Canonicalize UnaryTransformType types when they don't have a known underlying type.

Fixes https://llvm.org/bugs/show_bug.cgi?id=26014

Reviewed by Richard Smith.

llvm-svn: 264937

clang/include/clang/AST/ASTContext.h

@@ -129,6 +129,8 @@ class ASTContext : public RefCountedBase<ASTContext> {
   llvm::FoldingSet<PackExpansionType> PackExpansionTypes;
   mutable llvm::FoldingSet<ObjCObjectTypeImpl> ObjCObjectTypes;
   mutable llvm::FoldingSet<ObjCObjectPointerType> ObjCObjectPointerTypes;
+  mutable llvm::FoldingSet<DependentUnaryTransformType>
+    DependentUnaryTransformTypes;
   mutable llvm::FoldingSet<AutoType> AutoTypes;
   mutable llvm::FoldingSet<AtomicType> AtomicTypes;
   llvm::FoldingSet<AttributedType> AttributedTypes;

clang/include/clang/AST/Type.h

@@ -3633,6 +3633,28 @@ public:
   }
 };
 
+/// \brief Internal representation of canonical, dependent
+/// __underlying_type(type) types.
+///
+/// This class is used internally by the ASTContext to manage
+/// canonical, dependent types, only. Clients will only see instances
+/// of this class via UnaryTransformType nodes.
+class DependentUnaryTransformType : public UnaryTransformType,
+                                    public llvm::FoldingSetNode {
+public:
+  DependentUnaryTransformType(const ASTContext &C, QualType BaseType,
+                              UTTKind UKind);
+  void Profile(llvm::FoldingSetNodeID &ID) {
+    Profile(ID, getBaseType(), getUTTKind());
+  }
+
+  static void Profile(llvm::FoldingSetNodeID &ID, QualType BaseType,
+                      UTTKind UKind) {
+    ID.AddPointer(BaseType.getAsOpaquePtr());
+    ID.AddInteger((unsigned)UKind);
+  }
+};
+
 class TagType : public Type {
   /// Stores the TagDecl associated with this type. The decl may point to any
   /// TagDecl that declares the entity.

clang/lib/AST/ASTContext.cpp

@@ -4020,13 +4020,35 @@ QualType ASTContext::getUnaryTransformType(QualType BaseType,
                                            QualType UnderlyingType,
                                            UnaryTransformType::UTTKind Kind)
     const {
-  UnaryTransformType *Ty =
-    new (*this, TypeAlignment) UnaryTransformType (BaseType, UnderlyingType, 
-                                                   Kind,
-                                 UnderlyingType->isDependentType() ?
-                                 QualType() : getCanonicalType(UnderlyingType));
-  Types.push_back(Ty);
-  return QualType(Ty, 0);
+  UnaryTransformType *ut = nullptr;
+
+  if (BaseType->isDependentType()) {
+    // Look in the folding set for an existing type.
+    llvm::FoldingSetNodeID ID;
+    DependentUnaryTransformType::Profile(ID, getCanonicalType(BaseType), Kind);
+
+    void *InsertPos = nullptr;
+    DependentUnaryTransformType *Canon
+      = DependentUnaryTransformTypes.FindNodeOrInsertPos(ID, InsertPos);
+
+    if (!Canon) {
+      // Build a new, canonical __underlying_type(type) type.
+      Canon = new (*this, TypeAlignment)
+             DependentUnaryTransformType(*this, getCanonicalType(BaseType),
+                                         Kind);
+      DependentUnaryTransformTypes.InsertNode(Canon, InsertPos);
+    }
+    ut = new (*this, TypeAlignment) UnaryTransformType (BaseType,
+                                                        QualType(), Kind,
+                                                        QualType(Canon, 0));
+  } else {
+    QualType CanonType = getCanonicalType(UnderlyingType);
+    ut = new (*this, TypeAlignment) UnaryTransformType (BaseType,
+                                                        UnderlyingType, Kind,
+                                                        CanonType);
+  }
+  Types.push_back(ut);
+  return QualType(ut, 0);
 }
 
