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).
30 lines
1.4 KiB
Plaintext
30 lines
1.4 KiB
Plaintext
// Generic function with a value-carrying `!` return composes (ERR E5.1
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// sub-feature 8). A `$T: Type` generic whose return is `(T, !E)` monomorphizes
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// per call: `return try f()` propagates the closure's error, and each
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// monomorphization's success value flows through as the concrete `T`.
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// (Regression: confirms issue 0062 was an invalid-syntax repro — the bug only
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// appeared with the non-generic `T: Type` form; the `$T` form works.)
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#import "modules/std.sx";
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E :: error { Bad }
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wrap :: ($T: Type, f: Closure() -> (T, !E)) -> (T, !E) { return try f(); }
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main :: () -> i32 {
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// success, consumed by catch
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print("catch={}\n", wrap(i32, closure(() -> (i32, !E) { return 7; })) catch (e) -1); // 7
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// success, consumed by destructure (binds value + error slot); the value
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// slot is read only under an `if !err` guard (ERR E1.8 path-sensitivity)
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r, err := wrap(i32, closure(() -> (i32, !E) { return 9; }));
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if !err { print("destr={} ok=true\n", r); } // destr=9 ok=true
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// failure path: the raised tag propagates through the generic `try`
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print("fail={}\n", wrap(i32, closure(() -> (i32, !E) { raise error.Bad; }) ) catch (e) -1); // -1
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// a second monomorphization at a different T
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print("u8={}\n", wrap(u8, closure(() -> (u8, !E) { return 200; })) catch (e) 0); // 200
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return 0;
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}
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