diff --git a/compiler/rustc_errors/src/diagnostic.rs b/compiler/rustc_errors/src/diagnostic.rs
index ae23ef1e2553..96a4ed3218fb 100644
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/compiler/rustc_errors/src/diagnostic.rs
@@ -945,6 +945,11 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
             None,
             "Span must not be empty and have no suggestion",
         );
+        debug_assert_eq!(
+            parts.array_windows().find(|[a, b]| a.span.overlaps(b.span)),
+            None,
+            "suggestion must not have overlapping parts",
+        );
 
         self.push_suggestion(CodeSuggestion {
             substitutions: vec![Substitution { parts }],
diff --git a/compiler/rustc_errors/src/emitter.rs b/compiler/rustc_errors/src/emitter.rs
index 93b1e6b76152..b94370e8e9b4 100644
--- a/compiler/rustc_errors/src/emitter.rs
+++ b/compiler/rustc_errors/src/emitter.rs
@@ -2354,6 +2354,7 @@ impl HumanEmitter {
                         .sum();
                     let underline_start = (span_start_pos + start) as isize + offset;
                     let underline_end = (span_start_pos + start + sub_len) as isize + offset;
+                    assert!(underline_start >= 0 && underline_end >= 0);
                     let padding: usize = max_line_num_len + 3;
                     for p in underline_start..underline_end {
                         if let DisplaySuggestion::Underline = show_code_change
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 8869799ce90d..a56e0f3fae13 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -381,17 +381,6 @@ impl CodeSuggestion {
                 // Assumption: all spans are in the same file, and all spans
                 // are disjoint. Sort in ascending order.
                 substitution.parts.sort_by_key(|part| part.span.lo());
-                // Verify the assumption that all spans are disjoint
-                assert_eq!(
-                    substitution.parts.array_windows().find(|[a, b]| a.span.overlaps(b.span)),
-                    None,
-                    "all spans must be disjoint",
-                );
-
-                // Account for cases where we are suggesting the same code that's already
-                // there. This shouldn't happen often, but in some cases for multipart
-                // suggestions it's much easier to handle it here than in the origin.
-                substitution.parts.retain(|p| is_different(sm, &p.snippet, p.span));
 
                 // Find the bounding span.
                 let lo = substitution.parts.iter().map(|part| part.span.lo()).min()?;
@@ -481,12 +470,16 @@ impl CodeSuggestion {
                             _ => 1,
                         })
                         .sum();
-
-                    line_highlight.push(SubstitutionHighlight {
-                        start: (cur_lo.col.0 as isize + acc) as usize,
-                        end: (cur_lo.col.0 as isize + acc + len) as usize,
-                    });
-
+                    if !is_different(sm, &part.snippet, part.span) {
+                        // Account for cases where we are suggesting the same code that's already
+                        // there. This shouldn't happen often, but in some cases for multipart
+                        // suggestions it's much easier to handle it here than in the origin.
+                    } else {
+                        line_highlight.push(SubstitutionHighlight {
+                            start: (cur_lo.col.0 as isize + acc) as usize,
+                            end: (cur_lo.col.0 as isize + acc + len) as usize,
+                        });
+                    }
                     buf.push_str(&part.snippet);
                     let cur_hi = sm.lookup_char_pos(part.span.hi());
                     // Account for the difference between the width of the current code and the
diff --git a/src/tools/clippy/tests/ui/bool_assert_comparison.stderr b/src/tools/clippy/tests/ui/bool_assert_comparison.stderr
index 72aa6303a202..f823f08f31dc 100644
--- a/src/tools/clippy/tests/ui/bool_assert_comparison.stderr
+++ b/src/tools/clippy/tests/ui/bool_assert_comparison.stderr
@@ -272,8 +272,10 @@ LL |     assert_eq!(a!(), true);
    |
 help: replace it with `assert!(..)`
    |
-LL -     assert_eq!(a!(), true);
-LL +     assert!(a!());
+LL |         true
+...
+LL |
+LL ~     assert!(a!());
    |
 
 error: used `assert_eq!` with a literal bool
@@ -284,8 +286,10 @@ LL |     assert_eq!(true, b!());
    |
 help: replace it with `assert!(..)`
    |
-LL -     assert_eq!(true, b!());
-LL +     assert!(b!());
+LL |         true
+...
+LL |
+LL ~     assert!(b!());
    |
 
 error: used `debug_assert_eq!` with a literal bool