name: fn_sig_into_try::d
 Raw bytes (26): 0x[01, 01, 01, 01, 00, 04, 01, 1f, 01, 04, 0f, 00, 04, 0f, 00, 10, 02, 01, 05, 00, 0c, 01, 01, 01, 00, 02]
@@ -44,4 +47,5 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 1, 5) to (start + 0, 12)
     = (c0 - Zero)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/generics.cov-map b/tests/coverage/generics.cov-map
index 48e191c1156f..d082bd54493d 100644
--- a/tests/coverage/generics.cov-map
+++ b/tests/coverage/generics.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 17, 5) to (start + 2, 6)
+Highest counter ID seen: c0
 
 Function name: <generics::Firework<f64>>::set_strength
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 0a, 05, 02, 06]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 10, 5) to (start + 2, 6)
+Highest counter ID seen: c0
 
 Function name: <generics::Firework<i32> as core::ops::drop::Drop>::drop
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 11, 05, 02, 06]
@@ -21,6 +23,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 17, 5) to (start + 2, 6)
+Highest counter ID seen: c0
 
 Function name: <generics::Firework<i32>>::set_strength
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 0a, 05, 02, 06]
@@ -29,6 +32,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 10, 5) to (start + 2, 6)
+Highest counter ID seen: c0
 
 Function name: generics::main
 Raw bytes (24): 0x[01, 01, 00, 04, 01, 16, 01, 08, 0c, 05, 09, 09, 01, 16, 00, 02, 06, 04, 0b, 01, 05, 01, 00, 02]
@@ -40,4 +44,5 @@ Number of file 0 mappings: 4
 - Code(Counter(1)) at (prev + 9, 9) to (start + 1, 22)
 - Code(Zero) at (prev + 2, 6) to (start + 4, 11)
 - Code(Counter(0)) at (prev + 5, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/holes.cov-map b/tests/coverage/holes.cov-map
index 9350bd9a405c..3c740d80ea05 100644
--- a/tests/coverage/holes.cov-map
+++ b/tests/coverage/holes.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 37, 9) to (start + 0, 29)
+Highest counter ID seen: (none)
 
 Function name: holes::main
 Raw bytes (44): 0x[01, 01, 00, 08, 01, 08, 01, 06, 11, 01, 0f, 05, 00, 12, 01, 04, 05, 00, 12, 01, 07, 05, 00, 12, 01, 06, 05, 00, 12, 01, 06, 05, 03, 0f, 01, 0a, 05, 03, 0f, 01, 0a, 05, 01, 02]
@@ -20,6 +21,7 @@ Number of file 0 mappings: 8
 - Code(Counter(0)) at (prev + 6, 5) to (start + 3, 15)
 - Code(Counter(0)) at (prev + 10, 5) to (start + 3, 15)
 - Code(Counter(0)) at (prev + 10, 5) to (start + 1, 2)
+Highest counter ID seen: c0
 
 Function name: holes::main::_unused_fn (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 19, 05, 00, 17]
@@ -28,6 +30,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 25, 5) to (start + 0, 23)
+Highest counter ID seen: (none)
 
 Function name: holes::main::{closure#0} (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 12, 09, 02, 0a]
@@ -36,6 +39,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 18, 9) to (start + 2, 10)
+Highest counter ID seen: (none)
 
 Function name: holes::main::{closure#1} (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 3d, 09, 02, 0a]
@@ -44,4 +48,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 61, 9) to (start + 2, 10)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/if.cov-map b/tests/coverage/if.cov-map
index 2b5ae97b406d..8f12afac0272 100644
--- a/tests/coverage/if.cov-map
+++ b/tests/coverage/if.cov-map
@@ -10,4 +10,5 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 5, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/if_else.cov-map b/tests/coverage/if_else.cov-map
index c2111917e559..194ad6ca71f8 100644
--- a/tests/coverage/if_else.cov-map
+++ b/tests/coverage/if_else.cov-map
@@ -15,4 +15,5 @@ Number of file 0 mappings: 7
 - Code(Expression(1, Sub)) at (prev + 7, 5) to (start + 5, 6)
     = (c0 - c2)
 - Code(Counter(0)) at (prev + 6, 1) to (start + 0, 2)
+Highest counter ID seen: c2
 
diff --git a/tests/coverage/if_not.cov-map b/tests/coverage/if_not.cov-map
index 9e11ed787a88..a2c276b7bb77 100644
--- a/tests/coverage/if_not.cov-map
+++ b/tests/coverage/if_not.cov-map
@@ -20,4 +20,5 @@ Number of file 0 mappings: 10
     = (c0 - c3)
 - Code(Counter(3)) at (prev + 2, 12) to (start + 2, 6)
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c3
 
diff --git a/tests/coverage/ignore_run.cov-map b/tests/coverage/ignore_run.cov-map
index 9865efae0a1e..c8ad3821e16f 100644
--- a/tests/coverage/ignore_run.cov-map
+++ b/tests/coverage/ignore_run.cov-map
@@ -5,4 +5,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 13)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/inline-dead.cov-map b/tests/coverage/inline-dead.cov-map
index 96b907cbe153..411f16725bb0 100644
--- a/tests/coverage/inline-dead.cov-map
+++ b/tests/coverage/inline-dead.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 23, 1) to (start + 2, 2)
+Highest counter ID seen: (none)
 
 Function name: inline_dead::live::<false>
 Raw bytes (26): 0x[01, 01, 01, 01, 00, 04, 01, 0e, 01, 01, 09, 00, 02, 09, 00, 0f, 02, 02, 09, 00, 0a, 01, 02, 01, 00, 02]
@@ -18,6 +19,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 9) to (start + 0, 10)
     = (c0 - Zero)
 - Code(Counter(0)) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: c0
 
 Function name: inline_dead::main
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 04, 01, 03, 0a, 01, 06, 05, 01, 02]
@@ -27,6 +29,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 4, 1) to (start + 3, 10)
 - Code(Counter(0)) at (prev + 6, 5) to (start + 1, 2)
+Highest counter ID seen: c0
 
 Function name: inline_dead::main::{closure#0}
 Raw bytes (23): 0x[01, 01, 02, 00, 06, 01, 00, 03, 01, 07, 17, 01, 16, 00, 01, 17, 00, 18, 03, 01, 05, 00, 06]
@@ -40,4 +43,5 @@ Number of file 0 mappings: 3
 - Code(Zero) at (prev + 1, 23) to (start + 0, 24)
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 0, 6)
     = (Zero + (c0 - Zero))
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/inline.cov-map b/tests/coverage/inline.cov-map
index 2366a3bc5345..ab3a505e9250 100644
--- a/tests/coverage/inline.cov-map
+++ b/tests/coverage/inline.cov-map
@@ -11,6 +11,7 @@ Number of file 0 mappings: 5
     = (c0 + c1)
 - Code(Counter(1)) at (prev + 0, 17) to (start + 2, 6)
 - Code(Counter(0)) at (prev + 3, 5) to (start + 1, 2)
+Highest counter ID seen: c1
 
 Function name: inline::error
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 31, 01, 01, 14]
@@ -19,6 +20,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 49, 1) to (start + 1, 20)
+Highest counter ID seen: c0
 
 Function name: inline::length::<char>
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 1e, 01, 02, 02]
@@ -27,6 +29,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 30, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: inline::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 05, 01, 02, 02]
@@ -35,6 +38,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 5, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: inline::permutate::<char>
 Raw bytes (52): 0x[01, 01, 04, 01, 05, 02, 0d, 05, 0f, 09, 0d, 08, 01, 0f, 01, 02, 0e, 05, 02, 0f, 02, 06, 02, 02, 0f, 00, 14, 11, 01, 0d, 00, 0e, 06, 00, 12, 00, 16, 11, 00, 17, 04, 0a, 0d, 05, 0c, 02, 06, 0b, 03, 01, 00, 02]
@@ -57,6 +61,7 @@ Number of file 0 mappings: 8
 - Code(Counter(3)) at (prev + 5, 12) to (start + 2, 6)
 - Code(Expression(2, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c1 + (c2 + c3))
+Highest counter ID seen: c4
 
 Function name: inline::permutations::<char>
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 0a, 01, 03, 02]
@@ -65,6 +70,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 10, 1) to (start + 3, 2)
+Highest counter ID seen: c0
 
 Function name: inline::swap::<char>
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 23, 01, 04, 02]
@@ -73,4 +79,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 35, 1) to (start + 4, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/inner_items.cov-map b/tests/coverage/inner_items.cov-map
index 6ccc3f0bafc8..16e86b2cadea 100644
--- a/tests/coverage/inner_items.cov-map
+++ b/tests/coverage/inner_items.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 33, 9) to (start + 3, 10)
+Highest counter ID seen: c0
 
 Function name: <inner_items::main::InStruct as inner_items::main::InTrait>::trait_func
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 28, 09, 03, 0a]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 40, 9) to (start + 3, 10)
+Highest counter ID seen: c0
 
