diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs index 44602e6289940..e1073de49d305 100644 --- a/compiler/rustc_hir_typeck/src/method/suggest.rs +++ b/compiler/rustc_hir_typeck/src/method/suggest.rs @@ -2547,6 +2547,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { "you must specify a type for this binding, like `{concrete_type}`", ); + // FIXME: Maybe FileName::Anon should also be handled, + // otherwise there would be no suggestion if the source is STDIN for example. match (filename, parent_node) { ( FileName::Real(_), @@ -2568,6 +2570,44 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { Applicability::MaybeIncorrect, ); } + // For closure parameters with reference patterns (e.g., |&v|), suggest the type annotation + // on the pattern itself, e.g., |&v: &i32| + (FileName::Real(_), Node::Pat(pat)) + if let Node::Pat(binding_pat) = self.tcx.hir_node(hir_id) + && let hir::PatKind::Binding(..) = binding_pat.kind + && let Node::Pat(parent_pat) = parent_node + && 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!(": {type_annotation}"), + Applicability::MaybeIncorrect, + ); + } _ => { err.span_label(span, msg); } diff --git a/tests/ui/inference/ambiguous-numeric-in-closure-ref.fixed b/tests/ui/inference/ambiguous-numeric-in-closure-ref.fixed new file mode 100644 index 0000000000000..683d581d034b1 --- /dev/null +++ b/tests/ui/inference/ambiguous-numeric-in-closure-ref.fixed @@ -0,0 +1,14 @@ +// Test for better error message when numeric type is ambiguous in closure parameter with reference + +//@ run-rustfix + +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 new file mode 100644 index 0000000000000..eab309c701d69 --- /dev/null +++ b/tests/ui/inference/ambiguous-numeric-in-closure-ref.rs @@ -0,0 +1,14 @@ +// Test for better error message when numeric type is ambiguous in closure parameter with reference + +//@ run-rustfix + +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 new file mode 100644 index 0000000000000..0789581abea80 --- /dev/null +++ b/tests/ui/inference/ambiguous-numeric-in-closure-ref.stderr @@ -0,0 +1,29 @@ +error[E0689]: can't call method `pow` on ambiguous numeric type `{integer}` + --> $DIR/ambiguous-numeric-in-closure-ref.rs:6:35 + | +LL | let _ = (0..10).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 _ = (0..10).filter(|&v: &i32| v.pow(2) > 0); + | ++++++ + +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`.