Auto merge of #56145 - weiznich:re_rebalance_coherence, r=nikomatsakis

Implement the Re-rebalance coherence RFC

This is the first time I touch anything in the compiler so just tell me if I got something wrong.

Big thanks to @sgrif for the pointers where to look for those things.
cc #55437

src/doc/unstable-book/src/language-features/re-rebalance-coherence.md

@@ -0,0 +1,23 @@
+# `re_rebalance_coherence`
+
+The tracking issue for this feature is: [#55437]
+
+[#55437]: https://github.com/rust-lang/rust/issues/55437
+
+------------------------
+
+The `re_rebalance_coherence` feature tweaks the rules regarding which trait
+impls are allowed in crates.
+The following rule is used:
+
+Given `impl<P1..=Pn> Trait<T1..=Tn> for T0`, an impl is valid only if at
+least one of the following is true:
+- `Trait` is a local trait
+- All of
+  - At least one of the types `T0..=Tn` must be a local type. Let `Ti` be the
+    first such type.
+  - No uncovered type parameters `P1..=Pn` may appear in `T0..Ti` (excluding
+    `Ti`)
+
+
+See the [RFC](https://github.com/rust-lang/rfcs/blob/master/text/2451-re-rebalancing-coherence.md) for details.

src/librustc/traits/coherence.rs

@@ -371,43 +371,68 @@ fn orphan_check_trait_ref<'tcx>(tcx: TyCtxt<'_, '_, '_>,
              trait_ref);
     }
 
-    // First, create an ordered iterator over all the type parameters to the trait, with the self
-    // type appearing first.
-    // Find the first input type that either references a type parameter OR
-    // some local type.
-    for input_ty in trait_ref.input_types() {
-        if ty_is_local(tcx, input_ty, in_crate) {
-            debug!("orphan_check_trait_ref: ty_is_local `{:?}`", input_ty);
+    if tcx.features().re_rebalance_coherence {
+        // Given impl<P1..=Pn> Trait<T1..=Tn> for T0, an impl is valid only
+        // if at least one of the following is true:
+        //
+        // - Trait is a local trait
+        // (already checked in orphan_check prior to calling this function)
+        // - All of
+        //     - At least one of the types T0..=Tn must be a local type.
+        //      Let Ti be the first such type.
+        //     - No uncovered type parameters P1..=Pn may appear in T0..Ti (excluding Ti)
+        //
+        for input_ty in trait_ref.input_types() {
+            debug!("orphan_check_trait_ref: check ty `{:?}`", input_ty);
+            if ty_is_local(tcx, input_ty, in_crate) {
+                debug!("orphan_check_trait_ref: ty_is_local `{:?}`", input_ty);
+                return Ok(());
+            } else if let ty::Param(_) = input_ty.sty {
+                debug!("orphan_check_trait_ref: uncovered ty: `{:?}`", input_ty);
+                return Err(OrphanCheckErr::UncoveredTy(input_ty))
+            }
+        }
+        // If we exit above loop, never found a local type.
+        debug!("orphan_check_trait_ref: no local type");
+        Err(OrphanCheckErr::NoLocalInputType)
+    } else {
+        // First, create an ordered iterator over all the type
+        // parameters to the trait, with the self type appearing
+        // first.  Find the first input type that either references a
+        // type parameter OR some local type.
+        for input_ty in trait_ref.input_types() {
+            if ty_is_local(tcx, input_ty, in_crate) {
+                debug!("orphan_check_trait_ref: ty_is_local `{:?}`", input_ty);
 
-            // First local input type. Check that there are no
-            // uncovered type parameters.
-            let uncovered_tys = uncovered_tys(tcx, input_ty, in_crate);
-            for uncovered_ty in uncovered_tys {
-                if let Some(param) = uncovered_ty.walk()
-                    .find(|t| is_possibly_remote_type(t, in_crate))
-                {
-                    debug!("orphan_check_trait_ref: uncovered type `{:?}`", param);
-                    return Err(OrphanCheckErr::UncoveredTy(param));
+                // First local input type. Check that there are no
+                // uncovered type parameters.
+                let uncovered_tys = uncovered_tys(tcx, input_ty, in_crate);
+                for uncovered_ty in uncovered_tys {
+                    if let Some(param) = uncovered_ty.walk()
+                        .find(|t| is_possibly_remote_type(t, in_crate))
+                    {
+                        debug!("orphan_check_trait_ref: uncovered type `{:?}`", param);
+                        return Err(OrphanCheckErr::UncoveredTy(param));
+                    }
                 }
+
+                // OK, found local type, all prior types upheld invariant.
+                return Ok(());
             }
 
-            // OK, found local type, all prior types upheld invariant.
-            return Ok(());
-        }
-
-        // Otherwise, enforce invariant that there are no type
-        // parameters reachable.
-        if let Some(param) = input_ty.walk()
-            .find(|t| is_possibly_remote_type(t, in_crate))
-        {
-            debug!("orphan_check_trait_ref: uncovered type `{:?}`", param);
-            return Err(OrphanCheckErr::UncoveredTy(param));
+            // Otherwise, enforce invariant that there are no type
+            // parameters reachable.
+            if let Some(param) = input_ty.walk()
+                .find(|t| is_possibly_remote_type(t, in_crate))
+            {
+                debug!("orphan_check_trait_ref: uncovered type `{:?}`", param);
+                return Err(OrphanCheckErr::UncoveredTy(param));
+            }
         }
+        // If we exit above loop, never found a local type.
+        debug!("orphan_check_trait_ref: no local type");
+        Err(OrphanCheckErr::NoLocalInputType)
     }
-
-    // If we exit above loop, never found a local type.
-    debug!("orphan_check_trait_ref: no local type");
-    return Err(OrphanCheckErr::NoLocalInputType);
 }
 
 fn uncovered_tys<'tcx>(tcx: TyCtxt<'_, '_, '_>, ty: Ty<'tcx>, in_crate: InCrate)

src/libsyntax/feature_gate.rs

@@ -479,6 +479,9 @@ declare_features! (
 
     // Allows paths to enum variants on type aliases.
     (active, type_alias_enum_variants, "1.31.0", Some(49683), None),
+
+    // Re-Rebalance coherence
+    (active, re_rebalance_coherence, "1.32.0", Some(55437), None),
 );
 
 declare_features! (

src/test/run-pass/coherence/auxiliary/re_rebalance_coherence_lib.rs

@@ -0,0 +1,23 @@
+
+pub trait Backend{}
+pub trait SupportsDefaultKeyword {}
+
+impl SupportsDefaultKeyword for Postgres {}
+
+pub struct Postgres;
+
+impl Backend for Postgres {}
+
+pub struct AstPass<DB>(::std::marker::PhantomData<DB>);
+
+pub trait QueryFragment<DB: Backend> {}
+
+
+#[derive(Debug, Clone, Copy)]
+pub struct BatchInsert<'a, T: 'a, Tab> {
+    _marker: ::std::marker::PhantomData<(&'a T, Tab)>,
+}
+
+impl<'a, T:'a, Tab, DB> QueryFragment<DB> for BatchInsert<'a, T, Tab>
+where DB: SupportsDefaultKeyword + Backend,
+{}

src/test/run-pass/coherence/coherence-bigint-int.rs

@@ -1,5 +1,8 @@
 // run-pass
 // aux-build:coherence_lib.rs
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 
 // pretty-expanded FIXME #23616
 

src/test/run-pass/coherence/coherence-bigint-vecint.rs

@@ -1,5 +1,8 @@
 // run-pass
 // aux-build:coherence_lib.rs
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 
 // pretty-expanded FIXME #23616
 

src/test/run-pass/coherence/coherence-blanket.rs

@@ -1,6 +1,9 @@
 // run-pass
 #![allow(unused_imports)]
 // aux-build:coherence_lib.rs
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 
 // pretty-expanded FIXME #23616
 

src/test/run-pass/coherence/coherence-covered-type-parameter.rs

@@ -1,6 +1,9 @@
 // run-pass
 #![allow(dead_code)]
 // aux-build:coherence_lib.rs
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 
 // pretty-expanded FIXME #23616
 

src/test/run-pass/coherence/coherence-impl-in-fn.rs

@@ -1,4 +1,7 @@
 // run-pass
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 #![allow(dead_code)]
 #![allow(non_camel_case_types)]
 

src/test/run-pass/coherence/coherence-iterator-vec-any-elem.rs

@@ -1,4 +1,7 @@
 // run-pass
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 #![allow(dead_code)]
 // aux-build:coherence_lib.rs
 

src/test/run-pass/coherence/coherence-iterator-vec.rs

@@ -1,4 +1,7 @@
 // run-pass
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 #![allow(dead_code)]
 // aux-build:coherence_lib.rs
 

src/test/run-pass/coherence/coherence-multidispatch-tuple.rs

@@ -1,4 +1,7 @@
 // run-pass
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 #![allow(unused_imports)]
 // pretty-expanded FIXME #23616
 

src/test/run-pass/coherence/coherence-negative-impls-safe.rs

@@ -1,4 +1,7 @@
 // run-pass
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 #![allow(dead_code)]
 // pretty-expanded FIXME #23616
 

src/test/run-pass/coherence/coherence-rfc447-constrained.rs

@@ -1,4 +1,7 @@
 // run-pass
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 // check that trait matching can handle impls whose types are only
 // constrained by a projection.
 

src/test/run-pass/coherence/coherence-where-clause.rs

@@ -1,4 +1,8 @@
 // run-pass
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
+
 use std::fmt::Debug;
 use std::default::Default;
 

src/test/run-pass/coherence/coherence_copy_like.rs

@@ -1,4 +1,7 @@
 // run-pass
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 #![allow(dead_code)]
 // Test that we are able to introduce a negative constraint that
 // `MyType: !MyTrait` along with other "fundamental" wrappers.

