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Mark auto traits as coinductive
Coinductive traits are traits that when proving a predicate for them, `Type: Trait`, inside the predicate we can rely on itself to hold. For example, in `struct Foo(Foo)`, coinductive trait will succeed `Foo: Trait` and non-coinductive trait will fail unless there's an `impl Trait for Foo`. In Rust, only auto traits and `#[rustc_coinductive]` traits are coinductive, but previously we haven't considered auto traits coinductive.
| -rw-r--r-- | crates/hir-def/src/signatures.rs | 2 | ||||
| -rw-r--r-- | crates/hir-ty/src/tests/traits.rs | 34 |
2 files changed, 35 insertions, 1 deletions
diff --git a/crates/hir-def/src/signatures.rs b/crates/hir-def/src/signatures.rs index 10a38ec71e..45dab8859d 100644 --- a/crates/hir-def/src/signatures.rs +++ b/crates/hir-def/src/signatures.rs @@ -545,7 +545,7 @@ impl TraitSignature { let attrs = AttrFlags::query(db, id.into()); let source = loc.source(db); if source.value.auto_token().is_some() { - flags.insert(TraitFlags::AUTO); + flags.insert(TraitFlags::AUTO | TraitFlags::COINDUCTIVE); } if source.value.unsafe_token().is_some() { flags.insert(TraitFlags::UNSAFE); diff --git a/crates/hir-ty/src/tests/traits.rs b/crates/hir-ty/src/tests/traits.rs index 8233a00981..fad944589d 100644 --- a/crates/hir-ty/src/tests/traits.rs +++ b/crates/hir-ty/src/tests/traits.rs @@ -5377,3 +5377,37 @@ fn run_dyn<'b>(val: &dyn for<'a> Trait<'a, 'b>) {} "#]], ); } + +#[test] +fn recursive_auto_trait() { + check_types( + r#" +auto trait Send {} +impl<T> !Send for *const T {} + +struct Vec<T>(*const T); +impl<T: Send> Send for Vec<T> {} + +struct Node { + children: Vec<Node>, +} + +struct Holder<T>(T); + +trait Lock<T> { + fn get(&self) -> &T; +} + +impl<T: Send> Lock<T> for Holder<T> { + fn get(&self) -> &T { + &self.0 + } +} + +fn probe(h: &Holder<Node>) { + h.get(); + // ^^^^^^^ &'? Node +} + "#, + ); +} |