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).
37 lines
1.4 KiB
Plaintext
37 lines
1.4 KiB
Plaintext
// Value-carrying failable functions (ERR step E2.1a — the producer side of the
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// error-channel tuple ABI). A `-> (T, !E)` function returns EITHER a value OR
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// an error: `return v;` yields the success tuple `{v, 0}` (the compiler appends
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// the no-error slot), and `raise error.X` yields `{undef, tag}` (value slot
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// undefined, error slot = the tag). Today the result is consumed by
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// destructuring `v, err := f()` (which extracts both slots); the value-carrying
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// `try` / `catch` consumers land in E2.1b.
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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 * 10; // success → {n*10, 0}
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}
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main :: () -> i32 {
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r : i32 = 0;
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// The value slot is live only where the error is proven absent (ERR E1.8):
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// read `v1` under an `if !e1` guard, not after a bare tag-compare.
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v1, e1 := parse(5); // success → v1 = 50, e1 = no error
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if !e1 { r = r + v1; } // success → +50
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v2, e2 := parse(-1); // Bad
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if e2 == error.Bad { r = r + 7; } // true → +7
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if e2 == error.Empty { r = r + 200; } // false
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v3, e3 := parse(0); // Empty
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if e3 == error.Empty { r = r + 3; } // true → +3
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print("value-failable result: {}\n", r); // 50 + 7 + 3 = 60
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return r;
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}
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