Here's another thing that should be allowed that doesn't depend
on optimizations:
Any code path in a @nogc function that is guaranteed to abort the
program should be exempt from @nogc enforcement. This includes
assert(0) and throwing an Error.
Take std.exception.assumeWontThrow() as an example:
T assumeWontThrow(T)(lazy T expr,
string msg = null,
string file = __FILE__,
size_t line = __LINE__) nothrow
{
try
{
return expr;
}
catch(Exception e)
{
immutable tail = msg.empty ? "." : ": " ~ msg;
throw new AssertError("assumeWontThrow failed: Expression
did throw" ~
tail, file, line);
}
}
Currently, this cannot be @nogc, because it uses `new` and `~`.
However, this only happens in preparation to throwing the
AssertError, which in turn causes the program to abort. I guess
in this situation, it's ok to allocate on the GC heap.
With my proposed rule, assumeWontThrow can be deduced to be @nogc
iff expr is @nogc. This allows more functions to be @nogc.
