On Tuesday, 20 September 2016 at 22:38:33 UTC, Jonathan M Davis wrote:
On Tuesday, September 20, 2016 22:23:08 Yuxuan Shui via Digitalmars-d-learn wrote:
struct A {
  ulong[] x;
struct B {
  ulong x;
void main() {
  B[] b;
  const(B) xx = B(1);
  b ~= xx; // Works

  A[] c;
  const(A) yy = A([1]);
  c ~= yy; // Does not

What gives?

const(A) means that the ulong[] inside is const(ulong[]). When yy is copied to be appended to c, it goes from const(A) to A, which means that const(ulong[]) would need to be sliced and and set to ulong[], which would violate const, because it would mean that the last element in c could mutate then elements of its x, which would then mutate the elements in yy.

- Jonathan M Davis

That makes sense, thanks.

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