Keyword as a return type doesn't silence "no method found" errors

[inkreasing]

Code

struct A;

impl A {
    fn a() -> true {}
    fn b(&self) {}
    fn c(&self) {}
}

fn main() {
    let a = A;
    a.b();
    a.c();
}

Current output

Compiling playground v0.0.1 (/playground)
error: expected type, found keyword `true`
 --> src/lib.rs:4:15
  |
3 | impl A {
  |        - while parsing this item list starting here
4 |     fn a() -> true {}
  |               ^^^^ expected type
...
9 | }
  | - the item list ends here

error[E0599]: no method named `b` found for struct `A` in the current scope
  --> src/lib.rs:14:7
   |
 1 | struct A;
   | -------- method `b` not found for this struct
...
14 |     a.b();
   |       ^ method not found in `A`

error[E0599]: no method named `c` found for struct `A` in the current scope
  --> src/lib.rs:15:7
   |
 1 | struct A;
   | -------- method `c` not found for this struct
...
15 |     a.c();
   |       ^ method not found in `A`

For more information about this error, try `rustc --explain E0599`.
error: could not compile `playground` (lib) due to 3 previous errors

Desired output

Compiling playground v0.0.1 (/playground)
error: expected type, found keyword `true`
 --> src/lib.rs:4:15
  |
3 | impl A {
  |        - while parsing this item list starting here
4 |     fn a() -> true {}
  |               ^^^^ expected type
...
9 | }
  | - the item list ends here

error: could not compile `playground` (lib) due to 1 previous errors

Rationale and extra context

It is not useful to have the errors about the missing functions, because those are just caused by the previous error.
I sometimes write true instead of bool, so this sometimes happens to me and is not a unrealistic mistake.

@rustbot label +D-verbose

Other cases

Rust Version

rustc 1.100.0-nightly (330d31712 2026-09-17)
binary: rustc
commit-hash: 330d317121e16b5db8e5adc63595910528ff2ee7
commit-date: 2026-09-17
host: aarch64-apple-darwin
release: 1.100.0-nightly
LLVM version: 23.1.1

Anything else?

No response

[inkreasing]

@rustbot claim

[inkreasing]

Same issue also applies to

trait Test {
    fn a();
    fn b();
    fn c();
}

impl Test for () {
    fn a() -> true {}
    fn b() {}
    fn c() {}
}

which reports that the functions in the trait are not implemented.

[estebank]

We should leave this ticket open to try to recover more gracefully from any other number of parse errors in return types, like other keywords

struct A;

impl A {
    fn a() -> return {}
    fn b(&self) {}
    fn c(&self) {}
}

fn main() {
    let a = A;
    a.b();
    a.c();
}

and other things that are not valid syntax like:

struct A;

impl A {
    fn a() -> 1 + 1 {}
    fn b(&self) {}
    fn c(&self) {}
}

fn main() {
    let a = A;
    a.b();
    a.c();
}

I think that while parsing a return type, if we encounter a parse error, we should try to consume until the next {, ;, or }. If we haven't encountered }, assume that we can continue parsing the trait or impl.

[inkreasing]

When parsing a type declaration of a local variable the parser apparently tries to recover invalid parses as an expression, which can also have weird effects, but it kind of makes sense, if someone wrote a : instead of a = to assign.

fn main() {
    let a: return = 2;
    let b: 1 + 1 = 2;
}