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).
26 lines
913 B
Plaintext
26 lines
913 B
Plaintext
// Failable `or` value-terminator (ERR step E2.4a). `lhs or value` where `lhs`
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// is a value-carrying failable (`-> (T, !E)`): on success the result is the
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// LHS value; on failure the LHS error is discarded and the result is the
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// terminator value. The whole expression is non-failable (type T). The chain
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// form (`try a or try b`) needs fallback-target routing and lands in E2.4b.
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// Rejections: `examples/232-failable-or-reject.sx`.
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#import "modules/std.sx";
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E :: error { Bad, Empty }
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parse :: (n: i32) -> (i32, !E) {
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if n < 0 { raise error.Bad; }
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if n == 0 { raise error.Empty; }
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return n * 2;
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}
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main :: () -> i32 {
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a := parse(5) or 0; // success → 10
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b := parse(-1) or 99; // Bad → 99 (terminator)
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c := parse(0) or 7; // Empty → 7 (terminator)
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r := a + b + c; // 10 + 99 + 7 = 116
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print("or result: {}\n", r);
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return r;
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}
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