ff9e448f8c
Five adversarial reviews of the issue-0160 fix surfaced three more bugs in the touched optional-chain / optional-coercion code; all fixed here: 1. A COLD generic-instance getter through `?.` (`?*Vec(i64)` `.getter`, never called directly first) panicked with "unresolved type reached LLVM emission": a cold instance method is absent from resolveFuncByName, so the getter's return type resolved to .unresolved → a ?unresolved merge type. lowerOptionalChain and getterReturnTypeOnDeref now warm the monomorph (ensureGenericInstanceMethodLowered) before querying its return type. (The 0907 test passed only by luck — List(i64) is warmed by stdlib use; 0907 now also exercises a cold user generic.) 2. A real-field read through a `?*T` chain (`op?.field`, op: ?*T) reinterpreted the pointer bits as the field (silent garbage) — the some-branch real-field path didn't load through the pointer. It now derefs `?*T` before the field access. (Pre-existing — the else-branch predates 0160 — but it's the same function and a silent miscompile, so fixed here.) 3. `?[]T = array` skipped the array→slice promotion (corrupt .len/.ptr): the lowerVarDecl optional arm wrapped the raw array. It now coerces the value to the optional's child type (array→slice) before wrapping. Regression examples 0906/0907 extended to cover all three. Distinct PRE-EXISTING bugs the reviews surfaced in untouched subsystems are filed as issues 0161 (struct-literal vs scalar), 0162 (#run returning an optional aggregate), 0163 (untagged-union payload-binding match).
41 lines
1.7 KiB
Markdown
41 lines
1.7 KiB
Markdown
# 0162 — `#run` returning an optional aggregate fails the comptime VM reg→value bridge
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## Symptom
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A `#run` (or comptime const init) whose function returns an OPTIONAL value
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(`?T`, `?i64`, any optional) fails comptime evaluation with:
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`error: comptime init of 'X' failed: reg→value: aggregate shape not bridged yet`
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A non-optional return of the same type works. This is a pre-existing limitation
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in the comptime VM's register→value bridge for optional-typed results; it is
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orthogonal to issue 0160 (it reproduces for a value-init optional with no struct
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literal anywhere, and for a scalar optional `?i64`).
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## Reproduction
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```sx
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#import "modules/std.sx";
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T :: struct { a: i64 = 0; }
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mk :: () -> ?T { t : T = .{ a = 7 }; return t; }
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mk2 :: () -> ?i64 { return 5; }
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X :: #run mk(); // error: reg→value: aggregate shape not bridged yet
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Y :: #run mk2(); // same class of failure
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main :: () { print("ok\n"); }
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```
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Baseline that WORKS: `Z :: #run (() -> T { return .{ a = 7 }; })();` (non-optional).
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## Investigation prompt
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`src/ir/comptime_vm.zig` — the reg→value bridge (search "aggregate shape not
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bridged" / `regToValue`) handles scalars/structs/slices but bails on an
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OPTIONAL-typed result. An optional is `{payload, has_value}` (or a pointer for
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`?*T` / a sentinel for `?Closure`); the bridge needs to read the has_value flag
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and, when set, bridge the payload as its child type (recursively), producing a
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`Value` optional — and a null optional when clear. Add the `.optional` arm to
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the reg→value bridge (mirror the value→reg direction, which already builds
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optionals — see `makeStringList`/`writeField` optional handling). Verify with
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the repro (expect `X`/`Y` to evaluate, `main` prints ok). Add a
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`examples/comptime/06xx-...` regression.
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