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make path_statements lint machine applicable for statements with no effect #140830

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make path_statements lint machine applicable for statements with no effect #140830

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1 change: 1 addition & 0 deletions compiler/rustc_lint/messages.ftl
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Original file line number Diff line number Diff line change
Expand Up @@ -675,6 +675,7 @@ lint_path_statement_drop = path statement drops value
.suggestion = use `drop` to clarify the intent

lint_path_statement_no_effect = path statement with no effect
.suggestion = remove this statement

lint_pattern_in_bodiless = patterns aren't allowed in functions without bodies
.label = pattern not allowed in function without body
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5 changes: 4 additions & 1 deletion compiler/rustc_lint/src/lints.rs
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Expand Up @@ -2077,7 +2077,10 @@ pub(crate) enum PathStatementDropSub {

#[derive(LintDiagnostic)]
#[diag(lint_path_statement_no_effect)]
pub(crate) struct PathStatementNoEffect;
pub(crate) struct PathStatementNoEffect {
#[suggestion(lint_suggestion, code = "", applicability = "machine-applicable")]
pub suggestion: Span,
}

#[derive(LintDiagnostic)]
#[diag(lint_unused_delim)]
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6 changes: 5 additions & 1 deletion compiler/rustc_lint/src/unused.rs
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Expand Up @@ -568,7 +568,11 @@ impl<'tcx> LateLintPass<'tcx> for PathStatements {
};
cx.emit_span_lint(PATH_STATEMENTS, s.span, PathStatementDrop { sub })
} else {
cx.emit_span_lint(PATH_STATEMENTS, s.span, PathStatementNoEffect);
cx.emit_span_lint(
PATH_STATEMENTS,
s.span,
PathStatementNoEffect { suggestion: s.span },
);
}
}
}
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8 changes: 8 additions & 0 deletions tests/ui/lint/warn-path-statement.rs
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Expand Up @@ -14,4 +14,12 @@ fn main() {

let z = (Droppy,);
z; //~ ERROR path statement drops value

macro_rules! foo {
($e:expr) => {
$e;
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Note: I think you'll need a

//~^ ERROR: path statement with no effect

annotation here. I guess partly what I had in mind re. macros was also this case, where the suggestion is tied to removing $e;, though arguably maybe it's the invocation foo!(x); that should be removed.

Again, this is not blocking IMO.

};
}

foo!(x);
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@jieyouxu is this what you meant? Right now this is emitting the lint. Is the idea that this lint shouldn't be emitted the lint in this case or that it shouldn't be machine applicable?

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@jieyouxu jieyouxu Jun 17, 2025 •
edited
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I somehow completely lost this notification, sorry about that. Now that I read my own comment #140830 (review) back, I think what I had in mind at the time was stuff like having a path statement that comes from a macro expansion from another crate, where I think I thought that a machine-applicable suggestion in that case wouldn't be very actionable.

... But that can be a follow-up or further adjusted as suitable, and does not need to block this PR at all.

}
15 changes: 13 additions & 2 deletions tests/ui/lint/warn-path-statement.stderr
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Expand Up @@ -2,7 +2,7 @@ error: path statement with no effect
--> $DIR/warn-path-statement.rs:10:5
|
LL | x;
| ^^
| ^^ help: remove this statement
|
= note: requested on the command line with `-D path-statements`

Expand All @@ -18,5 +18,16 @@ error: path statement drops value
LL | z;
| ^^ help: use `drop` to clarify the intent: `drop(z);`

error: aborting due to 3 previous errors
error: path statement with no effect
--> $DIR/warn-path-statement.rs:20:13
|
LL | $e;
| ^^^ help: remove this statement
...
LL | foo!(x);
| ------- in this macro invocation
|
= note: this error originates in the macro `foo` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to 4 previous errors

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