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).
35 lines
1.7 KiB
Plaintext
35 lines
1.7 KiB
Plaintext
// Failable closure composition (ERR E5.1): a closure LITERAL passed as a
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// function-type argument and called inside the callee. Covers a bare failable
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// fn-type param (`cb: (T) -> (U, !)`), the idiomatic `Closure(...)` param
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// (try-propagated), and ∅-widening of a NON-failable closure literal into a
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// failable slot (the generated adapter wraps the value into `{value, 0}`).
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//
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// NOTE: the adapter is generated when the closure LITERAL flows directly into
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// the bare-fn slot. Passing a pre-bound closure *variable* into a bare-fn slot
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// is a separate coercion-site path, not yet handled — see CHECKPOINT-ERR.
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#import "modules/std.sx";
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E :: error { Neg }
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bare :: (cb: (i64) -> (i64, !E), n: i64) -> i64 { return cb(n) catch (e) -1; }
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chain :: (cb: Closure(i64) -> (i64, !E), n: i64) -> (i64, !E) { return try cb(n); }
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dbl :: (x: i64) -> (i64, !E) { if x < 0 { raise error.Neg; } return x * 2; }
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main :: () -> i32 {
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// failable closure literal through a bare fn-type param (matching ABI)
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print("bare ok={} err={}\n",
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bare(closure((x: i64) -> (i64, !E) { if x < 0 { raise error.Neg; } return x * 2; }), 5),
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bare(closure((x: i64) -> (i64, !E) => x * 2), -1)); // ok=10; err: arrow never raises → cb(-1) = -2
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// Closure(...) param, try-propagated, then caught at the call site
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print("chain ok={} err={}\n",
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chain(closure((x: i64) -> (i64, !E) => x + 6), 4) catch (e) 0, // 10
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chain(closure((x: i64) -> (i64, !E) { raise error.Neg; }), 1) catch (e) 0); // 0
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// NON-failable closure literal widened into the failable bare slot
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print("widen={}\n", bare(closure((x: i64) -> i64 => x + 1), 9)); // 10
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return 0;
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}
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