 Function name: inner_items::main
 Raw bytes (43): 0x[01, 01, 02, 01, 05, 01, 09, 07, 01, 03, 01, 07, 0f, 05, 07, 10, 02, 06, 02, 02, 06, 00, 07, 01, 24, 08, 00, 0f, 09, 00, 10, 02, 06, 06, 02, 06, 00, 07, 01, 02, 09, 05, 02]
@@ -31,6 +33,7 @@ Number of file 0 mappings: 7
 - Code(Expression(1, Sub)) at (prev + 2, 6) to (start + 0, 7)
     = (c0 - c2)
 - Code(Counter(0)) at (prev + 2, 9) to (start + 5, 2)
+Highest counter ID seen: c2
 
 Function name: inner_items::main::in_func
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 12, 05, 04, 06]
@@ -39,4 +42,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 18, 5) to (start + 4, 6)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/issue-83601.cov-map b/tests/coverage/issue-83601.cov-map
index f2447e3c92c8..c188cca1b517 100644
--- a/tests/coverage/issue-83601.cov-map
+++ b/tests/coverage/issue-83601.cov-map
@@ -9,4 +9,5 @@ Number of file 0 mappings: 3
 - Code(Counter(1)) at (prev + 3, 9) to (start + 1, 28)
 - Code(Expression(0, Sub)) at (prev + 2, 5) to (start + 3, 2)
     = (c1 - c2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/issue-84561.cov-map b/tests/coverage/issue-84561.cov-map
index d3c4671e0ba4..a8ad17574ba3 100644
--- a/tests/coverage/issue-84561.cov-map
+++ b/tests/coverage/issue-84561.cov-map
@@ -10,6 +10,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 1, 9) to (start + 0, 15)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 5) to (start + 0, 6)
+Highest counter ID seen: c1
 
 Function name: issue_84561::main
 Raw bytes (10): 0x[01, 01, 00, 01, 01, b4, 01, 01, 04, 02]
@@ -18,6 +19,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 180, 1) to (start + 4, 2)
+Highest counter ID seen: c0
 
 Function name: issue_84561::test1
 Raw bytes (50): 0x[01, 01, 00, 09, 01, 9a, 01, 01, 01, 0b, 05, 01, 0c, 00, 1e, 01, 01, 05, 00, 0b, 09, 00, 0c, 00, 1e, 01, 01, 0d, 01, 0b, 0d, 01, 0c, 00, 1e, 01, 01, 05, 03, 0b, 11, 03, 0c, 00, 1e, 01, 01, 01, 00, 02]
@@ -34,6 +36,7 @@ Number of file 0 mappings: 9
 - Code(Counter(0)) at (prev + 1, 5) to (start + 3, 11)
 - Code(Counter(4)) at (prev + 3, 12) to (start + 0, 30)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c4
 
 Function name: issue_84561::test2
 Raw bytes (20): 0x[01, 01, 00, 03, 01, b0, 01, 01, 01, 10, 05, 01, 11, 00, 23, 01, 01, 01, 00, 02]
@@ -44,6 +47,7 @@ Number of file 0 mappings: 3
 - Code(Counter(0)) at (prev + 176, 1) to (start + 1, 16)
 - Code(Counter(1)) at (prev + 1, 17) to (start + 0, 35)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: issue_84561::test2::call_print
 Raw bytes (10): 0x[01, 01, 00, 01, 01, a7, 01, 09, 02, 0a]
@@ -52,6 +56,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 167, 9) to (start + 2, 10)
+Highest counter ID seen: c0
 
 Function name: issue_84561::test3
 Raw bytes (375): 0x[01, 01, 31, 05, 09, 0d, 00, 15, 19, 12, 00, 15, 19, 21, 00, 1e, 00, 21, 00, 31, 00, 3d, 00, 2e, 45, 3d, 00, 42, 49, 45, 00, 3f, 51, 42, 49, 45, 00, 7a, 55, 51, 00, 7a, 55, 51, 00, 77, 5d, 7a, 55, 51, 00, 77, 61, 7a, 55, 51, 00, 72, 65, 77, 61, 7a, 55, 51, 00, 75, be, 01, c2, 01, 79, 69, 6d, 69, 6d, 69, 6d, c2, 01, 00, 69, 6d, c2, 01, 79, 69, 6d, bb, 01, 7d, 75, be, 01, c2, 01, 79, 69, 6d, b6, 01, 00, bb, 01, 7d, 75, be, 01, c2, 01, 79, 69, 6d, 33, 01, 08, 01, 03, 1c, 05, 04, 09, 01, 1c, 02, 02, 05, 04, 1f, 0d, 05, 05, 00, 1f, 06, 01, 05, 00, 1f, 15, 01, 09, 01, 1c, 12, 02, 05, 00, 1f, 0e, 01, 05, 00, 0f, 00, 00, 20, 00, 30, 21, 01, 05, 03, 0f, 00, 03, 20, 00, 30, 00, 00, 33, 00, 41, 00, 00, 4b, 00, 5a, 1e, 01, 05, 00, 0f, 00, 05, 09, 03, 10, 00, 05, 0d, 00, 1b, 00, 02, 0d, 00, 1c, 1a, 04, 09, 05, 06, 31, 06, 05, 03, 06, 22, 04, 05, 03, 06, 3d, 04, 09, 04, 06, 2e, 05, 08, 00, 0f, 45, 01, 09, 03, 0a, 2a, 05, 09, 03, 0a, 3f, 05, 08, 00, 0f, 51, 01, 09, 00, 13, 00, 03, 0d, 00, 1d, 3a, 03, 09, 00, 13, 00, 03, 0d, 00, 1d, 77, 03, 05, 00, 0f, 77, 01, 0c, 00, 13, 5d, 01, 0d, 00, 13, 56, 02, 0d, 00, 13, 72, 04, 05, 02, 13, 65, 03, 0d, 00, 13, 6e, 02, 0d, 00, 13, bb, 01, 03, 05, 00, 0f, 69, 01, 0c, 00, 13, 6d, 01, 0d, 03, 0e, 75, 04, 0d, 00, 13, c2, 01, 02, 0d, 00, 17, c2, 01, 01, 14, 00, 1b, 00, 01, 15, 00, 1b, 92, 01, 02, 15, 00, 1b, be, 01, 04, 0d, 00, 13, 7d, 03, 09, 00, 19, b6, 01, 02, 05, 00, 0f, b2, 01, 03, 09, 00, 22, 00, 02, 05, 00, 0f, 00, 03, 09, 00, 2c, 00, 02, 01, 00, 02]
@@ -182,4 +187,5 @@ Number of file 0 mappings: 51
 - Code(Zero) at (prev + 2, 5) to (start + 0, 15)
 - Code(Zero) at (prev + 3, 9) to (start + 0, 44)
 - Code(Zero) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: c31
 
diff --git a/tests/coverage/issue-85461.cov-map b/tests/coverage/issue-85461.cov-map
index d1c449b9a355..349bc2cab803 100644
--- a/tests/coverage/issue-85461.cov-map
+++ b/tests/coverage/issue-85461.cov-map
@@ -5,4 +5,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 8, 1) to (start + 3, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/issue-93054.cov-map b/tests/coverage/issue-93054.cov-map
index 024ef519fcff..38cb70a3f97a 100644
--- a/tests/coverage/issue-93054.cov-map
+++ b/tests/coverage/issue-93054.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 21, 1) to (start + 0, 29)
+Highest counter ID seen: (none)
 
 Function name: issue_93054::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 1d, 01, 00, 0d]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 29, 1) to (start + 0, 13)
+Highest counter ID seen: c0
 
 Function name: issue_93054::make (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 19, 01, 02, 02]
@@ -21,4 +23,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 25, 1) to (start + 2, 2)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/lazy_boolean.cov-map b/tests/coverage/lazy_boolean.cov-map
index 8dca205d33f2..fcb9d8f1ff5c 100644
--- a/tests/coverage/lazy_boolean.cov-map
+++ b/tests/coverage/lazy_boolean.cov-map
@@ -46,4 +46,5 @@ Number of file 0 mappings: 28
 - Code(Expression(6, Sub)) at (prev + 2, 12) to (start + 2, 6)
     = (c0 - c9)
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c9
 
diff --git a/tests/coverage/let_else_loop.cov-map b/tests/coverage/let_else_loop.cov-map
index 13d0d08adb11..04451596eae4 100644
--- a/tests/coverage/let_else_loop.cov-map
+++ b/tests/coverage/let_else_loop.cov-map
@@ -7,6 +7,7 @@ Number of file 0 mappings: 3
 - Code(Zero) at (prev + 22, 1) to (start + 1, 12)
 - Code(Zero) at (prev + 1, 15) to (start + 0, 22)
 - Code(Zero) at (prev + 0, 32) to (start + 0, 39)
+Highest counter ID seen: (none)
 
 Function name: let_else_loop::_loop_either_way (unused)
 Raw bytes (19): 0x[01, 01, 00, 03, 00, 0f, 01, 01, 14, 00, 01, 1c, 00, 23, 00, 01, 05, 00, 0c]
@@ -17,6 +18,7 @@ Number of file 0 mappings: 3
 - Code(Zero) at (prev + 15, 1) to (start + 1, 20)
 - Code(Zero) at (prev + 1, 28) to (start + 0, 35)
 - Code(Zero) at (prev + 1, 5) to (start + 0, 12)
+Highest counter ID seen: (none)
 
