In the site documentation of std.exception.assumeUnique there is code like:

 string letters()
 {
   char[] result = new char['z' - 'a' + 1];
   foreach (i, ref e; result)
   {
     e = 'a' + i;
   }
   return assumeUnique(result);
 }


But recent improvements of the D language make assumeUnique useless in this case, this compiles:

string lowercase() pure nothrow {
    auto result = new char['z' - 'a' + 1];
    foreach (i, ref c; result)
        c = cast(char)('a' + i);
    return result;
}
void main() {}


On the other hand currently (DMD 2.056head) 'a'+i can't be assigned to a char because the compiler doesn't see that the variable 'i' will never become too much big.

So in the documentation of std.exception.assumeUnique I suggest to explain that some usages (where the function is pure) of assumeUnique are not needed now.