 /// getAutoType - Return the uniqued reference to the 'auto' type which has been

clang/lib/AST/Type.cpp

@@ -2935,6 +2935,24 @@ void DependentDecltypeType::Profile(llvm::FoldingSetNodeID &ID,
   E->Profile(ID, Context, true);
 }
 
+UnaryTransformType::UnaryTransformType(QualType BaseType,
+                                       QualType UnderlyingType,
+                                       UTTKind UKind,
+                                       QualType CanonicalType)
+  : Type(UnaryTransform, CanonicalType, BaseType->isDependentType(),
+         BaseType->isInstantiationDependentType(),
+         BaseType->isVariablyModifiedType(),
+         BaseType->containsUnexpandedParameterPack())
+  , BaseType(BaseType), UnderlyingType(UnderlyingType), UKind(UKind)
+{}
+
+DependentUnaryTransformType::DependentUnaryTransformType(const ASTContext &C,
+                                                         QualType BaseType,
+                                                         UTTKind UKind)
+   : UnaryTransformType(BaseType, C.DependentTy, UKind, QualType())
+{}
+
+
 TagType::TagType(TypeClass TC, const TagDecl *D, QualType can)
   : Type(TC, can, D->isDependentType(), 
          /*InstantiationDependent=*/D->isDependentType(),
@@ -2951,17 +2969,6 @@ static TagDecl *getInterestingTagDecl(TagDecl *decl) {
   return decl;
 }
 
-UnaryTransformType::UnaryTransformType(QualType BaseType,
-                                       QualType UnderlyingType,
-                                       UTTKind UKind,
-                                       QualType CanonicalType)
-  : Type(UnaryTransform, CanonicalType, UnderlyingType->isDependentType(),
-         UnderlyingType->isInstantiationDependentType(),
-         UnderlyingType->isVariablyModifiedType(),
-         BaseType->containsUnexpandedParameterPack())
-  , BaseType(BaseType), UnderlyingType(UnderlyingType), UKind(UKind)
-{}
-
 TagDecl *TagType::getDecl() const {
   return getInterestingTagDecl(decl);
 }

clang/test/Modules/Inputs/PR26014/A.h

@@ -0,0 +1,13 @@
+#ifndef _LIBCPP_TYPE_TRAITS
+#define _LIBCPP_TYPE_TRAITS
+
+
+template <class _Tp>
+struct underlying_type
+{
+    typedef __underlying_type(_Tp) type;
+};
+
+#endif  // _LIBCPP_TYPE_TRAITS
+
+#include "B.h"

clang/test/Modules/Inputs/PR26014/B.h

@@ -0,0 +1,10 @@
+#ifndef _LIBCPP_TYPE_TRAITS
+#define _LIBCPP_TYPE_TRAITS
+
+template <class _Tp>
+struct underlying_type
+{
+    typedef __underlying_type(_Tp) type;
+};
+
+#endif  // _LIBCPP_TYPE_TRAITS

clang/test/Modules/Inputs/PR26014/module.modulemap

@@ -0,0 +1,9 @@
+module A {
+  header "A.h"
+  export *
+}
+
+module B {
+  header "B.h"
+  export *
+}

clang/test/Modules/pr26014.cpp

@@ -0,0 +1,7 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -I%S/Inputs/PR26014 -verify %s
+// RUN: %clang_cc1 -fmodules -fmodule-map-file=%S/Inputs/PR26014/module.modulemap -fmodules-cache-path=%t -I%S/Inputs/PR26014 -verify %s
+
+#include "A.h"
+
+// expected-no-diagnostics

clang/test/SemaCXX/underlying_type.cpp

@@ -55,3 +55,10 @@ namespace PR19966 {
     // expected-error@-2 {{constant expression}}
   };
 }
+
+template<typename T> void f(__underlying_type(T));
+template<typename T> void f(__underlying_type(T));
+enum E {};
+void PR26014() { f<E>(0); } // should not yield an ambiguity error.
+
+template<typename ...T> void f(__underlying_type(T) v); // expected-error {{declaration type contains unexpanded parameter pack 'T'}}