 Function name: let_else_loop::loopy
 Raw bytes (19): 0x[01, 01, 00, 03, 01, 09, 01, 01, 14, 00, 01, 1c, 00, 23, 05, 01, 01, 00, 02]
@@ -27,4 +29,5 @@ Number of file 0 mappings: 3
 - Code(Counter(0)) at (prev + 9, 1) to (start + 1, 20)
 - Code(Zero) at (prev + 1, 28) to (start + 0, 35)
 - Code(Counter(1)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/long_and_wide.cov-map b/tests/coverage/long_and_wide.cov-map
index 97aebf9b18ab..032b7fe102e8 100644
--- a/tests/coverage/long_and_wide.cov-map
+++ b/tests/coverage/long_and_wide.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 150, 1) to (start + 0, 21)
+Highest counter ID seen: c0
 
 Function name: long_and_wide::long_function
 Raw bytes (10): 0x[01, 01, 00, 01, 01, 10, 01, 84, 01, 02]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 16, 1) to (start + 132, 2)
+Highest counter ID seen: c0
 
 Function name: long_and_wide::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 07, 01, 04, 02]
@@ -21,6 +23,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 7, 1) to (start + 4, 2)
+Highest counter ID seen: c0
 
 Function name: long_and_wide::wide_function
 Raw bytes (10): 0x[01, 01, 00, 01, 01, 0e, 01, 00, 8b, 01]
@@ -29,4 +32,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 14, 1) to (start + 0, 139)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/loop-break.cov-map b/tests/coverage/loop-break.cov-map
index 890d5d84539e..63280a0bf7cb 100644
--- a/tests/coverage/loop-break.cov-map
+++ b/tests/coverage/loop-break.cov-map
@@ -11,4 +11,5 @@ Number of file 0 mappings: 5
 - Code(Counter(0)) at (prev + 1, 13) to (start + 0, 18)
 - Code(Counter(1)) at (prev + 1, 10) to (start + 0, 11)
 - Code(Counter(0)) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/loop_break_value.cov-map b/tests/coverage/loop_break_value.cov-map
index d8dca8a85c38..e48d078f6722 100644
--- a/tests/coverage/loop_break_value.cov-map
+++ b/tests/coverage/loop_break_value.cov-map
@@ -5,4 +5,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 4, 1) to (start + 10, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/loops_branches.cov-map b/tests/coverage/loops_branches.cov-map
index 9187dcbd8651..1d263611a3ab 100644
--- a/tests/coverage/loops_branches.cov-map
+++ b/tests/coverage/loops_branches.cov-map
@@ -75,6 +75,7 @@ Number of file 0 mappings: 20
 - Code(Counter(6)) at (prev + 3, 9) to (start + 0, 15)
 - Code(Expression(34, Add)) at (prev + 1, 5) to (start + 0, 6)
     = ((c9 + (((((c3 + Zero) + (c4 + Zero)) - c6) - Zero) - c4)) + c6)
+Highest counter ID seen: c9
 
 Function name: <loops_branches::DisplayTest as core::fmt::Display>::fmt
 Raw bytes (230): 0x[01, 01, 2b, 01, 00, 02, 00, a3, 01, 19, a7, 01, ab, 01, 00, 0d, 00, 15, a7, 01, ab, 01, 00, 0d, 00, 15, a3, 01, 19, a7, 01, ab, 01, 00, 0d, 00, 15, 9e, 01, 00, a3, 01, 19, a7, 01, ab, 01, 00, 0d, 00, 15, 9a, 01, 00, 9e, 01, 00, a3, 01, 19, a7, 01, ab, 01, 00, 0d, 00, 15, 9e, 01, 00, a3, 01, 19, a7, 01, ab, 01, 00, 0d, 00, 15, 9a, 01, 15, 9e, 01, 00, a3, 01, 19, a7, 01, ab, 01, 00, 0d, 00, 15, 93, 01, 25, 96, 01, 19, 9a, 01, 15, 9e, 01, 00, a3, 01, 19, a7, 01, ab, 01, 00, 0d, 00, 15, 14, 01, 22, 05, 01, 11, 00, 01, 12, 01, 0a, 02, 02, 10, 00, 15, 00, 01, 17, 00, 1b, 00, 00, 1c, 00, 1e, 06, 01, 0e, 00, 0f, 02, 01, 0d, 00, 1e, 25, 00, 1e, 00, 1f, 9e, 01, 02, 0d, 00, 0e, a3, 01, 00, 12, 00, 17, 9e, 01, 01, 10, 00, 15, 00, 00, 16, 01, 0e, 9a, 01, 02, 14, 00, 19, 00, 01, 1b, 00, 1f, 00, 00, 20, 00, 22, 4a, 01, 12, 00, 13, 9a, 01, 01, 11, 00, 22, 96, 01, 00, 22, 00, 23, 19, 03, 09, 00, 0f, 8f, 01, 01, 05, 00, 06]
@@ -156,6 +157,7 @@ Number of file 0 mappings: 20
 - Code(Counter(6)) at (prev + 3, 9) to (start + 0, 15)
 - Code(Expression(35, Add)) at (prev + 1, 5) to (start + 0, 6)
     = (((((((Zero + c3) + (Zero + c5)) - c6) - Zero) - c5) + c6) + c9)
+Highest counter ID seen: c9
 
 Function name: loops_branches::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 37, 01, 05, 02]
@@ -164,4 +166,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 55, 1) to (start + 5, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/macro_in_closure.cov-map b/tests/coverage/macro_in_closure.cov-map
index 2feaab717b5c..9614154a3668 100644
--- a/tests/coverage/macro_in_closure.cov-map
+++ b/tests/coverage/macro_in_closure.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 7, 28) to (start + 0, 45)
+Highest counter ID seen: c0
 
 Function name: macro_in_closure::WITH_BLOCK::{closure#0}
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 09, 1e, 02, 02]
@@ -13,4 +14,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 9, 30) to (start + 2, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/macro_name_span.cov-map b/tests/coverage/macro_name_span.cov-map
index f3ee44d2a5ab..58620452b2ba 100644
--- a/tests/coverage/macro_name_span.cov-map
+++ b/tests/coverage/macro_name_span.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 22, 28) to (start + 1, 64)
+Highest counter ID seen: c0
 
 Function name: macro_name_span::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 0b, 01, 02, 02]
@@ -13,4 +14,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 11, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/match_or_pattern.cov-map b/tests/coverage/match_or_pattern.cov-map
index 60b7024533d2..f6491ea262dc 100644
--- a/tests/coverage/match_or_pattern.cov-map
+++ b/tests/coverage/match_or_pattern.cov-map
@@ -72,4 +72,5 @@ Number of file 0 mappings: 25
     = (c14 + c15)
 - Code(Expression(26, Add)) at (prev + 2, 1) to (start + 0, 2)
     = ((c14 + c15) + c16)
+Highest counter ID seen: c16
 
diff --git a/tests/coverage/mcdc/condition-limit.cov-map b/tests/coverage/mcdc/condition-limit.cov-map
index 9d1e7518f9ea..a3e3b1d09c4d 100644
--- a/tests/coverage/mcdc/condition-limit.cov-map
+++ b/tests/coverage/mcdc/condition-limit.cov-map
@@ -87,4 +87,5 @@ Number of file 0 mappings: 18
     = ((((((c2 + c3) + c4) + c5) + c6) + c7) + (c0 - c1))
 - Code(Expression(37, Add)) at (prev + 1, 1) to (start + 0, 2)
     = (c8 + ((((((c2 + c3) + c4) + c5) + c6) + c7) + (c0 - c1)))
+Highest counter ID seen: c8
 
diff --git a/tests/coverage/mcdc/if.cov-map b/tests/coverage/mcdc/if.cov-map
index 576c9b14ed14..46960d31c01e 100644
--- a/tests/coverage/mcdc/if.cov-map
+++ b/tests/coverage/mcdc/if.cov-map
@@ -22,6 +22,7 @@ Number of file 0 mappings: 8
     = (c2 + (c0 - c1))
 - Code(Expression(2, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c3 + (c2 + (c0 - c1)))
+Highest counter ID seen: c3
 
 Function name: if::mcdc_check_b
 Raw bytes (64): 0x[01, 01, 04, 01, 05, 09, 02, 0d, 0f, 09, 02, 08, 01, 17, 01, 01, 09, 28, 03, 02, 01, 08, 00, 0e, 30, 05, 02, 01, 02, 00, 00, 08, 00, 09, 05, 00, 0d, 00, 0e, 30, 0d, 09, 02, 00, 00, 00, 0d, 00, 0e, 0d, 00, 0f, 02, 06, 0f, 02, 0c, 02, 06, 0b, 03, 01, 00, 02]
@@ -47,6 +48,7 @@ Number of file 0 mappings: 8
     = (c2 + (c0 - c1))
 - Code(Expression(2, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c3 + (c2 + (c0 - c1)))
+Highest counter ID seen: c3
 
 Function name: if::mcdc_check_both
 Raw bytes (64): 0x[01, 01, 04, 01, 05, 09, 02, 0d, 0f, 09, 02, 08, 01, 1f, 01, 01, 09, 28, 03, 02, 01, 08, 00, 0e, 30, 05, 02, 01, 02, 00, 00, 08, 00, 09, 05, 00, 0d, 00, 0e, 30, 0d, 09, 02, 00, 00, 00, 0d, 00, 0e, 0d, 00, 0f, 02, 06, 0f, 02, 0c, 02, 06, 0b, 03, 01, 00, 02]
@@ -72,6 +74,7 @@ Number of file 0 mappings: 8
     = (c2 + (c0 - c1))
 - Code(Expression(2, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c3 + (c2 + (c0 - c1)))
+Highest counter ID seen: c3
 
