• via Digitalmars-d-bugs (39/39) Apr 21 2014 https://issues.dlang.org/show_bug.cgi?id=12606

via Digitalmars-d-bugs <digitalmars-d-bugs puremagic.com> writes:

https://issues.dlang.org/show_bug.cgi?id=12606

          Issue ID: 12606
           Summary: Mismatch of array length during assignment should emit
                    better diagnostics
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Keywords: diagnostic
          Severity: enhancement
          Priority: P1
         Component: DMD
          Assignee: nobody puremagic.com
          Reporter: andrej.mitrovich gmail.com

-----
import std.range;

// ok
uint[256] arr1 = iota(0, 512).array[0 .. 256];

// diagnostic mentions int[] => uint[256], but no mention of length (128 !=
256)
uint[256] arr2 = iota(0, 512).array[0 .. 128];

void main() { }
-----

The first one is a relatively recent feature, where a slice can be converted to
a static array if the length is known. The length is also known for the second
declaration, but it's not being taken into account by the diagnostic:

Diagnostic:
test.d(6): Error: cannot implicitly convert expression ([0, 1, 2, 3, 4, 5, 6,
7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26,
27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46,
47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66,
67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86,
87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104,
105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120,
121, 122, 123, 124, 125, 126, 127]) of type int[] to uint[256]

Since the compiler knows the length of the slice it should mention the mismatch
of slice lengths when attempting to convert a dynamic array to a static array.

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