Two fixes for optional interactions surfaced by the #set/#get review. The
original issue 0160 mis-diagnosed (A) as an optional-chain bug; the chain works
fine for real fields. The actual bugs:
(A) A bare struct literal `.{ ... }` against an optional target `?T` was built
into the optional's {payload, has_value} layout instead of the inner T, then
re-wrapped — corrupting the value (a multi-field payload's first field clobbered
by the has_value flag, or a `?T` arg silently null) or failing LLVM
verification. lowerStructLiteral now builds the inner T, materializes it, and
wraps via coerceToType; lowerVarDecl's previously-UNCONDITIONAL optional wrap is
guarded so an already-`?T` value isn't double-wrapped. Fixed across var-decl,
arg, return, nested field, reassignment, and array-element contexts.
(B) `#get` accessors are now reachable through an optional chain (`obj?.getter`):
lowerOptionalChain dispatches the getter via a synthetic receiver, and
expr_typer types `obj?.getter` through a shared getterReturnTypeOnDeref helper
(handles `?T` and `?*T`, value and pointer optionals, and generic-instance
getters like List.len). The `#set` write side through `?.` is intentionally left
matching real-field behavior (optional-chain assignment unsupported).
Regression tests: examples/optionals/0906 (struct-literal → optional) and 0907
(accessor through chain). issues/0160 marked RESOLVED with the corrected root
cause.
A method `name :: (self: *T, value: V) #set { ... }` (or `=> expr;`) is the
write counterpart of a `#get` accessor: `obj.name = rhs` dispatches to it as
`obj.name(rhs)` when no real field matches. Plumbed parallel to `#get`:
- lexer/token `#set`; `FnDecl.is_set` + `Function.is_set`; parsed in the same
marker slot as `#get` (no return type, exactly self + one value param).
- get+set coexistence: a setter registers/mangles/dispatches under an effective
`name$set` name (`$` is illegal in sx identifiers, so unmistakable), keeping a
same-name `#get` under the plain `name`. Resolution is declaration-order-
independent: a plain read query picks the non-setter, a `name$set` write query
picks the setter (accessorEffName / accessorNameMatches / structMethodFn).
- write dispatch in lowerAssignment via tryLowerPropertyAssignment: plain assign
synthesizes `obj.name$set(rhs)`; compound `OP=` is get-modify-set and
evaluates the receiver EXACTLY ONCE (bound to a synthetic local); read-only
(#get-only) and write-only (#set-only + compound) emit clear diagnostics; a
real field of the same name still wins. Multi-assign property targets dispatch
the setter too (tryLowerPropertyStore, via a pre-lowered-Ref binding).
Payoff: List gains a `len` #set, so `xs.len = n` works; the `.items.len = N`
write workarounds in sched.sx + ui/* + platform/* revert to `xs.len = N`.
issues/0160 records an optional-chain interaction surfaced by the review (a
pre-existing `?T` value-optional read miscompile that blocks getter-through-`?.`).
