https://issues.dlang.org/show_bug.cgi?id=15240
--- Comment #1 from Kenji Hara <[email protected]> --- This is intentional behavior. In 'IsExpression', if the Type operand is invalid, the latter arguments are not analyzed. In this case, the type R in `static if (is(R == what)) ...` is undefined, then what is not evaluated. If you supply R as a valid type, the 'what' will cause an error. alias R = int; static if (is(R == what)) pragma(msg, "hi"); Prints: --- test.d(2): Error: undefined identifier 'what' --
