Skip to content

Improve error message for type mismatch in generator arguments #88911

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Sep 17, 2021
Merged
Show file tree
Hide file tree
Changes from all commits
Commits
File filter

Filter by extension

Filter by extension

Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
Original file line number Diff line number Diff line change
Expand Up @@ -730,7 +730,10 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
};

let found_did = match *found_trait_ty.kind() {
ty::Closure(did, _) | ty::Foreign(did) | ty::FnDef(did, _) => Some(did),
ty::Closure(did, _)
| ty::Foreign(did)
| ty::FnDef(did, _)
| ty::Generator(did, ..) => Some(did),
ty::Adt(def, _) => Some(def.did),
_ => None,
};
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -1250,33 +1250,40 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
trait_ref: ty::PolyTraitRef<'tcx>,
) -> String {
let inputs = trait_ref.skip_binder().substs.type_at(1);
let sig = if let ty::Tuple(inputs) = inputs.kind() {
tcx.mk_fn_sig(
inputs.iter().map(|k| k.expect_ty()),
tcx.mk_ty_infer(ty::TyVar(ty::TyVid::from_u32(0))),
false,
hir::Unsafety::Normal,
abi::Abi::Rust,
)
} else {
tcx.mk_fn_sig(
let sig = match inputs.kind() {
ty::Tuple(inputs)
if tcx.fn_trait_kind_from_lang_item(trait_ref.def_id()).is_some() =>
{
tcx.mk_fn_sig(
inputs.iter().map(|k| k.expect_ty()),
tcx.mk_ty_infer(ty::TyVar(ty::TyVid::from_u32(0))),
false,
hir::Unsafety::Normal,
abi::Abi::Rust,
)
}
_ => tcx.mk_fn_sig(
std::iter::once(inputs),
tcx.mk_ty_infer(ty::TyVar(ty::TyVid::from_u32(0))),
false,
hir::Unsafety::Normal,
abi::Abi::Rust,
)
),
};
trait_ref.rebind(sig).to_string()
}

let argument_is_closure = expected_ref.skip_binder().substs.type_at(0).is_closure();
let argument_kind = match expected_ref.skip_binder().substs.type_at(0) {
t if t.is_closure() => "closure",
t if t.is_generator() => "generator",
_ => "function",
};
let mut err = struct_span_err!(
self.tcx.sess,
span,
E0631,
"type mismatch in {} arguments",
if argument_is_closure { "closure" } else { "function" }
argument_kind
);

let found_str = format!("expected signature of `{}`", build_fn_sig_string(self.tcx, found));
Expand Down
19 changes: 19 additions & 0 deletions src/test/ui/generator/issue-88653.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,19 @@
// Regression test for #88653, where a confusing warning about a
// type mismatch in generator arguments was issued.

#![feature(generators, generator_trait)]

use std::ops::Generator;

fn foo(bar: bool) -> impl Generator<(bool,)> {
//~^ ERROR: type mismatch in generator arguments [E0631]
//~| NOTE: expected signature of `fn((bool,)) -> _`
|bar| {
//~^ NOTE: found signature of `fn(bool) -> _`
if bar {
yield bar;
}
}
}

fn main() {}
12 changes: 12 additions & 0 deletions src/test/ui/generator/issue-88653.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,12 @@
error[E0631]: type mismatch in generator arguments
--> $DIR/issue-88653.rs:8:22
|
LL | fn foo(bar: bool) -> impl Generator<(bool,)> {
| ^^^^^^^^^^^^^^^^^^^^^^^ expected signature of `fn((bool,)) -> _`
...
LL | |bar| {
| ----- found signature of `fn(bool) -> _`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0631`.