bjoernager/rust
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Add SEMICOLON_IN_EXPRESSIONS_FROM_MACROS lint

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cc #79813

This PR adds an allow-by-default future-compatibility lint
`SEMICOLON_IN_EXPRESSIONS_FROM_MACROS`. It fires when a trailing semicolon in a
macro body is ignored due to the macro being used in expression
position:

```rust
macro_rules! foo {
    () => {
        true; // WARN
    }
}

fn main() {
    let val = match true {
        true => false,
        _ => foo!()
    };
}
```

The lint takes its level from the macro call site, and
can be allowed for a particular macro by adding
`#[allow(semicolon_in_expressions_from_macros)]`.

The lint is set to warn for all internal rustc crates (when being built
by a stage1 compiler). After the next beta bump, we can enable
the lint for the bootstrap compiler as well.
This commit is contained in:
Aaron Hill 2020-12-07 18:55:00 -05:00
parent 0e190206e2
commit f9025512e7
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GPG key ID: B4087E510E98B164
10 changed files with 150 additions and 1 deletions
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src/bootstrap/bootstrap.py
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@ -833,6 +833,7 @@ class RustBuild(object):
target_linker = self.get_toml("linker", build_section)
if target_linker is not None:
env["RUSTFLAGS"] += " -C linker=" + target_linker
# cfg(bootstrap): Add `-Wsemicolon_in_expressions_from_macros` after the next beta bump
env["RUSTFLAGS"] += " -Wrust_2018_idioms -Wunused_lifetimes"
if self.get_toml("deny-warnings", "rust") != "false":
env["RUSTFLAGS"] += " -Dwarnings"