GenericEnvironment: Don't use the existential layout's protocols to build "nested" opened archetypes

Author: AnthonyLatsis

lib/AST/GenericEnvironment.cpp

@@ -349,16 +349,27 @@ GenericEnvironment::getOrCreateArchetypeFromInterfaceType(Type depType) {
 
     case Kind::OpenedExistential: {
       // FIXME: The existential layout's protocols might differ from the
-      // canonicalized set of protocols determined by the generic signature,
-      // so use the existential layout's version. We should align these at
+      // canonicalized set of protocols determined by the generic signature.
+      // Before NestedArchetypeType was removed, we used the former when
+      // building a root OpenedArchetypeType, and the latter when building
+      // nested archetypes.
+      // For compatibility, continue using the existential layout's version when
+      // the interface type is a generic parameter. We should align these at
       // some point.
-      auto layout = getOpenedExistentialType()->getExistentialLayout();
-      SmallVector<ProtocolDecl *, 4> protos;
-      for (auto protoType : layout.getProtocols())
-        protos.push_back(protoType->getDecl());
-      result = OpenedArchetypeType::getNew(this, requirements.anchor,
-                                           protos, superclass,
-                                           requirements.layout);
+      if (depType->is<GenericTypeParamType>()) {
+        auto layout = getOpenedExistentialType()->getExistentialLayout();
+        SmallVector<ProtocolDecl *, 2> protos;
+        for (auto protoType : layout.getProtocols())
+          protos.push_back(protoType->getDecl());
+
+        result = OpenedArchetypeType::getNew(this, requirements.anchor, protos,
+                                             superclass, requirements.layout);
+      } else {
+        result = OpenedArchetypeType::getNew(this, requirements.anchor,
+                                             requirements.protos, superclass,
+                                             requirements.layout);
+      }
+
       break;
     }
 

test/decl/protocol/protocols_with_self_or_assoc_reqs.swift

@@ -523,6 +523,17 @@ do {
   // expected-error@-3 {{cannot convert value of type 'Bool' to expected argument type 'C<UnfulfillableGenericRequirements>'}}
 }
 
+protocol RequirementFailures {
+  associatedtype A
+}
+extension RequirementFailures {
+  func method() where A: RequirementFailures {} // expected-note {{where 'Self.A' = '(RequirementFailures).A'}}
+}
+do {
+  let exist: any RequirementFailures
+  exist.method() // expected-error {{instance method 'method()' requires that '(RequirementFailures).A' conform to 'RequirementFailures'}}
+}
+
 // Settable storage members with a 'Self' result type may not be used with an
 // existential base.
 protocol P2 {