-----------------------------------
import std.stdio;
struct S { int a; }

int foo()
{
	S s;
	return bar(s.a);  // A
	//bar(s.a); return s.a; // B
}

int bar(ref int b)
{
	b = 5;
	return b;
}

enum y = foo();

void main()
{
	writeln(y);
}
-----------------------------------

Expected output: 5
Actual output: 0

Same thing occurs with either the "// A" line or the "// B" line uncommented.  Also occurs with "out" instead of "ref".