Trait methods can't be found by method resolution if the self type involves projections #121643
Description
I tried this code:
pub type Id<T> = <T as IdTrait>::T; pub trait IdTrait { type T: ?Sized; } impl<T: ?Sized> IdTrait for T { type T = T; } #[derive(Copy, Clone)] struct Foo; impl Foo { fn method(self: Id<Self>) { println!("hi!"); } } trait FooTrait { fn method2(self: Id<Self>); } impl FooTrait for Foo { fn method2(self) { // or `: Id<Self>`, makes no difference here println!("hi!"); } } pub fn main() { let foo = Foo; foo.method(); // works foo.method2(); // doesn't work Foo::method2(foo); // works }I expected to see this happen: Code compiles successfully
Instead, this happened:
error[E0599]: no method named `method2` found for struct `Foo` in the current scope --> <source>:31:9 | 12 | struct Foo; | ---------- method `method2` not found for this struct ... 20 | fn method2(self: Id<Self>); | -------- the method might not be found because of this arbitrary self type ... 31 | foo.method2(); // doesn't work | ^^^^^^^ | help: there is a method `method` with a similar name | 31 | foo.method(); // doesn't work | ~~~~~~ error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0599`. Compiler returned: 1 This is technically an old regression in 1.22, the code compiled fine up to Rust 1.21.