[Issue 13907] New: Surrogate pairs in wchar string literal will cause incorrect length match

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13907

          Issue ID: 13907
           Summary: Surrogate pairs in wchar string literal will cause
                    incorrect length match
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Keywords: accepts-invalid, rejects-valid
          Severity: normal
          Priority: P1
         Component: DMD
          Assignee: nobody at puremagic.com
          Reporter: k.hara.pg at gmail.com

Example code:

void f1(wchar[1] a) {}
void f2(wchar[2] a) {}
void f3(wchar[3] a) {}
auto f12(wchar[1]) { return 1; }
auto f12(wchar[2]) { return 2; }
void main()
{
    // Surrogate pair is used for U+10000
    wstring s = "\U00010000"w;
    assert(s.length == 2);

    // ok
    f2("\U00010000"w);
    f2("\U00010000");

    // Why the wstring length == 2 matches to wchar[1]?
    f1("\U00010000"w);
    f1("\U00010000" );

    // Why the wstring length == 2 matches to wchar[3]?
    f3("\U00010000"w);
    f3("\U00010000" );

    // This is ok, but...
    assert(f12("ab"w) == 2);

    // I think the wchar[2] version should be selected, but doesn't.
    assert(f12("\U00010000"w) == 2);
}

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