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feat: lower result<T, E> whose E is not a string - #242
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WIT scopes a case name to its enum; gravity emitted every case as an
unqualified package constant. Two enums sharing a case name, or a case
sharing a type's name, then redeclared an identifier and the bindings
failed go vet:
enum_collisions.go:41:2: PeerSvid redeclared in this block
The identity lift had to spell its `via` cases `via-peer-svid`, ... to
dodge `credential-kind`'s `peer-svid`. Every case constant is now the
enum's Go name followed by the case's (ViaPeerSvid,
CredentialKindPeerSvid, ShapePoint beside the record Point), as Go
spells an enumerated constant (http.MethodGet). The enum's qualified
name is already unique (arcjet#197), so its constants are too.
BREAKING: every enum constant is renamed (Red becomes ColorRed). The
upstream examples' tests are updated, and the regressions WIT drops the
comment that called constant qualification out of scope. Qualifying
only colliding names, as arcjet#197 does for types, was rejected: a new enum
would then rename an existing enum's constants.
Tests: imports::tests::test_enum_case_constants_are_named_for_their_enum
(fails without the fix) and the new enum-collisions example
(TestSharedCaseNamesStayDistinct, TestCaseNamedLikeAType; without the
fix go vet fails with the error above).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Gravity lowered only result<T, string> and result<_, string>; any other
err type panicked at generation:
not yet implemented: TODO(arcjet#4): implement remaining result conversion
so the identity lift had to return a `decision { ok: option<resolved>,
refused: option<refusal> }` record instead of result<resolved, refusal>.
The Go shape stays (T, error) / error. The err case comes back as a
*ResultError[E], a generic error type emitted once per file when any
function needs it; errors.As recovers the E, and a trap, a host failure
or any other error is never one. On the host side a function returns
&ResultError[E]{Value: e} for the err case; an error that is not a
*ResultError[E] has no WIT representation and traps the guest, as a
panic in a host function does. Enums, records and variants (including a
record dispatched directly as a variant case) work as E, with or
without an ok type.
ResultError.Error formats its value with %v, so each enum's private
type gains a String that answers the WIT case name ("untyped-peer"), and
the error text reads as WIT wrote it.
Tests: exports::tests::test_export_result_with_enum_err,
imports::tests::test_import_result_with_record_err (both fail without
the fix with the panic above),
imports::tests::test_enum_string_answers_the_wit_case,
factory::tests::test_result_error_only_when_needed, and the new
result-errors example: TestEnumErr, TestRecordErr, TestVariantErr,
TestErrWithoutOk, TestHostReturnsTypedErrs, TestHostPlainErrorTraps
(without the fix the bindings do not generate).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This was referenced Oct 7, 2026
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Any err type other than string panicked:
The Go shape stays
(T, error). The err case comes back as*ResultError[E], a generic error type that is emitted only when needed, anderrors.Asrecovers the E. A trap or a host failure is never aResultError.A host function returns
&ResultError[E]{Value: e}for the err case. Any other error has no WIT representation, so it traps the guest, as a panic in a host function already does.Each enum also gains a
String()that returns the WIT case name, soResultError.Error()reads as WIT spelled it.Tests:
exports::tests::test_export_result_with_enum_errimports::tests::test_import_result_with_record_errimports::tests::test_enum_string_answers_the_wit_casefactory::tests::test_result_error_only_when_neededresult-errorsexample: enum, record and variant E, with and without ok, from guest and from host, plus the trap🤖 Generated with Claude Code
https://claude.ai/code/session_01K99bnsYaj3w4MMWSF5hTMu