feat: mixed/union values at narrower declared boundaries + typed callbacks over unknown-element arrays#470
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Survey-driven object/Mixed covariance at callback + interface boundaries (85% → 88%, 262 → 269/307). illegalstudio#470 (mixed/union arg boundary) already landed in 5052070; this completes the family: - ARRAY-CALLBACK OBJECT/MIXED ELEMENTS (illegalstudio#519 / EC-28b): array_map fabricated an IntLiteral dummy for non-scalar elements, so a typed callback (`fn (FieldDescriptor $f) => ...`) over a `list<FieldDescriptor>` failed "expects Object, got Int". array_map now routes through the object-aware comparator_dummy_arg_for_elem (synthetic-var + env binding), and that helper gains a Mixed arm — a bare `array` element infers as Mixed (phpdoc generics aren't enforced on the PHP `array` type), and Mixed accepts any declared parameter at the runtime-enforced boundary. usort/uasort widen their element gate from Object to Object|Mixed so the same typed-comparator shape checks. Clears the array_map/usort/uasort `callback parameter expects Object, got Int` family (8). - INTERFACE COVARIANT SELF-RETURN (illegalstudio#547 / EC-53): a `withX(): static`/self implementation of an interface-typed return (PSR-7 immutability methods) cannot go through type_accepts — the class is not yet registered mid-schema. Accept it from the facts at hand (this validation IS the proof the class implements the interface). Clears FileResponse et al. `withStatus incompatible return type` (3). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
…backs over unknown-element arrays
Two boundary relaxations in `types_compatible`, both runtime-enforced PHP
that the checker statically rejected, plus the typed-callback fix they enable:
- A `mixed` VALUE flowing into a narrower declared type (param or return) is
legal PHP — the engine enforces it at runtime (TypeError on mismatch), and
the boxed-Mixed representation already funnels at the boundary. Trust the
declaration.
- A union VALUE with at least one member the declaration accepts crosses the
boundary (e.g. an `int|false` seek result passed to an `int` param on the
success path). A union with NO compatible member stays rejected.
`types_compatible` feeds only argument/return checks, so interface
conformance and property assignment are unaffected.
- Typed callbacks keep their declared contract over object/unknown-element
arrays: usort/uasort/array_map fabricated an `Int` placeholder when the
element type had no literal form, so a typed comparator/mapper failed
("callback parameter expects Object, got Int"). `array_element_type` now
yields `Mixed` for a `Mixed` receiver; `comparator_dummy_arg_for_elem`
binds a synthetic variable for Object/Mixed elements and binds `Mixed` for
`Never` (empty/unknown) elements — PHP never invokes the callback for an
empty array, so the declared contract stands unchecked.
Byte-parity vs PHP 8.5 on all regression tests. Known limit: array_map over
OBJECT-element arrays now passes the checker but still hits a pre-existing
EIR lowering wall — a backend follow-up.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Two related type-checker completeness fixes, both runtime-enforced PHP the checker statically rejected:
types_compatibleaccepts a Mixed VALUE into any declared type (param and return) and a UNION value with at least one member the declaration accepts (e.g. anint|falseseek result passed to anintparam on its success path — a union with NO compatible member stays rejected). Scoped to the arg/return check only; interface conformance and property assignment are unaffected. The boxed-Mixed representation already funnels at the boundary — verified byte-identical.usort/uasort/array_map callbacks keep their DECLARED parameter contract when the array's element type has no literal form: Object elements (array_map's scalar dummy builder had no Object arm and fabricated Int) and Mixed/Never elements (unknown-element
array-hinted values) now use a synthetic element binding.Byte-parity vs PHP 8.5 + 4 regression tests. Known limit noted in the commit: array_map over OBJECT-element arrays now passes the checker but the EIR lowering doesn't support object elements yet (pre-existing wall).