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Emit a warning on generic parameters with doc comments #91397

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Dec 1, 2021
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Emit a warning on generic parameters with doc comments #91397

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4 changes: 4 additions & 0 deletions compiler/rustc_lint/src/builtin.rs
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Expand Up @@ -1079,6 +1079,10 @@ impl EarlyLintPass for UnusedDocComment {
fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
}

fn check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam) {
warn_if_doc(cx, param.ident.span, "generic parameters", &param.attrs);
}
}

declare_lint! {
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3 changes: 3 additions & 0 deletions src/test/ui/lint/unused/unused-doc-comments-edge-cases.rs
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Expand Up @@ -26,4 +26,7 @@ fn doc_comment_on_expr(num: u8) -> bool {
num == 3
}

fn doc_comment_on_generic<#[doc = "x"] T>(val: T) {}
//~^ ERROR: unused doc comment
Comment on lines +29 to +30
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Perhaps it's also worth adding tests for

fn doc_comment_on_generic<
    /// x
    T>(val: T) {}
//~^^ ERROR: unused doc comment

and

fn doc_comment_on_generic</** foo */ T>(val: T) {}
//~^ ERROR: unused doc comment

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Oops, GitHub didn't show me that this was already approved.

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I don't think we need to test those, anyway - rustc represents them both as #[doc] under the hood. There are plenty of other tests that would fail if that weren't the case.


fn main() {}
10 changes: 9 additions & 1 deletion src/test/ui/lint/unused/unused-doc-comments-edge-cases.stderr
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Expand Up @@ -41,6 +41,14 @@ LL | num == 3
|
= help: use `//` for a plain comment

error: unused doc comment
--> $DIR/unused-doc-comments-edge-cases.rs:29:27
|
LL | fn doc_comment_on_generic<#[doc = "x"] T>(val: T) {}
| ^^^^^^^^^^^^ - rustdoc does not generate documentation for generic parameters
|
= help: use `//` for a plain comment

error[E0308]: mismatched types
--> $DIR/unused-doc-comments-edge-cases.rs:14:9
|
Expand All @@ -55,7 +63,7 @@ help: you might have meant to return this value
LL | return true;
| ++++++ +

error: aborting due to 5 previous errors
error: aborting due to 6 previous errors

Some errors have detailed explanations: E0308, E0658.
For more information about an error, try `rustc --explain E0308`.