Why doesn't to!MyEnumType(42) work

[Tommi]

On Monday, 16 July 2012 at 20:22:12 UTC, Era Scarecrow wrote:
>  MyEnumType y = cast(MyEnumType) 42; //Error: wtf is 42 anyways?

Like the previous fellow said, it's not an error.

To me that line of code says: "let's assign to MyEnumType 
variable y some value that's not valid (as type MyEnumType 
defines the word valid)". I think it's very useful to be able to 
assign values which are unambiguously invalid, like NaN to float, 
0xFF to char or some undefined value to enum. Sadly, with 
integral types there's no such value that could be seen as 
invalid.

And to reiterate my point:
If the call:

to!MyEnum(42)

...is supposed to be (and this I gather from the docs) under the 
hood the same as:

cast(MyEnum) 42

...which works, then, logically, to!MyEnum(42) should also work.