bjoernager/rust
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Suggest adding Result return type for associated method in E0277.

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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
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41
compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
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()
{