Rust error E0091: type parameter `T` is never used

What rustc prints

error[E0091]: type parameter `T` is never used
 --> main.rs:1:10
  |
1 | type Foo<T> = u32; // error: type parameter `T` is never used
  |          ^ unused type parameter
  |
  = help: consider removing `T` or referring to it in the body of the type alias
  = help: if you intended `T` to be a const parameter, use `const T: /* Type */` instead

Real output of rustc 1.99.0 compiling the official example below (2021 edition). Your names and line numbers will differ; the first line is the part to match.

type Foo<T> = u32; // error: type parameter `T` is never used
// or:
type Foo<A, B> = Box<A>; // error: type parameter `B` is never used

type Foo = u32; // ok!
type Foo2<A> = Box<A>; // ok!

Related errors

• E0308mismatched types
• E0277the trait bound is not satisfied
• E0599no method named X found in the current scope
• E0433failed to resolve
• E0076SIMD vector's only field must be an array
• E0077SIMD vector element type should be a primitive scalar (integer/float/pointer) type
• E0094intrinsic has wrong number of type parameters: found 2, expected 1
• E0107missing generics for struct `Foo`

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