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Auto merge of #13382 - lowr:fix/reorder-dyn-bounds-on-render, r=lowr

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fix: reorder dyn bounds on render

Fixes #13368

#13192 changed the order of dyn bounds, violating the [contract](3a69435af7/crates/hir-ty/src/display.rs (L896-L901)) with `write_bounds_like_dyn_trait()` on render. The projection bounds are expected to come right after the trait bound they are accompanied with.

Although the reordering procedure can be made a bit more efficient, I opted for relying only on the [invariants](3a69435af7/crates/hir-ty/src/lower.rs (L995-L998)) currently documented in `lower_dyn_trait()`. It's not the hottest path and dyn bounds tend to be short so I believe it shouldn't hurt performance noticeably.
This commit is contained in:
bors 2022-10-11 11:44:32 +00:00
commit d08f1c3dff
2 changed files with 33 additions and 1 deletions
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12
crates/hir-ty/src/display.rs
View file

@ -751,9 +751,19 @@ impl HirDisplay for Ty {
}
TyKind::BoundVar(idx) => idx.hir_fmt(f)?,
TyKind::Dyn(dyn_ty) => {
// Reorder bounds to satisfy `write_bounds_like_dyn_trait()`'s expectation.
// FIXME: `Iterator::partition_in_place()` or `Vec::drain_filter()` may make it
// more efficient when either of them hits stable.
let mut bounds: SmallVec<[_; 4]> =
dyn_ty.bounds.skip_binders().iter(Interner).cloned().collect();
let (auto_traits, others): (SmallVec<[_; 4]>, _) =
bounds.drain(1..).partition(|b| b.skip_binders().trait_id().is_some());
bounds.extend(others);
bounds.extend(auto_traits);
write_bounds_like_dyn_trait_with_prefix(
"dyn",
dyn_ty.bounds.skip_binders().interned(),
&bounds,
SizedByDefault::NotSized,
f,
)?;

22
crates/hir-ty/src/tests/display_source_code.rs
View file

@ -55,6 +55,28 @@ fn main() {
);
}
#[test]
fn render_dyn_ty_independent_of_order() {
check_types_source_code(
r#"
auto trait Send {}
trait A {
type Assoc;
}
trait B: A {}
fn test(
_: &(dyn A<Assoc = ()> + Send),
//^ &(dyn A<Assoc = ()> + Send)
_: &(dyn Send + A<Assoc = ()>),
//^ &(dyn A<Assoc = ()> + Send)
_: &dyn B<Assoc = ()>,
//^ &(dyn B<Assoc = ()>)
) {}
"#,
);
}
#[test]
fn render_dyn_for_ty() {
// FIXME