Rollup merge of #114322 - Urgau:fix-issue-110063, r=compiler-errors

Fix invalid slice coercion suggestion reported in turbofish

This PR fixes the invalid slice coercion suggestion reported in turbofish and inferred generics by not emitting them.

Fixes https://github.com/rust-lang/rust/issues/110063

2 files changed, 12 insertions, 3 deletions

diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
index 14020c05251..95485850d0e 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
@@ -3030,8 +3030,9 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                 self.report_similar_impl_candidates_for_root_obligation(&obligation, *trait_predicate, body_def_id, err);
             }
 
-            self.maybe_suggest_convert_to_slice(
+            self.suggest_convert_to_slice(
                 err,
+                obligation,
                 trait_ref,
                 impl_candidates.as_slice(),
                 span,
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
index 31f70bbd34d..46c31c77613 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -398,9 +398,10 @@ pub trait TypeErrCtxtExt<'tcx> {
         param_env: ty::ParamEnv<'tcx>,
     ) -> Vec<Option<(Span, (DefId, Ty<'tcx>))>>;
 
-    fn maybe_suggest_convert_to_slice(
+    fn suggest_convert_to_slice(
         &self,
         err: &mut Diagnostic,
+        obligation: &PredicateObligation<'tcx>,
         trait_ref: ty::PolyTraitRef<'tcx>,
         candidate_impls: &[ImplCandidate<'tcx>],
         span: Span,
@@ -3944,13 +3945,20 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
     /// If the type that failed selection is an array or a reference to an array,
     /// but the trait is implemented for slices, suggest that the user converts
     /// the array into a slice.
-    fn maybe_suggest_convert_to_slice(
+    fn suggest_convert_to_slice(
         &self,
         err: &mut Diagnostic,
+        obligation: &PredicateObligation<'tcx>,
         trait_ref: ty::PolyTraitRef<'tcx>,
         candidate_impls: &[ImplCandidate<'tcx>],
         span: Span,
     ) {
+        // We can only suggest the slice coersion for function arguments since the suggestion
+        // would make no sense in turbofish or call
+        let ObligationCauseCode::FunctionArgumentObligation { .. } = obligation.cause.code() else {
+            return;
+        };
+
         // Three cases where we can make a suggestion:
         // 1. `[T; _]` (array of T)
         // 2. `&[T; _]` (reference to array of T)