IRGen: Handle self-conformances in defineAssociatedTypeWitnessTableAccessFunction

rdar://46664811

Author: aschwaighofer

lib/IRGen/GenProto.cpp

@@ -1644,6 +1644,17 @@ void WitnessTableBuilder::defineAssociatedTypeWitnessTableAccessFunction(
   ProtocolDecl *associatedProtocol = requirement.getAssociatedRequirement();
 
   const ConformanceInfo *conformanceI = nullptr;
+
+  // Rewrite (abstract) self conformances to the concrete conformance.
+  if (associatedConformance.isAbstract() && !hasArchetype) {
+    // This must be a self conformance.
+    auto proto = associatedConformance.getRequirement();
+    assert(proto->requiresSelfConformanceWitnessTable());
+    assert(cast<ProtocolType>(associatedType)->getDecl() == proto);
+    auto concreteConformance = IGF.IGM.Context.getSelfConformance(proto);
+    associatedConformance = ProtocolConformanceRef(concreteConformance);
+  }
+
   if (associatedConformance.isConcrete()) {
     assert(associatedType->isEqual(associatedConformance.getConcrete()->getType()));
 

test/IRGen/associated_types.swift

@@ -93,5 +93,16 @@ func testFastRuncible<T: Runcible, U: FastRuncible>(_ t: T, u: U)
 // CHECK-NEXT: [[T1:%.*]] = bitcast i8* [[T0]] to void (%swift.type*, %swift.type*, i8**)*
 // CHECK-NEXT: call swiftcc void [[T1]](%swift.type* swiftself %T.RuncerType.Runcee, %swift.type* %T.RuncerType.Runcee, i8** %T.RuncerType.Runcee.Speedy)
 
+public protocol P0 {
+  associatedtype ErrorType : Swift.Error
+}
+
+public struct P0Impl : P0 {
+  public typealias ErrorType = Swift.Error
+}
+
+// CHECK: define{{.*}} swiftcc i8** @"$s16associated_types6P0ImplVAA0C0AA9ErrorTypeAaDP_s0E0PWT"(%swift.type* %P0Impl.ErrorType, %swift.type* %P0Impl, i8** %P0Impl.P0)
+// CHECK:  ret i8** @"$ss5ErrorWS"
+
 // CHECK: attributes [[NOUNWIND_READNONE]] = { nounwind readnone }