Implement C++1y decltype(auto).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@180610 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 22 insertions, 2 deletions

diff --git a/lib/Sema/SemaTemplateDeduction.cpp b/lib/Sema/SemaTemplateDeduction.cpp
index d559833c48..a681371c9b 100644
--- a/lib/Sema/SemaTemplateDeduction.cpp
+++ b/lib/Sema/SemaTemplateDeduction.cpp
@@ -3579,11 +3579,13 @@ namespace {
       // auto type deduced as T" in order for [temp.deduct.call]p3 to apply.
       if (isa<TemplateTypeParmType>(Replacement)) {
         QualType Result = Replacement;
-        TemplateTypeParmTypeLoc NewTL = TLB.push<TemplateTypeParmTypeLoc>(Result);
+        TemplateTypeParmTypeLoc NewTL =
+          TLB.push<TemplateTypeParmTypeLoc>(Result);
         NewTL.setNameLoc(TL.getNameLoc());
         return Result;
       } else {
-        QualType Result = RebuildAutoType(Replacement);
+        QualType Result = RebuildAutoType(Replacement,
+                                          TL.getTypePtr()->isDecltypeAuto());
         AutoTypeLoc NewTL = TLB.push<AutoTypeLoc>(Result);
         NewTL.setNameLoc(TL.getNameLoc());
         return Result;
@@ -3657,6 +3659,24 @@ Sema::DeduceAutoType(TypeSourceInfo *Type, Expr *&Init,
     return DAR_Succeeded;
   }
 
+  // If this is a 'decltype(auto)' specifier, do the decltype dance.
+  // Since 'decltype(auto)' can only occur at the top of the type, we
+  // don't need to go digging for it.
+  if (const AutoType *AT = Type->getType()->getAs<AutoType>()) {
+    if (AT->isDecltypeAuto()) {
+      if (isa<InitListExpr>(Init)) {
+        Diag(Init->getLocStart(), diag::err_decltype_auto_initializer_list);
+        return DAR_FailedAlreadyDiagnosed;
+      }
+
+      QualType Deduced = BuildDecltypeType(Init, Init->getLocStart());
+      // FIXME: Support a non-canonical deduced type for 'auto'.
+      Deduced = Context.getCanonicalType(Deduced);
+      Result = SubstituteAutoTransform(*this, Deduced).TransformType(Type);
+      return DAR_Succeeded;
+    }
+  }
+
   SourceLocation Loc = Init->getExprLoc();
 
   LocalInstantiationScope InstScope(*this);