8b613af96b
The type-erased value type is spelled Any (capital), per specs.md and type_resolver.zig. Lowercase 'any' is an undefined name that resolves to an empty-struct stub, which is why ?any appeared to silently discard the value. ?Any round-trips correctly (present/absent/unwrap all work), so there is no Any-TypeId canonicalization bug. Reword the 0165 cross-ref accordingly.
59 lines
2.9 KiB
Markdown
59 lines
2.9 KiB
Markdown
# 0171 — `?any` optional child is a non-canonical `any` TypeId (box-into-any rule misses, value silently discarded)
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> **RESOLVED — NOT A BUG (wrong casing in the repro).** The type-erased value
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> type is spelled **`Any`** (capital A), not lowercase `any` (specs.md §Types;
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> `src/ir/type_resolver.zig`: `if name == "Any" return .any`). Lowercase `any`
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> is an UNDEFINED type name that resolves to an empty-struct stub — which is why
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> `?any` appeared to "silently discard" / mis-resolve. The real `Any` optional
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> child works correctly: `?Any` round-trips — `x : ?Any = 42` tests present, a
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> `null` one tests absent, and `x!` unwraps. There is no `Any`-TypeId
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> canonicalization bug. (The confusing diagnostic for a lowercase `?any` —
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> "payload type is 'any'" instead of "unknown type 'any'" — is a minor
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> undefined-name-in-optional-child message-quality nit, not this issue.)
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## Symptom
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An optional whose child is `any` (`?any`) is broken. Baseline (before the issue
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0165 fix) silently DISCARDED the boxed value: `x : ?any = 42; v := x!` yields an
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empty box `any{}`, not `42` — the payload is lowered as a zero-size `{}`. After
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the 0165 fix the same code now produces a clean type-mismatch diagnostic
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(`cannot assign a value of type 'i64' to optional '?any': its payload type is
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'any'`), which is strictly better than silent corruption but still means `?any`
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does not work.
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## Root cause (from adversarial review of issue 0165)
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The box-into-`any` coercion rule (`src/ir/conversions.zig` ~line 57) keys on the
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BUILTIN `.any` enum TypeId. But an optional's child `any` is a SEPARATELY
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interned TypeId (observed `@enumFromInt(246)`, type-name `"any"`) that is NOT
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identity-equal to the builtin `.any`. So `classify(i64, child_any)` falls through
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to `.none`, returns the value unchanged (`i64`), and the wrap is invalid. The
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`any` type is not being canonicalized to the builtin TypeId when it appears as an
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optional child.
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## Reproduction
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```sx
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#import "modules/std.sx";
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main :: () {
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x : ?any = 42;
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v := x!;
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print("{}\n", v); // expected: a boxed 42; baseline yields empty any{}
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}
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```
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## Investigation prompt
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Canonicalize `any` as an optional child (and likely any other compound position)
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to the builtin `.any` TypeId at type-resolution/interning time, so the
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box-into-any rule in `src/ir/conversions.zig` classifies correctly and `?any`
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round-trips. Find where the optional child type is resolved/interned
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(`src/ir/types.zig` `optionalOf` / the type resolver) and ensure an `any` child
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maps to the canonical builtin TypeId rather than a fresh interned copy.
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Alternatively, make the box-into-any classifier compare by type-KIND
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(`info == .any`) rather than TypeId identity — but canonicalization is the more
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robust fix (it also fixes `==`, `size_of`, and any other identity check on the
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`any` child). Verify the repro round-trips a boxed value; add an
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`examples/types/01xx-optional-any.sx` regression. Low priority — `?any` is used
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nowhere in `library/` or `examples/`.
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