Rust error E0044: foreign items may not have type parameters

What rustc prints

error[E0044]: foreign items may not have type parameters
 --> main.rs:1:14
  |
1 | extern "C" { fn some_func<T>(x: T); }
  |              ^^^^^^^^^^^^^^^^^^^^^^ can't have type parameters
  |
  = help: replace the type parameters with concrete types like `u32`

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.

extern "C" { fn some_func<T>(x: T); }

extern "C" { fn some_func_i32(x: i32); }
extern "C" { fn some_func_i64(x: i64); }

Related errors

• E0308mismatched types
• E0277the trait bound is not satisfied
• E0599no method named X found in the current scope
• E0433failed to resolve
• E0033A trait type has been dereferenced
• E0038For any given trait `Trait` there may be a related _type_ called the _trait object type_ which is typically written as `dyn Trait`. In earlier editions of Rust, trait object types were written as plain `Trait` (just the name of the trait, written in type positions) but this was a bit too confusing, so we now write `dyn Trait`
• E0046not all trait items implemented, missing: `foo`
• E0049associated function `foo` has 0 type parameters but its trait declaration has 1 type parameter

All 518 Rust error codes · Rust crate data · Glossary