[Demangler] Fix OldRemangler to cope with single argument functions.

The Demangler can sometimes output ArgumentTuples containing a single argument
without placing that argument inside a Tuple node.  OldRemangler failed to take
account of this and either crashed or failed with an assertion failure depending
on whether assertions were enabled or not.

rdar://63678072

Author: al45tair

lib/Demangling/OldRemangler.cpp

@@ -164,27 +164,31 @@ static NodePointer applyParamLabels(NodePointer LabelList, NodePointer OrigType,
     auto ParamsType = Factory.createNode(Node::Kind::ArgumentTuple);
     auto Tuple = Factory.createNode(Node::Kind::Tuple);
 
-    auto OrigTuple = ArgTuple->getFirstChild()->getFirstChild();
-    assert(OrigTuple->getKind() == Node::Kind::Tuple);
-
-    for (unsigned i = 0, n = OrigTuple->getNumChildren(); i != n; ++i) {
-      const auto Label = LabelList->getChild(i);
+    auto processParameter = [&](NodePointer Label, NodePointer Param) {
       if (Label->getKind() == Node::Kind::FirstElementMarker) {
-        Tuple->addChild(OrigTuple->getChild(i), Factory);
-        continue;
+        Tuple->addChild(Param, Factory);
+        return;
       }
 
-      auto OrigElt = OrigTuple->getChild(i);
-      auto NewElt = Factory.createNode(Node::Kind::TupleElement);
-
-      NewElt->addChild(Factory.createNodeWithAllocatedText(
+      auto NewParam = Factory.createNode(Node::Kind::TupleElement);
+      NewParam->addChild(Factory.createNodeWithAllocatedText(
                            Node::Kind::TupleElementName, Label->getText()),
-                       Factory);
+                         Factory);
 
-      for (auto &Child : *OrigElt)
-        NewElt->addChild(Child, Factory);
+      for (auto &Child : *Param)
+        NewParam->addChild(Child, Factory);
+
+      Tuple->addChild(NewParam, Factory);
+    };
 
-      Tuple->addChild(NewElt, Factory);
+    auto OrigTuple = ArgTuple->getFirstChild()->getFirstChild();
+
+    if (OrigTuple->getKind() != Node::Kind::Tuple) {
+      processParameter(LabelList->getChild(0), OrigTuple);
+    } else {
+      for (unsigned i = 0, n = OrigTuple->getNumChildren(); i != n; ++i) {
+        processParameter(LabelList->getChild(i), OrigTuple->getChild(i));
+      }
     }
 
     auto Type = Factory.createNode(Node::Kind::Type);

test/Demangle/remangle.swift

@@ -9,6 +9,8 @@ RUN: diff %t.input %t.output
 // CHECK: Swift.(Mystruct in _7B40D7ED6632C2BEA2CA3BFFD57E3435)
 RUN: swift-demangle -remangle-objc-rt '$ss8Mystruct33_7B40D7ED6632C2BEA2CA3BFFD57E3435LLV' | %FileCheck %s
 
+// CHECK-OLD: r in _.?(Swift.UnsafeRawPointer) -> Swift.UnsafeRawPointer
+RUN: swift-demangle -remangle-objc-rt '$s1_1?1PSVSVF1rP' | %FileCheck -check-prefix CHECK-OLD %s
+
 // CHECK-GENERICEXT: Swift._ContiguousArrayStorage<(extension in Swift):Swift.FlattenSequence<StdlibCollectionUnittest.MinimalBidirectionalCollection<StdlibCollectionUnittest.MinimalBidirectionalCollection<Swift.Int>>>.Index>
 RUN: swift-demangle -remangle-objc-rt '$ss23_ContiguousArrayStorageCys15FlattenSequenceVsE5IndexVy24StdlibCollectionUnittest020MinimalBidirectionalH0VyAIySiGG_GGD' | %FileCheck -check-prefix CHECK-GENERICEXT %s
-