From d51ef5c1afc6491d9c224e12cc5c1e72a58bf81a Mon Sep 17 00:00:00 2001
From: lcnr <rust@lcnr.de>
Date: Thu, 23 Nov 2023 12:25:41 +0000
Subject: [PATCH] fix intercrate ambiguity causes

---
 .../src/traits/coherence.rs                   |  6 ++--
 .../{E0476.stderr => E0476.next.stderr}       |  8 ++---
 tests/ui/error-codes/E0476.old.stderr         | 31 +++++++++++++++++++
 tests/ui/error-codes/E0476.rs                 |  2 ++
 4 files changed, 41 insertions(+), 6 deletions(-)
 rename tests/ui/error-codes/{E0476.stderr => E0476.next.stderr} (92%)
 create mode 100644 tests/ui/error-codes/E0476.old.stderr

diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs
index 9119792e32439..f3993ec256676 100644
--- a/compiler/rustc_trait_selection/src/traits/coherence.rs
+++ b/compiler/rustc_trait_selection/src/traits/coherence.rs
@@ -1050,8 +1050,10 @@ impl<'a, 'tcx> ProofTreeVisitor<'tcx> for AmbiguityCausesVisitor<'a> {
         let mut ambiguity_cause = None;
         for cand in goal.candidates() {
             // FIXME: boiiii, using string comparisions here sure is scuffed.
-            if let inspect::ProbeKind::MiscCandidate { name: "coherence unknowable", result: _ } =
-                cand.kind()
+            if let inspect::ProbeKind::MiscCandidate {
+                name: "coherence unknowable",
+                result: Ok(_),
+            } = cand.kind()
             {
                 let lazily_normalize_ty = |ty: Ty<'tcx>| {
                     let mut fulfill_cx = <dyn TraitEngine<'tcx>>::new(infcx);
diff --git a/tests/ui/error-codes/E0476.stderr b/tests/ui/error-codes/E0476.next.stderr
similarity index 92%
rename from tests/ui/error-codes/E0476.stderr
rename to tests/ui/error-codes/E0476.next.stderr
index 0378ac6e8ec91..454dbecc7d01f 100644
--- a/tests/ui/error-codes/E0476.stderr
+++ b/tests/ui/error-codes/E0476.next.stderr
@@ -1,5 +1,5 @@
 error[E0119]: conflicting implementations of trait `CoerceUnsized<&Wrapper<_>>` for type `&Wrapper<_>`
-  --> $DIR/E0476.rs:9:1
+  --> $DIR/E0476.rs:11:1
    |
 LL | impl<'a, 'b, T, S> CoerceUnsized<&'a Wrapper<T>> for &'b Wrapper<S> where S: Unsize<T> {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -9,18 +9,18 @@ LL | impl<'a, 'b, T, S> CoerceUnsized<&'a Wrapper<T>> for &'b Wrapper<S> where S
              where 'b: 'a, T: Unsize<U>, T: ?Sized, U: ?Sized;
 
 error[E0476]: lifetime of the source pointer does not outlive lifetime bound of the object type
-  --> $DIR/E0476.rs:9:1
+  --> $DIR/E0476.rs:11:1
    |
 LL | impl<'a, 'b, T, S> CoerceUnsized<&'a Wrapper<T>> for &'b Wrapper<S> where S: Unsize<T> {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
 note: object type is valid for the lifetime `'a` as defined here
-  --> $DIR/E0476.rs:9:6
+  --> $DIR/E0476.rs:11:6
    |
 LL | impl<'a, 'b, T, S> CoerceUnsized<&'a Wrapper<T>> for &'b Wrapper<S> where S: Unsize<T> {}
    |      ^^
 note: source pointer is only valid for the lifetime `'b` as defined here
-  --> $DIR/E0476.rs:9:10
+  --> $DIR/E0476.rs:11:10
    |
 LL | impl<'a, 'b, T, S> CoerceUnsized<&'a Wrapper<T>> for &'b Wrapper<S> where S: Unsize<T> {}
    |          ^^
diff --git a/tests/ui/error-codes/E0476.old.stderr b/tests/ui/error-codes/E0476.old.stderr
new file mode 100644
index 0000000000000..454dbecc7d01f
--- /dev/null
+++ b/tests/ui/error-codes/E0476.old.stderr
@@ -0,0 +1,31 @@
+error[E0119]: conflicting implementations of trait `CoerceUnsized<&Wrapper<_>>` for type `&Wrapper<_>`
+  --> $DIR/E0476.rs:11:1
+   |
+LL | impl<'a, 'b, T, S> CoerceUnsized<&'a Wrapper<T>> for &'b Wrapper<S> where S: Unsize<T> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: conflicting implementation in crate `core`:
+           - impl<'a, 'b, T, U> CoerceUnsized<&'a U> for &'b T
+             where 'b: 'a, T: Unsize<U>, T: ?Sized, U: ?Sized;
+
+error[E0476]: lifetime of the source pointer does not outlive lifetime bound of the object type
+  --> $DIR/E0476.rs:11:1
+   |
+LL | impl<'a, 'b, T, S> CoerceUnsized<&'a Wrapper<T>> for &'b Wrapper<S> where S: Unsize<T> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: object type is valid for the lifetime `'a` as defined here
+  --> $DIR/E0476.rs:11:6
+   |
+LL | impl<'a, 'b, T, S> CoerceUnsized<&'a Wrapper<T>> for &'b Wrapper<S> where S: Unsize<T> {}
+   |      ^^
+note: source pointer is only valid for the lifetime `'b` as defined here
+  --> $DIR/E0476.rs:11:10
+   |
+LL | impl<'a, 'b, T, S> CoerceUnsized<&'a Wrapper<T>> for &'b Wrapper<S> where S: Unsize<T> {}
+   |          ^^
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0119, E0476.
+For more information about an error, try `rustc --explain E0119`.
diff --git a/tests/ui/error-codes/E0476.rs b/tests/ui/error-codes/E0476.rs
index d5e4b8d237274..e9afc7567260f 100644
--- a/tests/ui/error-codes/E0476.rs
+++ b/tests/ui/error-codes/E0476.rs
@@ -1,3 +1,5 @@
+// revisions: old next
+//[next] compile-flags: -Ztrait-solver=next-coherence
 #![feature(coerce_unsized)]
 #![feature(unsize)]