diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs index 3c3c979c05ec..a2ec7075fac9 100644 --- a/compiler/rustc_hir_typeck/src/method/suggest.rs +++ b/compiler/rustc_hir_typeck/src/method/suggest.rs @@ -2577,10 +2577,32 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { && matches!(parent_pat.kind, hir::PatKind::Ref(..)) => { err.span_label(span, "you must specify a type for this binding"); + + let mut ref_muts = Vec::new(); + let mut current_node = parent_node; + + while let Node::Pat(parent_pat) = current_node { + if let hir::PatKind::Ref(_, mutability) = parent_pat.kind { + ref_muts.push(mutability); + current_node = self.tcx.parent_hir_node(parent_pat.hir_id); + } else { + break; + } + } + + let mut type_annotation = String::new(); + for mutability in ref_muts.iter().rev() { + match mutability { + hir::Mutability::Mut => type_annotation.push_str("&mut "), + hir::Mutability::Not => type_annotation.push('&'), + } + } + type_annotation.push_str(&concrete_type); + err.span_suggestion_verbose( pat.span.shrink_to_hi(), "specify the type in the closure argument list", - format!(": &{concrete_type}"), + format!(": {type_annotation}"), Applicability::MaybeIncorrect, ); } diff --git a/tests/ui/inference/ambiguous-numeric-in-closure-ref.fixed b/tests/ui/inference/ambiguous-numeric-in-closure-ref.fixed index 0bb81c7df125..683d581d034b 100644 --- a/tests/ui/inference/ambiguous-numeric-in-closure-ref.fixed +++ b/tests/ui/inference/ambiguous-numeric-in-closure-ref.fixed @@ -6,4 +6,9 @@ fn main() { let _ = (0..10).filter(|&v: &i32| v.pow(2) > 0); //~^ ERROR can't call method `pow` on ambiguous numeric type `{integer}` //~| SUGGESTION &i32 + + let v = vec![0, 1, 2]; + let _ = v.iter().filter(|&&v: &&i32| v.pow(2) > 0); + //~^ ERROR can't call method `pow` on ambiguous numeric type `{integer}` + //~| SUGGESTION &&i32 } diff --git a/tests/ui/inference/ambiguous-numeric-in-closure-ref.rs b/tests/ui/inference/ambiguous-numeric-in-closure-ref.rs index 7a6f779ab832..eab309c701d6 100644 --- a/tests/ui/inference/ambiguous-numeric-in-closure-ref.rs +++ b/tests/ui/inference/ambiguous-numeric-in-closure-ref.rs @@ -6,4 +6,9 @@ fn main() { let _ = (0..10).filter(|&v| v.pow(2) > 0); //~^ ERROR can't call method `pow` on ambiguous numeric type `{integer}` //~| SUGGESTION &i32 + + let v = vec![0, 1, 2]; + let _ = v.iter().filter(|&&v| v.pow(2) > 0); + //~^ ERROR can't call method `pow` on ambiguous numeric type `{integer}` + //~| SUGGESTION &&i32 } diff --git a/tests/ui/inference/ambiguous-numeric-in-closure-ref.stderr b/tests/ui/inference/ambiguous-numeric-in-closure-ref.stderr index a2225d940a30..0789581abea8 100644 --- a/tests/ui/inference/ambiguous-numeric-in-closure-ref.stderr +++ b/tests/ui/inference/ambiguous-numeric-in-closure-ref.stderr @@ -11,6 +11,19 @@ help: specify the type in the closure argument list LL | let _ = (0..10).filter(|&v: &i32| v.pow(2) > 0); | ++++++ -error: aborting due to 1 previous error +error[E0689]: can't call method `pow` on ambiguous numeric type `{integer}` + --> $DIR/ambiguous-numeric-in-closure-ref.rs:11:37 + | +LL | let _ = v.iter().filter(|&&v| v.pow(2) > 0); + | - ^^^ + | | + | you must specify a type for this binding + | +help: specify the type in the closure argument list + | +LL | let _ = v.iter().filter(|&&v: &&i32| v.pow(2) > 0); + | +++++++ + +error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0689`.