Code
import std.bigint;
BigInt foo() {
return BigInt(128);
}
void main() {
BigInt bar = BigInt(128);
assert(foo() == bar);
assert(bar == foo()); // *** HERE
}
does not compile with the following error on the marked line:
test.d(10): Error: foo() is not an lvalue
It seems that is because of the ref parameter of the opEquals method in the BigInt structure. Obviously it is not needed for the parameter to be a reference in this case, though it could be thought as a possible performance tweak (I don't know for certain about the correctnes of this though).
Comment #1 by kennytm — 2011-05-11T10:40:22Z
Unfortunately an opEquals for a struct must take the signature of (ref const S s). See http://d-programming-language.org/operatoroverloading.html#equals. The rvalue problem here is a specialization of bug 5609. Allowing struct to have any signature is a duplicate of issue 3659.
*** This issue has been marked as a duplicate of issue 5609 ***