2 files changed, 93 insertions, 6 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index b89e2bcc800..9f964fab9cd 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -3111,14 +3111,46 @@ static bool CheckObjCTraitOperandConstraints(Sema &S, QualType T,
 /// \brief Check the constrains on expression operands to unary type expression
 /// and type traits.
 ///
-/// This is just a convenience wrapper around
-/// Sema::CheckUnaryExprOrTypeTraitOperand.
+/// Completes any types necessary and validates the constraints on the operand
+/// expression. The logic mostly mirrors the type-based overload, but may modify
+/// the expression as it completes the type for that expression through template
+/// instantiation, etc.
 bool Sema::CheckUnaryExprOrTypeTraitOperand(Expr *Op,
                                             UnaryExprOrTypeTrait ExprKind) {
-  return CheckUnaryExprOrTypeTraitOperand(Op->getType(),
-                                          Op->getExprLoc(),
-                                          Op->getSourceRange(),
-                                          ExprKind);
+  QualType ExprTy = Op->getType();
+
+  // C++ [expr.sizeof]p2: "When applied to a reference or a reference type,
+  //   the result is the size of the referenced type."
+  // C++ [expr.alignof]p3: "When alignof is applied to a reference type, the
+  //   result shall be the alignment of the referenced type."
+  if (const ReferenceType *Ref = ExprTy->getAs<ReferenceType>())
+    ExprTy = Ref->getPointeeType();
+
+  if (ExprKind == UETT_VecStep)
+    return CheckVecStepTraitOperandType(*this, ExprTy, Op->getExprLoc(),
+                                        Op->getSourceRange());
+
+  // Whitelist some types as extensions
+  if (!CheckExtensionTraitOperandType(*this, ExprTy, Op->getExprLoc(),
+                                      Op->getSourceRange(), ExprKind))
+    return false;
+
+  if (RequireCompleteExprType(Op,
+                              PDiag(diag::err_sizeof_alignof_incomplete_type)
+                              << ExprKind << Op->getSourceRange(),
+                              std::make_pair(SourceLocation(), PDiag(0))))
+    return true;
+
+  // Completeing the expression's type may have changed it.
+  ExprTy = Op->getType();
+  if (const ReferenceType *Ref = ExprTy->getAs<ReferenceType>())
+    ExprTy = Ref->getPointeeType();
+
+  if (CheckObjCTraitOperandConstraints(*this, ExprTy, Op->getExprLoc(),
+                                       Op->getSourceRange(), ExprKind))
+    return true;
+
+  return false;
 }
 
 /// \brief Check the constraints on operands to unary expression and type
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index a2433cad51a..9fccdb11c58 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -3246,6 +3246,61 @@ static void processTypeAttrs(TypeProcessingState &state, QualType &type,
   } while ((attrs = next));
 }
 
+/// \brief Ensure that the type of the given expression is complete.
+///
+/// This routine checks whether the expression \p E has a complete type. If the
+/// expression refers to an instantiable construct, that instantiation is
+/// performed as needed to complete its type. Furthermore
+/// Sema::RequireCompleteType is called for the expression's type (or in the
+/// case of a reference type, the referred-to type).
+///
+/// \param E The expression whose type is required to be complete.
+/// \param PD The partial diagnostic that will be printed out if the type cannot
+/// be completed.
+///
+/// \returns \c true if the type of \p E is incomplete and diagnosed, \c false
+/// otherwise.
+bool Sema::RequireCompleteExprType(Expr *E, const PartialDiagnostic &PD,
+                                   std::pair<SourceLocation,
+                                             PartialDiagnostic> Note) {
+  QualType T = E->getType();
+
+  // Fast path the case where the type is already complete.
+  if (!T->isIncompleteType())
+    return false;
+
+  // Incomplete array types may be completed by the initializer attached to
+  // their definitions. For static data members of class templates we need to
+  // instantiate the definition to get this initializer and complete the type.
+  if (T->isIncompleteArrayType()) {
+    if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E->IgnoreParens())) {
+      if (VarDecl *Var = dyn_cast<VarDecl>(DRE->getDecl())) {
+        if (Var->isStaticDataMember() &&
+            Var->getInstantiatedFromStaticDataMember()) {
+          InstantiateStaticDataMemberDefinition(E->getExprLoc(), Var);
+          // Update the type to the newly instantiated definition's type both
+          // here and within the expression.
+          T = Var->getDefinition()->getType();
+          E->setType(T);
+
+          // We still go on to try to complete the type independently, as it
+          // may also require instantiations or diagnostics if it remains
+          // incomplete.
+        }
+      }
+    }
+  }
+
+  // FIXME: Are there other cases which require instantiating something other
+  // than the type to complete the type of an expression?
+
+  // Look through reference types and complete the referred type.
+  if (const ReferenceType *Ref = T->getAs<ReferenceType>())
+    T = Ref->getPointeeType();
+
+  return RequireCompleteType(E->getExprLoc(), T, PD, Note);
+}
+
 /// @brief Ensure that the type T is a complete type.
 ///
 /// This routine checks whether the type @p T is complete in any