Preserve ambiguous glob lint for subtrait method picks

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -2415,7 +2415,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             }
         }
 
-        let lint_ambiguous = match probes[0].0.kind {
+        let lint_ambiguous = match child_candidate.kind {
             TraitCandidate(_, lint) => lint,
             _ => false,
         };

tests/ui/methods/supertrait-shadowing/ambiguous-glob-imported-subtrait.rs

@@ -0,0 +1,38 @@
+//@ check-fail
+//@ normalize-stderr: "error: aborting due to 1 previous error\n\n" -> "error: aborting due to 1 previous error\n"
+
+#![feature(supertrait_item_shadowing)]
+#![deny(ambiguous_glob_imported_traits)]
+#![allow(dead_code, unused_imports)]
+
+trait DefaultPolicy {
+    fn allow_action(&self) -> bool {
+        false
+    }
+}
+
+mod first_policy {
+    pub trait Role: crate::DefaultPolicy {
+        fn allow_action(&self) -> bool {
+            true
+        }
+    }
+
+    impl crate::DefaultPolicy for u8 {}
+    impl Role for u8 {}
+}
+
+mod second_policy {
+    pub trait Role: crate::DefaultPolicy {
+        fn audit_only(&self) {}
+    }
+}
+
+use first_policy::*;
+use second_policy::*;
+
+fn main() {
+    assert!(0u8.allow_action());
+    //~^ ERROR Use of ambiguously glob imported trait `Role`
+    //~| WARN this was previously accepted by the compiler but is being phased out
+}

tests/ui/methods/supertrait-shadowing/ambiguous-glob-imported-subtrait.stderr

@@ -0,0 +1,19 @@
+error: Use of ambiguously glob imported trait `Role`
+  --> $DIR/ambiguous-glob-imported-subtrait.rs:35:17
+   |
+LL | use first_policy::*;
+   |     ------------ `Role` imported ambiguously here
+...
+LL |     assert!(0u8.allow_action());
+   |                 ^^^^^^^^^^^^
+   |
+   = help: Import `Role` explicitly
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #147992 <https://github.com/rust-lang/rust/issues/147992>
+note: the lint level is defined here
+  --> $DIR/ambiguous-glob-imported-subtrait.rs:5:9
+   |
+LL | #![deny(ambiguous_glob_imported_traits)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error