On 6/16/16 3:43 PM, cy wrote:
I don't get it. Do I have to write a separate template for arrays
specifically or something?
NonConst foo(Constant: const NonConst, NonConst)(Constant bar) {
pragma(msg,"NonConst is ",NonConst);
pragma(msg,"Constant is ",Constant);
NonConst foo = bar;
return foo;
}
void main() {
const int bar = 42;
auto baz = foo(bar);
pragma(msg,typeof(baz));
baz = 23;
const(int[]) barr = [1,2,3];
auto bazz = foo(barr);
pragma(msg,typeof(bazz));
bazz[0] = 4;
}
/*
NonConst is int
Constant is const(int)
int
NonConst is const(int)[]
Constant is const(int)[]
const(int)[]
derp.d(16): Error: cannot modify const expression bazz[0]
Failed: ["dmd", "-v", "-o-", "derp.d", "-I."]
*/
1. Because const(int)[] is not the same as const(int[]). The former is a
*mutable* array of *constant* integers.
2. Yes, I see that you passed in const(int[]). IFTI was changed a while
back to automatically convert to tail-const versions when implying
parameters (to save on template bloat). So it deduces "Constant" to be
const(int)[].
Also, note that you cannot assign a const item containing references to
a non-const version of it. So even if NonConst was properly deduced, the
function would fail to compile.
-Steve
