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f17baefd7a
If you had something like:
struct G<T> {
func f<each U>(_: repeat each U) where T == (repeat each U) {}
}
We would fulfill 'each U' from the metadata for 'G<(repeat each U)>',
by taking apart the tuple metadata for `(repeat each U)` and forming
a pack.
However this code path was only intended to kick in for a tuple
conformance witness thunk. In the general case, this optimization
is not correct, because if 'each U' is substituted with a
one-element pack, the generic argument of `G<(repeat each U)>` is
just that one element's metadata, and not a tuple. In fact, we
cannot distinguish the one-element tuple case, because the wrapped
element may itself be a tuple.
The fix is to just split off FulfillmentMap::searchTupleTypeMetadata()
from searchTypeMetadata(), and only call the former when we're in
the specific situation that requires it.
- Fixes https://github.com/swiftlang/swift/issues/78191.
- Fixes rdar://problem/135325886.
14 lines
631 B
Swift
14 lines
631 B
Swift
// RUN: %target-swift-frontend -emit-ir %s -target %target-swift-5.9-abi-triple | %FileCheck %s
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struct G<T> {
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var t: T
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// Make sure we *don't* try to fulfill the pack from the tuple, because we cannot
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// distinguish the one-element case that way.
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// CHECK-LABEL: define {{.*}} void @"$s34variadic_generic_fulfillment_tuple1GV20fixOuterGenericParamyACyqd__qd__Qp_tGqd__qd__Qp_t_tRvd__qd__qd__Qp_tRszlF"(ptr noalias sret(%swift.opaque) %0, ptr noalias %1, {{i32|i64}} %2, ptr %"each U", ptr noalias swiftself %3)
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func fixOuterGenericParam<each U>(_ t: T) -> G<T> where T == (repeat each U) {
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return G<T>(t: t)
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}
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}
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