Bad diagnostic for associated types when forgetting type arguments

[estebank]

Given an incorrect order of associated types:

type Bar = Foo<C = u32, B = bool, A = String>;

struct Foo<A, B, C> {
    a: A,
    b: B,
    c: C
}

We currently identify the first argument as a type binding and emit two errors:

error[E0243]: wrong number of type arguments: expected 3, found 0
 --> src/main.rs:4:12
  |
4 | type Bar = Foo<C = u32, B = bool, A = String>;
  |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected 3 type arguments

error[E0229]: associated type bindings are not allowed here
 --> src/main.rs:4:16
  |
4 | type Bar = Foo<C = u32, B = bool, A = String>;
  |                ^^^^^^^ associated type not allowed here

Modify to emit only one error complaining only about the ordermissing type arguments.

[oli-obk]

I'm confused. There is no ordering problem here. Just the fact that you used associated type syntax instead of generic parameter syntax. If you put the associated types in the correct order, you still get the same error.

[estebank]

@oli-obk you're right, missed the type arguments in the struct. Still, the E0229 should not fire despite the lack of type arguments.

[hadronized]

To me the error is correct. You provided only associated types, no substitution for the type variables.

[estebank]

Current output:

error[E0107]: this struct takes 3 generic arguments but 0 generic arguments were supplied
 --> src/main.rs:4:12
  |
4 | type Bar = Foo<C = u32, B = bool, A = String>;
  |            ^^^ expected 3 generic arguments
  |
note: struct defined here, with 3 generic parameters: `A`, `B`, `C`
 --> src/main.rs:6:8
  |
6 | struct Foo<A, B, C> {
  |        ^^^ -  -  -
help: add missing generic arguments
  |
4 | type Bar = Foo<A, B, C, C = u32, B = bool, A = String>;
  |                ++++++++

error[E0229]: associated type bindings are not allowed here
 --> src/main.rs:4:16
  |
4 | type Bar = Foo<C = u32, B = bool, A = String>;
  |                ^^^^^^^ associated type not allowed here

I would still like to clarify that what the user did was set associated types and not set the generics.

[estebank]

Current output:

error[E0107]: struct takes 3 generic arguments but 0 generic arguments were supplied
 --> src/main.rs:4:12
  |
4 | type Bar = Foo<C = u32, B = bool, A = String>;
  |            ^^^ expected 3 generic arguments
  |
note: struct defined here, with 3 generic parameters: `A`, `B`, `C`
 --> src/main.rs:6:8
  |
6 | struct Foo<A, B, C> {
  |        ^^^ -  -  -
help: add missing generic arguments
  |
4 | type Bar = Foo<A, B, C, C = u32, B = bool, A = String>;
  |                ++++++++

error[E0229]: associated item constraints are not allowed here
 --> src/main.rs:4:16
  |
4 | type Bar = Foo<C = u32, B = bool, A = String>;
  |                ^^^^^^^ associated item constraint not allowed here
  |
help: to use `u32` as a generic argument specify it directly
  |
4 | type Bar = Foo<u32, B = bool, A = String>;
  |                ~~~