src/test/run-pass/coherence/re-rebalance-coherence.rs

@@ -0,0 +1,14 @@
+#![allow(dead_code)]
+#![feature(re_rebalance_coherence)]
+
+// run-pass
+// aux-build:re_rebalance_coherence_lib.rs
+
+extern crate re_rebalance_coherence_lib as lib;
+use lib::*;
+
+struct Oracle;
+impl Backend for Oracle {}
+impl<'a, T:'a, Tab> QueryFragment<Oracle> for BatchInsert<'a, T, Tab> {}
+
+fn main() {}

src/test/ui/coherence/auxiliary/re_rebalance_coherence_lib.rs

@@ -0,0 +1,23 @@
+
+pub trait Backend{}
+pub trait SupportsDefaultKeyword {}
+
+impl SupportsDefaultKeyword for Postgres {}
+
+pub struct Postgres;
+
+impl Backend for Postgres {}
+
+pub struct AstPass<DB>(::std::marker::PhantomData<DB>);
+
+pub trait QueryFragment<DB: Backend> {}
+
+
+#[derive(Debug, Clone, Copy)]
+pub struct BatchInsert<'a, T: 'a, Tab> {
+    _marker: ::std::marker::PhantomData<(&'a T, Tab)>,
+}
+
+impl<'a, T:'a, Tab, DB> QueryFragment<DB> for BatchInsert<'a, T, Tab>
+where DB: SupportsDefaultKeyword + Backend,
+{}

src/test/ui/coherence/coherence-all-remote.old.stderr

@@ -1,5 +1,5 @@
 error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
-  --> $DIR/coherence-all-remote.rs:6:1
+  --> $DIR/coherence-all-remote.rs:9:1
    |
 LL | impl<T> Remote1<T> for isize { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type parameter `T` must be used as the type parameter for some local type

src/test/ui/coherence/coherence-all-remote.re.stderr

@@ -0,0 +1,11 @@
+error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
+  --> $DIR/coherence-all-remote.rs:9:1
+   |
+LL | impl<T> Remote1<T> for isize { }
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type parameter `T` must be used as the type parameter for some local type
+   |
+   = note: only traits defined in the current crate can be implemented for a type parameter
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0210`.

src/test/ui/coherence/coherence-all-remote.rs

@@ -1,9 +1,13 @@
 // aux-build:coherence_lib.rs
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 
 extern crate coherence_lib as lib;
 use lib::Remote1;
 
 impl<T> Remote1<T> for isize { }
-//~^ ERROR E0210
+//[old]~^ ERROR E0210
+//[re]~^^ ERROR E0210
 
 fn main() { }

src/test/ui/coherence/coherence-bigint-param.old.stderr

@@ -1,5 +1,5 @@
 error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
-  --> $DIR/coherence-bigint-param.rs:8:1
+  --> $DIR/coherence-bigint-param.rs:11:1
    |
 LL | impl<T> Remote1<BigInt> for T { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type parameter `T` must be used as the type parameter for some local type

src/test/ui/coherence/coherence-bigint-param.re.stderr

@@ -0,0 +1,11 @@
+error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
+  --> $DIR/coherence-bigint-param.rs:11:1
+   |
+LL | impl<T> Remote1<BigInt> for T { }
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type parameter `T` must be used as the type parameter for some local type
+   |
+   = note: only traits defined in the current crate can be implemented for a type parameter
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0210`.

src/test/ui/coherence/coherence-bigint-param.rs

@@ -1,4 +1,7 @@
 // aux-build:coherence_lib.rs
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 
 extern crate coherence_lib as lib;
 use lib::Remote1;
@@ -6,6 +9,7 @@ use lib::Remote1;
 pub struct BigInt;
 
 impl<T> Remote1<BigInt> for T { }
-//~^ ERROR type parameter `T` must be used as the type parameter for some local type
+//[old]~^ ERROR type parameter `T` must be used as the type parameter for some local type
+//[re]~^^ ERROR E0210
 
 fn main() { }

src/test/ui/coherence/coherence-blanket-conflicts-with-blanket-implemented.old.stderr

@@ -1,10 +1,10 @@
 error[E0119]: conflicting implementations of trait `MyTrait`:
-  --> $DIR/coherence-blanket-conflicts-with-blanket-implemented.rs:24:1
+  --> $DIR/coherence-blanket-conflicts-with-blanket-implemented.rs:28:1
    |
 LL | impl<T:Even> MyTrait for T {
    | -------------------------- first implementation here
 ...
-LL | impl<T:Odd> MyTrait for T { //~ ERROR E0119
+LL | impl<T:Odd> MyTrait for T {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation
 
 error: aborting due to previous error

src/test/ui/coherence/coherence-blanket-conflicts-with-blanket-implemented.re.stderr

@@ -0,0 +1,12 @@
+error[E0119]: conflicting implementations of trait `MyTrait`:
+  --> $DIR/coherence-blanket-conflicts-with-blanket-implemented.rs:28:1
+   |
+LL | impl<T:Even> MyTrait for T {
+   | -------------------------- first implementation here
+...
+LL | impl<T:Odd> MyTrait for T {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0119`.

src/test/ui/coherence/coherence-blanket-conflicts-with-blanket-implemented.rs

@@ -1,3 +1,7 @@
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
+
 use std::fmt::Debug;
 use std::default::Default;
 
@@ -21,7 +25,10 @@ impl<T:Even> MyTrait for T {
     fn get(&self) -> usize { 0 }
 }
 
-impl<T:Odd> MyTrait for T { //~ ERROR E0119
+impl<T:Odd> MyTrait for T {
+//[old]~^ ERROR E0119
+//[re]~^^ ERROR E0119
+
     fn get(&self) -> usize { 0 }
 }
 

src/test/ui/coherence/coherence-blanket-conflicts-with-blanket-unimplemented.old.stderr

@@ -1,10 +1,10 @@
 error[E0119]: conflicting implementations of trait `MyTrait`:
-  --> $DIR/coherence-blanket-conflicts-with-blanket-unimplemented.rs:20:1
+  --> $DIR/coherence-blanket-conflicts-with-blanket-unimplemented.rs:24:1
    |
 LL | impl<T:Even> MyTrait for T {
    | -------------------------- first implementation here
 ...
-LL | impl<T:Odd> MyTrait for T { //~ ERROR E0119
+LL | impl<T:Odd> MyTrait for T {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation
 
 error: aborting due to previous error

src/test/ui/coherence/coherence-blanket-conflicts-with-blanket-unimplemented.re.stderr

@@ -0,0 +1,12 @@
+error[E0119]: conflicting implementations of trait `MyTrait`:
+  --> $DIR/coherence-blanket-conflicts-with-blanket-unimplemented.rs:24:1
+   |
+LL | impl<T:Even> MyTrait for T {
+   | -------------------------- first implementation here
+...
+LL | impl<T:Odd> MyTrait for T {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0119`.

src/test/ui/coherence/coherence-blanket-conflicts-with-blanket-unimplemented.rs

@@ -1,3 +1,7 @@
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
+
 use std::fmt::Debug;
 use std::default::Default;
 
@@ -17,7 +21,9 @@ impl<T:Even> MyTrait for T {
     fn get(&self) -> usize { 0 }
 }
 
-impl<T:Odd> MyTrait for T { //~ ERROR E0119
+impl<T:Odd> MyTrait for T {
+//[old]~^ ERROR E0119
+//[re]~^^ ERROR E0119
     fn get(&self) -> usize { 0 }
 }
 

src/test/ui/coherence/coherence-blanket-conflicts-with-specific-cross-crate.old.stderr

@@ -1,7 +1,7 @@
 error[E0119]: conflicting implementations of trait `go_trait::GoMut` for type `MyThingy`:
-  --> $DIR/coherence-blanket-conflicts-with-specific-cross-crate.rs:15:1
+  --> $DIR/coherence-blanket-conflicts-with-specific-cross-crate.rs:18:1
    |
-LL | impl GoMut for MyThingy { //~ ERROR conflicting implementations
+LL | impl GoMut for MyThingy {
    | ^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: conflicting implementation in crate `go_trait`:

src/test/ui/coherence/coherence-blanket-conflicts-with-specific-cross-crate.re.stderr

@@ -0,0 +1,13 @@
+error[E0119]: conflicting implementations of trait `go_trait::GoMut` for type `MyThingy`:
+  --> $DIR/coherence-blanket-conflicts-with-specific-cross-crate.rs:18:1
+   |
+LL | impl GoMut for MyThingy {
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: conflicting implementation in crate `go_trait`:
+           - impl<G> go_trait::GoMut for G
+             where G: go_trait::Go;
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0119`.

src/test/ui/coherence/coherence-blanket-conflicts-with-specific-cross-crate.rs

@@ -1,4 +1,7 @@
 // aux-build:go_trait.rs
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 
 extern crate go_trait;
 
@@ -12,7 +15,9 @@ impl Go for MyThingy {
     fn go(&self, arg: isize) { }
 }
 
-impl GoMut for MyThingy { //~ ERROR conflicting implementations
+impl GoMut for MyThingy {
+//[old]~^ ERROR conflicting implementations
+//[re]~^^ ERROR E0119
     fn go_mut(&mut self, arg: isize) { }
 }
 

src/test/ui/coherence/coherence-blanket-conflicts-with-specific-multidispatch.old.stderr

@@ -1,10 +1,10 @@
 error[E0119]: conflicting implementations of trait `MyTrait<MyType>` for type `MyType`:
-  --> $DIR/coherence-blanket-conflicts-with-specific-multidispatch.rs:22:1
+  --> $DIR/coherence-blanket-conflicts-with-specific-multidispatch.rs:26:1
    |
 LL | impl<T> MyTrait<T> for T {
    | ------------------------ first implementation here
 ...
-LL | impl MyTrait<MyType> for MyType { //~ ERROR E0119
+LL | impl MyTrait<MyType> for MyType {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `MyType`
 
 error: aborting due to previous error

src/test/ui/coherence/coherence-blanket-conflicts-with-specific-multidispatch.re.stderr

