Merge pull request swiftlang#72789 from slavapestov/two-test-cases-without-a-bug-and-a-bug-without-a-testcase

Two test cases without a bug and a bug without a testcase

Author: slavapestov

lib/AST/SubstitutionMap.cpp

@@ -355,16 +355,6 @@ SubstitutionMap::lookupConformance(CanType type, ProtocolDecl *proto) const {
   if (!type->isTypeParameter())
     return ProtocolConformanceRef::forInvalid();
 
-  // If the protocol is invertible, just do a global lookup. This avoids an
-  // infinite substitution issue by recognizing that these protocols are
-  // very simple (see rdar://119950540 for the general issue).
-  if (proto->getInvertibleProtocolKind()) {
-    auto substType = type.subst(*this);
-    if (!substType->isTypeParameter())
-      return proto->getModuleContext()->lookupConformance(substType, proto);
-    return ProtocolConformanceRef(proto);
-  }
-
   auto genericSig = getGenericSignature();
 
   auto getSignatureConformance =
@@ -396,6 +386,15 @@ SubstitutionMap::lookupConformance(CanType type, ProtocolDecl *proto) const {
     return ProtocolConformanceRef::forMissingOrInvalid(substType, proto);
   }
 
+  // If the protocol is invertible, fall back to a global lookup instead of
+  // evaluating a conformance path, to avoid an infinite substitution issue.
+  if (proto->getInvertibleProtocolKind()) {
+    auto substType = type.subst(*this);
+    if (!substType->isTypeParameter())
+      return proto->getModuleContext()->lookupConformance(substType, proto);
+    return ProtocolConformanceRef(proto);
+  }
+
   auto path = genericSig->getConformancePath(type, proto);
 
   ProtocolConformanceRef conformance;

test/Generics/rdar124697829.swift

@@ -0,0 +1,41 @@
+// RUN: %target-swift-frontend -emit-ir %s -disable-availability-checking
+
+// This is a generics test, but only IRGen exercised the substitution of
+// an abstract conformance with a type parameter -- in the type checker and
+// SIL, we only deal with archetypes.
+
+public protocol IteratorProtocol {
+  associatedtype Element
+}
+
+public protocol Sequence {
+  associatedtype Iterator: IteratorProtocol
+  associatedtype Element where Element == Iterator.Element
+}
+
+public struct IndexingIterator<S: Sequence>: IteratorProtocol {
+  public typealias Element = S.Element
+}
+
+public struct Array<Element>: Sequence {
+  public typealias Iterator = IndexingIterator<Self>
+}
+
+public protocol Publisher {
+  associatedtype Output
+}
+
+public struct SequencePublisher<Elements: Sequence>: Publisher {
+  public typealias Output = Elements.Element
+}
+
+public struct Map<Pub: Publisher, Output>: Publisher {}
+
+public func foo<T>(_: T) -> some Publisher {
+  bar(SequencePublisher<Array<T>>())
+}
+
+public func bar<Pub: Publisher>(_: Pub) -> some Publisher {
+  Map<Pub, Pub.Output>()
+}
+

test/Serialization/Inputs/protocol_with_self_conforming_existential_other.swift

@@ -0,0 +1,5 @@
+public protocol P1 {
+  associatedtype A: Sendable
+}
+
+public protocol P2: P1, Sendable where A == any P2 {}

test/Serialization/protocol_with_self_conforming_existential.swift

@@ -0,0 +1,11 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -emit-module %S/Inputs/protocol_with_self_conforming_existential_other.swift -emit-module-path %t/protocol_with_self_conforming_existential_other.swiftmodule
+// RUN: %target-swift-frontend -emit-silgen %s -I %t
+
+import protocol_with_self_conforming_existential_other
+
+// Declare a type conforming to P2, to force deserializing its
+// requirement signature.
+
+struct MyP2: P2 {}
+