AST: Use TypeTransform::transformSubMap() to transform SILFunctionType

Author: slavapestov

include/swift/AST/TypeTransform.h

@@ -193,33 +193,21 @@ case TypeKind::Id:
 
     case TypeKind::SILFunction: {
       auto fnTy = cast<SILFunctionType>(base);
-      bool changed = false;
-      auto updateSubs = [&](SubstitutionMap &subs) -> bool {
-        // This interface isn't suitable for doing most transformations on
-        // a substituted SILFunctionType, but it's too hard to come up with
-        // an assertion that meaningfully captures what restrictions are in
-        // place.  Generally the restriction that you can't naively substitute
-        // a SILFunctionType using AST mechanisms will have to be good enough.
-        SmallVector<Type, 4> newReplacements;
-        for (Type type : subs.getReplacementTypes()) {
-          auto transformed = doIt(type, TypePosition::Invariant);
-          newReplacements.push_back(transformed->getCanonicalType());
-          if (!type->isEqual(transformed))
-            changed = true;
-        }
-
-        if (changed) {
-          subs = SubstitutionMap::get(subs.getGenericSignature(),
-                                      newReplacements,
-                                      subs.getConformances());
-        }
-
-        return changed;
-      };
 
       if (fnTy->isPolymorphic())
         return fnTy;
 
+      auto updateSubs = [&](SubstitutionMap &subs) -> bool {
+        auto newSubs = asDerived().transformSubMap(subs);
+        if (subs && !newSubs)
+          return false;
+        if (subs == newSubs)
+          return false;
+
+        subs = newSubs;
+        return true;
+      };
+
       if (auto subs = fnTy->getInvocationSubstitutions()) {
         if (updateSubs(subs)) {
           return fnTy->withInvocationSubstitutions(subs);
@@ -234,6 +222,8 @@ case TypeKind::Id:
         return fnTy;
       }
 
+      bool changed = false;
+
       SmallVector<SILParameterInfo, 8> transInterfaceParams;
       for (SILParameterInfo param : fnTy->getParameters()) {
         if (transformSILParameter(pos.flipped(), param, changed))

lib/AST/TypeSubstitution.cpp

@@ -513,20 +513,6 @@ TypeSubstituter::transform(TypeBase *type, TypePosition position) {
     return Type(PackType::get(packExpansionTy->getASTContext(), eltTys));
   }
 
-  if (auto silFnTy = dyn_cast<SILFunctionType>(type)) {
-    if (silFnTy->isPolymorphic())
-      return std::nullopt;
-    if (auto subs = silFnTy->getInvocationSubstitutions()) {
-      auto newSubs = subs.subst(IFS);
-      return silFnTy->withInvocationSubstitutions(newSubs);
-    }
-    if (auto subs = silFnTy->getPatternSubstitutions()) {
-      auto newSubs = subs.subst(IFS);
-      return silFnTy->withPatternSubstitutions(newSubs);
-    }
-    return std::nullopt;
-  }
-
   auto oldLevel = level;
   SWIFT_DEFER { level = oldLevel; };