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 f7f787dea95..26c0b3beb37 100644 --- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs +++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs @@ -3807,13 +3807,13 @@ fn hint_missing_borrow<'tcx>( err: &mut Diagnostic, ) { let found_args = match found.kind() { - ty::FnPtr(f) => f.inputs().skip_binder().iter(), + ty::FnPtr(f) => infcx.replace_bound_vars_with_placeholders(*f).inputs().iter(), kind => { span_bug!(span, "found was converted to a FnPtr above but is now {:?}", kind) } }; let expected_args = match expected.kind() { - ty::FnPtr(f) => f.inputs().skip_binder().iter(), + ty::FnPtr(f) => infcx.replace_bound_vars_with_placeholders(*f).inputs().iter(), kind => { span_bug!(span, "expected was converted to a FnPtr above but is now {:?}", kind) } @@ -3824,12 +3824,12 @@ fn hint_missing_borrow<'tcx>( let args = fn_decl.inputs.iter().map(|ty| ty); - fn get_deref_type_and_refs(mut ty: Ty<'_>) -> (Ty<'_>, usize) { - let mut refs = 0; + fn get_deref_type_and_refs(mut ty: Ty<'_>) -> (Ty<'_>, Vec) { + let mut refs = vec![]; - while let ty::Ref(_, new_ty, _) = ty.kind() { + while let ty::Ref(_, new_ty, mutbl) = ty.kind() { ty = *new_ty; - refs += 1; + refs.push(*mutbl); } (ty, refs) @@ -3843,11 +3843,21 @@ fn hint_missing_borrow<'tcx>( let (expected_ty, expected_refs) = get_deref_type_and_refs(*expected_arg); if infcx.can_eq(param_env, found_ty, expected_ty).is_ok() { - if found_refs < expected_refs { - to_borrow.push((arg.span.shrink_to_lo(), "&".repeat(expected_refs - found_refs))); - } else if found_refs > expected_refs { + // FIXME: This could handle more exotic cases like mutability mismatches too! + if found_refs.len() < expected_refs.len() + && found_refs[..] == expected_refs[expected_refs.len() - found_refs.len()..] + { + to_borrow.push(( + arg.span.shrink_to_lo(), + expected_refs[..expected_refs.len() - found_refs.len()] + .iter() + .map(|mutbl| format!("&{}", mutbl.prefix_str())) + .collect::>() + .join(""), + )); + } else if found_refs.len() > expected_refs.len() { let mut span = arg.span.shrink_to_lo(); - let mut left = found_refs - expected_refs; + let mut left = found_refs.len() - expected_refs.len(); let mut ty = arg; while let hir::TyKind::Ref(_, mut_ty) = &ty.kind && left > 0 { span = span.with_hi(mut_ty.ty.span.lo()); diff --git a/tests/ui/suggestions/late-bound-in-borrow-closure-sugg.rs b/tests/ui/suggestions/late-bound-in-borrow-closure-sugg.rs new file mode 100644 index 00000000000..3bf6b7bb9b1 --- /dev/null +++ b/tests/ui/suggestions/late-bound-in-borrow-closure-sugg.rs @@ -0,0 +1,28 @@ +use std::cell::RefCell; +use std::collections::HashMap; +use std::rc::Rc; + +pub struct Trader<'a> { + closure: Box, +} + +impl<'a> Trader<'a> { + pub fn new() -> Self { + Trader { + closure: Box::new(|_| {}), + } + } + pub fn set_closure(&mut self, function: impl Fn(&mut Trader) + 'a) { + //foo + } +} + +fn main() { + let closure = |trader : Trader| { + println!("Woooosh!"); + }; + + let mut trader = Trader::new(); + trader.set_closure(closure); + //~^ ERROR type mismatch in closure arguments +} diff --git a/tests/ui/suggestions/late-bound-in-borrow-closure-sugg.stderr b/tests/ui/suggestions/late-bound-in-borrow-closure-sugg.stderr new file mode 100644 index 00000000000..6820af1fd45 --- /dev/null +++ b/tests/ui/suggestions/late-bound-in-borrow-closure-sugg.stderr @@ -0,0 +1,26 @@ +error[E0631]: type mismatch in closure arguments + --> $DIR/late-bound-in-borrow-closure-sugg.rs:26:24 + | +LL | let closure = |trader : Trader| { + | ----------------- found signature defined here +... +LL | trader.set_closure(closure); + | ----------- ^^^^^^^ expected due to this + | | + | required by a bound introduced by this call + | + = note: expected closure signature `for<'a, 'b> fn(&'a mut Trader<'b>) -> _` + found closure signature `for<'a> fn(Trader<'a>) -> _` +note: required by a bound in `Trader::<'a>::set_closure` + --> $DIR/late-bound-in-borrow-closure-sugg.rs:15:50 + | +LL | pub fn set_closure(&mut self, function: impl Fn(&mut Trader) + 'a) { + | ^^^^^^^^^^^^^^^ required by this bound in `Trader::<'a>::set_closure` +help: consider borrowing the argument + | +LL | let closure = |trader : &mut Trader| { + | ++++ + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0631`.