Merge pull request #85593 from slavapestov/lazy-opaque-type-decl

Serialization: Lazily deserialize OpaqueTypeDecl's underlying substitutions

include/swift/AST/Decl.h

@@ -761,6 +761,11 @@ protected:
     HasAnyUnavailableDuringLoweringValues : 1
   );
 
+  SWIFT_INLINE_BITFIELD(OpaqueTypeDecl, GenericTypeDecl, 1,
+    /// Whether we have lazily-loaded underlying substitutions.
+    HasLazyUnderlyingSubstitutions : 1
+  );
+
   SWIFT_INLINE_BITFIELD(ModuleDecl, TypeDecl, 1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+8,
     /// If the module is compiled as static library.
     StaticLibrary : 1,
@@ -3646,7 +3651,8 @@ private:
   OpaqueTypeDecl(ValueDecl *NamingDecl, GenericParamList *GenericParams,
                  DeclContext *DC,
                  GenericSignature OpaqueInterfaceGenericSignature,
-                 ArrayRef<TypeRepr *> OpaqueReturnTypeReprs);
+                 ArrayRef<TypeRepr *> OpaqueReturnTypeReprs,
+                 bool hasLazyUnderlyingSubstitutions);
 
   unsigned getNumOpaqueReturnTypeReprs() const {
     return NamingDeclAndHasOpaqueReturnTypeRepr.getInt()
@@ -3658,13 +3664,21 @@ private:
     return getNumOpaqueReturnTypeReprs();
   }
 
+  void loadLazyUnderlyingSubstitutions();
+
 public:
-  static OpaqueTypeDecl *get(
+  static OpaqueTypeDecl *create(
       ValueDecl *NamingDecl, GenericParamList *GenericParams,
       DeclContext *DC,
       GenericSignature OpaqueInterfaceGenericSignature,
       ArrayRef<TypeRepr *> OpaqueReturnTypeReprs);
 
+  static OpaqueTypeDecl *createDeserialized(
+      GenericParamList *GenericParams,
+      DeclContext *DC,
+      GenericSignature OpaqueInterfaceGenericSignature,
+      LazyMemberLoader *lazyLoader, uint64_t underlyingSubsData);
+
   ValueDecl *getNamingDecl() const {
     return NamingDeclAndHasOpaqueReturnTypeRepr.getPointer();
   }
@@ -3720,19 +3734,19 @@ public:
       bool typeCheckFunctionBodies=true) const;
 
   void setUniqueUnderlyingTypeSubstitutions(SubstitutionMap subs) {
-    assert(!UniqueUnderlyingType.has_value() && "resetting underlying type?!");
+    ASSERT(!Bits.OpaqueTypeDecl.HasLazyUnderlyingSubstitutions);
+    ASSERT(!UniqueUnderlyingType.has_value() && "resetting underlying type?!");
     UniqueUnderlyingType = subs;
   }
 
   bool hasConditionallyAvailableSubstitutions() const {
+    const_cast<OpaqueTypeDecl *>(this)->loadLazyUnderlyingSubstitutions();
+
     return ConditionallyAvailableTypes.has_value();
   }
 
   ArrayRef<ConditionallyAvailableSubstitutions *>
-  getConditionallyAvailableSubstitutions() const {
-    assert(ConditionallyAvailableTypes);
-    return ConditionallyAvailableTypes.value();
-  }
+  getConditionallyAvailableSubstitutions() const;
 
   void setConditionallyAvailableSubstitutions(
       ArrayRef<ConditionallyAvailableSubstitutions *> substitutions);

include/swift/AST/LazyResolver.h

@@ -63,6 +63,12 @@ public:
   uint64_t defaultDefinitionTypeData = 0;
 };
 
+class LazyOpaqueTypeData : public LazyContextData {
+public:
+  /// The context data used for loading the underlying type substitution map.
+  uint64_t underlyingSubsData = 0;
+};
+
 /// Context data for protocols.
 class LazyProtocolData : public LazyIterableDeclContextData {
 public:
@@ -138,6 +144,10 @@ public:
   // Returns the target parameter of the `@_specialize` attribute or null.
   virtual ValueDecl *loadTargetFunctionDecl(const AbstractSpecializeAttr *attr,
                                             uint64_t contextData) = 0;
+
+  /// Loads the underlying type substitution map of an opaque result declaration.
+  virtual void
+  finishOpaqueTypeDecl(OpaqueTypeDecl *opaqueDecl, uint64_t contextData) = 0;
 };
 
 /// A class that can lazily load conformances from a serialized format.