Eli helped me understand how evaluation contexts work.

llvm-svn: 113642
diff --git a/clang/lib/Parse/ParseExpr.cpp b/clang/lib/Parse/ParseExpr.cpp
index f2cf784..1c2b343 100644
--- a/clang/lib/Parse/ParseExpr.cpp
+++ b/clang/lib/Parse/ParseExpr.cpp
@@ -898,6 +898,10 @@
     if (ExpectAndConsume(tok::l_paren,
                          diag::err_expected_lparen_after, "noexcept"))
       return ExprError();
+    // C++ [expr.unary.noexcept]p1:
+    //   The noexcept operator determines whether the evaluation of its operand,
+    //   which is an unevaluated operand, can throw an exception.
+    EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated);
     ExprResult Result = ParseExpression();
     SourceLocation RParen = MatchRHSPunctuation(tok::r_paren, LParen);
     if (!Result.isInvalid())