@@ -0,0 +1,12 @@
+error[E0119]: conflicting implementations of trait `MyTrait<MyType>` for type `MyType`:
+  --> $DIR/coherence-blanket-conflicts-with-specific-multidispatch.rs:26:1
+   |
+LL | impl<T> MyTrait<T> for T {
+   | ------------------------ first implementation here
+...
+LL | impl MyTrait<MyType> for MyType {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `MyType`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0119`.

src/test/ui/coherence/coherence-blanket-conflicts-with-specific-multidispatch.rs

@@ -1,3 +1,7 @@
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
+
 use std::fmt::Debug;
 use std::default::Default;
 
@@ -19,7 +23,9 @@ struct MyType {
     dummy: usize
 }
 
-impl MyTrait<MyType> for MyType { //~ ERROR E0119
+impl MyTrait<MyType> for MyType {
+//[old]~^ ERROR E0119
+//[re]~^^ ERROR E0119
     fn get(&self) -> usize { (*self).clone() }
 }
 

src/test/ui/coherence/coherence-blanket-conflicts-with-specific-trait.old.stderr

@@ -1,10 +1,10 @@
 error[E0119]: conflicting implementations of trait `MyTrait` for type `MyType`:
-  --> $DIR/coherence-blanket-conflicts-with-specific-trait.rs:20:1
+  --> $DIR/coherence-blanket-conflicts-with-specific-trait.rs:24:1
    |
 LL | impl<T:OtherTrait> MyTrait for T {
    | -------------------------------- first implementation here
 ...
-LL | impl MyTrait for MyType { //~ ERROR E0119
+LL | impl MyTrait for MyType {
    | ^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `MyType`
 
 error: aborting due to previous error

src/test/ui/coherence/coherence-blanket-conflicts-with-specific-trait.re.stderr

@@ -0,0 +1,12 @@
+error[E0119]: conflicting implementations of trait `MyTrait` for type `MyType`:
+  --> $DIR/coherence-blanket-conflicts-with-specific-trait.rs:24:1
+   |
+LL | impl<T:OtherTrait> MyTrait for T {
+   | -------------------------------- first implementation here
+...
+LL | impl MyTrait for MyType {
+   | ^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `MyType`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0119`.

src/test/ui/coherence/coherence-blanket-conflicts-with-specific-trait.rs

@@ -1,6 +1,10 @@
 // Test that a blank impl for all T:PartialEq conflicts with an impl for some
 // specific T when T:PartialEq.
 
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
+
 trait OtherTrait {
     fn noop(&self);
 }
@@ -17,7 +21,9 @@ struct MyType {
     dummy: usize
 }
 
-impl MyTrait for MyType { //~ ERROR E0119
+impl MyTrait for MyType {
+//[old]~^ ERROR E0119
+//[re]~^^ ERROR E0119
     fn get(&self) -> usize { self.dummy }
 }
 

src/test/ui/coherence/coherence-blanket-conflicts-with-specific.old.stderr

@@ -1,10 +1,10 @@
 error[E0119]: conflicting implementations of trait `MyTrait` for type `MyType`:
-  --> $DIR/coherence-blanket-conflicts-with-specific.rs:19:1
+  --> $DIR/coherence-blanket-conflicts-with-specific.rs:23:1
    |
 LL | impl<T> MyTrait for T {
    | --------------------- first implementation here
 ...
-LL | impl MyTrait for MyType { //~ ERROR E0119
+LL | impl MyTrait for MyType {
    | ^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `MyType`
 
 error: aborting due to previous error

src/test/ui/coherence/coherence-blanket-conflicts-with-specific.re.stderr

@@ -0,0 +1,12 @@
+error[E0119]: conflicting implementations of trait `MyTrait` for type `MyType`:
+  --> $DIR/coherence-blanket-conflicts-with-specific.rs:23:1
+   |
+LL | impl<T> MyTrait for T {
+   | --------------------- first implementation here
+...
+LL | impl MyTrait for MyType {
+   | ^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `MyType`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0119`.

src/test/ui/coherence/coherence-blanket-conflicts-with-specific.rs

@@ -1,3 +1,7 @@
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
+
 use std::fmt::Debug;
 use std::default::Default;
 
@@ -16,7 +20,9 @@ struct MyType {
     dummy: usize
 }
 
-impl MyTrait for MyType { //~ ERROR E0119
+impl MyTrait for MyType {
+//[old]~^ ERROR E0119
+//[re]~^^ ERROR E0119
     fn get(&self) -> usize { self.dummy }
 }
 

src/test/ui/coherence/coherence-conflicting-negative-trait-impl.old.stderr

@@ -1,5 +1,5 @@
 error[E0119]: conflicting implementations of trait `std::marker::Send` for type `TestType<_>`:
-  --> $DIR/coherence-conflicting-negative-trait-impl.rs:10:1
+  --> $DIR/coherence-conflicting-negative-trait-impl.rs:13:1
    |
 LL | unsafe impl<T: MyTrait+'static> Send for TestType<T> {}
    | ---------------------------------------------------- first implementation here
@@ -8,7 +8,7 @@ LL | impl<T: MyTrait> !Send for TestType<T> {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `TestType<_>`
 
 error[E0119]: conflicting implementations of trait `std::marker::Send` for type `TestType<i32>`:
-  --> $DIR/coherence-conflicting-negative-trait-impl.rs:15:1
+  --> $DIR/coherence-conflicting-negative-trait-impl.rs:19:1
    |
 LL | unsafe impl<T:'static> Send for TestType<T> {}
    | ------------------------------------------- first implementation here

src/test/ui/coherence/coherence-conflicting-negative-trait-impl.re.stderr

@@ -0,0 +1,21 @@
+error[E0119]: conflicting implementations of trait `std::marker::Send` for type `TestType<_>`:
+  --> $DIR/coherence-conflicting-negative-trait-impl.rs:13:1
+   |
+LL | unsafe impl<T: MyTrait+'static> Send for TestType<T> {}
+   | ---------------------------------------------------- first implementation here
+LL | 
+LL | impl<T: MyTrait> !Send for TestType<T> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `TestType<_>`
+
+error[E0119]: conflicting implementations of trait `std::marker::Send` for type `TestType<i32>`:
+  --> $DIR/coherence-conflicting-negative-trait-impl.rs:19:1
+   |
+LL | unsafe impl<T:'static> Send for TestType<T> {}
+   | ------------------------------------------- first implementation here
+LL | 
+LL | impl !Send for TestType<i32> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `TestType<i32>`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0119`.

src/test/ui/coherence/coherence-conflicting-negative-trait-impl.rs

@@ -1,3 +1,6 @@
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 #![feature(optin_builtin_traits)]
 #![feature(overlapping_marker_traits)]
 
@@ -8,11 +11,13 @@ struct TestType<T>(::std::marker::PhantomData<T>);
 unsafe impl<T: MyTrait+'static> Send for TestType<T> {}
 
 impl<T: MyTrait> !Send for TestType<T> {}
-//~^ ERROR conflicting implementations of trait `std::marker::Send`
+//[old]~^ ERROR conflicting implementations of trait `std::marker::Send`
+//[re]~^^ ERROR E0119
 
 unsafe impl<T:'static> Send for TestType<T> {}
 
 impl !Send for TestType<i32> {}
-//~^ ERROR conflicting implementations of trait `std::marker::Send`
+//[old]~^ ERROR conflicting implementations of trait `std::marker::Send`
+//[re]~^^ ERROR E0119
 
 fn main() {}

src/test/ui/coherence/coherence-cow.a.stderr

@@ -1,7 +1,7 @@
 error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
-  --> $DIR/coherence-cow.rs:16:1
+  --> $DIR/coherence-cow.rs:18:1
    |
-LL | impl<T> Remote for Pair<T,Cover<T>> { } //[a]~ ERROR E0210
+LL | impl<T> Remote for Pair<T,Cover<T>> { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type parameter `T` must be used as the type parameter for some local type
    |
    = note: only traits defined in the current crate can be implemented for a type parameter

src/test/ui/coherence/coherence-cow.b.stderr

@@ -1,7 +1,7 @@
 error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
-  --> $DIR/coherence-cow.rs:19:1
+  --> $DIR/coherence-cow.rs:23:1
    |
-LL | impl<T> Remote for Pair<Cover<T>,T> { } //[b]~ ERROR E0210
+LL | impl<T> Remote for Pair<Cover<T>,T> { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type parameter `T` must be used as the type parameter for some local type
    |
    = note: only traits defined in the current crate can be implemented for a type parameter

src/test/ui/coherence/coherence-cow.c.stderr

@@ -1,5 +1,5 @@
 error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
-  --> $DIR/coherence-cow.rs:22:1
+  --> $DIR/coherence-cow.rs:28:1
    |
 LL | impl<T,U> Remote for Pair<Cover<T>,U> { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type parameter `T` must be used as the type parameter for some local type

src/test/ui/coherence/coherence-cow.re_a.stderr

@@ -0,0 +1,12 @@
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/coherence-cow.rs:18:1
+   |
+LL | impl<T> Remote for Pair<T,Cover<T>> { }
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
+   |
+   = note: the impl does not reference any types defined in this crate
+   = note: define and implement a trait or new type instead
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0117`.

src/test/ui/coherence/coherence-cow.re_b.stderr

@@ -0,0 +1,12 @@
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/coherence-cow.rs:23:1
+   |
+LL | impl<T> Remote for Pair<Cover<T>,T> { }
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
+   |
+   = note: the impl does not reference any types defined in this crate
+   = note: define and implement a trait or new type instead
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0117`.

src/test/ui/coherence/coherence-cow.re_c.stderr

@@ -0,0 +1,12 @@
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/coherence-cow.rs:28:1
+   |
+LL | impl<T,U> Remote for Pair<Cover<T>,U> { }
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
+   |
+   = note: the impl does not reference any types defined in this crate
+   = note: define and implement a trait or new type instead
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0117`.

src/test/ui/coherence/coherence-cow.rs

@@ -1,4 +1,6 @@
-// revisions: a b c
+// revisions: a b c re_a re_b re_c
+
+#![cfg_attr(any(re_a, re_b, re_c), feature(re_rebalance_coherence))]
 
