Bug 1386 – "string expected" when using allMembers-element in __traits(getMember, ...)

import std.stdio; struct Temp(T...) { alias void delegate(T) asdf; } class Asdf { Temp!(uint) asdf; Temp!(string) qwer; Temp!(real,real) yxcv; } void main() { foreach ( member; __traits(allMembers, Asdf) ) { Asdf a; writefln("%s %s", member, typeid(typeof(__traits(getMember, a, member)))); } }

__traits works only with strings known at compile time and in your example 'member' is evaluated at run-time. However, allMembers trait evaluates to an array literal, so there should be a way to iterate through it at compile time. Unfortunately, D doesn't have true 'static foreach' and you probably have to resort to hacks.

'member' should be evaluated at compile-time, since foreach usually works with CTFE. if not, the error should be "cannot evaluate ... at compile time".

I've tried everything to work around this, but nothing worked. In fact this prevents many thinkable uses of compile time introspection.

Leave the version number on the _earliest_ dmd version exhibiting the problem.

Also, you can work around this using a for-loop (I think) or recursive templates; and "blocker" refers to a bug sufficiently severe that Walter should drop everything else and fix this bug, or even possibly roll back to an earlier version that does not exhibit the bug.

Ok, sorry didn't know. Finally managed to compile a workaround: template Sequence(size_t count, size_t index = 0) { static if (index < count) alias Tuple!(index, Sequence!(count, index + 1)) Sequence; else alias Tuple!() Sequence; } static const members = __traits (allMembers, foo); foreach (i; Sequence!(members.length)) { foreach (p; ParameterTypeTuple!(__traits(getMember, foo, members[i]))) writefln(typeid(p)); }

As a way to index allMembers as a tuple, here's a template converting an array known at compile time to a tuple: template ArrayToTuple( alias Arr, U... ) { static if ( Arr.length ) { alias ArrayToTuple!( Arr[ 0..$-1 ], Arr[ $-1 ], U ) ArrayToTuple; } else { alias U ArrayToTuple; } }

allMembers returns a tuple now (svn r360) but this still doesn't work. Yields a strange error.

The error message is: test2.d(22): Error: no property '__T4TempTkZ' for type 'test2.Asdf' Some kind of junk tuple members are being included in allMembers.

In 2.055, The problem in comment #9 does not occur by fixing bug 2234. Therefore original sample code in comment #0 might work as expected. But class has a member interface Monitor, so > typeid(typeof(__traits(getMember, a, member)))) will fail to compile. If you change `class Asdf` into `struct Asdf`, you'll get following output: asdf test.Temp!(uint).Temp qwer test.Temp!(string).Temp yxcv test.Temp!(real,real).Temp