213cedf0b5
The trailing-`!`-after-the-value-type spelling (`-> T !`, `-> Tuple(A,B) !`) was a
redundant second way to write a failable return that the parser folded into the
same AST as the parenthesized `(T, !)` / `(A, B, !)` result list. Remove it so
there is ONE canonical spelling: the error channel always rides as the last slot
of the parenthesized list.
- parser: `parseFnReturnType` no longer folds a trailing `!` after a value type —
it rejects it with a located diagnostic ("a failable return is written `(T, !)`
… not `T !`"). This one chokepoint covers fn declarations, lambdas, fn-pointer
types `(A) -> R`, and closure types `Closure(A) -> R`. The error-ONLY `-> !` /
`-> !ErrSet` form is unaffected (parsed by parseTypeExpr as an error_type_expr).
- migrated every usage to canonical form across library/ + examples/ + issues/ +
tests/: `-> T !E` → `-> (T, !E)`; the value-carrying `-> Tuple(A, B) !` (which
FLATTENED to a multi-value failable) → `-> (A, B, !)`, preserving behavior. A
genuine single-tuple-value failable stays `-> (Tuple(A,B), !)`.
- parser unit tests: the "bare form folds" tests become "bare form is rejected";
canonical-form parse tests retained.
- docs: specs.md §12 + scattered refs and readme.md updated to the `(T, !)` form.
Behavior-preserving (the bare form was sugar for the same AST). Adversarial review
confirmed: rejection complete across all positions, every canonical form works on
both success/error paths, error-only `-> !` intact, no crashes. Full suite green
(unit tests + 850 corpus examples).
31 lines
1.0 KiB
Plaintext
31 lines
1.0 KiB
Plaintext
// Failable error-slot discard rejection (ERR step E1.8 — discard slice). The
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// error slot of a value-carrying failable cannot be dropped on a bare
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// destructure: it must be bound (`v, err := …`) and handled, or the failure
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// routed through `try` / `catch` / `or value` (all of which strip the error
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// channel, so they don't reach this check). Two rejected shapes here:
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// (1) omitting the error slot entirely (fewer names than slots), and
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// (2) binding it to `_`.
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// This file is expected to FAIL compilation (exit 1).
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//
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// Run: ./zig-out/bin/sx run examples/236-failable-discard-reject.sx
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#import "modules/std.sx";
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E :: error { Bad, Empty }
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pair :: (n: i32) -> (i32, i32, !E) {
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if n < 0 { raise error.Bad; }
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return .(n, n + 1);
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}
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parse :: (n: i32) -> (i32, !E) {
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if n < 0 { raise error.Bad; }
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return n * 2;
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}
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main :: () -> i32 {
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a, b := pair(5); // ERROR: error slot omitted (3 slots, 2 names)
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v, _ := parse(5); // ERROR: error slot discarded with `_`
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return a + b + v;
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}
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