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).
25 lines
1.2 KiB
Plaintext
25 lines
1.2 KiB
Plaintext
// Failable closure literals (ERR E5.1): a `closure(...)` literal may declare a
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// failable return type — `-> (T, !)` / `-> !Named` — in both block and arrow
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// body forms, and `raise` inside. Called directly through the bound local, the
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// error channel is consumed by `catch` / `or`; passed as a `Closure(...)`
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// parameter, it composes through the callee (here absorbed with `catch`).
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// (A capturing closure into a bare `(T)->U` slot, and a failable closure into a
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// non-failable slot, are rejected — see issue 0060 / the FFI-boundary rule.)
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#import "modules/std.sx";
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E :: error { Neg }
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runwith :: (cb: Closure(i64) -> (i64, !E), n: i64) -> i64 { return cb(n) catch (e) -1; }
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main :: () -> i32 {
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// block-body and arrow-body failable closures, called directly
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m := closure((x: i64) -> (i64, !E) { if x < 0 { raise error.Neg; } return x * 2; });
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n := closure((x: i64) -> (i64, !E) => x + 1);
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print("{} {} {} {}\n", m(5) catch (e) 0, m(-1) catch (e) 99, m(-1) or 7, n(40) catch (e) 0); // 10 99 7 41
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// failable closure passed as a Closure(...) parameter
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print("param ok={} err={}\n", runwith(m, 5), runwith(m, -1)); // 10 -1
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return 0;
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}
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