Merge pull request #7074 from jckarter/use-assoc-type-conformance-3.1

[3.1] SILGen: Mark associated type conformances as "used".

Author: ematejska

lib/SILGen/SILGenDecl.cpp

@@ -1242,9 +1242,9 @@ void SILGenModule::emitExternalDefinition(Decl *d) {
   case DeclKind::Struct:
   case DeclKind::Class: {
     // Emit witness tables.
-    for (auto c : cast<NominalTypeDecl>(d)->getLocalConformances(
-                    ConformanceLookupKind::All,
-                    nullptr, /*sorted=*/true)) {
+    auto nom = cast<NominalTypeDecl>(d);
+    for (auto c : nom->getLocalConformances(ConformanceLookupKind::All,
+                                            nullptr, /*sorted=*/true)) {
       auto *proto = c->getProtocol();
       if (Lowering::TypeConverter::protocolRequiresWitnessTable(proto) &&
           isa<NormalProtocolConformance>(c) &&
@@ -1606,7 +1606,7 @@ class SILGenConformance : public SILGenWitnessTable<SILGenConformance> {
 
       ProtocolConformanceRef conformance(protocol);
       // If the associated type requirement is satisfied by an associated type,
-      // these will all be null.
+      // these will all be abstract conformances.
       if (witness.getConformances()[0].isConcrete()) {
         auto foundConformance = std::find_if(witness.getConformances().begin(),
                                         witness.getConformances().end(),
@@ -1616,6 +1616,7 @@ class SILGenConformance : public SILGenWitnessTable<SILGenConformance> {
         assert(foundConformance != witness.getConformances().end());
         conformance = *foundConformance;
       }
+      SGM.useConformance(conformance);
 
       Entries.push_back(SILWitnessTable::AssociatedTypeProtocolWitness{
         td, protocol, conformance

test/SILGen/Inputs/external-associated-type-conformance.h

@@ -0,0 +1,11 @@
+@import Foundation;
+
+extern NSErrorDomain const BadErrorDomain;
+
+typedef enum __attribute__((ns_error_domain(BadErrorDomain), swift_name("BadError")))
+BadError: NSInteger {
+  BadBig,
+  BadSmall,
+} BadError;
+
+

test/SILGen/external-associated-type-conformance.swift

@@ -0,0 +1,12 @@
+// RUN: %target-swift-frontend -emit-silgen -import-objc-header %S/Inputs/external-associated-type-conformance.h %s | %FileCheck %s
+// REQUIRES: objc_interop
+
+extension BadError: LocalizedError {}
+
+// -- The _BridgedStoredNSError conformance...
+// CHECK-LABEL: sil_witness_table shared [fragile] BadError: _BridgedStoredNSError module __ObjC {
+// -- uses the `Code` type's _ErrorCodeProtocol conformance...
+// CHECK:           associated_type_protocol (Code: _ErrorCodeProtocol): BadError.Code: _ErrorCodeProtocol module __ObjC
+// CHECK:       }
+// -- so we have to emit that too
+// CHECK-LABEL: sil_witness_table shared [fragile] BadError.Code: _ErrorCodeProtocol module __ObjC