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Improve presentation of closure signature mismatch from Fn trait goal

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This commit is contained in:
Michael Goulet 2025-04-08 05:54:44 +00:00
parent c6c179662d
commit c5320454ed
5 changed files with 63 additions and 37 deletions
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76
compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
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@ -2,6 +2,7 @@ use core::ops::ControlFlow;
use std::borrow::Cow;
use std::path::PathBuf;
use rustc_abi::ExternAbi;
use rustc_ast::TraitObjectSyntax;
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::unord::UnordSet;
@ -2799,32 +2800,57 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
}
// Note any argument mismatches
let given_ty = params.skip_binder();
let ty::Tuple(given) = *params.skip_binder().kind() else {
return;
};
let expected_ty = trait_pred.skip_binder().trait_ref.args.type_at(1);
if let ty::Tuple(given) = given_ty.kind()
&& let ty::Tuple(expected) = expected_ty.kind()
{
if expected.len() != given.len() {
// Note number of types that were expected and given
err.note(
format!(
"expected a closure taking {} argument{}, but one taking {} argument{} was given",
given.len(),
pluralize!(given.len()),
expected.len(),
pluralize!(expected.len()),
)
);
} else if !self.same_type_modulo_infer(given_ty, expected_ty) {
// Print type mismatch
let (expected_args, given_args) = self.cmp(given_ty, expected_ty);
err.note_expected_found(
&"a closure with arguments",
expected_args,
&"a closure with arguments",
given_args,
);
}
let ty::Tuple(expected) = *expected_ty.kind() else {
return;
};
if expected.len() != given.len() {
// Note number of types that were expected and given
err.note(format!(
"expected a closure taking {} argument{}, but one taking {} argument{} was given",
given.len(),
pluralize!(given.len()),
expected.len(),
pluralize!(expected.len()),
));
return;
}
let given_ty = Ty::new_fn_ptr(
self.tcx,
params.rebind(self.tcx.mk_fn_sig(
given,
self.tcx.types.unit,
false,
hir::Safety::Safe,
ExternAbi::Rust,
)),
);
let expected_ty = Ty::new_fn_ptr(
self.tcx,
trait_pred.rebind(self.tcx.mk_fn_sig(
expected,
self.tcx.types.unit,
false,
hir::Safety::Safe,
ExternAbi::Rust,
)),
);
if !self.same_type_modulo_infer(given_ty, expected_ty) {
// Print type mismatch
let (expected_args, given_args) = self.cmp(expected_ty, given_ty);
err.note_expected_found(
&"a closure with signature",
expected_args,
&"a closure with signature",
given_args,
);
}
}