Bug 5877 – Cannot treat '__traits(parent, obj)' as a type

Since the introduction of __traits(parent) in commit 2e261cd6, it is possible that the __traits expression returns a type. However, the parser does not recognize this in an alias statement, and rejects the code. -------------------------------------------------------- class B { int x(); alias __traits(parent, x) S; static assert(is(B == S)); } -------------------------------------------------------- x.d(3): basic type expected, not __traits x.d(3): no identifier for declarator int x.d(3): semicolon expected to close alias declaration x.d(3): Declaration expected, not '__traits' -------------------------------------------------------- A workaround is to create an existing expression that returns a type: -------------------------------------------------------- class B { int x(); alias typeof(__traits(parent, x).init) S; static assert(is(B == S)); } -------------------------------------------------------- But it is better the __traits work without these hacks.

The same applies anywhere that expects a type, e.g. template (alias m, T = __traits(parent, m)) { // ^^^^^^^^^^^^^^^^^^^ __traits(parent, m) s; // ^^^^^^^^^^^^^^^^^^^ etc.

*** This issue has been marked as a duplicate of issue 7804 ***