Type substitution: When substituting SILFunctionTypes we substitute unbound Objective-C generic for bound ones (take 2)

IRGen does so. So don't assert on the case when there is a nested
Objective-C type.

(follow-up to #32027 rdar://63509292 which fixed the non-nested case)

rdar://66302139

Author: aschwaighofer

lib/AST/Type.cpp

@@ -4313,7 +4313,14 @@ case TypeKind::Id:
   case TypeKind::SILFunction: {
     auto fnTy = cast<SILFunctionType>(base);
     bool changed = false;
-
+    auto hasTypeErasedGenericClassType = [](Type ty) -> bool {
+      return ty.findIf([](Type subType) -> bool {
+        if (subType->getCanonicalType().isTypeErasedGenericClassType())
+          return true;
+        else
+          return false;
+      });
+    };
     auto updateSubs = [&](SubstitutionMap &subs) -> bool {
       // This interface isn't suitable for updating the substitution map in a
       // substituted SILFunctionType.
@@ -4323,9 +4330,8 @@ case TypeKind::Id:
         auto transformed = type.transformRec(fn);
         assert((type->isEqual(transformed) ||
                 (type->hasTypeParameter() && transformed->hasTypeParameter()) ||
-                (type->getCanonicalType().isTypeErasedGenericClassType() &&
-                 transformed->getCanonicalType()
-                     .isTypeErasedGenericClassType())) &&
+                (hasTypeErasedGenericClassType(type) &&
+                 hasTypeErasedGenericClassType(transformed))) &&
                "Substituted SILFunctionType can't be transformed into a "
                "concrete type");
         newReplacements.push_back(transformed->getCanonicalType());

test/IRGen/generic_classes_objc.sil

@@ -84,3 +84,13 @@ bb0(%0 : $Optional< @callee_guaranteed @substituted <τ_0_1> (@in_guaranteed Res
   %2 = tuple ()
   return %2 : $()
 }
+
+struct PlainGeneric<T> {}
+
+// This used to assert.
+sil @repo2 : $@convention(thin) (@guaranteed Optional< @callee_guaranteed @substituted <τ_0_1> (@in_guaranteed Result<τ_0_1, Error>) -> () for <PlainGeneric<ObjcGenericClass<SomeClass>>>>) -> () {
+bb0(%0 : $Optional< @callee_guaranteed @substituted <τ_0_1> (@in_guaranteed Result<τ_0_1, Error>) -> () for <PlainGeneric<ObjcGenericClass<SomeClass>>> >):
+  debug_value %0 : $Optional<@callee_guaranteed @substituted <τ_0_1> (@in_guaranteed Result<τ_0_1, Error>) -> () for <PlainGeneric<ObjcGenericClass<SomeClass>>>>, let, name "completion", argno 1
+  %2 = tuple ()
+  return %2 : $()
+}