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Auto merge of #78393 - SNCPlay42:match-if-guard, r=tmandry

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Always record reference to binding in match if guards

When encountering a binding from a `match` pattern in its `if` guard when computing a generator's interior types, we must always record the type of a reference to the binding because of how `if` guards are lowered to MIR. This was missed in #75213 because the binding in that test case was autorefed and we recorded that adjusted type anyway.

Fixes #78366
This commit is contained in:
bors 2020-10-30 07:05:57 +00:00
commit 8df58ae03a
2 changed files with 32 additions and 1 deletions
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12
compiler/rustc_typeck/src/check/generator_interior.rs
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@ -344,6 +344,18 @@ impl<'a, 'tcx> Visitor<'tcx> for InteriorVisitor<'a, 'tcx> {
// The type table might not have information for this expression
// if it is in a malformed scope. (#66387)
if let Some(ty) = self.fcx.typeck_results.borrow().expr_ty_opt(expr) {
if guard_borrowing_from_pattern {
// Match guards create references to all the bindings in the pattern that are used
// in the guard, e.g. `y if is_even(y) => ...` becomes `is_even(*r_y)` where `r_y`
// is a reference to `y`, so we must record a reference to the type of the binding.
let tcx = self.fcx.tcx;
let ref_ty = tcx.mk_ref(
// Use `ReErased` as `resolve_interior` is going to replace all the regions anyway.
tcx.mk_region(ty::RegionKind::ReErased),
ty::TypeAndMut { ty, mutbl: hir::Mutability::Not },
);
self.record(ref_ty, scope, Some(expr), expr.span, guard_borrowing_from_pattern);
}
self.record(ty, scope, Some(expr), expr.span, guard_borrowing_from_pattern);
} else {
self.fcx.tcx.sess.delay_span_bug(expr.span, "no type for node");

21
src/test/ui/generator/yielding-in-match-guards.rs
View File

@ -1,4 +1,4 @@
// check-pass
// build-pass
// edition:2018
// This test is derived from
@ -11,6 +11,7 @@
// of the underlying generator.
async fn f() -> u8 { 1 }
async fn foo() -> [bool; 10] { [false; 10] }
pub async fn g(x: u8) {
match x {
@ -19,6 +20,24 @@ pub async fn g(x: u8) {
}
}
// #78366: check the reference to the binding is recorded even if the binding is not autorefed
async fn h(x: usize) {
match x {
y if foo().await[y] => (),
_ => (),
}
}
async fn i(x: u8) {
match x {
y if f().await == y + 1 => (),
_ => (),
}
}
fn main() {
let _ = g(10);
let _ = h(9);
let _ = i(8);
}