user0/rust
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

make fn() -> _ {} suggestion MachineApplicable

Browse source
This commit is contained in:
Michael Goulet 2022-04-24 20:11:51 -07:00
parent a7197189cd
commit ae42f22ba0
2 changed files with 20 additions and 22 deletions
Download patch file Download diff file Expand all files Collapse all files

37
compiler/rustc_typeck/src/collect.rs
View file

@ -41,7 +41,7 @@ use rustc_middle::ty::subst::InternalSubsts;
use rustc_middle::ty::util::Discr;
use rustc_middle::ty::util::IntTypeExt;
use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, Ty, TyCtxt};
use rustc_middle::ty::{ReprOptions, ToPredicate, TypeFoldable};
use rustc_middle::ty::{ReprOptions, ToPredicate};
use rustc_session::lint;
use rustc_session::parse::feature_err;
use rustc_span::symbol::{kw, sym, Ident, Symbol};
@ -2004,28 +2004,29 @@ fn infer_return_ty_for_fn_sig<'tcx>(
visitor.visit_ty(ty);
let mut diag = bad_placeholder(tcx, visitor.0, "return type");
let ret_ty = fn_sig.skip_binder().output();
if !ret_ty.references_error() {
if !ret_ty.is_closure() {
let ret_ty_str = match ret_ty.kind() {
// Suggest a function pointer return type instead of a unique function definition
// (e.g. `fn() -> i32` instead of `fn() -> i32 { f }`, the latter of which is invalid
// syntax)
ty::FnDef(..) => ret_ty.fn_sig(tcx).to_string(),
_ => ret_ty.to_string(),
};
if ret_ty.is_suggestable() {
diag.span_suggestion(
ty.span,
"replace with the correct return type",
ret_ty.to_string(),
Applicability::MachineApplicable,
);
} else if matches!(ret_ty.kind(), ty::FnDef(..)) {
let fn_sig = ret_ty.fn_sig(tcx);
if fn_sig.skip_binder().inputs_and_output.iter().all(|t| t.is_suggestable()) {
diag.span_suggestion(
ty.span,
"replace with the correct return type",
ret_ty_str,
Applicability::MaybeIncorrect,
fn_sig.to_string(),
Applicability::MachineApplicable,
);
} else {
// We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
// to prevent the user from getting a papercut while trying to use the unique closure
// syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
}
} else if ret_ty.is_closure() {
// We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
// to prevent the user from getting a papercut while trying to use the unique closure
// syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
}
diag.emit();

5
src/test/ui/type-alias-impl-trait/issue-77179.stderr
View file

@ -2,10 +2,7 @@ error[E0121]: the placeholder `_` is not allowed within types on item signatures
--> $DIR/issue-77179.rs:7:22
|
LL | fn test() -> Pointer<_> {
| --------^-
| | |
| | not allowed in type signatures
| help: replace with the correct return type: `Pointer<i32>`
| ^ not allowed in type signatures
error: aborting due to previous error