in 《A 30-minute Introduction to Rust》 rustc dangling.rs output need update #17588
Comments
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The 30 minute guide is being re-done in #16641 , so while this is an error, it's already going away shortly. |
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Closed since #16641 was merged. |
lnicola
pushed a commit
to lnicola/rust
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Jul 28, 2024
feat: Add incorrect case diagnostics for enum variant fields and all variables/params
Updates the incorrect case diagnostic to check:
1. Fields of enum variants. Example:
```rust
enum Foo {
Variant { nonSnake: u8 }
}
```
2. All variable bindings, instead of just let bindings and certain match arm patters. Examples:
```rust
match 1 { nonSnake => () }
match 1 { nonSnake @ 1 => () }
match 1 { nonSnake1 @ nonSnake2 => () } // slightly cursed, but these both introduce new
// bindings that are bound to the same value.
const ONE: i32 = 1;
match 1 { nonSnake @ ONE } // ONE is ignored since it is not a binding
match Some(1) { Some(nonSnake) => () }
struct Foo { field: u8 }
match (Foo { field: 1 } ) {
Foo { field: nonSnake } => ();
}
struct Foo { nonSnake: u8 } // diagnostic here, at definition
match (Foo { nonSnake: 1 } ) { // no diagnostic here...
Foo { nonSnake } => (); // ...or here, since these are not where the name is introduced
}
for nonSnake in [] {}
struct Foo(u8);
for Foo(nonSnake) in [] {}
```
3. All parameter bindings, instead of just top-level binding identifiers. Examples:
```rust
fn func(nonSnake: u8) {} // worked before
struct Foo { field: u8 }
fn func(Foo { field: nonSnake }: Foo) {} // now get diagnostic for nonSnake
```
This is accomplished by changing the way binding identifier patterns are filtered:
- Previously, all binding idents were skipped, except a few classes of "good" binding locations that were checked.
- Now, all binding idents are checked, except field shorthands which are skipped.
Moving from a whitelist to a blacklist potentially makes the analysis more brittle:
If new pattern types are added in the future where ident pats don't introduce new names, then they may incorrectly create diagnostics.
But the benefit of the blacklist approach is simplicity: I think a whitelist approach would need to recursively visit patterns to collect renaming candidates?
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Save this program as dangling.rs. When you try to compile this program with rustc dangling.rs, you'll get an interesting (and long) error message:
rustc 0.12.0
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