The following program 
"
module main;

import std.stdio;

enum TEST_ENUM : string
{
	E_INT = int.stringof,
	E_FLOAT = float.stringof
}

void main( string[] args )
{
	writeln( "Hello World!" );
}
"
produces the following error when compiled in release mode on DMD2.048:
"
Building Debug\DTest.exe...
main.d(7): Error: Integer constant expression expected instead of "int"c
main.d(8): Error: Integer constant expression expected instead of "float"c
main.d(7): Error: Integer constant expression expected instead of "int"c
main.d(8): Error: Integer constant expression expected instead of "float"c
"

however it does compile fine in Release mode.