Supersedes #26120 (https://github.com/nim-lang/Nim/pull/26120), which
fixed the reported case but left the `tfShallow` half of the same
condition open.
Since #25860 array literals are materialized into temporaries so that
`lent` results keep valid backing storage. In an async proc such a
temporary is lifted into the closure environment, and the environment is
filled with an `nkFastAsgn`, i.e. without `needToCopy`. `genGenericAsgn`
then emitted `genericShallowAssign` from the static const array, and for
the `string` elements that ends in `unsureAsgnRef` ->
`incRef(usrToCell(literal))` on memory that has no GC header:
proc f() {.async.} =
for ip in ["::1", "2001:db8::", "::"]:
await sleepAsync(1)
`OnStatic` sources must therefore always take the `genericAssign` path.
Note that the guard has to dominate the `tfShallow` test as well, not
just the `needToCopy` one: a `{.shallow.}` destination assigned from a
`const` crashes in exactly the same way. This is the precedence
`genOptAsgnTuple` and `genOptAsgnObject` already use, so
`genGenericAsgn` now agrees with its two siblings instead of
contradicting them.
refc only; the other GCs do not reference count in `unsureAsgnRef`.
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
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