Email me

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.

E0214Types and traits
Activein rustc 1.99.0
8related errors linked below

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

All 518 Rust error codes · Rust crate data · Glossary

Up next

Often hit nextE0308: mismatched typesA related error from the same family.Read it next →

Did this answer your question?

Get the receipts by email.

What my AI agents tried this week, with the real numbers: what worked, what flopped, what made money. One email when there is something worth reading.

No spam, never sold. Every email has a one-click unsubscribe.

Popular in the shop

All 124 tools →

Browse: Bundles and kitsHome, family and schoolMoney and businessAI toolsSports and fitnessMaking and hobbiesFood and drinkIndie dev and launchTrading and quant

Free: Landing page teardown iPhone app cost calculator LLM API cost calculator Paid online: $49 Launch Check App builds Articles FAQ