AST: Add a new overload of getContextSubstitutionMap()

Author: slavapestov

include/swift/AST/Types.h

@@ -1289,26 +1289,22 @@ class alignas(1 << TypeAlignInBits) TypeBase
   /// Otherwise, it returns the type itself.
   Type getReferenceStorageReferent();
 
-  /// Determine the set of substitutions that should be applied to a
-  /// type spelled within the given DeclContext to treat it as a
-  /// member of this type.
+  /// Assumes this is a nominal type. Returns a substitution map that sends each
+  /// generic parameter of the declaration's generic signature to the corresponding
+  /// generic argument of this nominal type.
   ///
-  /// For example, given:
-  /// \code
-  /// struct X<T, U> { }
-  /// extension X {
-  ///   typealias SomeArray = [T]
-  /// }
-  /// \endcode
+  /// Eg: Array<Int> ---> { Element := Int }
+  SubstitutionMap getContextSubstitutionMap();
+
+  /// More general form of the above that handles additional cases:
   ///
-  /// Asking for the member substitutions of \c X<Int,String> within
-  /// the context of the extension above will produce substitutions T
-  /// -> Int and U -> String suitable for mapping the type of
-  /// \c SomeArray.
+  /// 1) dc is the nominal type itself or an unconstrained extension
+  /// 2) dc is a superclass
+  /// 3) dc is a protocol
   ///
-  /// \param genericEnv If non-null and the type is nested inside of a
-  /// generic function, generic parameters of the outer context are
-  /// mapped to context archetypes of this generic environment.
+  /// In Case 2) and 3), the substitution map has the generic signature of the dc,
+  /// and not the nominal. In Case 1), this is the same as the no-argument overload
+  /// of getContextSubstitutionMap().
   SubstitutionMap getContextSubstitutionMap(const DeclContext *dc,
                                             GenericEnvironment *genericEnv=nullptr);
 

include/swift/SILOptimizer/OptimizerBridgingImpl.h

@@ -415,8 +415,7 @@ void BridgedPassContext::loadFunction(BridgedFunction function, bool loadCallees
 
 BridgedSubstitutionMap BridgedPassContext::getContextSubstitutionMap(BridgedType type) const {
   swift::SILType ty = type.unbridged();
-  auto *ntd = ty.getASTType()->getAnyNominal();
-  return ty.getASTType()->getContextSubstitutionMap(ntd);
+  return ty.getASTType()->getContextSubstitutionMap();
 }
 
 BridgedType BridgedPassContext::getBuiltinIntegerType(SwiftInt bitWidth) const {

lib/AST/ASTMangler.cpp

@@ -1976,10 +1976,9 @@ void ASTMangler::appendRetroactiveConformances(Type type, GenericSignature sig)
     if (type->hasUnboundGenericType())
       return;
 
-    auto nominal = type->getAnyNominal();
-    if (!nominal) return;
+    if (!type->getAnyNominal()) return;
 
-    subMap = type->getContextSubstitutionMap(nominal);
+    subMap = type->getContextSubstitutionMap();
   }
 
   appendRetroactiveConformances(subMap, sig);

lib/AST/Type.cpp

@@ -3043,8 +3043,7 @@ getForeignRepresentable(Type type, ForeignLanguage language,
       auto specialized = type->getASTContext()
         .getSpecializedConformance(type,
              cast<NormalProtocolConformance>(result.getConformance()),
-             boundGenericType->getContextSubstitutionMap(
-                                                 boundGenericType->getDecl()));
+             boundGenericType->getContextSubstitutionMap());
       result = ForeignRepresentationInfo::forBridged(specialized);
     }
   }

lib/AST/TypeSubstitution.cpp

@@ -805,6 +805,10 @@ TypeBase::getContextSubstitutions(const DeclContext *dc,
   return substitutions;
 }
 
+SubstitutionMap TypeBase::getContextSubstitutionMap() {
+  return getContextSubstitutionMap(getAnyNominal(), nullptr);
+}
+
 SubstitutionMap TypeBase::getContextSubstitutionMap(
     const DeclContext *dc,
     GenericEnvironment *genericEnv) {

lib/IRGen/Fulfillment.cpp

@@ -361,7 +361,7 @@ bool FulfillmentMap::searchNominalTypeMetadata(IRGenModule &IGM,
 
   bool hadFulfillment = false;
 
-  auto subs = type->getContextSubstitutionMap(nominal);
+  auto subs = type->getContextSubstitutionMap();
 
   GenericTypeRequirements requirements(IGM, nominal);
 

lib/IRGen/GenMeta.cpp

@@ -4929,7 +4929,7 @@ namespace {
     }
 
     SubstitutionMap genericSubstitutions() {
-      return type->getContextSubstitutionMap(type->getAnyNominal());
+      return type->getContextSubstitutionMap();
     }
 
     MetadataTrailingFlags getTrailingFlags() {

lib/IRGen/GenProto.cpp

@@ -2991,7 +2991,7 @@ MetadataResponse MetadataPath::followComponent(IRGenFunction &IGF,
     GenericTypeRequirements requirements(IGF.IGM, nominal);
     auto &requirement = requirements.getRequirements()[reqtIndex];
 
-    auto subs = sourceKey.Type->getContextSubstitutionMap(nominal);
+    auto subs = type->getContextSubstitutionMap();
     auto sub = requirement.getTypeParameter().subst(subs)->getCanonicalType();
 
     // In either case, we need to change the type.

lib/IRGen/GenRecord.h

@@ -209,7 +209,7 @@ class RecordTypeInfoImpl : public Base,
       if (auto likeType = rawLayout->getResolvedScalarLikeType(structDecl)) {
         if (rawLayout->shouldMoveAsLikeType()) {
           auto astT = T.getASTType();
-          auto subs = astT->getContextSubstitutionMap(structDecl);
+          auto subs = astT->getContextSubstitutionMap();
           auto loweredLikeType = IGF.IGM.getLoweredType(likeType->subst(subs));
           auto &likeTypeInfo = IGF.IGM.getTypeInfo(loweredLikeType);
 
@@ -286,7 +286,7 @@ class RecordTypeInfoImpl : public Base,
       if (auto likeType = rawLayout->getResolvedScalarLikeType(structDecl)) {
         if (rawLayout->shouldMoveAsLikeType()) {
           auto astT = T.getASTType();
-          auto subs = astT->getContextSubstitutionMap(structDecl);
+          auto subs = astT->getContextSubstitutionMap();
           auto loweredLikeType = IGF.IGM.getLoweredType(likeType->subst(subs));
           auto &likeTypeInfo = IGF.IGM.getTypeInfo(loweredLikeType);
 

lib/IRGen/GenType.cpp

@@ -2942,7 +2942,7 @@ static bool tryEmitDeinitCall(IRGenFunction &IGF,
          && !deinitTy->hasError()
          && "deinit should have only one parameter");
 
-  auto substitutions = ty->getContextSubstitutionMap(nominal);
+  auto substitutions = ty->getContextSubstitutionMap();
 
   CalleeInfo info(deinitTy,
                   deinitTy->substGenericArgs(IGF.getSILModule(),