AST: Remove derivedSubs parameter from getOverrideSubstitutions()

We can apply a substitution map afterwards if needed.

Author: slavapestov

include/swift/AST/SubstitutionMap.h

@@ -199,17 +199,15 @@ class SubstitutionMap {
   /// written in terms of the generic signature of 'baseDecl'.
   static SubstitutionMap
   getOverrideSubstitutions(const ValueDecl *baseDecl,
-                           const ValueDecl *derivedDecl,
-                           Optional<SubstitutionMap> derivedSubs);
+                           const ValueDecl *derivedDecl);
 
   /// Variant of the above for when we have the generic signatures but not
   /// the decls for 'derived' and 'base'.
   static SubstitutionMap
   getOverrideSubstitutions(const ClassDecl *baseClass,
                            const ClassDecl *derivedClass,
                            GenericSignature baseSig,
-                           GenericSignature derivedSig,
-                           Optional<SubstitutionMap> derivedSubs);
+                           GenericSignature derivedSig);
 
   /// Combine two substitution maps as follows.
   ///

lib/AST/ConcreteDeclRef.cpp

@@ -36,11 +36,9 @@ ConcreteDeclRef ConcreteDeclRef::getOverriddenDecl() const {
 
   SubstitutionMap subs;
   if (baseSig) {
-    Optional<SubstitutionMap> derivedSubMap;
+    subs = SubstitutionMap::getOverrideSubstitutions(baseDecl, derivedDecl);
     if (derivedSig)
-      derivedSubMap = getSubstitutions();
-    subs = SubstitutionMap::getOverrideSubstitutions(baseDecl, derivedDecl,
-                                                     derivedSubMap);
+      subs = subs.subst(getSubstitutions());
   }
   return ConcreteDeclRef(baseDecl, subs);
 }

lib/AST/SubstitutionMap.cpp

@@ -497,8 +497,7 @@ SubstitutionMap::getProtocolSubstitutions(ProtocolDecl *protocol,
 SubstitutionMap
 SubstitutionMap::getOverrideSubstitutions(
                                       const ValueDecl *baseDecl,
-                                      const ValueDecl *derivedDecl,
-                                      Optional<SubstitutionMap> derivedSubs) {
+                                      const ValueDecl *derivedDecl) {
   // For overrides within a protocol hierarchy, substitute the Self type.
   if (auto baseProto = baseDecl->getDeclContext()->getSelfProtocolDecl()) {
     auto baseSig = baseDecl->getInnermostDeclContext()
@@ -515,44 +514,33 @@ SubstitutionMap::getOverrideSubstitutions(
       ->getGenericSignatureOfContext();
 
   return getOverrideSubstitutions(baseClass, derivedClass,
-                                  baseSig, derivedSig,
-                                  derivedSubs);
+                                  baseSig, derivedSig);
 }
 
 SubstitutionMap
 SubstitutionMap::getOverrideSubstitutions(const ClassDecl *baseClass,
                                           const ClassDecl *derivedClass,
                                           GenericSignature baseSig,
-                                          GenericSignature derivedSig,
-                                          Optional<SubstitutionMap> derivedSubs) {
+                                          GenericSignature derivedSig) {
   if (baseSig.isNull())
     return SubstitutionMap();
 
-  auto *M = baseClass->getParentModule();
-
   unsigned baseDepth = 0;
   SubstitutionMap baseSubMap;
   if (auto baseClassSig = baseClass->getGenericSignature()) {
     baseDepth = baseClassSig.getGenericParams().back()->getDepth() + 1;
 
     auto derivedClassTy = derivedClass->getDeclaredInterfaceType();
-    if (derivedSubs)
-      derivedClassTy = derivedClassTy.subst(*derivedSubs);
-    auto baseClassTy = derivedClassTy->getSuperclassForDecl(baseClass);
-    if (baseClassTy->is<ErrorType>())
-      return SubstitutionMap();
-
-    baseSubMap = baseClassTy->getContextSubstitutionMap(M, baseClass);
+    baseSubMap = derivedClassTy->getContextSubstitutionMap(
+        baseClass->getParentModule(), baseClass);
   }
 
   unsigned origDepth = 0;
   if (auto derivedClassSig = derivedClass->getGenericSignature())
     origDepth = derivedClassSig.getGenericParams().back()->getDepth() + 1;
 
