Variables should have the ability to be @nogc

[Marco Leise via Digitalmars-d]

I "solved" it with a UDA called GcScan in my code. It can be
attached to any field or type and is a tri-state. In the
undecided case (GcScan.auto) it recursively scans for potential
GC pointers, excluding those marked GcScan.no. In the decided
case (GcScan.yes/no) it simply assumes the user knows better
and short-circuits the recursion.

If I use a third party struct that contains pointers and does
not use my GcScan UDA, but is known not to point to GC memory,
I'd tag the outer level with @GcScan.no.

Memory allocation via malloc is also wrapped in a function (a
typed allocator) that takes GcScan as a hint, so it may or may
not add the freshly allocated memory as a GC range. Again,
GcScan.auto would trigger auto-detection from the type.

-- 
Marco