We know that arrays can be initialized by a single element value: void main() { int value = 1; int[2] a = value; assert(a == [ 1, 1 ]); } The bug is that it does not work when the elements are fixed-length arrays themselves: void main() { int[3] value = [ 1, 2, 3 ]; int[3][2] a = value; // <-- COMPILATION ERROR assert(a == [ [ 1, 2, 3 ], [ 1, 2, 3 ] ]); } Error: mismatched array lengths, 6 and 3 On the other hand, the array can be initialized by an element-of-an-element: void main() { // Note: This is the type of an element of array elements int value = 1; int[3][2] a = value; assert(a == [ [ 1, 1, 1 ], [ 1, 1, 1 ] ]); } Is that a feature or perhaps a consequence of the reported bug? Ali
From the spec: "If a slice operator appears as the lvalue of an assignment expression, and the type of the rvalue is the same as the element type of the lvalue, then the lvalue's array contents are set to the rvalue. " Assuming that single value initialization is a semantic equivalent of slice expression, the code should work.
I looked a little bit at function 'visit(AssignExp exp)' inside dmd/src/dmd/expressionsem.d. I think this is related to the fact that a static array initialization's left-hand expression treated as a dynamic array. This is evident in the following error message: int[3][2][1] arr = 1.5; // Error: cannot implicitly convert expression `1.5` of type `double` to `int[]` Note how the error message says int[] instead of int[3][2][1]. I suspect this is a bug due to code reuse in implementation.
@benjones created dlang/dmd pull request #10600 "Fix issue 10562 dont flatten arrays to 1D when " fixing this issue: - Fix issue 10562 dont flatten arrays to 1D when being assigned to an array https://github.com/dlang/dmd/pull/10600
dlang/dmd pull request #10600 "Fix issue 10562 dont flatten arrays to 1D when " was merged into master: - 7c900d46148b0020b7f7e3b2c569faaf49869694 by Ben Jones: Fix issue 10562 dont flatten arrays to 1D when being assigned to an array https://github.com/dlang/dmd/pull/10600