Suggest adding Result return type for associated method in E0277.

For following:

```rust
struct A;
impl A {
    fn test4(&self) {
        let mut _file = File::create("foo.txt")?;
        //~^ ERROR the `?` operator can only be used in a method
    }
```
Suggest:

```rust
impl A {
    fn test4(&self) -> Result<(), Box<dyn std::error::Error>> {
        let mut _file = File::create("foo.txt")?;
        //~^ ERROR the `?` operator can only be used in a method

    Ok(())
    }
}
```

For #125997
This commit is contained in:
surechen 2024-07-23 10:24:45 +08:00
parent cefe1dcef0
commit b4b991e66f
4 changed files with 111 additions and 7 deletions

View File

@ -4612,6 +4612,9 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
})
}
// For E0277 when use `?` operator, suggest adding
// a suitable return type in `FnSig`, and a default
// return value at the end of the function's body.
pub(super) fn suggest_add_result_as_return_type(
&self,
obligation: &PredicateObligation<'tcx>,
@ -4622,19 +4625,47 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
return;
}
// Only suggest for local function and associated method,
// because this suggest adding both return type in
// the `FnSig` and a default return value in the body, so it
// is not suitable for foreign function without a local body,
// and neighter for trait method which may be also implemented
// in other place, so shouldn't change it's FnSig.
fn choose_suggest_items<'tcx, 'hir>(
tcx: TyCtxt<'tcx>,
node: hir::Node<'hir>,
) -> Option<(&'hir hir::FnDecl<'hir>, hir::BodyId)> {
match node {
hir::Node::Item(item) if let hir::ItemKind::Fn(sig, _, body_id) = item.kind => {
Some((sig.decl, body_id))
}
hir::Node::ImplItem(item)
if let hir::ImplItemKind::Fn(sig, body_id) = item.kind =>
{
let parent = tcx.parent_hir_node(item.hir_id());
if let hir::Node::Item(item) = parent
&& let hir::ItemKind::Impl(imp) = item.kind
&& imp.of_trait.is_none()
{
return Some((sig.decl, body_id));
}
None
}
_ => None,
}
}
let node = self.tcx.hir_node_by_def_id(obligation.cause.body_id);
if let hir::Node::Item(item) = node
&& let hir::ItemKind::Fn(sig, _, body_id) = item.kind
&& let hir::FnRetTy::DefaultReturn(ret_span) = sig.decl.output
if let Some((fn_decl, body_id)) = choose_suggest_items(self.tcx, node)
&& let hir::FnRetTy::DefaultReturn(ret_span) = fn_decl.output
&& self.tcx.is_diagnostic_item(sym::FromResidual, trait_pred.def_id())
&& trait_pred.skip_binder().trait_ref.args.type_at(0).is_unit()
&& let ty::Adt(def, _) = trait_pred.skip_binder().trait_ref.args.type_at(1).kind()
&& self.tcx.is_diagnostic_item(sym::Result, def.did())
{
let body = self.tcx.hir().body(body_id);
let mut sugg_spans =
vec![(ret_span, " -> Result<(), Box<dyn std::error::Error>>".to_string())];
let body = self.tcx.hir().body(body_id);
if let hir::ExprKind::Block(b, _) = body.value.kind
&& b.expr.is_none()
{

View File

@ -33,6 +33,25 @@ macro_rules! mac {
};
}
struct A;
impl A {
fn test4(&self) -> Result<(), Box<dyn std::error::Error>> {
let mut _file = File::create("foo.txt")?;
//~^ ERROR the `?` operator can only be used in a method
Ok(())
}
fn test5(&self) -> Result<(), Box<dyn std::error::Error>> {
let mut _file = File::create("foo.txt")?;
//~^ ERROR the `?` operator can only be used in a method
println!();
Ok(())
}
}
fn main() -> Result<(), Box<dyn std::error::Error>> {
let mut _file = File::create("foo.txt")?;
//~^ ERROR the `?` operator can only be used in a function

View File

@ -27,6 +27,21 @@ macro_rules! mac {
};
}
struct A;
impl A {
fn test4(&self) {
let mut _file = File::create("foo.txt")?;
//~^ ERROR the `?` operator can only be used in a method
}
fn test5(&self) {
let mut _file = File::create("foo.txt")?;
//~^ ERROR the `?` operator can only be used in a method
println!();
}
}
fn main() {
let mut _file = File::create("foo.txt")?;
//~^ ERROR the `?` operator can only be used in a function

View File

@ -37,8 +37,47 @@ LL + Ok(())
LL + }
|
error[E0277]: the `?` operator can only be used in a method that returns `Result` or `Option` (or another type that implements `FromResidual`)
--> $DIR/return-from-residual-sugg-issue-125997.rs:34:48
|
LL | fn test4(&self) {
| --------------- this function should return `Result` or `Option` to accept `?`
LL | let mut _file = File::create("foo.txt")?;
| ^ cannot use the `?` operator in a method that returns `()`
|
= help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
help: consider adding return type
|
LL ~ fn test4(&self) -> Result<(), Box<dyn std::error::Error>> {
LL | let mut _file = File::create("foo.txt")?;
LL |
LL ~
LL + Ok(())
LL + }
|
error[E0277]: the `?` operator can only be used in a method that returns `Result` or `Option` (or another type that implements `FromResidual`)
--> $DIR/return-from-residual-sugg-issue-125997.rs:39:48
|
LL | fn test5(&self) {
| --------------- this function should return `Result` or `Option` to accept `?`
LL | let mut _file = File::create("foo.txt")?;
| ^ cannot use the `?` operator in a method that returns `()`
|
= help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
help: consider adding return type
|
LL ~ fn test5(&self) -> Result<(), Box<dyn std::error::Error>> {
LL | let mut _file = File::create("foo.txt")?;
LL |
LL | println!();
LL ~
LL + Ok(())
LL + }
|
error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
--> $DIR/return-from-residual-sugg-issue-125997.rs:31:44
--> $DIR/return-from-residual-sugg-issue-125997.rs:46:44
|
LL | fn main() {
| --------- this function should return `Result` or `Option` to accept `?`
@ -81,6 +120,6 @@ LL + Ok(())
LL + }
|
error: aborting due to 4 previous errors
error: aborting due to 6 previous errors
For more information about this error, try `rustc --explain E0277`.