f3745653e1
Enforce the shadowing restrictions from RFC 1560 for today's macros
This PR enforces a weakened version of the shadowing restrictions from RFC 1560. More specifically,
- If a macro expansion contains a `macro_rules!` macro definition that is used outside of the expansion, the defined macro may not shadow an existing macro.
- If a macro expansion contains a `#[macro_use] extern crate` macro import that is used outside of the expansion, the imported macro may not shadow an existing macro.
This is a [breaking-change]. For example,
```rust
macro_rules! m { () => {} }
macro_rules! n { () => {
macro_rules! m { () => {} } //< This shadows an existing macro.
m!(); //< This is inside the expansion that generated `m`'s definition, so it is OK.
} }
n!();
m!(); //< This use of `m` is outside the expansion, so it causes the shadowing to be an error.
```
r? @nrc
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|---|---|---|
| .. | ||
| astencode.rs | ||
| Cargo.toml | ||
| creader.rs | ||
| csearch.rs | ||
| cstore.rs | ||
| decoder.rs | ||
| diagnostics.rs | ||
| encoder.rs | ||
| index_builder.rs | ||
| index.rs | ||
| lib.rs | ||
| loader.rs | ||
| macro_import.rs | ||
| schema.rs | ||