utf code unit sequence validity (non-)checking

[spir]

Hello,


I just noted noted that D's builtin *string types do not behave the same way in front of invalid code unit sequences. For instance:

void main () {
    assert("hæ?" == "\x68\xc3\xa6\x3f");
    // Note: removing \xa6 thus makes invalid utf8.

    string s1 = "\x68\xc3\x3f";
    // ==> OK, accepted -- but write-ing indeed produces "h�?".

    dstring s4 = "\x68\xc3\x3f";
    // ==> compile-time Error: invalid UTF-8 sequence
}

I guess this is because, while converting from string to dstring, meaning while decoding code units to code points, D is forced to check sequence validity. But this is not needed, and not done, for utf8 string. Am I right on this?
If yes, isn't it risky to let utf8 (and wstrings?) unchecked? I mean, to have a concrete safety difference with dstrings? I know there are utf checking routines in the std lib, but for dstrings one does not need no call them explicitely.
(Note that this checking is done at compile-time for source code literals.)


denis
-- -- -- -- -- -- --
vit esse estrany ☣

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