Merge pull request #25614 from harlanhaskins/i-saw-lookup-ignoring-super-clause-5.1

[Sema] Compute superclass of deserialized protocols via generic signature

Author: Harlan Haskins

include/swift/Serialization/ModuleFormat.h

@@ -52,7 +52,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR = 493; // backing variables
+const uint16_t SWIFTMODULE_VERSION_MINOR = 495; // remove superclass from ProtocolLayout
 
 using DeclIDField = BCFixed<31>;
 
@@ -997,7 +997,6 @@ namespace decls_block {
     BCFixed<1>,             // objc?
     BCFixed<1>,             // existential-type-supported?
     GenericEnvironmentIDField, // generic environment
-    TypeIDField,            // superclass
     AccessLevelField,       // access level
     BCArray<DeclIDField>    // inherited types
     // Trailed by the generic parameters (if any), the members record, and

lib/AST/NameLookup.cpp

@@ -21,6 +21,7 @@
 #include "swift/AST/ClangModuleLoader.h"
 #include "swift/AST/DebuggerClient.h"
 #include "swift/AST/ExistentialLayout.h"
+#include "swift/AST/GenericSignature.h"
 #include "swift/AST/LazyResolver.h"
 #include "swift/AST/Initializer.h"
 #include "swift/AST/NameLookupRequests.h"
@@ -2039,6 +2040,25 @@ SuperclassDeclRequest::evaluate(Evaluator &evaluator,
                                 NominalTypeDecl *subject) const {
   auto &Ctx = subject->getASTContext();
 
+  // Protocols may get their superclass bound from a `where Self : Superclass`
+  // clause.
+  if (auto *proto = dyn_cast<ProtocolDecl>(subject)) {
+    // If the protocol came from a serialized module, compute the superclass via
+    // its generic signature.
+    if (proto->wasDeserialized()) {
+      auto superTy = proto->getGenericSignature()
+          ->getSuperclassBound(proto->getSelfInterfaceType());
+      if (superTy)
+        return superTy->getClassOrBoundGenericClass();
+    }
+
+    // Otherwise check the where clause.
+    auto selfBounds = getSelfBoundsFromWhereClause(proto);
+    for (auto inheritedNominal : selfBounds.decls)
+      if (auto classDecl = dyn_cast<ClassDecl>(inheritedNominal))
+        return classDecl;
+  }
+
   for (unsigned i : indices(subject->getInherited())) {
     // Find the inherited declarations referenced at this position.
     auto inheritedTypes = evaluateOrDefault(evaluator,
@@ -2058,15 +2078,6 @@ SuperclassDeclRequest::evaluate(Evaluator &evaluator,
     }
   }
 
-  // Protocols also support '... where Self : Superclass'.
-  auto *proto = dyn_cast<ProtocolDecl>(subject);
-  if (proto == nullptr)
-    return nullptr;
-
-  auto selfBounds = getSelfBoundsFromWhereClause(proto);
-  for (auto inheritedNominal : selfBounds.decls)
-    if (auto classDecl = dyn_cast<ClassDecl>(inheritedNominal))
-      return classDecl;
 
   return nullptr;
 }

lib/Sema/TypeCheckRequestFunctions.cpp

@@ -16,6 +16,7 @@
 #include "swift/AST/TypeCheckRequests.h"
 #include "swift/AST/Decl.h"
 #include "swift/AST/ExistentialLayout.h"
+#include "swift/AST/GenericSignature.h"
 #include "swift/AST/NameLookupRequests.h"
 #include "swift/AST/TypeLoc.h"
 #include "swift/AST/Types.h"
@@ -84,6 +85,15 @@ SuperclassTypeRequest::evaluate(Evaluator &evaluator,
                                 TypeResolutionStage stage) const {
   assert(isa<ClassDecl>(nominalDecl) || isa<ProtocolDecl>(nominalDecl));
 
+  // If this is a protocol that came from a serialized module, compute the
+  // superclass via its generic signature.
+  if (auto *proto = dyn_cast<ProtocolDecl>(nominalDecl)) {
+    if (proto->wasDeserialized()) {
+      return proto->getGenericSignature()
+          ->getSuperclassBound(proto->getSelfInterfaceType());
+    }
+  }
+
   for (unsigned int idx : indices(nominalDecl->getInherited())) {
     auto result = evaluator(InheritedTypeRequest{nominalDecl, idx, stage});
 

lib/Serialization/Deserialization.cpp

@@ -3291,15 +3291,13 @@ class swift::DeclDeserializer {
     DeclContextID contextID;
     bool isImplicit, isClassBounded, isObjC, existentialTypeSupported;
     GenericEnvironmentID genericEnvID;
-    TypeID superclassID;
     uint8_t rawAccessLevel;
     ArrayRef<uint64_t> rawInheritedIDs;
 
     decls_block::ProtocolLayout::readRecord(scratch, nameID, contextID,
                                             isImplicit, isClassBounded, isObjC,
                                             existentialTypeSupported,
-                                            genericEnvID, superclassID,
-                                            rawAccessLevel, rawInheritedIDs);
+                                            genericEnvID, rawAccessLevel, rawInheritedIDs);
 
     auto DC = MF.getDeclContext(contextID);
     if (declOrOffset.isComplete())
@@ -3310,7 +3308,6 @@ class swift::DeclDeserializer {
                                              /*TrailingWhere=*/nullptr);
     declOrOffset = proto;
 
-    proto->setSuperclass(MF.getType(superclassID));
     proto->setRequiresClass(isClassBounded);
     proto->setExistentialTypeSupported(existentialTypeSupported);
 

lib/Serialization/Serialization.cpp

@@ -3334,7 +3334,6 @@ void Serializer::writeDecl(const Decl *D) {
                                  /*resolver=*/nullptr),
                                addGenericEnvironmentRef(
                                                 proto->getGenericEnvironment()),
-                               addTypeRef(proto->getSuperclass()),
                                rawAccessLevel,
                                inherited);
 

test/Serialization/Inputs/class-bound-protocol.swift

@@ -0,0 +1,15 @@
+public protocol P: C {}
+
+public class C: P {
+  public init() {}
+  public func funcInClass() {}
+}
+
+public protocol GenericP: GenericC<Int> {}
+
+public class GenericC<T> {
+  public init() {}
+  public func funcInClass() {}
+}
+
+extension GenericC: GenericP where T == Int {}

test/Serialization/use-class-bound-protocol.swift

@@ -0,0 +1,14 @@
+// RUN: %empty-directory(%t)
+
+// RUN: %target-swift-frontend -emit-module-path %t/ClassBoundProtocol.swiftmodule %S/Inputs/class-bound-protocol.swift -module-name ClassBoundProtocol
+// RUN: %target-swift-frontend -typecheck %s -I %t
+
+import ClassBoundProtocol
+
+func f() {
+  let p: P = C()
+  p.funcInClass()
+
+  let genericP: GenericP = GenericC<Int>()
+  genericP.funcInClass()
+}