Index: include/clang/Parse/Parser.h
===================================================================
--- include/clang/Parse/Parser.h
+++ include/clang/Parse/Parser.h
@@ -1685,7 +1685,8 @@
     DSC_trailing, // C++11 trailing-type-specifier in a trailing return type
     DSC_alias_declaration, // C++11 type-specifier-seq in an alias-declaration
     DSC_top_level, // top-level/namespace declaration context
-    DSC_template_type_arg // template type argument context
+    DSC_template_type_arg, // template type argument context
+    DSC_constexpr // constexpr declaration context
   };
 
   /// Is this a context in which we are parsing just a type-specifier (or
@@ -1695,6 +1696,7 @@
     case DSC_normal:
     case DSC_class:
     case DSC_top_level:
+    case DSC_constexpr:
       return false;
 
     case DSC_template_type_arg:
Index: lib/Parse/ParseDecl.cpp
===================================================================
--- lib/Parse/ParseDecl.cpp
+++ lib/Parse/ParseDecl.cpp
@@ -2143,7 +2143,7 @@
   }
 
   // Issue diagnostic and remove constexpr specfier if present.
-  if (DS.isConstexprSpecified()) {
+  if (DS.isConstexprSpecified() && DSC != DSC_constexpr) {
     Diag(DS.getConstexprSpecLoc(), diag::err_typename_invalid_constexpr);
     DS.ClearConstexprSpec();
   }
Index: lib/Parse/ParseExprCXX.cpp
===================================================================
--- lib/Parse/ParseExprCXX.cpp
+++ lib/Parse/ParseExprCXX.cpp
@@ -1688,7 +1688,7 @@
   // type-specifier-seq
   DeclSpec DS(AttrFactory);
   DS.takeAttributesFrom(attrs);
-  ParseSpecifierQualifierList(DS);
+  ParseSpecifierQualifierList(DS, AS_none, DSC_constexpr);
 
   // declarator
   Declarator DeclaratorInfo(DS, Declarator::ConditionContext);
Index: lib/Sema/SemaExprCXX.cpp
===================================================================
--- lib/Sema/SemaExprCXX.cpp
+++ lib/Sema/SemaExprCXX.cpp
@@ -2583,7 +2583,10 @@
       return ExprError();
   }
 
-  return Condition;
+  return ActOnFinishFullExpr(Condition.get(),
+                             Condition.get()->getExprLoc(),
+                             false, /* DiscardedValue */
+                             Condition.get()->isCXX11ConstantExpr(Context));
 }
 
 /// CheckCXXBooleanCondition - Returns true if a conversion to bool is invalid.
Index: test/CXX/drs/dr9xx.cpp
===================================================================
--- test/CXX/drs/dr9xx.cpp
+++ test/CXX/drs/dr9xx.cpp
@@ -44,3 +44,35 @@
   D d{};
 #endif
 }
+
+namespace dr948 {
+#if __cplusplus >= 201103L
+  // This test verifies the functionality specified by DR948:
+  // http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#948
+
+  class A {
+  public:
+     constexpr A(int v) : v(v) { }
+     constexpr operator int() const { return v; }
+  private:
+     int v;
+  };
+
+  constexpr int id(int x)
+  {
+    return x;
+  }
+
+  void f() {
+     if (constexpr int i = id(101)) { }
+     switch (constexpr int i = id(2)) { default: break; case 2: break; }
+     for (; constexpr int i = id(0); ) { }
+     while (constexpr int i = id(0)) { }
+
+     if (constexpr A i = 101) { }
+     switch (constexpr A i = 2) { default: break; case 2: break; }
+     for (; constexpr A i = 0; ) { }
+     while (constexpr A i = 0) { }
+  }
+#endif
+}