[Issue 4939] New: Some compile-time length tests of array concats

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=4939

           Summary: Some compile-time length tests of array concats
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: accepts-invalid, diagnostic
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: bearophile_hugs at eml.cc


--- Comment #0 from bearophile_hugs at eml.cc 2010-09-25 08:50:01 PDT ---
This is a wrong D2 program, because the lengths of the arrays don't match:


// Program #1
void main() {
    int[2] a1;
    int[3] a2;
    int[6] result;
    result[] = a1 ~ a2;
}


It compiles with no errors, because a1~a2 produces a dynamic array, despite its
length is determined at compile-time. I'd like the compile to catch this bug at
compile-time.

The situation in Program #1 is not so common, but a little more refined
implementation of the same kind of tests may catch at compile-time more common
cases, like:


// Program #2
void main() {
    int[] a1 = new int[2];
    int[] a2 = new int[3];
    int[6] result;
    result[] = a1 ~ a2; // Error
    a1 ~= 0;
    result[] = a1 ~ a2;
}


// Program #3
void main() {
    int[] a1 = new int[2];
    int[] a2 = new int[3];
    int[] result = new int[6];
    result[] = a1 ~ a2; // Error
}

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