TypeDecoder: Push one-element tuple unwrapping down into createTupleType() implementations [5.9]

include/swift/Demangling/TypeDecoder.h

@@ -1052,13 +1052,6 @@ class TypeDecoder {
           return *optError;
       }
 
-      // Unwrap unlabeled one-element tuples.
-      //
-      // FIXME: The behavior of one-element labeled tuples is inconsistent throughout
-      // the different re-implementations of type substitution and pack expansion.
-      if (elements.size() == 1 && labels[0].empty())
-        return elements[0];
-
       return Builder.createTupleType(elements, labels);
     }
     case NodeKind::TupleElement:

lib/AST/ASTDemangler.cpp

@@ -328,6 +328,17 @@ Type ASTBuilder::createBoundGenericType(GenericTypeDecl *decl,
 }
 
 Type ASTBuilder::createTupleType(ArrayRef<Type> eltTypes, ArrayRef<StringRef> labels) {
+  // Unwrap unlabeled one-element tuples.
+  //
+  // FIXME: The behavior of one-element labeled tuples is inconsistent
+  // throughout the different re-implementations of type substitution
+  // and pack expansion.
+  if (eltTypes.size() == 1 &&
+      !eltTypes[0]->is<PackExpansionType>() &&
+      labels[0].empty()) {
+    return eltTypes[0];
+  }
+
   SmallVector<TupleTypeElt, 4> elements;
   elements.reserve(eltTypes.size());
   for (unsigned i : indices(eltTypes)) {

stdlib/public/runtime/MetadataLookup.cpp

@@ -1960,6 +1960,14 @@ class DecodedMetadataBuilder {
   TypeLookupErrorOr<BuiltType>
   createTupleType(llvm::ArrayRef<BuiltType> elements,
                   llvm::ArrayRef<StringRef> labels) const {
+    // Unwrap unlabeled one-element tuples.
+    //
+    // FIXME: The behavior of one-element labeled tuples is inconsistent
+    // throughout the different re-implementations of type substitution
+    // and pack expansion.
+    if (elements.size() == 1 && labels[0].empty())
+      return elements[0];
+
     for (auto element : elements) {
       if (!element.isMetadata()) {
         return TYPE_LOOKUP_ERROR_FMT("Tried to build a tuple type where "

test/DebugInfo/variadic-generics.swift

@@ -1,5 +1,5 @@
 // RUN: %target-swift-frontend -emit-ir %s -g -o - \
-// RUN:    -parse-as-library -module-name a | %IRGenFileCheck %s
+// RUN:    -parse-as-library -module-name a -disable-availability-checking | %IRGenFileCheck %s
 
 public func foo<each T>(args: repeat each T) {
   // CHECK: define {{.*}} @"$s1a3foo4argsyxxQp_tRvzlF"
@@ -21,3 +21,35 @@ public func foo<each T>(args: repeat each T) {
   // CHECK-DAG: ![[TYPE_PACK_TY]] = !DIDerivedType(tag: DW_TAG_pointer_type, name: "$sBpD"
 }
 
+// Test ASTDemangler round-tripping of various pack expansion types
+
+public func paramExpansionWithPattern<each T>(args: repeat Array<each T>) {}
+
+public func paramExpansionWithMemberType<each T: Sequence>(args: repeat each T, elements: repeat (each T).Element) {}
+
+public func tupleExpansion<each T>(args: (repeat each T)) {}
+
+public func tupleExpansionWithPattern<each T>(args: (repeat Array<each T>)) {}
+
+// FIXME: Crashes due to unrelated bug
+// public func tupleExpansionWithMemberType<each T: Sequence>(args: repeat each T, elements: (repeat (each T).Element)) {}
+
+public func functionExpansion<each T>(args: (repeat each T) -> ()) {}
+
+public func functionExpansionWithPattern<each T>(args: (repeat Array<each T>) -> ()) {}
+
+public func functionExpansionWithMemberType<each T: Sequence>(args: repeat each T, elements: (repeat (each T).Element) -> ()) {}
+
+public struct G<each T> {}
+
+public func nominalExpansion<each T>(args: G<repeat each T>) {}
+
+public func nominalExpansionWithPattern<each T>(args: G<repeat Array<each T>>) {}
+
+public func nominalExpansionWithMemberType<each T: Sequence>(args: repeat each T, elements: G<repeat (each T).Element>) {}
+
+//
+
+public typealias First<T, U> = T
+
+public func concreteExpansion<each T>(args: repeat each T, concrete: repeat First<Int, each T>) {}