https://issues.dlang.org/show_bug.cgi?id=14878
--- Comment #1 from Kenji Hara <k.hara...@gmail.com> --- (In reply to Martin Nowak from comment #0) > static assert(!__traits(compiles, (T) @safe {})); > static assert(!is(typeof((T) @safe {}))); `(T) @safe {}` is a lambda with untyped parameter name T. Following static asserts work as you expects. static assert(!__traits(compiles, (T b) @safe {})); static assert(!is(typeof((T b) @safe {}))); --