Rust errors / Types and traits
Rust compiler error · checked with rustc 1.99.0
Rust error E0109: type arguments are not allowed on builtin type `u32`
What it meansYou tried to provide a generic argument to a type which doesn't need it.
What rustc prints
error[E0109]: type arguments are not allowed on builtin type `u32` --> main.rs:1:14 | 1 | type X = u32<i32>; // error: type arguments are not allowed for this type | --- ^^^ type argument not allowed | | | not allowed on builtin type `u32` | help: primitive type `u32` doesn't have generic parameters | 1 - type X = u32<i32>; // error: type arguments are not allowed for this type 1 + type X = u32; // error: type arguments are not allowed for this type |
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.
The compiler team's explanation
You tried to provide a generic argument to a type which doesn't need it.
Erroneous code example:
type X = u32<i32>; // error: type arguments are not allowed for this type
type Y = bool<'static>; // error: lifetime parameters are not allowed on
// this typeCheck that you used the correct argument and that the definition is correct.
Example:
type X = u32; // ok!
type Y = bool; // ok!Note that generic arguments for enum variant constructors go after the variant, not after the enum. For example, you would write Option::None::<u32>, rather than Option::<u32>::None.
From rustc --explain E0109 (1.99.0), part of the Rust project, MIT or Apache-2.0. Official page.
Related errors
- E0308mismatched types
- E0277the trait bound is not satisfied
- E0599no method named X found in the current scope
- E0433failed to resolve
- E0094intrinsic has wrong number of type parameters: found 2, expected 1
- E0107missing generics for struct `Foo`
- E0116cannot define inherent `impl` for a type outside of the crate where the type is defined
- E0117only traits defined in the current crate can be implemented for types defined outside of the crate
Up next
Often hit nextE0308: mismatched typesA related error from the same family.Read it next →Did this answer your question?