 // aux-build:coherence_lib.rs
 
@@ -12,14 +14,19 @@ use lib::{Remote,Pair};
 
 pub struct Cover<T>(T);
 
-#[cfg(a)]
-impl<T> Remote for Pair<T,Cover<T>> { } //[a]~ ERROR E0210
+#[cfg(any(a, re_a))]
+impl<T> Remote for Pair<T,Cover<T>> { }
+//[a]~^ ERROR E0210
+//[re_a]~^^ ERROR E0117
 
-#[cfg(b)]
-impl<T> Remote for Pair<Cover<T>,T> { } //[b]~ ERROR E0210
+#[cfg(any(b, re_b))]
+impl<T> Remote for Pair<Cover<T>,T> { }
+//[b]~^ ERROR E0210
+//[re_b]~^^ ERROR E0117
 
-#[cfg(c)]
+#[cfg(any(c, re_c))]
 impl<T,U> Remote for Pair<Cover<T>,U> { }
 //[c]~^ ERROR type parameter `T` must be used as the type parameter for some local type
+//[re_c]~^^ ERROR E0117
 
 fn main() { }

src/test/ui/coherence/coherence-cross-crate-conflict.old.stderr

@@ -1,5 +1,5 @@
 error[E0119]: conflicting implementations of trait `trait_impl_conflict::Foo` for type `isize`:
-  --> $DIR/coherence-cross-crate-conflict.rs:8:1
+  --> $DIR/coherence-cross-crate-conflict.rs:12:1
    |
 LL | impl<A> Foo for A {
    | ^^^^^^^^^^^^^^^^^
@@ -8,7 +8,7 @@ LL | impl<A> Foo for A {
            - impl trait_impl_conflict::Foo for isize;
 
 error[E0210]: type parameter `A` must be used as the type parameter for some local type (e.g., `MyStruct<A>`)
-  --> $DIR/coherence-cross-crate-conflict.rs:8:1
+  --> $DIR/coherence-cross-crate-conflict.rs:12:1
    |
 LL | impl<A> Foo for A {
    | ^^^^^^^^^^^^^^^^^ type parameter `A` must be used as the type parameter for some local type

src/test/ui/coherence/coherence-cross-crate-conflict.re.stderr

@@ -0,0 +1,21 @@
+error[E0119]: conflicting implementations of trait `trait_impl_conflict::Foo` for type `isize`:
+  --> $DIR/coherence-cross-crate-conflict.rs:12:1
+   |
+LL | impl<A> Foo for A {
+   | ^^^^^^^^^^^^^^^^^
+   |
+   = note: conflicting implementation in crate `trait_impl_conflict`:
+           - impl trait_impl_conflict::Foo for isize;
+
+error[E0210]: type parameter `A` must be used as the type parameter for some local type (e.g., `MyStruct<A>`)
+  --> $DIR/coherence-cross-crate-conflict.rs:12:1
+   |
+LL | impl<A> Foo for A {
+   | ^^^^^^^^^^^^^^^^^ type parameter `A` must be used as the type parameter for some local type
+   |
+   = note: only traits defined in the current crate can be implemented for a type parameter
+
+error: aborting due to 2 previous errors
+
+Some errors occurred: E0119, E0210.
+For more information about an error, try `rustc --explain E0119`.

src/test/ui/coherence/coherence-cross-crate-conflict.rs

@@ -2,12 +2,18 @@
 // generalizes the one upstream
 
 // aux-build:trait_impl_conflict.rs
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
+
 extern crate trait_impl_conflict;
 use trait_impl_conflict::Foo;
 
 impl<A> Foo for A {
-    //~^ ERROR type parameter `A` must be used as the type parameter for some local type
-    //~| ERROR conflicting implementations of trait `trait_impl_conflict::Foo` for type `isize`
+    //[old]~^ ERROR type parameter `A` must be used as the type parameter for some local type
+    //[old]~| ERROR conflicting implementations of trait `trait_impl_conflict::Foo` for type `isize`
+    //[re]~^^^ ERROR E0119
+    //[re]~| ERROR E0210
 }
 
 fn main() {

src/test/ui/coherence/coherence-default-trait-impl.old.stderr

@@ -1,11 +1,11 @@
 error[E0199]: implementing the trait `MySafeTrait` is not unsafe
-  --> $DIR/coherence-default-trait-impl.rs:7:1
+  --> $DIR/coherence-default-trait-impl.rs:10:1
    |
 LL | unsafe impl MySafeTrait for Foo {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0200]: the trait `MyUnsafeTrait` requires an `unsafe impl` declaration
-  --> $DIR/coherence-default-trait-impl.rs:12:1
+  --> $DIR/coherence-default-trait-impl.rs:16:1
    |
 LL | impl MyUnsafeTrait for Foo {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/coherence/coherence-default-trait-impl.re.stderr

@@ -0,0 +1,16 @@
+error[E0199]: implementing the trait `MySafeTrait` is not unsafe
+  --> $DIR/coherence-default-trait-impl.rs:10:1
+   |
+LL | unsafe impl MySafeTrait for Foo {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0200]: the trait `MyUnsafeTrait` requires an `unsafe impl` declaration
+  --> $DIR/coherence-default-trait-impl.rs:16:1
+   |
+LL | impl MyUnsafeTrait for Foo {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
+Some errors occurred: E0199, E0200.
+For more information about an error, try `rustc --explain E0199`.

src/test/ui/coherence/coherence-default-trait-impl.rs

@@ -1,3 +1,6 @@
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 #![feature(optin_builtin_traits)]
 
 auto trait MySafeTrait {}
@@ -5,11 +8,13 @@ auto trait MySafeTrait {}
 struct Foo;
 
 unsafe impl MySafeTrait for Foo {}
-//~^ ERROR implementing the trait `MySafeTrait` is not unsafe
+//[old]~^ ERROR implementing the trait `MySafeTrait` is not unsafe
+//[re]~^^ ERROR E0199
 
 unsafe auto trait MyUnsafeTrait {}
 
 impl MyUnsafeTrait for Foo {}
-//~^ ERROR the trait `MyUnsafeTrait` requires an `unsafe impl` declaration
+//[old]~^ ERROR the trait `MyUnsafeTrait` requires an `unsafe impl` declaration
+//[re]~^^ ERROR E0200
 
 fn main() {}

src/test/ui/coherence/coherence-error-suppression.old.stderr

@@ -1,7 +1,7 @@
 error[E0412]: cannot find type `DoesNotExist` in this scope
-  --> $DIR/coherence-error-suppression.rs:9:14
+  --> $DIR/coherence-error-suppression.rs:13:14
    |
-LL | impl Foo for DoesNotExist {} //~ ERROR cannot find type `DoesNotExist` in this scope
+LL | impl Foo for DoesNotExist {}
    |              ^^^^^^^^^^^^ not found in this scope
 
 error: aborting due to previous error

src/test/ui/coherence/coherence-error-suppression.re.stderr

@@ -0,0 +1,9 @@
+error[E0412]: cannot find type `DoesNotExist` in this scope
+  --> $DIR/coherence-error-suppression.rs:13:14
+   |
+LL | impl Foo for DoesNotExist {}
+   |              ^^^^^^^^^^^^ not found in this scope
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0412`.

src/test/ui/coherence/coherence-error-suppression.rs

@@ -1,12 +1,18 @@
 // check that error types in coherence do not cause error cascades.
 
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
+
 trait Foo {}
 
 impl Foo for i8 {}
 impl Foo for i16 {}
 impl Foo for i32 {}
 impl Foo for i64 {}
-impl Foo for DoesNotExist {} //~ ERROR cannot find type `DoesNotExist` in this scope
+impl Foo for DoesNotExist {}
+//[old]~^ ERROR cannot find type `DoesNotExist` in this scope
+//[re]~^^ ERROR E0412
 impl Foo for u8 {}
 impl Foo for u16 {}
 impl Foo for u32 {}

src/test/ui/coherence/coherence-fundamental-trait-objects.old.stderr

@@ -1,5 +1,5 @@
 error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
-  --> $DIR/coherence-fundamental-trait-objects.rs:12:1
+  --> $DIR/coherence-fundamental-trait-objects.rs:15:1
    |
 LL | impl Misc for dyn Fundamental<Local> {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate

src/test/ui/coherence/coherence-fundamental-trait-objects.re.stderr

@@ -0,0 +1,12 @@
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/coherence-fundamental-trait-objects.rs:15:1
+   |
+LL | impl Misc for dyn Fundamental<Local> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
+   |
+   = note: the impl does not reference any types defined in this crate
+   = note: define and implement a trait or new type instead
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0117`.

src/test/ui/coherence/coherence-fundamental-trait-objects.rs

@@ -3,6 +3,9 @@
 // are distinct.
 
 // aux-build:coherence_fundamental_trait_lib.rs
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 
 extern crate coherence_fundamental_trait_lib;
 
@@ -10,6 +13,7 @@ use coherence_fundamental_trait_lib::{Fundamental, Misc};
 
 pub struct Local;
 impl Misc for dyn Fundamental<Local> {}
-//~^ ERROR E0117
+//[old]~^ ERROR E0117
+//[re]~^^ ERROR E0117
 
 fn main() {}

src/test/ui/coherence/coherence-impl-trait-for-trait-object-safe.old.stderr

@@ -1,7 +1,7 @@
 error[E0038]: the trait `NotObjectSafe` cannot be made into an object
-  --> $DIR/coherence-impl-trait-for-trait-object-safe.rs:7:6
+  --> $DIR/coherence-impl-trait-for-trait-object-safe.rs:11:6
    |
-LL | impl NotObjectSafe for NotObjectSafe { } //~ ERROR E0038
+LL | impl NotObjectSafe for NotObjectSafe { }
    |      ^^^^^^^^^^^^^ the trait `NotObjectSafe` cannot be made into an object
    |
    = note: method `eq` references the `Self` type in its arguments or return type

src/test/ui/coherence/coherence-impl-trait-for-trait-object-safe.re.stderr

@@ -0,0 +1,11 @@
+error[E0038]: the trait `NotObjectSafe` cannot be made into an object
+  --> $DIR/coherence-impl-trait-for-trait-object-safe.rs:11:6
+   |
+LL | impl NotObjectSafe for NotObjectSafe { }
+   |      ^^^^^^^^^^^^^ the trait `NotObjectSafe` cannot be made into an object
+   |
+   = note: method `eq` references the `Self` type in its arguments or return type
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0038`.

src/test/ui/coherence/coherence-impl-trait-for-trait-object-safe.rs

@@ -1,9 +1,15 @@
 // Test that we give suitable error messages when the user attempts to
 // impl a trait `Trait` for its own object type.
 
