bjoernager/rust
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Auto merge of #96150 - est31:unused_macro_rules, r=petrochenkov

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Implement a lint to warn about unused macro rules

This implements a new lint to warn about unused macro rules (arms/matchers), similar to the `unused_macros` lint added by #41907 that warns about entire macros.

```rust
macro_rules! unused_empty {
    (hello) => { println!("Hello, world!") };
    () => { println!("empty") }; //~ ERROR: 1st rule of macro `unused_empty` is never used
}

fn main() {
    unused_empty!(hello);
}
```

Builds upon #96149 and #96156.

Fixes #73576
This commit is contained in:
bors 2022-05-12 00:08:08 +00:00
commit 0cd939e36c
34 changed files with 400 additions and 78 deletions
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2
compiler/rustc_resolve/src/lib.rs
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@ -975,6 +975,7 @@ pub struct Resolver<'a> {
local_macro_def_scopes: FxHashMap<LocalDefId, Module<'a>>,
ast_transform_scopes: FxHashMap<LocalExpnId, Module<'a>>,
unused_macros: FxHashMap<LocalDefId, (NodeId, Ident)>,
unused_macro_rules: FxHashMap<(LocalDefId, usize), (Ident, Span)>,
proc_macro_stubs: FxHashSet<LocalDefId>,
/// Traces collected during macro resolution and validated when it's complete.
single_segment_macro_resolutions:
@ -1374,6 +1375,7 @@ impl<'a> Resolver<'a> {
potentially_unused_imports: Vec::new(),
struct_constructors: Default::default(),
unused_macros: Default::default(),
unused_macro_rules: Default::default(),
proc_macro_stubs: Default::default(),
single_segment_macro_resolutions: Default::default(),
multi_segment_macro_resolutions: Default::default(),