SIL: More robust substituted function type lowering.

include/swift/AST/Types.h

@@ -953,7 +953,7 @@ class alignas(1 << TypeAlignInBits) TypeBase
                 CanType subst,
                 ArchetypeType *upperBound,
                 ArrayRef<ProtocolConformanceRef> substConformances)> substFn);
-  
+
   /// Determines whether this type is similar to \p other as defined by
   /// \p matchOptions.
   bool matches(Type other, TypeMatchOptions matchOptions);

include/swift/SIL/AbstractionPattern.h

@@ -1406,6 +1406,33 @@ class AbstractionPattern {
   /// is the corresponding value passed?
   CallingConventionKind getParameterConvention(TypeConverter &TC) const;
 
+  /// Generate the abstraction pattern for lowering the substituted SIL
+  /// function type for a function type matching this abstraction pattern.
+  ///
+  /// This abstraction pattern must be a function abstraction pattern, matching
+  /// \c substType .
+  ///
+  /// Where the abstraction pattern involves substitutable types, in order
+  /// to minimize function conversions, we extract those positions out into
+  /// fresh generic arguments, with the minimum set of constraints necessary
+  /// to maintain the calling convention (such as passed-directly or
+  /// passed-indirectly) as well as satisfy requirements of where the generic
+  /// argument structurally appears in the type.
+  /// The goal is for similar-shaped generic function types to remain
+  /// canonically equivalent, like `(T, U) -> ()`, `(T, T) -> ()`,
+  /// `(U, T) -> ()` or `(T, T.A) -> ()` when given substitutions that produce
+  /// the same function types.
+  ///
+  /// Returns a new AbstractionPattern to use for type lowering, as well as
+  /// the SubstitutionMap used to map `substType` into the new abstraction
+  /// pattern's generic environment, and the coroutine yield type mapped into
+  /// the generic environment of the new abstraction pattern.
+  std::tuple<AbstractionPattern, SubstitutionMap, AbstractionPattern>
+  getSubstFunctionTypePattern(CanAnyFunctionType substType,
+                              TypeConverter &TC,
+                              AbstractionPattern coroutineYieldOrigType,
+                              CanType coroutineYieldSubstType) const;
+
   void dump() const LLVM_ATTRIBUTE_USED;
   void print(raw_ostream &OS) const;
 

lib/IRGen/GenDecl.cpp

@@ -1738,7 +1738,8 @@ void IRGenerator::emitDynamicReplacements() {
   llvm::SmallSet<OpaqueTypeArchetypeType *, 8> origUniqueOpaqueTypes;
   for (auto *newFunc : DynamicReplacements) {
     auto newResultTy = newFunc->getLoweredFunctionType()
-             ->getAllResultsInterfaceType()
+             ->getAllResultsSubstType(newFunc->getModule(),
+                                      TypeExpansionContext::minimal())
              .getASTType();
     if (!newResultTy->hasOpaqueArchetype())
       continue;
@@ -1750,8 +1751,9 @@ void IRGenerator::emitDynamicReplacements() {
     auto *origFunc = newFunc->getDynamicallyReplacedFunction();
     assert(origFunc);
     auto origResultTy = origFunc->getLoweredFunctionType()
-                            ->getAllResultsInterfaceType()
-                            .getASTType();
+                  ->getAllResultsSubstType(origFunc->getModule(),
+                                           TypeExpansionContext::minimal())
+                  .getASTType();
     assert(origResultTy->hasOpaqueArchetype());
     origResultTy.visit([&](CanType ty) {
       if (auto opaque = ty->getAs<OpaqueTypeArchetypeType>())

lib/IRGen/LoadableByAddress.cpp

@@ -1401,7 +1401,8 @@ SILArgument *LoadableStorageAllocation::replaceArgType(SILBuilder &argBuilder,
 void LoadableStorageAllocation::insertIndirectReturnArgs() {
   GenericEnvironment *genEnv = getSubstGenericEnvironment(pass.F);
   auto loweredTy = pass.F->getLoweredFunctionType();
-  SILType resultStorageType = loweredTy->getAllResultsInterfaceType();
+  SILType resultStorageType = loweredTy->getAllResultsSubstType(pass.F->getModule(),
+                                                                pass.F->getTypeExpansionContext());
   auto canType = resultStorageType.getASTType();
   if (canType->hasTypeParameter()) {
     assert(genEnv && "Expected a GenericEnv");