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
+
 // If the trait is not object-safe, we give a more tailored message
 // because we're such schnuckels:
 trait NotObjectSafe { fn eq(&self, other: Self); }
-impl NotObjectSafe for NotObjectSafe { } //~ ERROR E0038
+impl NotObjectSafe for NotObjectSafe { }
+//[old]~^ ERROR E0038
+//[re]~^^ ERROR E0038
 
 fn main() { }

src/test/ui/coherence/coherence-impl-trait-for-trait.old.stderr

@@ -1,19 +1,19 @@
 error[E0371]: the object type `(dyn Baz + 'static)` automatically implements the trait `Foo`
-  --> $DIR/coherence-impl-trait-for-trait.rs:9:1
+  --> $DIR/coherence-impl-trait-for-trait.rs:13:1
    |
-LL | impl Foo for Baz { }   //~ ERROR E0371
+LL | impl Foo for Baz { }
    | ^^^^^^^^^^^^^^^^ `(dyn Baz + 'static)` automatically implements trait `Foo`
 
 error[E0371]: the object type `(dyn Baz + 'static)` automatically implements the trait `Bar`
-  --> $DIR/coherence-impl-trait-for-trait.rs:10:1
+  --> $DIR/coherence-impl-trait-for-trait.rs:16:1
    |
-LL | impl Bar for Baz { }   //~ ERROR E0371
+LL | impl Bar for Baz { }
    | ^^^^^^^^^^^^^^^^ `(dyn Baz + 'static)` automatically implements trait `Bar`
 
 error[E0371]: the object type `(dyn Baz + 'static)` automatically implements the trait `Baz`
-  --> $DIR/coherence-impl-trait-for-trait.rs:11:1
+  --> $DIR/coherence-impl-trait-for-trait.rs:19:1
    |
-LL | impl Baz for Baz { }   //~ ERROR E0371
+LL | impl Baz for Baz { }
    | ^^^^^^^^^^^^^^^^ `(dyn Baz + 'static)` automatically implements trait `Baz`
 
 error: aborting due to 3 previous errors

src/test/ui/coherence/coherence-impl-trait-for-trait.re.stderr

@@ -0,0 +1,21 @@
+error[E0371]: the object type `(dyn Baz + 'static)` automatically implements the trait `Foo`
+  --> $DIR/coherence-impl-trait-for-trait.rs:13:1
+   |
+LL | impl Foo for Baz { }
+   | ^^^^^^^^^^^^^^^^ `(dyn Baz + 'static)` automatically implements trait `Foo`
+
+error[E0371]: the object type `(dyn Baz + 'static)` automatically implements the trait `Bar`
+  --> $DIR/coherence-impl-trait-for-trait.rs:16:1
+   |
+LL | impl Bar for Baz { }
+   | ^^^^^^^^^^^^^^^^ `(dyn Baz + 'static)` automatically implements trait `Bar`
+
+error[E0371]: the object type `(dyn Baz + 'static)` automatically implements the trait `Baz`
+  --> $DIR/coherence-impl-trait-for-trait.rs:19:1
+   |
+LL | impl Baz for Baz { }
+   | ^^^^^^^^^^^^^^^^ `(dyn Baz + 'static)` automatically implements trait `Baz`
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0371`.

src/test/ui/coherence/coherence-impl-trait-for-trait.rs

@@ -1,14 +1,24 @@
 // Test that we give suitable error messages when the user attempts to
 // impl a trait `Trait` for its own object type.
 
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
+
 trait Foo { fn dummy(&self) { } }
 trait Bar: Foo { }
 trait Baz: Bar { }
 
 // Supertraits of Baz are not legal:
-impl Foo for Baz { }   //~ ERROR E0371
-impl Bar for Baz { }   //~ ERROR E0371
-impl Baz for Baz { }   //~ ERROR E0371
+impl Foo for Baz { }
+//[old]~^ ERROR E0371
+//[re]~^^ ERROR E0371
+impl Bar for Baz { }
+//[old]~^ ERROR E0371
+//[re]~^^ ERROR E0371
+impl Baz for Baz { }
+//[old]~^ ERROR E0371
+//[re]~^^ ERROR E0371
 
 // But other random traits are:
 trait Other { }

src/test/ui/coherence/coherence-impls-copy.old.stderr

@@ -1,5 +1,5 @@
 error[E0119]: conflicting implementations of trait `std::marker::Copy` for type `i32`:
-  --> $DIR/coherence-impls-copy.rs:5:1
+  --> $DIR/coherence-impls-copy.rs:8:1
    |
 LL | impl Copy for i32 {}
    | ^^^^^^^^^^^^^^^^^
@@ -8,7 +8,7 @@ LL | impl Copy for i32 {}
            - impl std::marker::Copy for i32;
 
 error[E0119]: conflicting implementations of trait `std::marker::Copy` for type `&NotSync`:
-  --> $DIR/coherence-impls-copy.rs:31:1
+  --> $DIR/coherence-impls-copy.rs:37:1
    |
 LL | impl Copy for &'static NotSync {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -18,7 +18,7 @@ LL | impl Copy for &'static NotSync {}
              where T: ?Sized;
 
 error[E0119]: conflicting implementations of trait `std::marker::Copy` for type `&[NotSync]`:
-  --> $DIR/coherence-impls-copy.rs:38:1
+  --> $DIR/coherence-impls-copy.rs:45:1
    |
 LL | impl Copy for &'static [NotSync] {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -28,25 +28,25 @@ LL | impl Copy for &'static [NotSync] {}
              where T: ?Sized;
 
 error[E0206]: the trait `Copy` may not be implemented for this type
-  --> $DIR/coherence-impls-copy.rs:23:15
+  --> $DIR/coherence-impls-copy.rs:27:15
    |
 LL | impl Copy for &'static mut MyType {}
    |               ^^^^^^^^^^^^^^^^^^^ type is not a structure or enumeration
 
 error[E0206]: the trait `Copy` may not be implemented for this type
-  --> $DIR/coherence-impls-copy.rs:27:15
+  --> $DIR/coherence-impls-copy.rs:32:15
    |
 LL | impl Copy for (MyType, MyType) {}
    |               ^^^^^^^^^^^^^^^^ type is not a structure or enumeration
 
 error[E0206]: the trait `Copy` may not be implemented for this type
-  --> $DIR/coherence-impls-copy.rs:34:15
+  --> $DIR/coherence-impls-copy.rs:40:15
    |
 LL | impl Copy for [MyType] {}
    |               ^^^^^^^^ type is not a structure or enumeration
 
 error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
-  --> $DIR/coherence-impls-copy.rs:5:1
+  --> $DIR/coherence-impls-copy.rs:8:1
    |
 LL | impl Copy for i32 {}
    | ^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
@@ -55,7 +55,7 @@ LL | impl Copy for i32 {}
    = note: define and implement a trait or new type instead
 
 error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
-  --> $DIR/coherence-impls-copy.rs:27:1
+  --> $DIR/coherence-impls-copy.rs:32:1
    |
 LL | impl Copy for (MyType, MyType) {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
@@ -64,7 +64,7 @@ LL | impl Copy for (MyType, MyType) {}
    = note: define and implement a trait or new type instead
 
 error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
-  --> $DIR/coherence-impls-copy.rs:34:1
+  --> $DIR/coherence-impls-copy.rs:40:1
    |
 LL | impl Copy for [MyType] {}
    | ^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
@@ -73,7 +73,7 @@ LL | impl Copy for [MyType] {}
    = note: define and implement a trait or new type instead
 
 error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
-  --> $DIR/coherence-impls-copy.rs:38:1
+  --> $DIR/coherence-impls-copy.rs:45:1
    |
 LL | impl Copy for &'static [NotSync] {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate

src/test/ui/coherence/coherence-impls-copy.re.stderr

@@ -0,0 +1,87 @@
+error[E0119]: conflicting implementations of trait `std::marker::Copy` for type `i32`:
+  --> $DIR/coherence-impls-copy.rs:8:1
+   |
+LL | impl Copy for i32 {}
+   | ^^^^^^^^^^^^^^^^^
+   |
+   = note: conflicting implementation in crate `core`:
+           - impl std::marker::Copy for i32;
+
+error[E0119]: conflicting implementations of trait `std::marker::Copy` for type `&NotSync`:
+  --> $DIR/coherence-impls-copy.rs:37:1
+   |
+LL | impl Copy for &'static NotSync {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: conflicting implementation in crate `core`:
+           - impl<T> std::marker::Copy for &T
+             where T: ?Sized;
+
+error[E0119]: conflicting implementations of trait `std::marker::Copy` for type `&[NotSync]`:
+  --> $DIR/coherence-impls-copy.rs:45:1
+   |
+LL | impl Copy for &'static [NotSync] {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: conflicting implementation in crate `core`:
+           - impl<T> std::marker::Copy for &T
+             where T: ?Sized;
+
+error[E0206]: the trait `Copy` may not be implemented for this type
+  --> $DIR/coherence-impls-copy.rs:27:15
+   |
+LL | impl Copy for &'static mut MyType {}
+   |               ^^^^^^^^^^^^^^^^^^^ type is not a structure or enumeration
+
+error[E0206]: the trait `Copy` may not be implemented for this type
+  --> $DIR/coherence-impls-copy.rs:32:15
+   |
+LL | impl Copy for (MyType, MyType) {}
+   |               ^^^^^^^^^^^^^^^^ type is not a structure or enumeration
+
+error[E0206]: the trait `Copy` may not be implemented for this type
+  --> $DIR/coherence-impls-copy.rs:40:15
+   |
+LL | impl Copy for [MyType] {}
+   |               ^^^^^^^^ type is not a structure or enumeration
+
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/coherence-impls-copy.rs:8:1
+   |
+LL | impl Copy for i32 {}
+   | ^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
+   |
+   = note: the impl does not reference any types defined in this crate
+   = note: define and implement a trait or new type instead
+
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/coherence-impls-copy.rs:32:1
+   |
+LL | impl Copy for (MyType, MyType) {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
+   |
+   = note: the impl does not reference any types defined in this crate
+   = note: define and implement a trait or new type instead
+
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/coherence-impls-copy.rs:40:1
+   |
+LL | impl Copy for [MyType] {}
+   | ^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
+   |
+   = note: the impl does not reference any types defined in this crate
+   = note: define and implement a trait or new type instead
+
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/coherence-impls-copy.rs:45:1
+   |
+LL | impl Copy for &'static [NotSync] {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
+   |
+   = note: the impl does not reference any types defined in this crate
+   = note: define and implement a trait or new type instead
+
+error: aborting due to 10 previous errors
+
+Some errors occurred: E0117, E0119, E0206.
+For more information about an error, try `rustc --explain E0117`.

