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Treat trailing semicolon as a statement in macro call

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See https://github.com/rust-lang/rust/issues/61733#issuecomment-716188981

We now preserve the trailing semicolon in a macro invocation, even if
the macro expands to nothing. As a result, the following code no longer
compiles:

```rust
macro_rules! empty {
    () => { }
}

fn foo() -> bool { //~ ERROR mismatched
    { true } //~ ERROR mismatched
    empty!();
}
```

Previously, `{ true }` would be considered the trailing expression, even
though there's a semicolon in `empty!();`

This makes macro expansion more token-based.
This commit is contained in:
Aaron Hill 2020-10-25 17:14:19 -04:00
parent 499ebcfdf3
commit e78e9d4a06
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GPG key ID: B4087E510E98B164
6 changed files with 77 additions and 2 deletions
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5
compiler/rustc_lint/src/redundant_semicolon.rs
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@ -42,6 +42,11 @@ impl EarlyLintPass for RedundantSemicolons {
fn maybe_lint_redundant_semis(cx: &EarlyContext<'_>, seq: &mut Option<(Span, bool)>) {
if let Some((span, multiple)) = seq.take() {
// FIXME: Find a better way of ignoring the trailing
// semicolon from macro expansion
if span == rustc_span::DUMMY_SP {
return;
}
cx.struct_span_lint(REDUNDANT_SEMICOLONS, span, |lint| {
let (msg, rem) = if multiple {
("unnecessary trailing semicolons", "remove these semicolons")