For E0277 suggest adding Result return type for function which using QuesionMark ? in the body.

This commit is contained in:
surechen 2024-06-09 17:20:25 +08:00
parent f3ff2f16c8
commit 0b3fec9388
7 changed files with 218 additions and 0 deletions

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@ -1010,6 +1010,7 @@ pub struct Block<'hir> {
pub hir_id: HirId,
/// Distinguishes between `unsafe { ... }` and `{ ... }`.
pub rules: BlockCheckMode,
/// The span includes the curly braces `{` and `}` around the block.
pub span: Span,
/// If true, then there may exist `break 'a` values that aim to
/// break out of this block early.

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@ -4586,6 +4586,47 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
_ => "/* value */".to_string(),
})
}
fn suggest_add_result_as_return_type(
&self,
obligation: &PredicateObligation<'tcx>,
err: &mut Diag<'_>,
trait_ref: ty::PolyTraitRef<'tcx>,
) {
if ObligationCauseCode::QuestionMark != *obligation.cause.code().peel_derives() {
return;
}
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
&& self.tcx.is_diagnostic_item(sym::FromResidual, trait_ref.def_id())
&& let ty::Tuple(l) = trait_ref.skip_binder().args.type_at(0).kind()
&& l.len() == 0
&& let ty::Adt(def, _) = trait_ref.skip_binder().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())];
if let hir::ExprKind::Block(b, _) = body.value.kind
&& b.expr.is_none()
{
sugg_spans.push((
// The span will point to the closing curly brace `}` of the block.
b.span.shrink_to_hi().with_lo(b.span.hi() - BytePos(1)),
"\n Ok(())\n}".to_string(),
));
}
err.multipart_suggestion_verbose(
format!("consider adding return type"),
sugg_spans,
Applicability::MaybeIncorrect,
);
}
}
}
/// Add a hint to add a missing borrow or remove an unnecessary one.

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@ -612,6 +612,10 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
&mut err,
trait_predicate,
);
self.suggest_add_result_as_return_type(&obligation,
&mut err,
trait_ref);
if self.suggest_add_reference_to_arg(
&obligation,
&mut err,

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@ -0,0 +1,42 @@
//@ run-rustfix
#![allow(unused_imports)]
#![allow(dead_code)]
use std::fs::File;
use std::io::prelude::*;
fn test1() -> Result<(), Box<dyn std::error::Error>> {
let mut _file = File::create("foo.txt")?;
//~^ ERROR the `?` operator can only be used in a function
Ok(())
}
fn test2() -> Result<(), Box<dyn std::error::Error>> {
let mut _file = File::create("foo.txt")?;
//~^ ERROR the `?` operator can only be used in a function
println!();
Ok(())
}
macro_rules! mac {
() => {
fn test3() -> Result<(), Box<dyn std::error::Error>> {
let mut _file = File::create("foo.txt")?;
//~^ ERROR the `?` operator can only be used in a function
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
mac!();
Ok(())
}

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@ -0,0 +1,34 @@
//@ run-rustfix
#![allow(unused_imports)]
#![allow(dead_code)]
use std::fs::File;
use std::io::prelude::*;
fn test1() {
let mut _file = File::create("foo.txt")?;
//~^ ERROR the `?` operator can only be used in a function
}
fn test2() {
let mut _file = File::create("foo.txt")?;
//~^ ERROR the `?` operator can only be used in a function
println!();
}
macro_rules! mac {
() => {
fn test3() {
let mut _file = File::create("foo.txt")?;
//~^ ERROR the `?` operator can only be used in a function
println!();
}
};
}
fn main() {
let mut _file = File::create("foo.txt")?;
//~^ ERROR the `?` operator can only be used in a function
mac!();
}

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@ -0,0 +1,86 @@
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:10:44
|
LL | fn test1() {
| ---------- this function should return `Result` or `Option` to accept `?`
LL | let mut _file = File::create("foo.txt")?;
| ^ cannot use the `?` operator in a function that returns `()`
|
= help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
help: consider adding return type
|
LL ~ fn test1() -> 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 function that returns `Result` or `Option` (or another type that implements `FromResidual`)
--> $DIR/return-from-residual-sugg-issue-125997.rs:15:44
|
LL | fn test2() {
| ---------- this function should return `Result` or `Option` to accept `?`
LL | let mut _file = File::create("foo.txt")?;
| ^ cannot use the `?` operator in a function that returns `()`
|
= help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
help: consider adding return type
|
LL ~ fn test2() -> 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
|
LL | fn main() {
| --------- this function should return `Result` or `Option` to accept `?`
LL | let mut _file = File::create("foo.txt")?;
| ^ cannot use the `?` operator in a function that returns `()`
|
= help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
help: consider adding return type
|
LL ~ fn main() -> Result<(), Box<dyn std::error::Error>> {
LL | let mut _file = File::create("foo.txt")?;
LL |
LL | mac!();
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:23:52
|
LL | fn test3() {
| ---------- this function should return `Result` or `Option` to accept `?`
LL | let mut _file = File::create("foo.txt")?;
| ^ cannot use the `?` operator in a function that returns `()`
...
LL | mac!();
| ------ in this macro invocation
|
= help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
= note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)
help: consider adding return type
|
LL ~ fn test3() -> Result<(), Box<dyn std::error::Error>> {
LL | let mut _file = File::create("foo.txt")?;
LL |
LL | println!();
LL ~
LL + Ok(())
LL + }
|
error: aborting due to 4 previous errors
For more information about this error, try `rustc --explain E0277`.

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@ -8,6 +8,16 @@ LL | std::fs::File::open("foo")?;
| ^ cannot use the `?` operator in a function that returns `()`
|
= help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
help: consider adding return type
|
LL ~ fn main() -> Result<(), Box<dyn std::error::Error>> {
LL | // error for a `Try` type on a non-`Try` fn
...
LL | try_trait_generic::<()>();
LL +
LL + Ok(())
LL + }
|
error[E0277]: the `?` operator can only be applied to values that implement `Try`
--> $DIR/try-operator-on-main.rs:10:5