 Function name: if::mcdc_check_neither
 Raw bytes (64): 0x[01, 01, 04, 01, 05, 09, 02, 0d, 0f, 09, 02, 08, 01, 07, 01, 01, 09, 28, 03, 02, 01, 08, 00, 0e, 30, 05, 02, 01, 02, 00, 00, 08, 00, 09, 05, 00, 0d, 00, 0e, 30, 0d, 09, 02, 00, 00, 00, 0d, 00, 0e, 0d, 00, 0f, 02, 06, 0f, 02, 0c, 02, 06, 0b, 03, 01, 00, 02]
@@ -97,6 +100,7 @@ Number of file 0 mappings: 8
     = (c2 + (c0 - c1))
 - Code(Expression(2, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c3 + (c2 + (c0 - c1)))
+Highest counter ID seen: c3
 
 Function name: if::mcdc_check_not_tree_decision
 Raw bytes (87): 0x[01, 01, 08, 01, 05, 02, 09, 05, 09, 0d, 1e, 02, 09, 11, 1b, 0d, 1e, 02, 09, 0a, 01, 31, 01, 03, 0a, 28, 05, 03, 03, 08, 00, 15, 30, 05, 02, 01, 02, 03, 00, 09, 00, 0a, 02, 00, 0e, 00, 0f, 30, 09, 1e, 03, 02, 00, 00, 0e, 00, 0f, 0b, 00, 14, 00, 15, 30, 11, 0d, 02, 00, 00, 00, 14, 00, 15, 11, 00, 16, 02, 06, 1b, 02, 0c, 02, 06, 17, 03, 01, 00, 02]
@@ -132,6 +136,7 @@ Number of file 0 mappings: 10
     = (c3 + ((c0 - c1) - c2))
 - Code(Expression(5, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c4 + (c3 + ((c0 - c1) - c2)))
+Highest counter ID seen: c4
 
 Function name: if::mcdc_check_tree_decision
 Raw bytes (87): 0x[01, 01, 08, 01, 05, 05, 0d, 05, 0d, 0d, 11, 09, 02, 1b, 1f, 0d, 11, 09, 02, 0a, 01, 27, 01, 03, 09, 28, 04, 03, 03, 08, 00, 15, 30, 05, 02, 01, 02, 00, 00, 08, 00, 09, 05, 00, 0e, 00, 0f, 30, 0d, 0a, 02, 00, 03, 00, 0e, 00, 0f, 0a, 00, 13, 00, 14, 30, 11, 09, 03, 00, 00, 00, 13, 00, 14, 1b, 00, 16, 02, 06, 1f, 02, 0c, 02, 06, 17, 03, 01, 00, 02]
@@ -167,6 +172,7 @@ Number of file 0 mappings: 10
     = (c2 + (c0 - c1))
 - Code(Expression(5, Add)) at (prev + 3, 1) to (start + 0, 2)
     = ((c3 + c4) + (c2 + (c0 - c1)))
+Highest counter ID seen: c4
 
 Function name: if::mcdc_nested_if
 Raw bytes (124): 0x[01, 01, 0d, 01, 05, 02, 09, 05, 09, 1b, 15, 05, 09, 1b, 15, 05, 09, 11, 15, 02, 09, 2b, 32, 0d, 2f, 11, 15, 02, 09, 0e, 01, 3b, 01, 01, 09, 28, 03, 02, 01, 08, 00, 0e, 30, 05, 02, 01, 00, 02, 00, 08, 00, 09, 02, 00, 0d, 00, 0e, 30, 09, 32, 02, 00, 00, 00, 0d, 00, 0e, 1b, 01, 09, 01, 0d, 28, 06, 02, 01, 0c, 00, 12, 30, 16, 15, 01, 02, 00, 00, 0c, 00, 0d, 16, 00, 11, 00, 12, 30, 0d, 11, 02, 00, 00, 00, 11, 00, 12, 0d, 00, 13, 02, 0a, 2f, 02, 0a, 00, 0b, 32, 01, 0c, 02, 06, 27, 03, 01, 00, 02]
@@ -215,4 +221,5 @@ Number of file 0 mappings: 14
     = ((c0 - c1) - c2)
 - Code(Expression(9, Add)) at (prev + 3, 1) to (start + 0, 2)
     = ((c3 + (c4 + c5)) + ((c0 - c1) - c2))
+Highest counter ID seen: c5
 
diff --git a/tests/coverage/mcdc/inlined_expressions.cov-map b/tests/coverage/mcdc/inlined_expressions.cov-map
index bfde7d75d622..4f44e0f2b855 100644
--- a/tests/coverage/mcdc/inlined_expressions.cov-map
+++ b/tests/coverage/mcdc/inlined_expressions.cov-map
@@ -18,4 +18,5 @@ Number of file 0 mappings: 6
     false = c3
 - Code(Expression(1, Add)) at (prev + 1, 1) to (start + 0, 2)
     = ((c2 + c3) + (c0 - c1))
+Highest counter ID seen: c3
 
diff --git a/tests/coverage/mcdc/nested_if.cov-map b/tests/coverage/mcdc/nested_if.cov-map
index 3da98ff4a514..3bed49e7a12d 100644
--- a/tests/coverage/mcdc/nested_if.cov-map
+++ b/tests/coverage/mcdc/nested_if.cov-map
@@ -56,6 +56,7 @@ Number of file 0 mappings: 20
     = (c2 + (c0 - c1))
 - Code(Expression(12, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c3 + (c2 + (c0 - c1)))
+Highest counter ID seen: c8
 
 Function name: nested_if::nested_if_in_condition
 Raw bytes (120): 0x[01, 01, 0b, 01, 05, 05, 11, 05, 11, 1e, 15, 05, 11, 11, 15, 1e, 15, 05, 11, 09, 02, 0d, 2b, 09, 02, 0e, 01, 07, 01, 01, 09, 28, 06, 02, 01, 08, 00, 2e, 30, 05, 02, 01, 02, 00, 00, 08, 00, 09, 30, 0d, 09, 02, 00, 00, 00, 0d, 00, 2e, 05, 00, 10, 00, 11, 28, 03, 02, 00, 10, 00, 16, 30, 11, 1e, 01, 00, 02, 00, 10, 00, 11, 1e, 00, 15, 00, 16, 30, 15, 1a, 02, 00, 00, 00, 15, 00, 16, 17, 00, 19, 00, 1d, 1a, 00, 27, 00, 2c, 0d, 00, 2f, 02, 06, 2b, 02, 0c, 02, 06, 27, 03, 01, 00, 02]
@@ -101,6 +102,7 @@ Number of file 0 mappings: 14
     = (c2 + (c0 - c1))
 - Code(Expression(9, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c3 + (c2 + (c0 - c1)))
+Highest counter ID seen: c5
 
 Function name: nested_if::nested_in_then_block_in_condition
 Raw bytes (176): 0x[01, 01, 12, 01, 05, 05, 11, 05, 11, 3a, 15, 05, 11, 11, 15, 33, 19, 11, 15, 19, 1d, 19, 1d, 1d, 2e, 33, 19, 11, 15, 3a, 15, 05, 11, 09, 02, 0d, 47, 09, 02, 14, 01, 22, 01, 01, 09, 28, 09, 02, 01, 08, 00, 4b, 30, 05, 02, 01, 02, 00, 00, 08, 00, 09, 30, 0d, 09, 02, 00, 00, 00, 0d, 00, 4b, 05, 00, 10, 00, 11, 28, 03, 02, 00, 10, 00, 16, 30, 11, 3a, 01, 00, 02, 00, 10, 00, 11, 3a, 00, 15, 00, 16, 30, 15, 36, 02, 00, 00, 00, 15, 00, 16, 33, 00, 1c, 00, 1d, 28, 06, 02, 00, 1c, 00, 22, 30, 19, 2e, 01, 02, 00, 00, 1c, 00, 1d, 19, 00, 21, 00, 22, 30, 26, 1d, 02, 00, 00, 00, 21, 00, 22, 26, 00, 25, 00, 29, 2b, 00, 33, 00, 38, 36, 00, 44, 00, 49, 0d, 00, 4c, 02, 06, 47, 02, 0c, 02, 06, 43, 03, 01, 00, 02]
@@ -165,6 +167,7 @@ Number of file 0 mappings: 20
     = (c2 + (c0 - c1))
 - Code(Expression(16, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c3 + (c2 + (c0 - c1)))
+Highest counter ID seen: c7
 
