Suggest single quotes when char expected, str provided by chordtoll · Pull Request #92507 · rust-lang/rust (original) (raw)

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If a type mismatch occurs where a char is expected and a string literal is provided, suggest changing the double quotes to single quotes.

We already provide this suggestion in the other direction ( ' -> " ).

Especially useful for new rust devs used to a language in which single/double quotes are interchangeable.

Fixes #92479.

rustbot added the T-compiler

Relevant to the compiler team, which will review and decide on the PR/issue.

label

Jan 3, 2022

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @petrochenkov (or someone else) soon.

Please see the contribution instructions for more information.

@chordtoll Could you please add a test that demonstrates the new suggestion?

We already provide this suggestion in the other direction ( ' -> " ).

Looks like we actually do not.
let s: &str = 'abc'; has the "abc" suggestion from the lexer just because multi-character literals are impossible.
However, let s: &str = 'a'; produces a "mismatched types" error without the suggestion.
So maybe you can also add another branch to the same match in compiler/rustc_infer/src/infer/error_reporting/mod.rs to address this opposite case.

r=me after squashing commits.

📌 Commit 3087c4d has been approved by petrochenkov

bors added S-waiting-on-bors

Status: Waiting on bors to run and complete tests. Bors will change the label on completion.

and removed S-waiting-on-author

Status: This is awaiting some action (such as code changes or more information) from the author.

labels

Jan 4, 2022

if let Some(code) =
code.strip_prefix('"').and_then(\|s
{
if code.chars().nth(1).is_none() {

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Oh no, I think my suggestion also fires for empty string literals "", sorry 😟! I think it's too late to change in this PR since it's already approved.

if code.chars().nth(1).is_none() {
if code.chars().nth(1).is_none() && !code.is_empty() {

Hmm that code is not that self-explanatory.

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Good point- I'll open another PR to add the 0-character check

bors added a commit to rust-lang-ci/rust that referenced this pull request

Jan 4, 2022

…askrgr

Rollup of 7 pull requests

Successful merges:

rust-lang#91754 (Modifications to std::io::Stdin on Windows so that there is no longer a 4-byte buffer minimum in read().)
rust-lang#91884 (Constify Box<T, A> methods)
rust-lang#92107 (Actually set IMAGE_SCN_LNK_REMOVE for .rmeta)
rust-lang#92456 (Make the documentation of builtin macro attributes accessible)
rust-lang#92507 (Suggest single quotes when char expected, str provided)
rust-lang#92525 (intra-doc: Make Receiver::into_iter into a clickable link)
rust-lang#92532 (revert rust-lang#92254 "Bump gsgdt to 0.1.3")

Failed merges:

r? @ghost @rustbot modify labels: rollup

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request

Feb 8, 2022

Do not suggest char literal for zero-length strings

PR rust-lang#92507 adds a hint to switch to single quotes when a char is expected and a single-character string literal is provided.

The check to ensure the string literal is one character long missed the 0-char case, and would incorrectly offer the hint.

This PR adds the missing check, and a test case to confirm the new behavior.