Start support for protocol witness tables

Author: aschwaighofer

include/swift/IRGen/Linking.h

@@ -126,6 +126,11 @@ inline bool isEmbedded(const ProtocolConformance *c) {
   return c->getType()->getASTContext().LangOpts.hasFeature(Feature::Embedded);
 }
 
+inline bool isEmbeddedWithoutEmbeddedExitentials(const ProtocolConformance *c) {
+  return isEmbedded(c) && !c->getType()->getASTContext().
+    LangOpts.hasFeature(Feature::EmbeddedExistentials);
+}
+
 /// A link entity is some sort of named declaration, combined with all
 /// the information necessary to distinguish specific implementations
 /// of the declaration from each other.
@@ -1137,7 +1142,7 @@ class LinkEntity {
   }
 
   static LinkEntity forProtocolWitnessTable(const ProtocolConformance *C) {
-    if (isEmbedded(C)) {
+    if (isEmbeddedWithoutEmbeddedExitentials(C)) {
       assert(C->getProtocol()->requiresClass());
     }
 

lib/IRGen/GenProto.cpp

@@ -2731,7 +2731,8 @@ static void addWTableTypeMetadata(IRGenModule &IGM,
 void IRGenModule::emitSILWitnessTable(SILWitnessTable *wt) {
   if (Context.LangOpts.hasFeature(Feature::Embedded)) {
     // In Embedded Swift, only class-bound wtables are allowed.
-    if (!wt->getConformance()->getProtocol()->requiresClass())
+    if (!wt->getConformance()->getProtocol()->requiresClass() &&
+        !Context.LangOpts.hasFeature(Feature::EmbeddedExistentials))
       return;
   }
 
@@ -3752,7 +3753,9 @@ llvm::Value *irgen::emitWitnessTableRef(IRGenFunction &IGF,
   auto proto = conformance.getProtocol();
 
   // In Embedded Swift, only class-bound wtables are allowed.
-  if (srcType->getASTContext().LangOpts.hasFeature(Feature::Embedded)) {
+  auto &langOpts = srcType->getASTContext().LangOpts;
+  if (langOpts.hasFeature(Feature::Embedded) &&
+      !langOpts.hasFeature(Feature::EmbeddedExistentials)) {
     assert(proto->requiresClass());
   }
 

lib/IRGen/IRGenModule.cpp

@@ -1486,7 +1486,9 @@ bool IRGenerator::canEmitWitnessTableLazily(SILWitnessTable *wt) {
 
 void IRGenerator::addLazyWitnessTable(const ProtocolConformance *Conf) {
   // In Embedded Swift, only class-bound wtables are allowed.
-  if (SIL.getASTContext().LangOpts.hasFeature(Feature::Embedded)) {
+  auto &langOpts = SIL.getASTContext().LangOpts;
+  if (langOpts.hasFeature(Feature::Embedded) &&
+      !langOpts.hasFeature(Feature::EmbeddedExistentials)) {
     assert(Conf->getProtocol()->requiresClass());
   }
 

test/embedded/existential.swift

@@ -70,9 +70,70 @@ func test() {
     let _: any Any = (StructWithClass(), StructWithClass())
 }
 
+protocol Basic  {
+  func a()
+}
+
+protocol Derived : Basic {
+  func b()
+}
+
+class Implementor : Derived {
+  func a() { print("a") }
+  func b() { print("b") }
+}
+
+extension Int : Derived {
+  func a() { print("a Int \(self)") }
+  func b() { print("b Int \(self)") }
+}
+
+struct MyStruct : Derived {
+  var x = 5
+  func a() { print("a MyStruct \(self.x)") }
+  func b() { print("b MyStruct") }
+}
+
+enum MyEnum : Derived {
+    case a
+    case b(Int)
+
+  func a() {
+    print("a MyEnum ")
+    switch self  {
+      case .a: break
+      case .b(let x):
+        print(x)
+    }
+  }
+
+  func b() {
+    print("b MyEnum ")
+  }
+}
+
+func test2(_ p: any Derived) {
+  p.a()
+  p.b()
+}
+
 @main
 struct Main {
-    static func main() {
-        test()
-    }
+  static func main() {
+    test()
+
+// OUTPUT: a
+// OUTPUT: b
+// OUTPUT: a Int 5
+// OUTPUT: b Int 5
+// OUTPUT: a MyStruct 5
+// OUTPUT: b MyStruct
+// OUTPUT: a MyEnum
+// OUTPUT: 5
+// OUTPUT: b MyEnum
+    test2(Implementor())
+    test2(5)
+    test2(MyStruct())
+    test2(MyEnum.b(5))
+  }
 }