A wrong D2 program:

void foo(immutable ref int[5] a) {}
void bar(const ref int[5] a) {}
void main() {
    const int[5] arr1;
    foo(arr1); // line 5
    immutable int[5] arr2;
    bar(arr2); // line 7
}


DMD 2.055 prints:

test.d(5): Error: function test.foo (ref immutable immutable(int[5u]) a) is not callable using argument types (const(int[5u]))
test.d(5): Error: cast(immutable(int[5u]))arr1 is not an lvalue
test.d(7): Error: cast(const(int[5u]))arr2 is not an lvalue

The first error message is almost good, but why does it print "immutable immutable"?

I think the second error message is useless.

In line 7 the bar(arr2) call gives just a "arr2 is not an lvalue" that I think is not good enough.


So for this program I think a better error message printout is something like:

test.d(5): Error: function test.foo(ref immutable(int[5]) a) is not callable using argument types (const(int[5])).
test.d(7): Error: function test.foo(ref const(int[5]) a) is not callable using argument types (immutable(int[5])).