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digitalmars.D.bugs - [Issue 13205] New: Analysis improvement of compile-time array slices


          Issue ID: 13205
           Summary: Analysis improvement of compile-time array slices
           Product: D
           Version: D2
          Hardware: x86
                OS: Windows
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: DMD
          Assignee: nobody puremagic.com
          Reporter: bearophile_hugs eml.cc

I suggest to improve a little the compile-time analysis of slice length copies.
This code shows a compile-time accepts-invalid and a compile-time rejects-valid
enhancement requests:

void foo(int[8]) {}
void main() {
    int[100] a;
    int[8] b;
    const int i = 20;
    b[] = a[i .. i + 9]; // OK, detected at compile-time
    int j = 20;
    b[] = a[j .. j + 9]; // Bad, missed at compile-time
    foo(a[j .. j + 8]);  // Bad, wrongly detected at compile-time

test.d(6,9): Error: mismatched array lengths, 8 and 9
test.d(9,8): Error: function test.foo (int[8] _param_0) is not callable using
argument types (int[])

See also Issue 4939

Jul 26 2014