Duplicate errors for missing trait instance in struct definition

Code

trait With {
    type Assoc;
}

struct Foo(<u32 as With>::Assoc);

fn use_foo(f: Foo) {
    drop(f);
}

Current output

error[E0277]: the trait bound `u32: With` is not satisfied
 --> src/lib.rs:5:12
  |
5 | struct Foo(<u32 as With>::Assoc);
  |            ^^^^^^^^^^^^^^^^^^^^ the trait `With` is not implemented for `u32`
  |
help: this trait has no implementations, consider adding one
 --> src/lib.rs:1:1
  |
1 | trait With {
  | ^^^^^^^^^^

error[E0277]: the trait bound `u32: With` is not satisfied in `Foo`
 --> src/lib.rs:7:15
  |
7 | fn use_foo(f: Foo) {
  |               ^^^ within `Foo`, the trait `With` is not implemented for `u32`
  |
help: this trait has no implementations, consider adding one
 --> src/lib.rs:1:1
  |
1 | trait With {
  | ^^^^^^^^^^
note: required because it appears within the type `Foo`
 --> src/lib.rs:5:8
  |
5 | struct Foo(<u32 as With>::Assoc);
  |        ^^^
  = help: unsized fn params are gated as an unstable feature
help: function arguments must have a statically known size, borrowed types always have a known size
  |
7 | fn use_foo(f: &Foo) {
  |               +

error[E0277]: the trait bound `u32: With` is not satisfied in `Foo`
   --> src/lib.rs:8:10
    |
  8 |     drop(f);
    |     ---- ^ within `Foo`, the trait `With` is not implemented for `u32`
    |     |
    |     required by a bound introduced by this call
    |
help: this trait has no implementations, consider adding one
   --> src/lib.rs:1:1
    |
  1 | trait With {
    | ^^^^^^^^^^
note: required because it appears within the type `Foo`
   --> src/lib.rs:5:8
    |
  5 | struct Foo(<u32 as With>::Assoc);
    |        ^^^
note: required by an implicit `Sized` bound in `std::mem::drop`
   --> /playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/mem/mod.rs:971:19
    |
971 | pub const fn drop<T>(_x: T)
    |                   ^ required by the implicit `Sized` requirement on this type parameter in `drop`

Desired output

error[E0277]: the trait bound `u32: With` is not satisfied
 --> src/lib.rs:5:12
  |
5 | struct Foo(<u32 as With>::Assoc);
  |            ^^^^^^^^^^^^^^^^^^^^ the trait `With` is not implemented for `u32`
  |
help: this trait has no implementations, consider adding one
 --> src/lib.rs:1:1
  |
1 | trait With {
  | ^^^^^^^^^^

Rationale and extra context

Errors in the definition of a struct should not cause all uses of the struct to error too.

Other cases

trait With {
    type Assoc;
}

struct Foo(<u32 as With>::Assoc);

trait Other {}

impl Other for Foo {}

Rust Version

rustc 1.93.0 (254b59607 2026-01-19)
binary: rustc
commit-hash: 254b59607d4417e9dffbc307138ae5c86280fe4c
commit-date: 2026-01-19
host: x86_64-unknown-linux-gnu
release: 1.93.0
LLVM version: 21.1.8

Anything else?

No response

Start by reproducing the Rust snippet and comparing diagnostics for the struct definition, its use, and the Other implementation case. Trace how the compiler propagates the missing trait-instance error from the struct definition into later uses, then add regression coverage showing that only the definition error remains and the duplicate downstream errors disappear.