Fix ICE for ambiguous candidates on method probing

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -2383,18 +2383,24 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             }
         }
 
-        // They are all the same, so if any of them is ambiguous, we report the pick as ambiguous.
-        let is_ambiguously_imported = probes.iter().any(|(p, _)| match p.kind {
-            TraitCandidate { is_ambiguously_imported, .. } => is_ambiguously_imported,
-            _ => false,
+        let ambiguously_imported_import_ids = probes.iter().find_map(|(p, _)| match p.kind {
+            TraitCandidate { is_ambiguously_imported, .. } => {
+                is_ambiguously_imported.then_some(p.import_ids)
+            }
+            _ => None,
         });
 
+        let (is_ambiguously_imported, import_ids) = match ambiguously_imported_import_ids {
+            Some(import_ids) => (true, import_ids),
+            None => (false, probes[0].0.import_ids),
+        };
+
         // FIXME: check the return type here somehow.
         // If so, just use this trait and call it a day.
         Some(Pick {
             item: probes[0].0.item,
             kind: TraitPick { is_ambiguously_imported },
-            import_ids: probes[0].0.import_ids,
+            import_ids,
             autoderefs: 0,
             autoref_or_ptr_adjustment: None,
             self_ty,

tests/ui/imports/ambiguous-trait-with-mixed-import-paths.rs

@@ -0,0 +1,29 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/162857>.
+//@ check-pass
+
+mod vis1 {
+    pub trait Visitor {
+        fn visit_b(&self);
+        fn visit_c(&self);
+    }
+}
+
+mod vis2 {
+    pub trait Visitor {}
+}
+
+use crate::{vis1::*, vis2::*};
+
+pub struct Impl;
+
+impl vis1::Visitor for Impl {
+    fn visit_b(&self) {}
+
+    fn visit_c(&self) {
+        self.visit_b();
+        //~^ WARN: use of ambiguously glob imported trait `Visitor` [ambiguous_glob_imported_traits]
+        //~| WARN: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+    }
+}
+
+fn main() {}

tests/ui/imports/ambiguous-trait-with-mixed-import-paths.stderr

@@ -0,0 +1,16 @@
+warning: use of ambiguously glob imported trait `Visitor`
+  --> $DIR/ambiguous-trait-with-mixed-import-paths.rs:23:14
+   |
+LL | use crate::{vis1::*, vis2::*};
+   |             ---- `Visitor` imported ambiguously here
+...
+LL |         self.visit_b();
+   |              ^^^^^^^
+   |
+   = help: import `Visitor` 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 #152822 <https://github.com/rust-lang/rust/issues/152822>
+   = note: `#[warn(ambiguous_glob_imported_traits)]` (part of `#[warn(future_incompatible)]`) on by default
+
+warning: 1 warning emitted
+