Hint for Vec<String, String> #83250
Description
Given the following code: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=5f472854b25b6ccce15820ca0dd45c19
fn foo() {
let _z: Vec<String, String> = vec![]; // A vector of string pairs, right?
}The current output is:
error[E0658]: use of unstable library feature 'allocator_api'
--> src/lib.rs:2:25
|
2 | let _z: Vec<String, String> = vec![]; // A vector of string pairs, right?
| ^^^^^^
|
= note: see issue #32838 <https://github.com/rust-lang/rust/issues/32838> for more information
error[E0277]: the trait bound `String: Allocator` is not satisfied
--> src/lib.rs:2:13
|
2 | let _z: Vec<String, String> = vec![]; // A vector of string pairs, right?
| ^^^^^^^^^^^^^^^^^^^ the trait `Allocator` is not implemented for `String`
error[E0308]: mismatched types
--> src/lib.rs:2:35
|
2 | let _z: Vec<String, String> = vec![]; // A vector of string pairs, right?
| ------------------- ^^^^^^ expected struct `String`, found struct `std::alloc::Global`
| |
| expected due to this
|
= note: expected struct `Vec<String, String>`
found struct `Vec<_, std::alloc::Global>`
= note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
error: aborting due to 3 previous errors
Ideally the output should look like:
The above, plus:
hint: for a Vec of String pairs, try Vec<(String, String)>
Rationale: The current error messages assume that users know Vec has a second type param, which is rarely used. A vector of pairs is a fairly common type, and I suspect a lot of people make the mistake of forgetting the parentheses.
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Area: Messages for errors, warnings, and lintsArea: Suggestions generated by the compiler applied by `cargo fix`Category: An issue proposing an enhancement or a PR with one.Diagnostics: An error or lint that needs small tweaks.Relevant to the compiler team, which will review and decide on the PR/issue.