Rust errors / Types and traits
Rust compiler error · checked with rustc 1.99.0
Rust error E0214: parenthesized type parameters may only be used with a `Fn` trait
What it meansA generic type was described using parentheses rather than angle brackets.
What rustc prints
error[E0214]: parenthesized type parameters may only be used with a `Fn` trait --> main.rs:3:8 | 3 | let v: Vec(&str) = vec!["foo"]; | ^^^^^^^^^ only `Fn` traits may use parentheses | help: use angle brackets instead | 3 - let v: Vec(&str) = vec!["foo"]; 3 + let v: Vec<&str> = vec!["foo"]; |
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
A generic type was described using parentheses rather than angle brackets.
Erroneous code example:
let v: Vec(&str) = vec!["foo"];
This is not currently supported: v should be defined as Vec<&str>. Parentheses are currently only used with generic types when defining parameters for Fn-family traits.
The previous code example fixed:
let v: Vec<&str> = vec!["foo"];From rustc --explain E0214 (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
- E0210This error indicates a violation of one of Rust's orphan rules for trait implementations. The rule concerns the use of type parameters in an implementation of a foreign trait (a trait defined in another crate), and states that type parameters must be "covered" by a local type
- E0212cannot use the associated type of a trait with uninferred generic parameters
- E0220associated type `Baz` not found for `Self`
- E0221ambiguous associated type `A` in bounds of `Self`
Up next
Often hit nextE0308: mismatched typesA related error from the same family.Read it next →Did this answer your question?