 Function name: nested_if::nested_single_condition_decision
 Raw bytes (85): 0x[01, 01, 06, 01, 05, 05, 11, 05, 11, 09, 02, 0d, 17, 09, 02, 0b, 01, 17, 01, 04, 09, 28, 03, 02, 04, 08, 00, 29, 30, 05, 02, 01, 02, 00, 00, 08, 00, 09, 30, 0d, 09, 02, 00, 00, 00, 0d, 00, 29, 05, 00, 10, 00, 11, 20, 11, 0a, 00, 10, 00, 11, 11, 00, 14, 00, 19, 0a, 00, 23, 00, 27, 0d, 00, 2a, 02, 06, 17, 02, 0c, 02, 06, 13, 03, 01, 00, 02]
@@ -198,4 +201,5 @@ Number of file 0 mappings: 11
     = (c2 + (c0 - c1))
 - Code(Expression(4, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c3 + (c2 + (c0 - c1)))
+Highest counter ID seen: c4
 
diff --git a/tests/coverage/mcdc/non_control_flow.cov-map b/tests/coverage/mcdc/non_control_flow.cov-map
index d5383a197616..677e31e404e4 100644
--- a/tests/coverage/mcdc/non_control_flow.cov-map
+++ b/tests/coverage/mcdc/non_control_flow.cov-map
@@ -33,6 +33,7 @@ Number of file 0 mappings: 10
     false = c3
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 1, 2)
     = (c1 + ((c2 + c3) + c4))
+Highest counter ID seen: c4
 
 Function name: non_control_flow::assign_3_bis
 Raw bytes (85): 0x[01, 01, 07, 07, 11, 09, 0d, 01, 05, 05, 09, 16, 1a, 05, 09, 01, 05, 0a, 01, 1b, 01, 00, 2c, 03, 01, 09, 00, 0a, 01, 00, 0d, 00, 0e, 28, 05, 03, 00, 0d, 00, 18, 30, 05, 1a, 01, 03, 02, 00, 0d, 00, 0e, 05, 00, 12, 00, 13, 30, 09, 16, 03, 00, 02, 00, 12, 00, 13, 13, 00, 17, 00, 18, 30, 0d, 11, 02, 00, 00, 00, 17, 00, 18, 03, 01, 05, 01, 02]
@@ -66,6 +67,7 @@ Number of file 0 mappings: 10
     false = c4
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 1, 2)
     = ((c2 + c3) + c4)
+Highest counter ID seen: c4
 
 Function name: non_control_flow::assign_and
 Raw bytes (64): 0x[01, 01, 04, 07, 0e, 09, 0d, 01, 05, 01, 05, 08, 01, 0c, 01, 00, 21, 03, 01, 09, 00, 0a, 01, 00, 0d, 00, 0e, 28, 03, 02, 00, 0d, 00, 13, 30, 05, 0e, 01, 02, 00, 00, 0d, 00, 0e, 05, 00, 12, 00, 13, 30, 09, 0d, 02, 00, 00, 00, 12, 00, 13, 03, 01, 05, 01, 02]
@@ -91,6 +93,7 @@ Number of file 0 mappings: 8
     false = c3
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 1, 2)
     = ((c2 + c3) + (c0 - c1))
+Highest counter ID seen: c3
 
 Function name: non_control_flow::assign_or
 Raw bytes (64): 0x[01, 01, 04, 07, 0d, 05, 09, 01, 05, 01, 05, 08, 01, 11, 01, 00, 20, 03, 01, 09, 00, 0a, 01, 00, 0d, 00, 0e, 28, 03, 02, 00, 0d, 00, 13, 30, 05, 0e, 01, 00, 02, 00, 0d, 00, 0e, 0e, 00, 12, 00, 13, 30, 09, 0d, 02, 00, 00, 00, 12, 00, 13, 03, 01, 05, 01, 02]
@@ -117,6 +120,7 @@ Number of file 0 mappings: 8
     false = c3
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 1, 2)
     = ((c1 + c2) + c3)
+Highest counter ID seen: c3
 
 Function name: non_control_flow::foo
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 25, 01, 02, 02]
@@ -125,6 +129,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 37, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: non_control_flow::func_call
 Raw bytes (52): 0x[01, 01, 03, 01, 05, 0b, 02, 09, 0d, 06, 01, 29, 01, 01, 0a, 28, 03, 02, 01, 09, 00, 0f, 30, 05, 02, 01, 02, 00, 00, 09, 00, 0a, 05, 00, 0e, 00, 0f, 30, 09, 0d, 02, 00, 00, 00, 0e, 00, 0f, 07, 01, 01, 00, 02]
@@ -146,6 +151,7 @@ Number of file 0 mappings: 6
     false = c3
 - Code(Expression(1, Add)) at (prev + 1, 1) to (start + 0, 2)
     = ((c2 + c3) + (c0 - c1))
+Highest counter ID seen: c3
 
 Function name: non_control_flow::right_comb_tree
 Raw bytes (139): 0x[01, 01, 13, 07, 1a, 0b, 19, 0f, 15, 13, 11, 09, 0d, 01, 05, 01, 05, 05, 19, 05, 19, 4a, 15, 05, 19, 4a, 15, 05, 19, 46, 11, 4a, 15, 05, 19, 46, 11, 4a, 15, 05, 19, 0e, 01, 20, 01, 00, 41, 03, 01, 09, 00, 0a, 01, 00, 0d, 00, 0e, 28, 06, 05, 00, 0d, 00, 2a, 30, 05, 1a, 01, 02, 00, 00, 0d, 00, 0e, 05, 00, 13, 00, 14, 30, 4a, 19, 02, 03, 00, 00, 13, 00, 14, 4a, 00, 19, 00, 1a, 30, 46, 15, 03, 04, 00, 00, 19, 00, 1a, 46, 00, 1f, 00, 20, 30, 42, 11, 04, 05, 00, 00, 1f, 00, 20, 42, 00, 24, 00, 27, 30, 09, 0d, 05, 00, 00, 00, 24, 00, 27, 03, 01, 05, 01, 02]
@@ -201,4 +207,5 @@ Number of file 0 mappings: 14
     false = c3
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 1, 2)
     = (((((c2 + c3) + c4) + c5) + c6) + (c0 - c1))
+Highest counter ID seen: c6
 
diff --git a/tests/coverage/nested_loops.cov-map b/tests/coverage/nested_loops.cov-map
index 35d92594e75e..c145d4c58433 100644
--- a/tests/coverage/nested_loops.cov-map
+++ b/tests/coverage/nested_loops.cov-map
@@ -48,4 +48,5 @@ Number of file 0 mappings: 13
     = (c1 + c2)
 - Code(Expression(22, Add)) at (prev + 2, 1) to (start + 0, 2)
     = (c4 + c3)
+Highest counter ID seen: c6
 
diff --git a/tests/coverage/no_cov_crate.cov-map b/tests/coverage/no_cov_crate.cov-map
index 75234f6c3b7b..28d0d9ff8ab1 100644
--- a/tests/coverage/no_cov_crate.cov-map
+++ b/tests/coverage/no_cov_crate.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 20, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: no_cov_crate::add_coverage_2
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 18, 01, 02, 02]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 24, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: no_cov_crate::add_coverage_not_called (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 1d, 01, 02, 02]
@@ -21,6 +23,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 29, 1) to (start + 2, 2)
+Highest counter ID seen: (none)
 
 Function name: no_cov_crate::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 4d, 01, 0b, 02]
@@ -29,6 +32,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 77, 1) to (start + 11, 2)
+Highest counter ID seen: c0
 
 Function name: no_cov_crate::nested_fns::outer
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 31, 05, 02, 23, 01, 0c, 05, 00, 06]
@@ -38,6 +42,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 49, 5) to (start + 2, 35)
 - Code(Counter(0)) at (prev + 12, 5) to (start + 0, 6)
+Highest counter ID seen: c0
 
 Function name: no_cov_crate::nested_fns::outer_both_covered
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 3f, 05, 02, 17, 01, 0b, 05, 00, 06]
@@ -47,6 +52,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 63, 5) to (start + 2, 23)
 - Code(Counter(0)) at (prev + 11, 5) to (start + 0, 6)
+Highest counter ID seen: c0
 
 Function name: no_cov_crate::nested_fns::outer_both_covered::inner
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 43, 09, 01, 17, 05, 01, 18, 02, 0e, 02, 02, 14, 02, 0e, 01, 03, 09, 00, 0a]
@@ -60,4 +66,5 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 20) to (start + 2, 14)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 3, 9) to (start + 0, 10)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/no_spans.cov-map b/tests/coverage/no_spans.cov-map
index 30171c3f3193..7f43b68fa904 100644
--- a/tests/coverage/no_spans.cov-map
+++ b/tests/coverage/no_spans.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 26, 28) to (start + 0, 29)
+Highest counter ID seen: c0
 
 Function name: no_spans::affected_function::{closure#0}
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 1b, 0c, 00, 0e]
@@ -13,4 +14,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 27, 12) to (start + 0, 14)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/no_spans_if_not.cov-map b/tests/coverage/no_spans_if_not.cov-map
index bc3e14eddd54..9cb7e6a6cff2 100644
--- a/tests/coverage/no_spans_if_not.cov-map
+++ b/tests/coverage/no_spans_if_not.cov-map
@@ -9,6 +9,7 @@ Number of file 0 mappings: 3
 - Code(Expression(0, Sub)) at (prev + 2, 13) to (start + 0, 15)
     = (c0 - Zero)
 - Code(Zero) at (prev + 2, 13) to (start + 0, 15)
+Highest counter ID seen: c0
 
