This program:

enum TEST = "test";

string valid = "this is a " ~ TEST;
char[] sabotage = cast( char[] )"this is a " ~ TEST;
string no_longer_valid = "this is a " ~ TEST; 

void main() {}


Fails to compile with this error:
Error: cannot implicitly convert expression ("this is a test") of type char[] to string

Commenting out the "char[] sabotage..." allows the program to compile.