src/test/ui/coherence/coherence-impls-copy.rs

@@ -1,11 +1,15 @@
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 #![feature(optin_builtin_traits)]
 
 use std::marker::Copy;
 
 impl Copy for i32 {}
-//~^ ERROR conflicting implementations of trait `std::marker::Copy` for type `i32`:
-//~| ERROR only traits defined in the current crate can be implemented for arbitrary types
-
+//[old]~^ ERROR conflicting implementations of trait `std::marker::Copy` for type `i32`:
+//[old]~| ERROR only traits defined in the current crate can be implemented for arbitrary types
+//[re]~^^^ ERROR E0119
+//[re]~| ERROR E0117
 enum TestE {
   A
 }
@@ -21,23 +25,27 @@ impl Clone for TestE { fn clone(&self) -> Self { *self } }
 impl Copy for MyType {}
 
 impl Copy for &'static mut MyType {}
-//~^ ERROR the trait `Copy` may not be implemented for this type
+//[old]~^ ERROR the trait `Copy` may not be implemented for this type
+//[re]~^^ ERROR E0206
 impl Clone for MyType { fn clone(&self) -> Self { *self } }
 
 impl Copy for (MyType, MyType) {}
-//~^ ERROR the trait `Copy` may not be implemented for this type
-//~| ERROR only traits defined in the current crate can be implemented for arbitrary types
-
+//[old]~^ ERROR the trait `Copy` may not be implemented for this type
+//[old]~| ERROR only traits defined in the current crate can be implemented for arbitrary types
+//[re]~^^^ ERROR E0206
+//[re]~| ERROR E0117
 impl Copy for &'static NotSync {}
-//~^ ERROR conflicting implementations of trait `std::marker::Copy` for type `&NotSync`:
-
+//[old]~^ ERROR conflicting implementations of trait `std::marker::Copy` for type `&NotSync`:
+//[re]~^^  ERROR E0119
 impl Copy for [MyType] {}
-//~^ ERROR the trait `Copy` may not be implemented for this type
-//~| ERROR only traits defined in the current crate can be implemented for arbitrary types
-
+//[old]~^ ERROR the trait `Copy` may not be implemented for this type
+//[old]~| ERROR only traits defined in the current crate can be implemented for arbitrary types
+//[re]~^^^ ERROR E0206
+//[re]~| ERROR E0117
 impl Copy for &'static [NotSync] {}
-//~^ ERROR conflicting implementations of trait `std::marker::Copy` for type `&[NotSync]`:
-//~| ERROR only traits defined in the current crate can be implemented for arbitrary types
-
+//[old]~^ ERROR conflicting implementations of trait `std::marker::Copy` for type `&[NotSync]`:
+//[old]~| ERROR only traits defined in the current crate can be implemented for arbitrary types
+//[re]~^^^ ERROR E0119
+//[re]~| ERROR E0117
 fn main() {
 }

src/test/ui/coherence/coherence-impls-send.old.stderr

@@ -1,5 +1,5 @@
 error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
-  --> $DIR/coherence-impls-send.rs:17:1
+  --> $DIR/coherence-impls-send.rs:20:1
    |
 LL | unsafe impl Send for (MyType, MyType) {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
@@ -8,13 +8,13 @@ LL | unsafe impl Send for (MyType, MyType) {}
    = note: define and implement a trait or new type instead
 
 error[E0321]: cross-crate traits with a default impl, like `std::marker::Send`, can only be implemented for a struct/enum type, not `&'static NotSync`
-  --> $DIR/coherence-impls-send.rs:20:1
+  --> $DIR/coherence-impls-send.rs:24:1
    |
 LL | unsafe impl Send for &'static NotSync {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't implement cross-crate trait with a default impl for non-struct/enum type
 
 error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
-  --> $DIR/coherence-impls-send.rs:23:1
+  --> $DIR/coherence-impls-send.rs:28:1
    |
 LL | unsafe impl Send for [MyType] {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
@@ -23,7 +23,7 @@ LL | unsafe impl Send for [MyType] {}
    = note: define and implement a trait or new type instead
 
 error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
-  --> $DIR/coherence-impls-send.rs:26:1
+  --> $DIR/coherence-impls-send.rs:32:1
    |
 LL | unsafe impl Send for &'static [NotSync] {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate

src/test/ui/coherence/coherence-impls-send.re.stderr

@@ -0,0 +1,37 @@
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/coherence-impls-send.rs:20:1
+   |
+LL | unsafe impl Send for (MyType, MyType) {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
+   |
+   = note: the impl does not reference any types defined in this crate
+   = note: define and implement a trait or new type instead
+
+error[E0321]: cross-crate traits with a default impl, like `std::marker::Send`, can only be implemented for a struct/enum type, not `&'static NotSync`
+  --> $DIR/coherence-impls-send.rs:24:1
+   |
+LL | unsafe impl Send for &'static NotSync {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't implement cross-crate trait with a default impl for non-struct/enum type
+
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/coherence-impls-send.rs:28:1
+   |
+LL | unsafe impl Send for [MyType] {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
+   |
+   = note: the impl does not reference any types defined in this crate
+   = note: define and implement a trait or new type instead
+
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/coherence-impls-send.rs:32:1
+   |
+LL | unsafe impl Send for &'static [NotSync] {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
+   |
+   = note: the impl does not reference any types defined in this crate
+   = note: define and implement a trait or new type instead
+
+error: aborting due to 4 previous errors
+
+Some errors occurred: E0117, E0321.
+For more information about an error, try `rustc --explain E0117`.

src/test/ui/coherence/coherence-impls-send.rs

@@ -1,3 +1,6 @@
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 #![feature(optin_builtin_traits)]
 #![feature(overlapping_marker_traits)]
 
@@ -15,16 +18,20 @@ impl !Sync for NotSync {}
 unsafe impl Send for TestE {}
 unsafe impl Send for MyType {}
 unsafe impl Send for (MyType, MyType) {}
-//~^ ERROR E0117
+//[old]~^ ERROR E0117
+//[re]~^^ ERROR E0117
 
 unsafe impl Send for &'static NotSync {}
-//~^ ERROR E0321
+//[old]~^ ERROR E0321
+//[re]~^^ ERROR E0321
 
 unsafe impl Send for [MyType] {}
-//~^ ERROR E0117
+//[old]~^ ERROR E0117
+//[re]~^^ ERROR E0117
 
 unsafe impl Send for &'static [NotSync] {}
-//~^ ERROR E0117
+//[old]~^ ERROR E0117
+//[re]~^^ ERROR E0117
 
 fn main() {
 }

src/test/ui/coherence/coherence-impls-sized.old.stderr

@@ -1,61 +1,61 @@
-error[E0322]: explicit impls for the `Sized` trait are not permitted
-  --> $DIR/coherence-impls-sized.rs:14:1
-   |
-LL | impl Sized for TestE {} //~ ERROR E0322
-   | ^^^^^^^^^^^^^^^^^^^^ impl of 'Sized' not allowed
-
 error[E0322]: explicit impls for the `Sized` trait are not permitted
   --> $DIR/coherence-impls-sized.rs:17:1
    |
-LL | impl Sized for MyType {} //~ ERROR E0322
+LL | impl Sized for TestE {}
+   | ^^^^^^^^^^^^^^^^^^^^ impl of 'Sized' not allowed
+
+error[E0322]: explicit impls for the `Sized` trait are not permitted
+  --> $DIR/coherence-impls-sized.rs:22:1
+   |
+LL | impl Sized for MyType {}
    | ^^^^^^^^^^^^^^^^^^^^^ impl of 'Sized' not allowed
 
