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fix(rt): handle zero-sized function types in decode and ZST recognition #813

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Merged
automergerpr-permission-manager merged 4 commits into from
Mar 28, 2026
Merged

fix(rt): handle zero-sized function types in decode and ZST recognition #813

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554ee33
test(rt): expose closure zero-sized decode thunk via terminate-on-thunk
Stevengre Mar 23, 2026
ea760c0
fix(rt): decode zero-sized function types and recognize them as ZSTs
Stevengre Mar 23, 2026
3aa012d
chore(test): remove closure-staged expected output
Stevengre Mar 26, 2026
07b03c2
Merge branch 'master' into jh/zero-sized-decode
dkcumming Mar 27, 2026
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3 changes: 3 additions & 0 deletions kmir/src/kmir/kdist/mir-semantics/rt/data.md
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Expand Up @@ -1921,6 +1921,9 @@ Zero-sized types can be decoded trivially into their respective representation.
// zero-sized array
rule <k> #decodeConstant(constantKindZeroSized, _TY, typeInfoArrayType(_, _))
=> Range(.List) ... </k>
// zero-sized function item (e.g., closures without captures)
rule <k> #decodeConstant(constantKindZeroSized, _TY, typeInfoFunType(_))
=> Aggregate(variantIdx(0), .List) ... </k>
```

Allocated constants of reference type with a single provenance map entry are decoded as references
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5 changes: 3 additions & 2 deletions kmir/src/kmir/kdist/mir-semantics/rt/types.md
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Expand Up @@ -320,8 +320,9 @@ Slices, `str`s and dynamic types require it, and any `Ty` that `is_sized` does
rule #zeroSizedType(typeInfoTupleType(.Tys, _)) => true
rule #zeroSizedType(typeInfoStructType(_, _, .Tys, _)) => true
rule #zeroSizedType(typeInfoVoidType) => true
// FIXME: Only unit tuples, empty structs, and void are recognized here; other
// zero-sized types (e.g. single-variant enums, function or closure items,
rule #zeroSizedType(typeInfoFunType(_)) => true
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@chatgpt-codex-connector chatgpt-codex-connector Bot Mar 26, 2026

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P1 Badge Exclude invalid lookup sentinel from ZST function rule

#zeroSizedType(typeInfoFunType(_)) => true now also matches the sentinel returned by lookupTy on missing entries (typeInfoFunType(" ** INVALID LOOKUP CALL **") in rt/value.md), so unresolved type IDs are silently treated as zero-sized. That changes behavior in places that gate on #zeroSizedType (notably pointer projection compatibility in #pointeeProjection and zero-sized local materialization in rvalueRef), allowing execution to proceed with fabricated ZST behavior instead of surfacing a missing-type-table condition; this can corrupt proof behavior when type extraction is incomplete.

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// FIXME: Only unit tuples, empty structs, void, and function items are
// recognized here; other zero-sized types (e.g. single-variant enums,
// newtype wrappers around ZSTs) still fall through because we do not consult
// the layout metadata yet. Update once we rely on machineSize(0).
rule #zeroSizedType(_) => false [owise]
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6 changes: 5 additions & 1 deletion kmir/src/tests/integration/test_integration.py
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Expand Up @@ -41,6 +41,9 @@
'iter-eq-copied-take-dereftruncate': ['repro'],
'spl-multisig-iter-eq-copied-next': ['repro'],
}
PROVE_TERMINATE_ON_THUNK = [
'closure-staged',
]
PROVE_SHOW_SPECS = [
'local-raw-fail',
'interior-mut-fail',
Expand Down Expand Up @@ -84,7 +87,8 @@ def test_prove(rs_file: Path, kmir: KMIR, update_expected_output: bool) -> None:
if update_expected_output and not should_show:
pytest.skip()

prove_opts = ProveOpts(rs_file, smir=is_smir)
should_terminate_on_thunk = rs_file.stem in PROVE_TERMINATE_ON_THUNK
prove_opts = ProveOpts(rs_file, smir=is_smir, terminate_on_thunk=should_terminate_on_thunk)
printer = PrettyPrinter(kmir.definition)
cterm_show = CTermShow(printer.print)

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