 Function name: no_spans_if_not::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 0b, 01, 02, 02]
@@ -17,4 +18,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 11, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/overflow.cov-map b/tests/coverage/overflow.cov-map
index cb31f3d1f3e4..f842ce3e896b 100644
--- a/tests/coverage/overflow.cov-map
+++ b/tests/coverage/overflow.cov-map
@@ -25,6 +25,7 @@ Number of file 0 mappings: 9
 - Code(Expression(6, Add)) at (prev + 1, 9) to (start + 0, 23)
     = (c1 + (c2 + c3))
 - Code(Counter(4)) at (prev + 2, 5) to (start + 1, 2)
+Highest counter ID seen: c4
 
 Function name: overflow::might_overflow
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 05, 01, 01, 12, 05, 01, 13, 02, 06, 02, 02, 06, 00, 07, 01, 01, 09, 05, 02]
@@ -38,4 +39,5 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 9) to (start + 5, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/panic_unwind.cov-map b/tests/coverage/panic_unwind.cov-map
index f6089ce55ae2..f4a7894cc1cc 100644
--- a/tests/coverage/panic_unwind.cov-map
+++ b/tests/coverage/panic_unwind.cov-map
@@ -25,6 +25,7 @@ Number of file 0 mappings: 9
 - Code(Expression(6, Add)) at (prev + 1, 9) to (start + 0, 23)
     = (c1 + (c2 + c3))
 - Code(Counter(4)) at (prev + 2, 5) to (start + 1, 2)
+Highest counter ID seen: c4
 
 Function name: panic_unwind::might_panic
 Raw bytes (21): 0x[01, 01, 01, 01, 05, 03, 01, 04, 01, 01, 14, 05, 02, 09, 01, 19, 02, 02, 0c, 03, 02]
@@ -37,4 +38,5 @@ Number of file 0 mappings: 3
 - Code(Counter(1)) at (prev + 2, 9) to (start + 1, 25)
 - Code(Expression(0, Sub)) at (prev + 2, 12) to (start + 3, 2)
     = (c0 - c1)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/partial_eq.cov-map b/tests/coverage/partial_eq.cov-map
index 6c39ac0e378b..21c8714ac99b 100644
--- a/tests/coverage/partial_eq.cov-map
+++ b/tests/coverage/partial_eq.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 12, 5) to (start + 2, 6)
+Highest counter ID seen: c0
 
 Function name: partial_eq::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 11, 01, 0a, 02]
@@ -13,4 +14,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 17, 1) to (start + 10, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/simple_loop.cov-map b/tests/coverage/simple_loop.cov-map
index 541f7bf8fbdc..b6f1e8f6afe6 100644
--- a/tests/coverage/simple_loop.cov-map
+++ b/tests/coverage/simple_loop.cov-map
@@ -15,4 +15,5 @@ Number of file 0 mappings: 7
 - Code(Counter(0)) at (prev + 4, 13) to (start + 0, 18)
 - Code(Counter(2)) at (prev + 2, 10) to (start + 3, 10)
 - Code(Counter(0)) at (prev + 6, 1) to (start + 0, 2)
+Highest counter ID seen: c2
 
diff --git a/tests/coverage/simple_match.cov-map b/tests/coverage/simple_match.cov-map
index 49819b23482f..b62edf12650c 100644
--- a/tests/coverage/simple_match.cov-map
+++ b/tests/coverage/simple_match.cov-map
@@ -27,4 +27,5 @@ Number of file 0 mappings: 10
 - Code(Counter(2)) at (prev + 4, 13) to (start + 7, 14)
 - Code(Counter(3)) at (prev + 10, 13) to (start + 0, 15)
 - Code(Counter(4)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c4
 
diff --git a/tests/coverage/sort_groups.cov-map b/tests/coverage/sort_groups.cov-map
index 361b70fb74f7..4e7ed059c879 100644
--- a/tests/coverage/sort_groups.cov-map
+++ b/tests/coverage/sort_groups.cov-map
@@ -10,6 +10,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: sort_groups::generic_fn::<()>
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 11, 01, 01, 0c, 05, 01, 0d, 02, 06, 02, 02, 06, 00, 07, 01, 01, 01, 00, 02]
@@ -23,6 +24,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: sort_groups::generic_fn::<char>
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 11, 01, 01, 0c, 05, 01, 0d, 02, 06, 02, 02, 06, 00, 07, 01, 01, 01, 00, 02]
@@ -36,6 +38,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: sort_groups::generic_fn::<i32>
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 11, 01, 01, 0c, 05, 01, 0d, 02, 06, 02, 02, 06, 00, 07, 01, 01, 01, 00, 02]
@@ -49,6 +52,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: sort_groups::main
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 06, 01, 04, 23, 05, 04, 24, 02, 06, 02, 02, 06, 00, 07, 01, 01, 05, 02, 02]
@@ -62,6 +66,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 5) to (start + 2, 2)
+Highest counter ID seen: c1
 
 Function name: sort_groups::other_fn
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 17, 01, 00, 11]
@@ -70,4 +75,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 23, 1) to (start + 0, 17)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/test_harness.cov-map b/tests/coverage/test_harness.cov-map
index f75328b11c9a..b513b3d05494 100644
--- a/tests/coverage/test_harness.cov-map
+++ b/tests/coverage/test_harness.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 10, 1) to (start + 0, 16)
+Highest counter ID seen: c0
 
 Function name: test_harness::unused (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 07, 01, 00, 0f]
@@ -13,4 +14,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 7, 1) to (start + 0, 15)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/tight_inf_loop.cov-map b/tests/coverage/tight_inf_loop.cov-map
index 7fe3146b0809..2d2d59bf013e 100644
--- a/tests/coverage/tight_inf_loop.cov-map
+++ b/tests/coverage/tight_inf_loop.cov-map
@@ -9,4 +9,5 @@ Number of file 0 mappings: 3
 - Code(Zero) at (prev + 2, 9) to (start + 0, 16)
 - Code(Expression(0, Sub)) at (prev + 1, 6) to (start + 1, 2)
     = (c0 - Zero)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/trivial.cov-map b/tests/coverage/trivial.cov-map
index 874e294a1c49..05f64896d9ec 100644
--- a/tests/coverage/trivial.cov-map
+++ b/tests/coverage/trivial.cov-map
@@ -5,4 +5,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 13)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/try_error_result.cov-map b/tests/coverage/try_error_result.cov-map
index 11a99f5395ec..246a1ba738b2 100644
--- a/tests/coverage/try_error_result.cov-map
+++ b/tests/coverage/try_error_result.cov-map
@@ -10,6 +10,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 13) to (start + 0, 26)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 2, 5) to (start + 0, 6)
+Highest counter ID seen: c1
 
 Function name: <try_error_result::Thing2>::call
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 34, 05, 01, 18, 05, 02, 0d, 00, 14, 02, 02, 0d, 00, 13, 01, 02, 05, 00, 06]
@@ -23,6 +24,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 13) to (start + 0, 19)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 2, 5) to (start + 0, 6)
+Highest counter ID seen: c1
 
 Function name: try_error_result::call
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 05, 01, 01, 14, 05, 02, 09, 00, 10, 02, 02, 09, 00, 0f, 01, 02, 01, 00, 02]
@@ -36,6 +38,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 9) to (start + 0, 15)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: try_error_result::main
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 71, 01, 02, 0c, 05, 03, 05, 00, 06, 02, 02, 05, 00, 0b, 01, 01, 01, 00, 02]
@@ -49,6 +52,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 5) to (start + 0, 11)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: try_error_result::test1
 Raw bytes (75): 0x[01, 01, 08, 01, 07, 00, 09, 03, 0d, 12, 1d, 03, 0d, 1b, 0d, 1f, 00, 11, 00, 0b, 01, 0d, 01, 02, 17, 03, 07, 09, 00, 0e, 12, 02, 09, 04, 1a, 1d, 06, 0d, 00, 29, 11, 00, 29, 00, 2a, 00, 01, 0d, 00, 2a, 00, 00, 2a, 00, 2b, 0e, 04, 0d, 00, 2a, 00, 00, 2a, 00, 2b, 0d, 03, 05, 00, 0b, 17, 01, 01, 00, 02]
@@ -79,6 +83,7 @@ Number of file 0 mappings: 11
 - Code(Counter(3)) at (prev + 3, 5) to (start + 0, 11)
 - Code(Expression(5, Add)) at (prev + 1, 1) to (start + 0, 2)
     = (((c4 + Zero) + Zero) + c3)
+Highest counter ID seen: c7
 