-error[E0322]: explicit impls for the `Sized` trait are not permitted
-  --> $DIR/coherence-impls-sized.rs:20:1
-   |
-LL | impl Sized for (MyType, MyType) {} //~ ERROR E0322
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl of 'Sized' not allowed
-
-error[E0322]: explicit impls for the `Sized` trait are not permitted
-  --> $DIR/coherence-impls-sized.rs:24:1
-   |
-LL | impl Sized for &'static NotSync {} //~ ERROR E0322
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl of 'Sized' not allowed
-
 error[E0322]: explicit impls for the `Sized` trait are not permitted
   --> $DIR/coherence-impls-sized.rs:27:1
    |
-LL | impl Sized for [MyType] {} //~ ERROR E0322
+LL | impl Sized for (MyType, MyType) {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl of 'Sized' not allowed
+
+error[E0322]: explicit impls for the `Sized` trait are not permitted
+  --> $DIR/coherence-impls-sized.rs:34:1
+   |
+LL | impl Sized for &'static NotSync {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl of 'Sized' not allowed
+
+error[E0322]: explicit impls for the `Sized` trait are not permitted
+  --> $DIR/coherence-impls-sized.rs:39:1
+   |
+LL | impl Sized for [MyType] {}
    | ^^^^^^^^^^^^^^^^^^^^^^^ impl of 'Sized' not allowed
 
 error[E0322]: explicit impls for the `Sized` trait are not permitted
-  --> $DIR/coherence-impls-sized.rs:31:1
+  --> $DIR/coherence-impls-sized.rs:46:1
    |
-LL | impl Sized for &'static [NotSync] {} //~ ERROR E0322
+LL | impl Sized for &'static [NotSync] {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl of 'Sized' not allowed
 
 error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
-  --> $DIR/coherence-impls-sized.rs:20:1
+  --> $DIR/coherence-impls-sized.rs:27:1
    |
-LL | impl Sized for (MyType, MyType) {} //~ ERROR E0322
+LL | impl Sized for (MyType, MyType) {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
    |
    = note: the impl does not reference any types defined in this crate
    = note: define and implement a trait or new type instead
 
 error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
-  --> $DIR/coherence-impls-sized.rs:27:1
+  --> $DIR/coherence-impls-sized.rs:39:1
    |
-LL | impl Sized for [MyType] {} //~ ERROR E0322
+LL | impl Sized for [MyType] {}
    | ^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
    |
    = note: the impl does not reference any types defined in this crate
    = note: define and implement a trait or new type instead
 
 error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
-  --> $DIR/coherence-impls-sized.rs:31:1
+  --> $DIR/coherence-impls-sized.rs:46:1
    |
-LL | impl Sized for &'static [NotSync] {} //~ ERROR E0322
+LL | impl Sized for &'static [NotSync] {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
    |
    = note: the impl does not reference any types defined in this crate

src/test/ui/coherence/coherence-impls-sized.re.stderr

@@ -0,0 +1,67 @@
+error[E0322]: explicit impls for the `Sized` trait are not permitted
+  --> $DIR/coherence-impls-sized.rs:17:1
+   |
+LL | impl Sized for TestE {}
+   | ^^^^^^^^^^^^^^^^^^^^ impl of 'Sized' not allowed
+
+error[E0322]: explicit impls for the `Sized` trait are not permitted
+  --> $DIR/coherence-impls-sized.rs:22:1
+   |
+LL | impl Sized for MyType {}
+   | ^^^^^^^^^^^^^^^^^^^^^ impl of 'Sized' not allowed
+
+error[E0322]: explicit impls for the `Sized` trait are not permitted
+  --> $DIR/coherence-impls-sized.rs:27:1
+   |
+LL | impl Sized for (MyType, MyType) {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl of 'Sized' not allowed
+
+error[E0322]: explicit impls for the `Sized` trait are not permitted
+  --> $DIR/coherence-impls-sized.rs:34:1
+   |
+LL | impl Sized for &'static NotSync {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl of 'Sized' not allowed
+
+error[E0322]: explicit impls for the `Sized` trait are not permitted
+  --> $DIR/coherence-impls-sized.rs:39:1
+   |
+LL | impl Sized for [MyType] {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^ impl of 'Sized' not allowed
+
+error[E0322]: explicit impls for the `Sized` trait are not permitted
+  --> $DIR/coherence-impls-sized.rs:46:1
+   |
+LL | impl Sized for &'static [NotSync] {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl of 'Sized' not allowed
+
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/coherence-impls-sized.rs:27:1
+   |
+LL | impl Sized for (MyType, MyType) {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
+   |
+   = note: the impl does not reference any types defined in this crate
+   = note: define and implement a trait or new type instead
+
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/coherence-impls-sized.rs:39:1
+   |
+LL | impl Sized for [MyType] {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
+   |
+   = note: the impl does not reference any types defined in this crate
+   = note: define and implement a trait or new type instead
+
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/coherence-impls-sized.rs:46:1
+   |
+LL | impl Sized for &'static [NotSync] {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
+   |
+   = note: the impl does not reference any types defined in this crate
+   = note: define and implement a trait or new type instead
+
+error: aborting due to 9 previous errors
+
+Some errors occurred: E0117, E0322.
+For more information about an error, try `rustc --explain E0117`.

src/test/ui/coherence/coherence-impls-sized.rs

@@ -1,3 +1,6 @@
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 #![feature(optin_builtin_traits)]
 
 use std::marker::Copy;
@@ -11,26 +14,41 @@ struct MyType;
 struct NotSync;
 impl !Sync for NotSync {}
 
-impl Sized for TestE {} //~ ERROR E0322
-//~^ impl of 'Sized' not allowed
+impl Sized for TestE {}
+//[old]~^ ERROR E0322
+//[old]~| impl of 'Sized' not allowed
+//[re]~^^^ ERROR E0322
 
-impl Sized for MyType {} //~ ERROR E0322
-//~^ impl of 'Sized' not allowed
+impl Sized for MyType {}
+//[old]~^ ERROR E0322
+//[old]~| impl of 'Sized' not allowed
+//[re]~^^^ ERROR E0322
 
-impl Sized for (MyType, MyType) {} //~ ERROR E0322
-//~^ impl of 'Sized' not allowed
-//~| ERROR E0117
+impl Sized for (MyType, MyType) {}
+//[old]~^ ERROR E0322
+//[old]~| impl of 'Sized' not allowed
+//[old]~| ERROR E0117
+//[re]~^^^^ ERROR E0322
+//[re]~| ERROR E0117
 
-impl Sized for &'static NotSync {} //~ ERROR E0322
-//~^ impl of 'Sized' not allowed
+impl Sized for &'static NotSync {}
+//[old]~^ ERROR E0322
+//[old]~| impl of 'Sized' not allowed
+//[re]~^^^ ERROR E0322
 
-impl Sized for [MyType] {} //~ ERROR E0322
-//~^ impl of 'Sized' not allowed
-//~| ERROR E0117
+impl Sized for [MyType] {}
+//[old]~^ ERROR E0322
+//[old]~| impl of 'Sized' not allowed
+//[old]~| ERROR E0117
+//[re]~^^^^ ERROR E0322
+//[re]~| ERROR E0117
 
-impl Sized for &'static [NotSync] {} //~ ERROR E0322
-//~^ impl of 'Sized' not allowed
-//~| ERROR E0117
+impl Sized for &'static [NotSync] {}
+//[old]~^ ERROR E0322
+//[old]~| impl of 'Sized' not allowed
+//[old]~| ERROR E0117
+//[re]~^^^^ ERROR E0322
+//[re]~| ERROR E0117
 
 fn main() {
 }

src/test/ui/coherence/coherence-inherited-assoc-ty-cycle-err.old.stderr

@@ -1,12 +1,12 @@
 error[E0391]: cycle detected when processing `Trait`
-  --> $DIR/coherence-inherited-assoc-ty-cycle-err.rs:9:1
+  --> $DIR/coherence-inherited-assoc-ty-cycle-err.rs:12:1
    |
 LL | trait Trait<T> { type Assoc; }
    | ^^^^^^^^^^^^^^
    |
    = note: ...which again requires processing `Trait`, completing the cycle
 note: cycle used when coherence checking all impls of trait `Trait`
-  --> $DIR/coherence-inherited-assoc-ty-cycle-err.rs:9:1
+  --> $DIR/coherence-inherited-assoc-ty-cycle-err.rs:12:1
    |
 LL | trait Trait<T> { type Assoc; }
    | ^^^^^^^^^^^^^^

src/test/ui/coherence/coherence-inherited-assoc-ty-cycle-err.re.stderr

@@ -0,0 +1,16 @@
+error[E0391]: cycle detected when processing `Trait`
+  --> $DIR/coherence-inherited-assoc-ty-cycle-err.rs:12:1
+   |
+LL | trait Trait<T> { type Assoc; }
+   | ^^^^^^^^^^^^^^
+   |
+   = note: ...which again requires processing `Trait`, completing the cycle
+note: cycle used when coherence checking all impls of trait `Trait`
+  --> $DIR/coherence-inherited-assoc-ty-cycle-err.rs:12:1
+   |
+LL | trait Trait<T> { type Assoc; }
+   | ^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0391`.

src/test/ui/coherence/coherence-inherited-assoc-ty-cycle-err.rs

@@ -4,10 +4,14 @@
 //
 // No we expect to run into a more user-friendly cycle error instead.
 
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 #![feature(specialization)]
 
 trait Trait<T> { type Assoc; }
-//~^ cycle detected
+//[old]~^ cycle detected
+//[re]~^^ ERROR E0391
 
 impl<T> Trait<T> for Vec<T> {
     type Assoc = ();

src/test/ui/coherence/coherence-lone-type-parameter.old.stderr

@@ -1,5 +1,5 @@
 error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
-  --> $DIR/coherence-lone-type-parameter.rs:6:1
+  --> $DIR/coherence-lone-type-parameter.rs:9:1
    |
 LL | impl<T> Remote for T { }
    | ^^^^^^^^^^^^^^^^^^^^ type parameter `T` must be used as the type parameter for some local type

src/test/ui/coherence/coherence-lone-type-parameter.re.stderr

@@ -0,0 +1,11 @@
+error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
+  --> $DIR/coherence-lone-type-parameter.rs:9:1
+   |
+LL | impl<T> Remote for T { }
+   | ^^^^^^^^^^^^^^^^^^^^ type parameter `T` must be used as the type parameter for some local type
+   |
+   = note: only traits defined in the current crate can be implemented for a type parameter
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0210`.

src/test/ui/coherence/coherence-lone-type-parameter.rs

@@ -1,9 +1,14 @@
 // aux-build:coherence_lib.rs
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 
 extern crate coherence_lib as lib;
 use lib::Remote;
 
 impl<T> Remote for T { }
-//~^ ERROR type parameter `T` must be used as the type parameter for some local type
+//[old]~^ ERROR type parameter `T` must be used as the type parameter for some local type
+//[re]~^^ ERROR E0210
+
 
 fn main() { }

src/test/ui/coherence/coherence-negative-impls-safe.old.stderr

@@ -1,5 +1,5 @@
 error[E0198]: negative impls cannot be unsafe
-  --> $DIR/coherence-negative-impls-safe.rs:7:1
+  --> $DIR/coherence-negative-impls-safe.rs:10:1
    |
 LL | unsafe impl !Send for TestType {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/coherence/coherence-negative-impls-safe.re.stderr

