[Mangling] Handle mangling involving bound generic "protocols".

include/swift/Demangling/DemangleNodes.def

@@ -35,6 +35,7 @@ NODE(AutoClosureType)
 NODE(BoundGenericClass)
 NODE(BoundGenericEnum)
 NODE(BoundGenericStructure)
+NODE(BoundGenericProtocol)
 NODE(BoundGenericOtherNominalType)
 NODE(BoundGenericTypeAlias)
 NODE(BuiltinTypeName)

lib/Demangling/Demangler.cpp

@@ -1332,6 +1332,9 @@ NodePointer Demangler::demangleBoundGenericArgs(NodePointer Nominal,
     case Node::Kind::Enum:
       kind = Node::Kind::BoundGenericEnum;
       break;
+    case Node::Kind::Protocol:
+      kind = Node::Kind::BoundGenericProtocol;
+      break;
     case Node::Kind::OtherNominalType:
       kind = Node::Kind::BoundGenericOtherNominalType;
       break;

lib/Demangling/NodePrinter.cpp

@@ -266,6 +266,7 @@ class NodePrinter {
     case Node::Kind::BoundGenericClass:
     case Node::Kind::BoundGenericEnum:
     case Node::Kind::BoundGenericStructure:
+    case Node::Kind::BoundGenericProtocol:
     case Node::Kind::BoundGenericOtherNominalType:
     case Node::Kind::BoundGenericTypeAlias:
     case Node::Kind::BuiltinTypeName:
@@ -540,6 +541,15 @@ class NodePrinter {
       return;
     }
 
+    // Print the conforming type for a "bound" protocol node "as" the protocol
+    // type.
+    if (Node->getKind() == Node::Kind::BoundGenericProtocol) {
+      printChildren(Node->getChild(1));
+      Printer << " as ";
+      print(Node->getChild(0));
+      return;
+    }
+
     SugarType sugarType = findSugar(Node);
 
     switch (sugarType) {
@@ -1558,6 +1568,7 @@ NodePointer NodePrinter::print(NodePointer Node, bool asPrefixContext) {
   case Node::Kind::BoundGenericClass:
   case Node::Kind::BoundGenericStructure:
   case Node::Kind::BoundGenericEnum:
+  case Node::Kind::BoundGenericProtocol:
   case Node::Kind::BoundGenericOtherNominalType:
   case Node::Kind::BoundGenericTypeAlias:
     printBoundGeneric(Node);

lib/Demangling/OldRemangler.cpp

@@ -1872,6 +1872,11 @@ void Remangler::mangleBoundGenericOtherNominalType(Node *node) {
   mangleAnyNominalType(node, ctx);
 }
 
+void Remangler::mangleBoundGenericProtocol(Node *node) {
+  EntityContext ctx;
+  mangleAnyNominalType(node, ctx);
+}
+
 void Remangler::mangleBoundGenericTypeAlias(Node *node) {
   EntityContext ctx;
   mangleAnyNominalType(node, ctx);

lib/Demangling/Remangler.cpp

@@ -484,6 +484,7 @@ void Remangler::mangleGenericArgs(Node *node, char &Separator) {
     case Node::Kind::BoundGenericStructure:
     case Node::Kind::BoundGenericEnum:
     case Node::Kind::BoundGenericClass:
+    case Node::Kind::BoundGenericProtocol:
     case Node::Kind::BoundGenericTypeAlias: {
       NodePointer unboundType = node->getChild(0);
       assert(unboundType->getKind() == Node::Kind::Type);
@@ -596,6 +597,10 @@ void Remangler::mangleBoundGenericOtherNominalType(Node *node) {
   mangleAnyNominalType(node);
 }
 
+void Remangler::mangleBoundGenericProtocol(Node *node) {
+  mangleAnyNominalType(node);
+}
+
 void Remangler::mangleBoundGenericTypeAlias(Node *node) {
   mangleAnyNominalType(node);
 }
@@ -2053,13 +2058,15 @@ bool Demangle::isSpecialized(Node *node) {
     case Node::Kind::BoundGenericClass:
     case Node::Kind::BoundGenericOtherNominalType:
     case Node::Kind::BoundGenericTypeAlias:
+    case Node::Kind::BoundGenericProtocol:
       return true;
 
     case Node::Kind::Structure:
     case Node::Kind::Enum:
     case Node::Kind::Class:
     case Node::Kind::TypeAlias:
     case Node::Kind::OtherNominalType:
+    case Node::Kind::Protocol:
       return isSpecialized(node->getChild(0));
 
     case Node::Kind::Extension:
@@ -2090,8 +2097,10 @@ NodePointer Demangle::getUnspecialized(Node *node, NodeFactory &Factory) {
     case Node::Kind::BoundGenericStructure:
     case Node::Kind::BoundGenericEnum:
     case Node::Kind::BoundGenericClass:
+    case Node::Kind::BoundGenericProtocol:
     case Node::Kind::BoundGenericOtherNominalType:
-    case Node::Kind::BoundGenericTypeAlias: {
+    case Node::Kind::BoundGenericTypeAlias:
+    {
       NodePointer unboundType = node->getChild(0);
       assert(unboundType->getKind() == Node::Kind::Type);
       NodePointer nominalType = unboundType->getChild(0);

lib/IDE/TypeReconstruction.cpp

@@ -2268,6 +2268,14 @@ static void VisitNode(
     VisitNodeBoundGeneric(ast, node, result);
     break;
 
+  case Demangle::Node::Kind::BoundGenericProtocol:
+    if (node->getNumChildren() < 2)
+      return;
+
+    // Only visit the conforming type.
+    VisitNode(ast, node->getChild(1), result);
+    break;
+
   case Demangle::Node::Kind::BoundGenericTypeAlias:
     VisitNodeGenericTypealias(ast, node, result);
     break;

test/DebugInfo/DumpDeclFromMangledName.swift

@@ -68,6 +68,32 @@ extension Outer.GenericInner {
   }
 }
 
+// Mangling for generic typealiases.
+protocol P {
+  associatedtype A
+}
+
+protocol Q {
+  associatedtype B: P
+  typealias ProtocolTypeAliasThing = B.A
+}
+
+struct ConformsToP: P {
+  typealias A = Int
+}
+
+struct ConformsToQ: Q {
+  typealias B = ConformsToP
+}
+
+struct Blah {
+  typealias SomeQ = ConformsToQ
+
+  func foo() {
+    let bar: SomeQ.ProtocolTypeAliasThing? = nil
+  }
+}
+
 func main() -> Int {
   var p : Patatino<Int> = Patatino(23);
   return 0

test/Demangle/Inputs/manglings.txt

@@ -317,3 +317,4 @@ $S4blah8PatatinoaySiGD ---> blah.Patatino<Swift.Int>
 $SSiSHsWP ---> protocol witness table for Swift.Int : Swift.Hashable in Swift
 $S7TestMod5OuterV3Fooayx_SiGD ---> TestMod.Outer<A>.Foo<Swift.Int>
 $Ss17_VariantSetBufferO05CocoaC0ayx_GD ---> Swift._VariantSetBuffer<A>.CocoaBuffer
+$S2t21QP22ProtocolTypeAliasThingayAA4BlahV5SomeQa_GSgD ---> t2.Blah.SomeQ as t2.Q.ProtocolTypeAliasThing?