Fix serialization for structural opaque result types

Author: DougGregor

include/swift/AST/Decl.h

@@ -2719,8 +2719,8 @@ class OpaqueTypeDecl final :
   /// abstracted underlying types.
   GenericSignature OpaqueInterfaceGenericSignature;
 
-  /// The generic parameter that represents the underlying type.
-  GenericTypeParamType *UnderlyingInterfaceType;
+  /// The underlying type, which will involve the opaque generic parameters.
+  Type UnderlyingInterfaceType;
 
   /// If known, the underlying type and conformances of the opaque type,
   /// expressed as a SubstitutionMap for the opaque interface generic signature.
@@ -2734,7 +2734,7 @@ class OpaqueTypeDecl final :
                  DeclContext *DC,
                  GenericSignature OpaqueInterfaceGenericSignature,
                  ArrayRef<OpaqueReturnTypeRepr *> OpaqueReturnTypeReprs,
-                 GenericTypeParamType *UnderlyingInterfaceType);
+                 Type UnderlyingInterfaceType);
 
   unsigned getNumOpaqueReturnTypeReprs() const {
     return NamingDeclAndHasOpaqueReturnTypeRepr.getInt()
@@ -2752,7 +2752,7 @@ class OpaqueTypeDecl final :
       DeclContext *DC,
       GenericSignature OpaqueInterfaceGenericSignature,
       ArrayRef<OpaqueReturnTypeRepr *> OpaqueReturnTypeReprs,
-      GenericTypeParamType *UnderlyingInterfaceType);
+      Type UnderlyingInterfaceType);
 
   ValueDecl *getNamingDecl() const {
     return NamingDeclAndHasOpaqueReturnTypeRepr.getPointer();
@@ -2794,10 +2794,7 @@ class OpaqueTypeDecl final :
   }
 
   /// The underlying interface type describing the whole opaque type.
-  ///
-  /// FIXME: Structured opaque types will generalize this to an
-  /// arbitrary type.
-  GenericTypeParamType *getUnderlyingInterfaceType() const {
+  Type getUnderlyingInterfaceType() const {
     return UnderlyingInterfaceType;
   }
 

lib/APIDigester/ModuleAnalyzerNodes.cpp

@@ -1518,7 +1518,7 @@ SwiftDeclCollector::constructTypeNode(Type T, TypeInitInfo Info) {
     if (auto OTA = T->getAs<OpaqueTypeArchetypeType>()) {
       if (auto *D = OTA->getDecl()) {
         if (auto SubMap = D->getUnderlyingTypeSubstitutions()) {
-          T = Type(D->getUnderlyingInterfaceType()).
+          T = D->getUnderlyingInterfaceType().
             subst(*SubMap)->getCanonicalType();
         }
       }

lib/AST/ASTDumper.cpp

@@ -567,7 +567,7 @@ namespace {
       OS << " naming_decl=";
       printDeclName(OTD->getNamingDecl());
       PrintWithColorRAII(OS, TypeColor) << " opaque_interface="
-        << Type(OTD->getUnderlyingInterfaceType()).getString();
+        << OTD->getUnderlyingInterfaceType().getString();
       OS << " in "
          << OTD->getOpaqueInterfaceGenericSignature()->getAsString();
       if (auto underlyingSubs = OTD->getUnderlyingTypeSubstitutions()) {

lib/AST/Decl.cpp

@@ -7782,7 +7782,7 @@ OpaqueTypeDecl::OpaqueTypeDecl(ValueDecl *NamingDecl,
                                GenericSignature OpaqueInterfaceGenericSignature,
                                ArrayRef<OpaqueReturnTypeRepr *>
                                    OpaqueReturnTypeReprs,
-                               GenericTypeParamType *UnderlyingInterfaceType)
+                               Type UnderlyingInterfaceType)
     : GenericTypeDecl(DeclKind::OpaqueType, DC, Identifier(), SourceLoc(), {},
                       GenericParams),
       NamingDeclAndHasOpaqueReturnTypeRepr(
@@ -7807,7 +7807,7 @@ OpaqueTypeDecl *OpaqueTypeDecl::get(
       DeclContext *DC,
       GenericSignature OpaqueInterfaceGenericSignature,
       ArrayRef<OpaqueReturnTypeRepr *> OpaqueReturnTypeReprs,
-      GenericTypeParamType *UnderlyingInterfaceType) {
+      Type UnderlyingInterfaceType) {
   ASTContext &ctx = DC->getASTContext();
   auto size = totalSizeToAlloc<OpaqueReturnTypeRepr *>(
       OpaqueReturnTypeReprs.size());

lib/Serialization/Deserialization.cpp

@@ -3458,7 +3458,7 @@ class DeclDeserializer {
     auto declContext = MF.getDeclContext(contextID);
     auto interfaceSig = MF.getGenericSignature(interfaceSigID);
     auto interfaceType = MF.getType(interfaceTypeID);
-    
+
     // Check for reentrancy.
     if (declOrOffset.isComplete())
       return cast<OpaqueTypeDecl>(declOrOffset.get());
@@ -3469,7 +3469,7 @@ class DeclDeserializer {
     auto opaqueDecl = OpaqueTypeDecl::get(
         /*NamingDecl=*/ nullptr, genericParams, declContext,
         interfaceSig, /*OpaqueReturnTypeReprs*/ { },
-        interfaceType->castTo<GenericTypeParamType>());
+        interfaceType);
     declOrOffset = opaqueDecl;
 
     auto namingDecl = cast<ValueDecl>(MF.getDecl(namingDeclID));

test/Serialization/Inputs/OpaqueTypeStructured.swift

@@ -0,0 +1,16 @@
+public protocol P { }
+public protocol Q { }
+
+extension Int: P { }
+extension Double: Q { }
+
+public protocol R {
+  associatedtype A
+  func f() -> A
+}
+
+public struct X: R {
+  public func f() -> (some P, [some Q]) {
+    return (1, [3.14159, 2.71828])
+  }
+}

test/Serialization/opaque_type_structured.swift

@@ -0,0 +1,16 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -emit-module -o %t -enable-library-evolution %S/Inputs/OpaqueTypeStructured.swift
+// RUN: %target-swift-frontend -emit-sil -I %t %s | %FileCheck -check-prefix=SIL %s
+// RUN: %target-swift-ide-test -print-module -source-filename %s -module-to-print OpaqueTypeStructured -I %t | %FileCheck -check-prefix=AST %s
+import OpaqueTypeStructured
+
+func acceptR<T: R>(_: T) { }
+
+// AST: func f() -> (some P, [some Q])
+
+func passAnX(x: X) {
+  // SIL: $@convention(method) (@in_guaranteed X) -> (@out @_opaqueReturnTypeOf("$s20OpaqueTypeStructured1XV1fQr_SayQrGtyF", 0) __, @owned Array<@_opaqueReturnTypeOf("$s20OpaqueTypeStructured1XV1fQr_SayQrGtyF", 1) __>)
+  acceptR(x)
+  let _: X.A = x.f()
+}
+