Assert prints an "array of char" when used why to!string

[monarch_dodra]

Code:

----
import std.conv;
void main() {
  static assert(
    is(typeof(("Failure: " ~ to!string(55)) == string))
  );
  static assert(0 , ("Failure: " ~ to!string(55)));
}
----
main.d(7): Error: static assert  
['F','a','i','l','u','r','e',':',' ','5','5']
----

The problem is the ugly-ass "print as array of individual 
characters".

I really don't understand what is going on, since the compile 
type of my string is indeed "string".

If I remove the "to!string", I get:
----
main.d(7): Error: static assert  "Failure"
----

1) Is this the "normal" behavior, or a "known limitation"?
2) Is there a "workaround"?

FYI, this was originally produced by code from Phobos, but was 
trimmed by me here.