[ASTMangler] Add support for mangling generic typealiases.

<rdar://problem/39915946>

Author: Davide Italiano

include/swift/Demangling/DemangleNodes.def

@@ -36,6 +36,7 @@ NODE(BoundGenericClass)
 NODE(BoundGenericEnum)
 NODE(BoundGenericStructure)
 NODE(BoundGenericOtherNominalType)
+NODE(BoundGenericTypeAlias)
 NODE(BuiltinTypeName)
 NODE(CFunctionPointer)
 CONTEXT_NODE(Class)

lib/AST/ASTMangler.cpp

@@ -739,15 +739,31 @@ void ASTMangler::appendType(Type type) {
       auto aliasTy = cast<NameAliasType>(tybase);
 
       // It's not possible to mangle the context of the builtin module.
-      // FIXME: We also cannot yet mangle references to typealiases that
-      // involve generics.
+      // For the DWARF output we want to mangle the type alias + context,
+      // unless the type alias references a builtin type.
       TypeAliasDecl *decl = aliasTy->getDecl();
       if (decl->getModuleContext() == decl->getASTContext().TheBuiltinModule) {
         return appendType(aliasTy->getSinglyDesugaredType());
       }
 
-      // For the DWARF output we want to mangle the type alias + context,
-      // unless the type alias references a builtin type.
+      if (type->isSpecialized()) {
+        // Try to mangle the entire name as a substitution.
+        if (tryMangleSubstitution(tybase))
+          return;
+
+        appendAnyGenericType(decl);
+        bool isFirstArgList = true;
+        if (auto *nominalType = type->getAs<NominalType>()) {
+          if (nominalType->getParent())
+            type = nominalType->getParent();
+        }
+        appendBoundGenericArgs(type, isFirstArgList);
+        appendRetroactiveConformances(type);
+        appendOperator("G");
+        addSubstitution(type.getPointer());
+        return;
+      }
+
       return appendAnyGenericType(decl);
     }
 

lib/Demangling/Demangler.cpp

@@ -1324,6 +1324,9 @@ NodePointer Demangler::demangleBoundGenericArgs(NodePointer Nominal,
     case Node::Kind::OtherNominalType:
       kind = Node::Kind::BoundGenericOtherNominalType;
       break;
+    case Node::Kind::TypeAlias:
+      kind = Node::Kind::BoundGenericTypeAlias;
+      break;
     default:
       return nullptr;
   }

lib/Demangling/NodePrinter.cpp

@@ -267,6 +267,7 @@ class NodePrinter {
     case Node::Kind::BoundGenericEnum:
     case Node::Kind::BoundGenericStructure:
     case Node::Kind::BoundGenericOtherNominalType:
+    case Node::Kind::BoundGenericTypeAlias:
     case Node::Kind::BuiltinTypeName:
     case Node::Kind::Class:
     case Node::Kind::DependentGenericType:
@@ -1549,6 +1550,7 @@ NodePointer NodePrinter::print(NodePointer Node, bool asPrefixContext) {
   case Node::Kind::BoundGenericStructure:
   case Node::Kind::BoundGenericEnum:
   case Node::Kind::BoundGenericOtherNominalType:
+  case Node::Kind::BoundGenericTypeAlias:
     printBoundGeneric(Node);
     return nullptr;
   case Node::Kind::DynamicSelf:

lib/Demangling/OldRemangler.cpp

@@ -1875,6 +1875,11 @@ void Remangler::mangleBoundGenericOtherNominalType(Node *node) {
   mangleAnyNominalType(node, ctx);
 }
 
+void Remangler::mangleBoundGenericTypeAlias(Node *node) {
+  EntityContext ctx;
+  mangleAnyNominalType(node, ctx);
+}
+
 void Remangler::mangleTypeList(Node *node) {
   mangleChildNodes(node); // all types
   Out << '_';

lib/Demangling/Remangler.cpp

@@ -459,6 +459,7 @@ void Remangler::mangleAnyNominalType(Node *node) {
     case Node::Kind::Enum: return mangleAnyGenericType(node, "O");
     case Node::Kind::Class: return mangleAnyGenericType(node, "C");
     case Node::Kind::OtherNominalType: return mangleAnyGenericType(node, "XY");
+    case Node::Kind::TypeAlias: return mangleAnyGenericType(node, "a");
     default:
       unreachable("bad nominal type kind");
   }
@@ -477,7 +478,8 @@ void Remangler::mangleGenericArgs(Node *node, char &Separator) {
     case Node::Kind::BoundGenericOtherNominalType:
     case Node::Kind::BoundGenericStructure:
     case Node::Kind::BoundGenericEnum:
-    case Node::Kind::BoundGenericClass: {
+    case Node::Kind::BoundGenericClass:
+    case Node::Kind::BoundGenericTypeAlias: {
       NodePointer unboundType = node->getChild(0);
       assert(unboundType->getKind() == Node::Kind::Type);
       NodePointer nominalType = unboundType->getChild(0);
@@ -589,6 +591,10 @@ void Remangler::mangleBoundGenericOtherNominalType(Node *node) {
   mangleAnyNominalType(node);
 }
 
+void Remangler::mangleBoundGenericTypeAlias(Node *node) {
+  mangleAnyNominalType(node);
+}
+
 void Remangler::mangleBuiltinTypeName(Node *node) {
   Buffer << 'B';
   StringRef text = node->getText();
@@ -2034,6 +2040,7 @@ bool Demangle::isSpecialized(Node *node) {
     case Node::Kind::BoundGenericEnum:
     case Node::Kind::BoundGenericClass:
     case Node::Kind::BoundGenericOtherNominalType:
+    case Node::Kind::BoundGenericTypeAlias:
       return true;
 
     case Node::Kind::Structure:
@@ -2069,7 +2076,8 @@ NodePointer Demangle::getUnspecialized(Node *node, NodeFactory &Factory) {
     case Node::Kind::BoundGenericStructure:
     case Node::Kind::BoundGenericEnum:
     case Node::Kind::BoundGenericClass:
-    case Node::Kind::BoundGenericOtherNominalType: {
+    case Node::Kind::BoundGenericOtherNominalType:
+    case Node::Kind::BoundGenericTypeAlias: {
       NodePointer unboundType = node->getChild(0);
       assert(unboundType->getKind() == Node::Kind::Type);
       NodePointer nominalType = unboundType->getChild(0);

test/Demangle/Inputs/manglings.txt

@@ -319,4 +319,5 @@ _$S3BBBBf0602365061_ ---> _$S3BBBBf0602365061_
 _$S3BBBBi0602365061_ ---> _$S3BBBBi0602365061_
 _$S3BBBBv0602365061_ ---> _$S3BBBBv0602365061_
 _T0lxxxmmmTk ---> _T0lxxxmmmTk
+$S4blah8PatatinoaySiGD -> blah.Patatino<Swift.Int>