[Demangler] Fix OldRemangler to cope with Type nodes in a couple of places.

The Demangler can wrap types in a Node::Kind::Type node; these need to be
handled by following the node's first child pointer.  Failing to do this led to
a crash or assertion failure in some cases.

rdar://63678171

Author: al45tair

lib/Demangling/OldRemangler.cpp

@@ -1823,6 +1823,9 @@ void Remangler::mangleAnyNominalType(Node *node, EntityContext &ctx) {
   }
 
   switch (node->getKind()) {
+  case Node::Kind::Type:
+    mangleAnyNominalType(node->getChild(0), ctx);
+    break;
   case Node::Kind::OtherNominalType:
     // Mangle unknown type kinds as structures since we can't change the old
     // mangling. Give the mangling an artificial "private discriminator" so that
@@ -1866,6 +1869,9 @@ void Remangler::mangleOtherNominalType(Node *node, EntityContext &ctx) {
 void Remangler::mangleNominalType(Node *node, char kind, EntityContext &ctx,
                                   StringRef artificialPrivateDiscriminator) {
   SubstitutionEntry entry;
+  if (node->getKind() == Node::Kind::Type) {
+    node = node->getChild(0);
+  }
   if (trySubstitution(node, entry)) return;
   mangleNamedEntity(node, kind, "", ctx, artificialPrivateDiscriminator);
   addSubstitution(entry);

test/Demangle/remangle.swift

@@ -9,6 +9,9 @@ RUN: diff %t.input %t.output
 // CHECK: Swift.(Mystruct in _7B40D7ED6632C2BEA2CA3BFFD57E3435)
 RUN: swift-demangle -remangle-objc-rt '$ss8Mystruct33_7B40D7ED6632C2BEA2CA3BFFD57E3435LLV' | %FileCheck %s
 
+// CHECK-OLD2: Swift.Int.related decl 'B' for protocol self-conformance descriptor for Swift.IteratorProtocol
+RUN: swift-demangle -remangle-objc-rt '$sSiStMSLB_p' | %FileCheck -check-prefix CHECK-OLD2 %s
+
 // CHECK-GENERICEXT: Swift._ContiguousArrayStorage<(extension in Swift):Swift.FlattenSequence<StdlibCollectionUnittest.MinimalBidirectionalCollection<StdlibCollectionUnittest.MinimalBidirectionalCollection<Swift.Int>>>.Index>
 RUN: swift-demangle -remangle-objc-rt '$ss23_ContiguousArrayStorageCys15FlattenSequenceVsE5IndexVy24StdlibCollectionUnittest020MinimalBidirectionalH0VyAIySiGG_GGD' | %FileCheck -check-prefix CHECK-GENERICEXT %s