 Function name: try_error_result::test2
 Raw bytes (358): 0x[01, 01, 3b, 01, 07, 05, 09, 03, 0d, 41, 11, 4a, 15, 41, 11, 42, 1d, 46, 19, 4a, 15, 41, 11, 4a, 15, 41, 11, 46, 19, 4a, 15, 41, 11, 42, 1d, 46, 19, 4a, 15, 41, 11, 5e, 25, 49, 21, 49, 21, 5e, 25, 49, 21, 8a, 01, 2d, 8e, 01, 29, 92, 01, 41, 03, 0d, 92, 01, 41, 03, 0d, 8e, 01, 29, 92, 01, 41, 03, 0d, 8a, 01, 2d, 8e, 01, 29, 92, 01, 41, 03, 0d, a6, 01, 35, 45, 31, 45, 31, a6, 01, 35, 45, 31, ba, 01, 3d, 4d, 39, 4d, 39, ba, 01, 3d, 4d, 39, c3, 01, 0d, c7, 01, db, 01, cb, 01, cf, 01, 11, 15, d3, 01, d7, 01, 19, 1d, 21, 25, df, 01, e3, 01, 29, 2d, e7, 01, eb, 01, 31, 35, 39, 3d, 28, 01, 3d, 01, 03, 17, 03, 08, 09, 00, 0e, 92, 01, 02, 09, 04, 1a, 41, 06, 0d, 00, 2f, 11, 00, 2f, 00, 30, 4a, 00, 31, 03, 35, 15, 04, 11, 00, 12, 46, 02, 11, 04, 12, 3e, 05, 11, 00, 14, 46, 00, 17, 00, 41, 19, 00, 41, 00, 42, 42, 00, 43, 00, 5f, 1d, 00, 5f, 00, 60, 3e, 01, 0d, 00, 20, 5a, 01, 11, 00, 14, 49, 00, 17, 00, 41, 21, 00, 41, 00, 42, 5e, 00, 43, 00, 60, 25, 00, 60, 00, 61, 5a, 01, 0d, 00, 20, 86, 01, 04, 11, 00, 14, 8e, 01, 00, 17, 00, 42, 29, 00, 42, 00, 43, 8a, 01, 00, 44, 00, 61, 2d, 00, 61, 00, 62, 86, 01, 01, 0d, 00, 20, a2, 01, 01, 11, 00, 14, 45, 00, 17, 01, 36, 31, 01, 36, 00, 37, a6, 01, 01, 12, 00, 2f, 35, 00, 2f, 00, 30, a2, 01, 01, 0d, 00, 20, b6, 01, 01, 11, 00, 14, 4d, 00, 17, 01, 36, 39, 02, 11, 00, 12, ba, 01, 01, 12, 00, 2f, 3d, 01, 11, 00, 12, b6, 01, 02, 0d, 00, 20, 0d, 03, 05, 00, 0b, bf, 01, 01, 01, 00, 02]
@@ -207,4 +212,5 @@ Number of file 0 mappings: 40
 - Code(Counter(3)) at (prev + 3, 5) to (start + 0, 11)
 - Code(Expression(47, Add)) at (prev + 1, 1) to (start + 0, 2)
     = ((((c4 + c5) + ((c6 + c7) + (c8 + c9))) + ((c10 + c11) + ((c12 + c13) + (c14 + c15)))) + c3)
+Highest counter ID seen: c19
 
diff --git a/tests/coverage/unicode.cov-map b/tests/coverage/unicode.cov-map
index 06a2c930498b..ac4e691ea7ab 100644
--- a/tests/coverage/unicode.cov-map
+++ b/tests/coverage/unicode.cov-map
@@ -22,6 +22,7 @@ Number of file 0 mappings: 9
     = ((c0 - c2) + c3)
 - Code(Expression(3, Add)) at (prev + 2, 5) to (start + 1, 2)
     = (c4 + ((c0 - c2) + c3))
+Highest counter ID seen: c4
 
 Function name: unicode::他 (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 1e, 19, 00, 25]
@@ -30,6 +31,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 30, 25) to (start + 0, 37)
+Highest counter ID seen: (none)
 
 Function name: unicode::申し訳ございません
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 18, 01, 02, 02]
@@ -38,4 +40,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 24, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/unreachable.cov-map b/tests/coverage/unreachable.cov-map
index 09d3b2345431..d4a5936a7848 100644
--- a/tests/coverage/unreachable.cov-map
+++ b/tests/coverage/unreachable.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 15, 39) to (start + 0, 71)
+Highest counter ID seen: (none)
 
 Function name: unreachable::unreachable_function (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 11, 01, 01, 25]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 17, 1) to (start + 1, 37)
+Highest counter ID seen: (none)
 
 Function name: unreachable::unreachable_intrinsic (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 16, 01, 01, 2c]
@@ -21,4 +23,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 22, 1) to (start + 1, 44)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/unused.cov-map b/tests/coverage/unused.cov-map
index 9383d1e90ac2..9f1ad59ce83d 100644
--- a/tests/coverage/unused.cov-map
+++ b/tests/coverage/unused.cov-map
@@ -17,6 +17,7 @@ Number of file 0 mappings: 6
 - Code(Expression(3, Add)) at (prev + 1, 9) to (start + 0, 15)
     = (c1 + c2)
 - Code(Counter(3)) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: c3
 
 Function name: unused::foo::<u32>
 Raw bytes (42): 0x[01, 01, 04, 01, 0f, 05, 09, 03, 0d, 05, 09, 06, 01, 03, 01, 01, 12, 03, 02, 0b, 00, 11, 0a, 01, 09, 00, 0f, 09, 00, 13, 00, 19, 0f, 01, 09, 00, 0f, 0d, 02, 01, 00, 02]
@@ -37,6 +38,7 @@ Number of file 0 mappings: 6
 - Code(Expression(3, Add)) at (prev + 1, 9) to (start + 0, 15)
     = (c1 + c2)
 - Code(Counter(3)) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: c3
 
 Function name: unused::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 25, 01, 04, 02]
@@ -45,6 +47,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 37, 1) to (start + 4, 2)
+Highest counter ID seen: c0
 
 Function name: unused::unused_func (unused)
 Raw bytes (24): 0x[01, 01, 00, 04, 00, 13, 01, 01, 0e, 00, 01, 0f, 02, 06, 00, 02, 06, 00, 07, 00, 01, 01, 00, 02]
@@ -56,6 +59,7 @@ Number of file 0 mappings: 4
 - Code(Zero) at (prev + 1, 15) to (start + 2, 6)
 - Code(Zero) at (prev + 2, 6) to (start + 0, 7)
 - Code(Zero) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: (none)
 
 Function name: unused::unused_func2 (unused)
 Raw bytes (24): 0x[01, 01, 00, 04, 00, 19, 01, 01, 0e, 00, 01, 0f, 02, 06, 00, 02, 06, 00, 07, 00, 01, 01, 00, 02]
@@ -67,6 +71,7 @@ Number of file 0 mappings: 4
 - Code(Zero) at (prev + 1, 15) to (start + 2, 6)
 - Code(Zero) at (prev + 2, 6) to (start + 0, 7)
 - Code(Zero) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: (none)
 
 Function name: unused::unused_func3 (unused)
 Raw bytes (24): 0x[01, 01, 00, 04, 00, 1f, 01, 01, 0e, 00, 01, 0f, 02, 06, 00, 02, 06, 00, 07, 00, 01, 01, 00, 02]
@@ -78,6 +83,7 @@ Number of file 0 mappings: 4
 - Code(Zero) at (prev + 1, 15) to (start + 2, 6)
 - Code(Zero) at (prev + 2, 6) to (start + 0, 7)
 - Code(Zero) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: (none)
 
 Function name: unused::unused_template_func::<_> (unused)
 Raw bytes (34): 0x[01, 01, 00, 06, 00, 0b, 01, 01, 12, 00, 02, 0b, 00, 11, 00, 01, 09, 00, 0f, 00, 00, 13, 00, 19, 00, 01, 09, 00, 0f, 00, 02, 01, 00, 02]
@@ -91,4 +97,5 @@ Number of file 0 mappings: 6
 - Code(Zero) at (prev + 0, 19) to (start + 0, 25)
 - Code(Zero) at (prev + 1, 9) to (start + 0, 15)
 - Code(Zero) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/unused_mod.cov-map b/tests/coverage/unused_mod.cov-map
index 241cb2610ffc..af10906fa3c5 100644
--- a/tests/coverage/unused_mod.cov-map
+++ b/tests/coverage/unused_mod.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 4, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: unused_mod::unused_module::never_called_function (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 02, 01, 02, 02]
@@ -13,4 +14,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 2, 1) to (start + 2, 2)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/uses_crate.cov-map b/tests/coverage/uses_crate.cov-map
index 9c06eab70050..5c23f8826971 100644
--- a/tests/coverage/uses_crate.cov-map
+++ b/tests/coverage/uses_crate.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 27, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: used_crate::used_only_from_bin_crate_generic_function::<&alloc::vec::Vec<i32>>
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 13, 01, 02, 02]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 19, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: used_crate::used_only_from_bin_crate_generic_function::<&str>
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 13, 01, 02, 02]
@@ -21,6 +23,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 19, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: used_crate::used_with_same_type_from_bin_crate_and_lib_crate_generic_function::<&str>
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 1f, 01, 02, 02]
@@ -29,6 +32,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 31, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: uses_crate::main
 Raw bytes (9): 0x[01, 02, 00, 01, 01, 0c, 01, 07, 02]
@@ -37,4 +41,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 12, 1) to (start + 7, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/uses_inline_crate.cov-map b/tests/coverage/uses_inline_crate.cov-map
index 55ceb46b0602..a6909768162b 100644
--- a/tests/coverage/uses_inline_crate.cov-map
+++ b/tests/coverage/uses_inline_crate.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 44, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: used_inline_crate::used_inline_function
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 14, 01, 06, 0f, 05, 06, 10, 02, 06, 02, 02, 06, 00, 07, 01, 01, 05, 01, 02]
@@ -18,6 +19,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 5) to (start + 1, 2)
+Highest counter ID seen: c1
 