   SubstitutionMap origSubMap;
-  if (derivedSubs)
-    origSubMap = *derivedSubs;
-  else if (derivedSig)
+  if (derivedSig)
     origSubMap = derivedSig->getIdentitySubstitutionMap();
 
   return combineSubstitutionMaps(baseSubMap, origSubMap,

lib/AST/Type.cpp

@@ -4989,7 +4989,7 @@ Type TypeBase::adjustSuperclassMemberDeclType(const ValueDecl *baseDecl,
                                               const ValueDecl *derivedDecl,
                                               Type memberType) {
   auto subs = SubstitutionMap::getOverrideSubstitutions(
-      baseDecl, derivedDecl, /*derivedSubs=*/None);
+      baseDecl, derivedDecl);
 
   if (auto *genericMemberType = memberType->getAs<GenericFunctionType>()) {
     memberType = FunctionType::get(genericMemberType->getParams(),

lib/SILGen/SILGenExpr.cpp

@@ -3665,8 +3665,8 @@ SILGenModule::emitKeyPathComponentForDecl(SILLocation loc,
     // to reference the overridden declaration instead.
     if (baseDecl != externalDecl) {
       externalSubs = SubstitutionMap::getOverrideSubstitutions(baseDecl,
-                                                               externalDecl,
-                                                               externalSubs);
+                                                               externalDecl)
+          .subst(externalSubs);
       externalDecl = baseDecl;
     }
   }

lib/SILGen/SILGenPoly.cpp

@@ -4224,7 +4224,7 @@ SILGenFunction::emitVTableThunk(SILDeclRef base,
                                   SILType::getPrimitiveObjectType(derivedFTy),
                                   subs, args, derivedYields);
     auto overrideSubs = SubstitutionMap::getOverrideSubstitutions(
-        base.getDecl(), derived.getDecl(), /*derivedSubs=*/subs);
+        base.getDecl(), derived.getDecl()).subst(subs);
 
     YieldInfo derivedYieldInfo(SGM, derived, derivedFTy, subs);
     YieldInfo baseYieldInfo(SGM, base, thunkTy, overrideSubs);

lib/Sema/CodeSynthesis.cpp

@@ -639,7 +639,8 @@ synthesizeDesignatedInitOverride(AbstractFunctionDecl *fn, void *context) {
   SubstitutionMap subs;
   if (auto *genericEnv = fn->getGenericEnvironment())
     subs = genericEnv->getForwardingSubstitutionMap();
-  subs = SubstitutionMap::getOverrideSubstitutions(superclassCtor, fn, subs);
+  subs = SubstitutionMap::getOverrideSubstitutions(superclassCtor, fn)
+      .subst(subs);
   ConcreteDeclRef ctorRef(superclassCtor, subs);
 
   auto type = superclassCtor->getInitializerInterfaceType().subst(subs);

lib/Sema/TypeCheckDeclOverride.cpp

@@ -620,8 +620,7 @@ static bool parameterTypesMatch(const ValueDecl *derivedDecl,
   if (baseParams->size() != derivedParams->size())
     return false;
 
-  auto subs = SubstitutionMap::getOverrideSubstitutions(baseDecl, derivedDecl,
-                                                        /*derivedSubs=*/None);
+  auto subs = SubstitutionMap::getOverrideSubstitutions(baseDecl, derivedDecl);
 
   for (auto i : indices(baseParams->getArray())) {
     auto *baseParam = baseParams->get(i);