dstep/internal/Reflection.d:205:0 expression "objcObject_"c == cast(char[])field is not constant or does not evaluate to a bool

[Robert Lumley]

hi all :) i'm new to D and i'm trying to get step to compile on 
the Mac.  below is the template that gives the error: 
dstep/internal/Reflection.d:205:0 expression "objcObject_"c == 
cast(char[])field is not constant or does not evaluate to a bool

private template hasFieldImpl (T, string field, size_t i)
{
static if (T.tupleof.length == i)
  const hasFieldImpl = false;

else static if (T.tupleof[i].stringof[1 + T.stringof.length + 2 
.. $] == field)
  const hasFieldImpl = true;

else
  const hasFieldImpl = hasFieldImpl!(T, field, i + 1);  }

there error is on the line else static..

thanks very much