 Function name: used_inline_crate::used_only_from_bin_crate_generic_function::<&alloc::vec::Vec<i32>>
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 21, 01, 02, 02]
@@ -26,6 +28,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 33, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: used_inline_crate::used_only_from_bin_crate_generic_function::<&str>
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 21, 01, 02, 02]
@@ -34,6 +37,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 33, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: used_inline_crate::used_with_same_type_from_bin_crate_and_lib_crate_generic_function::<&str>
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 31, 01, 02, 02]
@@ -42,6 +46,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 49, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: uses_inline_crate::main
 Raw bytes (9): 0x[01, 02, 00, 01, 01, 0c, 01, 0a, 02]
@@ -50,4 +55,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 12, 1) to (start + 10, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/while.cov-map b/tests/coverage/while.cov-map
index 4d813a935a05..29493a651dcb 100644
--- a/tests/coverage/while.cov-map
+++ b/tests/coverage/while.cov-map
@@ -10,4 +10,5 @@ Number of file 0 mappings: 4
     = (c0 + Zero)
 - Code(Zero) at (prev + 0, 21) to (start + 2, 6)
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/while_early_ret.cov-map b/tests/coverage/while_early_ret.cov-map
index c883eb4baf20..6254dfbcf010 100644
--- a/tests/coverage/while_early_ret.cov-map
+++ b/tests/coverage/while_early_ret.cov-map
@@ -23,4 +23,5 @@ Number of file 0 mappings: 9
 - Code(Counter(2)) at (prev + 6, 5) to (start + 0, 11)
 - Code(Expression(4, Add)) at (prev + 1, 1) to (start + 0, 2)
     = ((c3 + c4) + c2)
+Highest counter ID seen: c4
 
diff --git a/tests/coverage/yield.cov-map b/tests/coverage/yield.cov-map
index a273c688e248..578994a45305 100644
--- a/tests/coverage/yield.cov-map
+++ b/tests/coverage/yield.cov-map
@@ -39,6 +39,7 @@ Number of file 0 mappings: 16
 - Code(Expression(10, Add)) at (prev + 1, 14) to (start + 0, 52)
     = (c9 + c10)
 - Code(Counter(11)) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: c11
 
 Function name: yield::main::{closure#0}
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 09, 08, 01, 10, 05, 02, 10, 01, 06]
@@ -48,6 +49,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 9, 8) to (start + 1, 16)
 - Code(Counter(1)) at (prev + 2, 16) to (start + 1, 6)
+Highest counter ID seen: c1
 
 Function name: yield::main::{closure#1}
 Raw bytes (24): 0x[01, 01, 00, 04, 01, 18, 08, 01, 10, 05, 02, 09, 00, 10, 09, 01, 09, 00, 10, 0d, 01, 10, 01, 06]
@@ -59,4 +61,5 @@ Number of file 0 mappings: 4
 - Code(Counter(1)) at (prev + 2, 9) to (start + 0, 16)
 - Code(Counter(2)) at (prev + 1, 9) to (start + 0, 16)
 - Code(Counter(3)) at (prev + 1, 16) to (start + 1, 6)
+Highest counter ID seen: c3
 
diff --git a/tests/ui/lint/non-local-defs/consts.rs b/tests/ui/lint/non-local-defs/consts.rs
index d8a497e43e50..5b9dab3cfd36 100644
--- a/tests/ui/lint/non-local-defs/consts.rs
+++ b/tests/ui/lint/non-local-defs/consts.rs
@@ -63,6 +63,13 @@ fn main() {
 
         1
     };
+
+    const _: () = {
+        const _: () = {
+            impl Test {}
+            //~^ WARN non-local `impl` definition
+        };
+    };
 }
 
 trait Uto9 {}
diff --git a/tests/ui/lint/non-local-defs/consts.stderr b/tests/ui/lint/non-local-defs/consts.stderr
index 7f76056c0210..4bf50bae5eac 100644
--- a/tests/ui/lint/non-local-defs/consts.stderr
+++ b/tests/ui/lint/non-local-defs/consts.stderr
@@ -95,7 +95,21 @@ LL |         impl Test {
    = note: this lint may become deny-by-default in the edition 2024 and higher, see the tracking issue <https://github.com/rust-lang/rust/issues/120363>
 
 warning: non-local `impl` definition, `impl` blocks should be written at the same level as their item
-  --> $DIR/consts.rs:72:9
+  --> $DIR/consts.rs:69:13
+   |
+LL |         const _: () = {
+   |         ----------- move the `impl` block outside of this constant `_` and up 3 bodies
+LL |             impl Test {}
+   |             ^^^^^----
+   |                  |
+   |                  `Test` is not local
+   |
+   = note: an `impl` is never scoped, even when it is nested inside an item, as it may impact type checking outside of that item, which can be the case if neither the trait or the self type are at the same nesting level as the `impl`
+   = note: items in an anonymous const item (`const _: () = { ... }`) are treated as in the same scope as the anonymous const's declaration for the purpose of this lint
+   = note: this lint may become deny-by-default in the edition 2024 and higher, see the tracking issue <https://github.com/rust-lang/rust/issues/120363>
+
+warning: non-local `impl` definition, `impl` blocks should be written at the same level as their item
+  --> $DIR/consts.rs:79:9
    |
 LL |     let _a = || {
    |              -- move the `impl` block outside of this closure `<unnameable>` and up 2 bodies
@@ -109,7 +123,7 @@ LL |         impl Uto9 for Test {}
    = note: this lint may become deny-by-default in the edition 2024 and higher, see the tracking issue <https://github.com/rust-lang/rust/issues/120363>
 
 warning: non-local `impl` definition, `impl` blocks should be written at the same level as their item
-  --> $DIR/consts.rs:79:9
+  --> $DIR/consts.rs:86:9
    |
 LL |       type A = [u32; {
    |  ____________________-
@@ -126,5 +140,5 @@ LL | |     }];
    = note: an `impl` is never scoped, even when it is nested inside an item, as it may impact type checking outside of that item, which can be the case if neither the trait or the self type are at the same nesting level as the `impl`
    = note: this lint may become deny-by-default in the edition 2024 and higher, see the tracking issue <https://github.com/rust-lang/rust/issues/120363>
 
-warning: 8 warnings emitted
+warning: 9 warnings emitted
 
diff --git a/tests/ui/lint/non-local-defs/convoluted-locals-131474-with-mods.rs b/tests/ui/lint/non-local-defs/convoluted-locals-131474-with-mods.rs
new file mode 100644
index 000000000000..cef0f0205e80
--- /dev/null
+++ b/tests/ui/lint/non-local-defs/convoluted-locals-131474-with-mods.rs
@@ -0,0 +1,34 @@
+// This test check that no matter the nesting of const-anons and modules
+// we consider them as transparent.
+//
+// Similar to https://github.com/rust-lang/rust/issues/131474
+
+//@ check-pass
+
+pub mod tmp {
+    pub mod tmp {
+        pub struct Test;
+    }
+}
+
+const _: () = {
+    const _: () = {
+        const _: () = {
+            const _: () = {
+                impl tmp::tmp::Test {}
+            };
+        };
+    };
+};
+
+const _: () = {
+    const _: () = {
+        mod tmp {
+            pub(super) struct InnerTest;
+        }
+
+        impl tmp::InnerTest {}
+    };
+};
+
+fn main() {}
diff --git a/tests/ui/lint/non-local-defs/convoluted-locals-131474.rs b/tests/ui/lint/non-local-defs/convoluted-locals-131474.rs
new file mode 100644
index 000000000000..4881723f13bc
--- /dev/null
+++ b/tests/ui/lint/non-local-defs/convoluted-locals-131474.rs
@@ -0,0 +1,24 @@
+// This test check that no matter the nesting of const-anons we consider
+// them as transparent.
+//
+// https://github.com/rust-lang/rust/issues/131474
+
+//@ check-pass
+
+pub struct Test;
+
+const _: () = {
+    const _: () = {
+        impl Test {}
+    };
+};
+
+const _: () = {
+    const _: () = {
+        struct InnerTest;
+
+        impl InnerTest {}
+    };
+};
+
+fn main() {}
diff --git a/tests/ui/lint/non-local-defs/local.rs b/tests/ui/lint/non-local-defs/local.rs
index 166ee88c0210..f7ecd68f59e9 100644
--- a/tests/ui/lint/non-local-defs/local.rs
+++ b/tests/ui/lint/non-local-defs/local.rs
@@ -51,3 +51,10 @@ fn bitflags() {
         impl Flags {}
     };
 }
+
+fn bitflags_internal() {
+    const _: () = {
+        struct InternalFlags;
+        impl InternalFlags {}
+    };
+}
diff --git a/triagebot.toml b/triagebot.toml
index 231a7bba1f7c..60ec1043aadb 100644
--- a/triagebot.toml
+++ b/triagebot.toml
@@ -970,6 +970,7 @@ bootstrap = [
     "@albertlarsan68",
     "@onur-ozkan",
     "@kobzol",
+    "@jieyouxu",
 ]
 infra-ci = [
     "@Mark-Simulacrum",