[Serialization] Drop inherited conformances on classes (swiftlang#23347)

These can be recreated if needed in a client library. To do this, I've
added a new ConformanceLookupKind::NonInherited, which can also be
used elsewhere in the project where we're already filtering out
inherited conformances some other way.

Note that this doesn't drop inherited conformances from the entire
serialized interface, just from the list that a class explicitly
declares. They still get referenced sometimes.

rdar://problem/50541451 and possibly others

Author: jrose-apple

include/swift/AST/DeclContext.h

@@ -149,6 +149,8 @@ enum class ConformanceLookupKind : unsigned {
   All,
   /// Only the explicit conformance.
   OnlyExplicit,
+  /// All conformances except for inherited ones.
+  NonInherited,
 };
 
 /// Describes a diagnostic for a conflict between two protocol

lib/AST/ConformanceLookupTable.cpp

@@ -989,10 +989,30 @@ void ConformanceLookupTable::lookupConformances(
                        return true;
 
                      // If we are to filter out this result, do so now.
-                     if (lookupKind == ConformanceLookupKind::OnlyExplicit &&
-                         entry->getKind() != ConformanceEntryKind::Explicit &&
-                         entry->getKind() != ConformanceEntryKind::Synthesized)
-                       return false;
+                     switch (lookupKind) {
+                     case ConformanceLookupKind::OnlyExplicit:
+                       switch (entry->getKind()) {
+                       case ConformanceEntryKind::Explicit:
+                       case ConformanceEntryKind::Synthesized:
+                         break;
+                       case ConformanceEntryKind::Implied:
+                       case ConformanceEntryKind::Inherited:
+                         return false;
+                       }
+                       break;
+                     case ConformanceLookupKind::NonInherited:
+                       switch (entry->getKind()) {
+                       case ConformanceEntryKind::Explicit:
+                       case ConformanceEntryKind::Synthesized:
+                       case ConformanceEntryKind::Implied:
+                         break;
+                       case ConformanceEntryKind::Inherited:
+                         return false;
+                       }
+                       break;
+                     case ConformanceLookupKind::All:
+                       break;
+                     }
 
                      // Record the protocol.
                      if (protocols)

lib/SILGen/SILGenDecl.cpp

@@ -1436,7 +1436,7 @@ void SILGenModule::emitExternalDefinition(Decl *d) {
   case DeclKind::Class: {
     // Emit witness tables.
     auto nom = cast<NominalTypeDecl>(d);
-    for (auto c : nom->getLocalConformances(ConformanceLookupKind::All,
+    for (auto c : nom->getLocalConformances(ConformanceLookupKind::NonInherited,
                                             nullptr)) {
       auto *proto = c->getProtocol();
       if (Lowering::TypeConverter::protocolRequiresWitnessTable(proto) &&

lib/SILGen/SILGenType.cpp

@@ -976,7 +976,7 @@ class SILGenType : public TypeMemberVisitor<SILGenType> {
     // Emit witness tables for conformances of concrete types. Protocol types
     // are existential and do not have witness tables.
     for (auto *conformance : theType->getLocalConformances(
-                               ConformanceLookupKind::All, nullptr)) {
+                               ConformanceLookupKind::NonInherited, nullptr)) {
       if (conformance->isComplete()) {
         if (auto *normal = dyn_cast<NormalProtocolConformance>(conformance))
           SGM.getWitnessTable(normal);

lib/Serialization/Serialization.cpp

@@ -3217,7 +3217,7 @@ void Serializer::writeDecl(const Decl *D) {
     auto contextID = addDeclContextRef(theClass->getDeclContext());
 
     auto conformances = theClass->getLocalConformances(
-                          ConformanceLookupKind::All, nullptr);
+                          ConformanceLookupKind::NonInherited, nullptr);
 
     SmallVector<TypeID, 4> inheritedTypes;
     for (auto inherited : theClass->getInherited()) {

lib/TBDGen/TBDGen.cpp

@@ -114,7 +114,8 @@ void TBDGenVisitor::addBaseConformanceDescriptor(
 }
 
 void TBDGenVisitor::addConformances(DeclContext *DC) {
-  for (auto conformance : DC->getLocalConformances()) {
+  for (auto conformance : DC->getLocalConformances(
+                            ConformanceLookupKind::NonInherited)) {
     auto protocol = conformance->getProtocol();
     auto needsWTable =
         Lowering::TypeConverter::protocolRequiresWitnessTable(protocol);

validation-test/Serialization/conformance-removed.swift

@@ -1,9 +1,9 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-build-swift -emit-sil -emit-module-path %t/SwiftLib.swiftmodule -I %S/Inputs/conformance-removed/ %S/Inputs/conformance-removed/SwiftLib.swift -Xcc -DUSE_PROTO
-// RUN: not --crash %target-build-swift -typecheck -I %t -I %S/Inputs/custom-modules/ %s 2>&1 | %FileCheck %s
+// RUN: %target-build-swift -emit-module -emit-module-path %t/SwiftLib.swiftmodule -I %S/Inputs/conformance-removed/ %S/Inputs/conformance-removed/SwiftLib.swift -Xcc -DUSE_PROTO
+// RUN: not grep SomeProto %t/SwiftLib.swiftmodule
+// RUN: %target-build-swift -typecheck -I %t -I %S/Inputs/custom-modules/ %s
 
 // REQUIRES: objc_interop
 
 import SwiftLib
 class Rdar28282310: Sub {}
-// CHECK: If you're seeing a crash here, check that your SDK and dependencies are at least as new as the versions used to build 'SwiftLib'