@@ -0,0 +1,9 @@
+error[E0198]: negative impls cannot be unsafe
+  --> $DIR/coherence-negative-impls-safe.rs:10:1
+   |
+LL | unsafe impl !Send for TestType {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0198`.

src/test/ui/coherence/coherence-negative-impls-safe.rs

@@ -1,3 +1,6 @@
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 #![feature(optin_builtin_traits)]
 
 use std::marker::Send;
@@ -5,6 +8,7 @@ use std::marker::Send;
 struct TestType;
 
 unsafe impl !Send for TestType {}
-//~^ ERROR negative impls cannot be unsafe
+//[old]~^ ERROR negative impls cannot be unsafe
+//[re]~^^ ERROR E0198
 
 fn main() {}

src/test/ui/coherence/coherence-no-direct-lifetime-dispatch.old.stderr

@@ -1,9 +1,9 @@
 error[E0119]: conflicting implementations of trait `MyTrait`:
-  --> $DIR/coherence-no-direct-lifetime-dispatch.rs:6:1
+  --> $DIR/coherence-no-direct-lifetime-dispatch.rs:10:1
    |
 LL | impl<T> MyTrait for T {}
    | --------------------- first implementation here
-LL | impl<T: 'static> MyTrait for T {} //~ ERROR E0119
+LL | impl<T: 'static> MyTrait for T {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation
 
 error: aborting due to previous error

src/test/ui/coherence/coherence-no-direct-lifetime-dispatch.re.stderr

@@ -0,0 +1,11 @@
+error[E0119]: conflicting implementations of trait `MyTrait`:
+  --> $DIR/coherence-no-direct-lifetime-dispatch.rs:10:1
+   |
+LL | impl<T> MyTrait for T {}
+   | --------------------- first implementation here
+LL | impl<T: 'static> MyTrait for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0119`.

src/test/ui/coherence/coherence-no-direct-lifetime-dispatch.rs

@@ -1,8 +1,14 @@
 // Test that you cannot *directly* dispatch on lifetime requirements
 
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
+
 trait MyTrait { fn foo() {} }
 
 impl<T> MyTrait for T {}
-impl<T: 'static> MyTrait for T {} //~ ERROR E0119
+impl<T: 'static> MyTrait for T {}
+//[old]~^ ERROR E0119
+//[re]~^^ ERROR E0119
 
 fn main() {}

src/test/ui/coherence/coherence-orphan.old.stderr

@@ -1,5 +1,5 @@
 error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
-  --> $DIR/coherence-orphan.rs:11:1
+  --> $DIR/coherence-orphan.rs:13:1
    |
 LL | impl TheTrait<usize> for isize { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
@@ -8,7 +8,7 @@ LL | impl TheTrait<usize> for isize { }
    = note: define and implement a trait or new type instead
 
 error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
-  --> $DIR/coherence-orphan.rs:18:1
+  --> $DIR/coherence-orphan.rs:21:1
    |
 LL | impl !Send for Vec<isize> { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate

src/test/ui/coherence/coherence-orphan.re.stderr

@@ -0,0 +1,21 @@
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/coherence-orphan.rs:13:1
+   |
+LL | impl TheTrait<usize> for isize { }
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
+   |
+   = note: the impl does not reference any types defined in this crate
+   = note: define and implement a trait or new type instead
+
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/coherence-orphan.rs:21:1
+   |
+LL | impl !Send for Vec<isize> { }
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
+   |
+   = note: the impl does not reference any types defined in this crate
+   = note: define and implement a trait or new type instead
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0117`.

src/test/ui/coherence/coherence-orphan.rs

@@ -1,5 +1,7 @@
 // aux-build:coherence_orphan_lib.rs
+// revisions: old re
 
+#![cfg_attr(re, feature(re_rebalance_coherence))]
 #![feature(optin_builtin_traits)]
 
 extern crate coherence_orphan_lib as lib;
@@ -9,13 +11,15 @@ use lib::TheTrait;
 struct TheType;
 
 impl TheTrait<usize> for isize { }
-//~^ ERROR E0117
+//[old]~^ ERROR E0117
+//[re]~^^ ERROR E0117
 
 impl TheTrait<TheType> for isize { }
 
 impl TheTrait<isize> for TheType { }
 
 impl !Send for Vec<isize> { }
-//~^ ERROR E0117
+//[old]~^ ERROR E0117
+//[re]~^^ ERROR E0117
 
 fn main() { }

src/test/ui/coherence/coherence-overlap-all-t-and-tuple.old.stderr

@@ -1,10 +1,10 @@
 error[E0119]: conflicting implementations of trait `From<(_,)>` for type `(_,)`:
-  --> $DIR/coherence-overlap-all-t-and-tuple.rs:16:1
+  --> $DIR/coherence-overlap-all-t-and-tuple.rs:20:1
    |
 LL | impl <T> From<T> for T {
    | ---------------------- first implementation here
 ...
-LL | impl <T11, U11> From<(U11,)> for (T11,) { //~ ERROR E0119
+LL | impl <T11, U11> From<(U11,)> for (T11,) {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(_,)`
 
 error: aborting due to previous error

src/test/ui/coherence/coherence-overlap-all-t-and-tuple.re.stderr

@@ -0,0 +1,12 @@
+error[E0119]: conflicting implementations of trait `From<(_,)>` for type `(_,)`:
+  --> $DIR/coherence-overlap-all-t-and-tuple.rs:20:1
+   |
+LL | impl <T> From<T> for T {
+   | ---------------------- first implementation here
+...
+LL | impl <T11, U11> From<(U11,)> for (T11,) {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(_,)`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0119`.

src/test/ui/coherence/coherence-overlap-all-t-and-tuple.rs

@@ -6,6 +6,10 @@
 //
 // Seems pretty basic, but then there was issue #24241. :)
 
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
+
 trait From<U> {
     fn foo() {}
 }
@@ -13,7 +17,9 @@ trait From<U> {
 impl <T> From<T> for T {
 }
 
-impl <T11, U11> From<(U11,)> for (T11,) { //~ ERROR E0119
+impl <T11, U11> From<(U11,)> for (T11,) {
+//[old]~^ ERROR E0119
+//[re]~^^ ERROR E0119
 }
 
 fn main() { }

src/test/ui/coherence/coherence-overlap-downstream-inherent.old.stderr

@@ -1,18 +1,18 @@
 error[E0592]: duplicate definitions with name `dummy`
-  --> $DIR/coherence-overlap-downstream-inherent.rs:7:26
+  --> $DIR/coherence-overlap-downstream-inherent.rs:11:26
    |
 LL | impl<T:Sugar> Sweet<T> { fn dummy(&self) { } }
    |                          ^^^^^^^^^^^^^^^^^^^ duplicate definitions for `dummy`
-LL | //~^ ERROR E0592
+...
 LL | impl<T:Fruit> Sweet<T> { fn dummy(&self) { } }
    |                          ------------------- other definition for `dummy`
 
 error[E0592]: duplicate definitions with name `f`
-  --> $DIR/coherence-overlap-downstream-inherent.rs:13:38
+  --> $DIR/coherence-overlap-downstream-inherent.rs:18:38
    |
 LL | impl<X, T> A<T, X> where T: Bar<X> { fn f(&self) {} }
    |                                      ^^^^^^^^^^^^^^ duplicate definitions for `f`
-LL | //~^ ERROR E0592
+...
 LL | impl<X> A<i32, X> { fn f(&self) {} }
    |                     -------------- other definition for `f`
    |

src/test/ui/coherence/coherence-overlap-downstream-inherent.re.stderr

@@ -0,0 +1,23 @@
+error[E0592]: duplicate definitions with name `dummy`
+  --> $DIR/coherence-overlap-downstream-inherent.rs:11:26
+   |
+LL | impl<T:Sugar> Sweet<T> { fn dummy(&self) { } }
+   |                          ^^^^^^^^^^^^^^^^^^^ duplicate definitions for `dummy`
+...
+LL | impl<T:Fruit> Sweet<T> { fn dummy(&self) { } }
+   |                          ------------------- other definition for `dummy`
+
+error[E0592]: duplicate definitions with name `f`
+  --> $DIR/coherence-overlap-downstream-inherent.rs:18:38
+   |
+LL | impl<X, T> A<T, X> where T: Bar<X> { fn f(&self) {} }
+   |                                      ^^^^^^^^^^^^^^ duplicate definitions for `f`
+...
+LL | impl<X> A<i32, X> { fn f(&self) {} }
+   |                     -------------- other definition for `f`
+   |
+   = note: downstream crates may implement trait `Bar<_>` for type `i32`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0592`.

src/test/ui/coherence/coherence-overlap-downstream-inherent.rs

@@ -1,17 +1,23 @@
 // Tests that we consider `T: Sugar + Fruit` to be ambiguous, even
 // though no impls are found.
 
+// revisions: old re
+
+#![cfg_attr(re, feature(re_rebalance_coherence))]
+
 struct Sweet<X>(X);
 pub trait Sugar {}
 pub trait Fruit {}
 impl<T:Sugar> Sweet<T> { fn dummy(&self) { } }
-//~^ ERROR E0592
+//[old]~^ ERROR E0592
+//[re]~^^ ERROR E0592
 impl<T:Fruit> Sweet<T> { fn dummy(&self) { } }
 
 trait Bar<X> {}
 struct A<T, X>(T, X);
 impl<X, T> A<T, X> where T: Bar<X> { fn f(&self) {} }
-//~^ ERROR E0592
+//[old]~^ ERROR E0592
+//[re]~^^ ERROR E0592
 impl<X> A<i32, X> { fn f(&self) {} }
 
 fn main() {}