Add support for GCC's '__auto_type' extension, per the GCC manual:

https://gcc.gnu.org/onlinedocs/gcc/Typeof.html

Differences from the GCC extension:
 * __auto_type is also permitted in C++ (but only in places where
   it could appear in C), allowing its use in headers that might
   be shared across C and C++, or used from C++98
 * __auto_type can be combined with a declarator, as with C++ auto
   (for instance, "__auto_type *p")
 * multiple variables can be declared in a single __auto_type
   declaration, with the C++ semantics (the deduced type must be
   the same in each case)

This patch also adds a missing restriction on applying typeof to
a bit-field, which GCC has historically rejected in C (due to
lack of clarity as to whether the operand should be promoted).
The same restriction also applies to __auto_type in C (in both
GCC and Clang).

This also fixes PR25449.

Patch by Nicholas Allegra!

llvm-svn: 252690

6 files changed, 18 insertions, 10 deletions

diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 4009915619d..18240e79d80 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -3983,20 +3983,20 @@ QualType ASTContext::getUnaryTransformType(QualType BaseType,
 /// getAutoType - Return the uniqued reference to the 'auto' type which has been
 /// deduced to the given type, or to the canonical undeduced 'auto' type, or the
 /// canonical deduced-but-dependent 'auto' type.
-QualType ASTContext::getAutoType(QualType DeducedType, bool IsDecltypeAuto,
+QualType ASTContext::getAutoType(QualType DeducedType, AutoTypeKeyword Keyword,
                                  bool IsDependent) const {
-  if (DeducedType.isNull() && !IsDecltypeAuto && !IsDependent)
+  if (DeducedType.isNull() && Keyword == AutoTypeKeyword::Auto && !IsDependent)
     return getAutoDeductType();
 
   // Look in the folding set for an existing type.
   void *InsertPos = nullptr;
   llvm::FoldingSetNodeID ID;
-  AutoType::Profile(ID, DeducedType, IsDecltypeAuto, IsDependent);
+  AutoType::Profile(ID, DeducedType, Keyword, IsDependent);
   if (AutoType *AT = AutoTypes.FindNodeOrInsertPos(ID, InsertPos))
     return QualType(AT, 0);
 
   AutoType *AT = new (*this, TypeAlignment) AutoType(DeducedType,
-                                                     IsDecltypeAuto,
+                                                     Keyword,
                                                      IsDependent);
   Types.push_back(AT);
   if (InsertPos)
@@ -4036,7 +4036,7 @@ QualType ASTContext::getAtomicType(QualType T) const {
 QualType ASTContext::getAutoDeductType() const {
   if (AutoDeductTy.isNull())
     AutoDeductTy = QualType(
-      new (*this, TypeAlignment) AutoType(QualType(), /*decltype(auto)*/false,
+      new (*this, TypeAlignment) AutoType(QualType(), AutoTypeKeyword::Auto,
                                           /*dependent*/false),
       0);
   return AutoDeductTy;
diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
index ccc6931a5ff..824cc180109 100644
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -1746,7 +1746,7 @@ QualType ASTNodeImporter::VisitAutoType(const AutoType *T) {
       return QualType();
   }
   
-  return Importer.getToContext().getAutoType(ToDeduced, T->isDecltypeAuto(), 
+  return Importer.getToContext().getAutoType(ToDeduced, T->getKeyword(),
                                              /*IsDependent*/false);
 }
 
diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index c3432839c2e..7f2ef495a20 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -2653,9 +2653,11 @@ void CXXNameMangler::mangleType(const UnaryTransformType *T) {
 void CXXNameMangler::mangleType(const AutoType *T) {
   QualType D = T->getDeducedType();
   // <builtin-type> ::= Da  # dependent auto
-  if (D.isNull())
+  if (D.isNull()) {
+    assert(T->getKeyword() != AutoTypeKeyword::GNUAutoType &&
+           "shouldn't need to mangle __auto_type!");
     Out << (T->isDecltypeAuto() ? "Dc" : "Da");
-  else
+  } else
     mangleType(D);
 }
 
diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp
index 5c30ae28b34..01e17588feb 100644
--- a/clang/lib/AST/MicrosoftMangle.cpp
+++ b/clang/lib/AST/MicrosoftMangle.cpp
@@ -1818,6 +1818,8 @@ void MicrosoftCXXNameMangler::mangleFunctionType(const FunctionType *T,
       Out << '?';
       mangleQualifiers(ResultType.getLocalQualifiers(), /*IsMember=*/false);
       Out << '?';
+      assert(AT->getKeyword() != AutoTypeKeyword::GNUAutoType &&
+             "shouldn't need to mangle __auto_type!");
       mangleSourceName(AT->isDecltypeAuto() ? "<decltype-auto>" : "<auto>");
       Out << '@';
     } else {
diff --git a/clang/lib/AST/Type.cpp b/clang/lib/AST/Type.cpp
index 40fe903feab..611218ff917 100644
--- a/clang/lib/AST/Type.cpp
+++ b/clang/lib/AST/Type.cpp
@@ -948,7 +948,7 @@ public:
           == T->getDeducedType().getAsOpaquePtr())
       return QualType(T, 0);
 
-    return Ctx.getAutoType(deducedType, T->isDecltypeAuto(),
+    return Ctx.getAutoType(deducedType, T->getKeyword(),
                            T->isDependentType());
   }
 
diff --git a/clang/lib/AST/TypePrinter.cpp b/clang/lib/AST/TypePrinter.cpp
index 0bb50c6ba81..b4810d63c80 100644
--- a/clang/lib/AST/TypePrinter.cpp
+++ b/clang/lib/AST/TypePrinter.cpp
@@ -835,7 +835,11 @@ void TypePrinter::printAutoBefore(const AutoType *T, raw_ostream &OS) {
   if (!T->getDeducedType().isNull()) {
     printBefore(T->getDeducedType(), OS);
   } else {
-    OS << (T->isDecltypeAuto() ? "decltype(auto)" : "auto");
+    switch (T->getKeyword()) {
+    case AutoTypeKeyword::Auto: OS << "auto"; break;
+    case AutoTypeKeyword::DecltypeAuto: OS << "decltype(auto)"; break;
+    case AutoTypeKeyword::GNUAutoType: OS << "__auto_type"; break;
+    }
     spaceBeforePlaceHolder(OS);
   }
 }