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).
21 lines
932 B
Plaintext
21 lines
932 B
Plaintext
// A closure literal whose body `raise`s but is annotated non-failable (or has
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// no `!` in its return) gets a LAMBDA-SPECIFIC diagnostic telling the user to
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// declare the failable return explicitly (ERR E5.1 sub-feature 1). This is the
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// closure analog of the top-level "raise is only valid inside a failable
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// function" error — failability is never inferred for a lambda, it must be
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// declared, so a raising lambda with no `!` is a hard error pointing at the fix.
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#import "modules/std.sx";
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E :: error { Neg }
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take :: (cb: Closure(i32) -> (i32, !E), x: i32) -> i32 { return cb(x) catch (e) -1; }
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main :: () -> i32 {
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// `-> i32` (non-failable) but the body raises → lambda-specific hint:
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// "lambda body raises; declare its return type explicitly with
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// `-> (T, !)` or `-> (T, !Named)`"
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print("{}\n", take(closure((x: i32) -> i32 { if x < 0 { raise error.Neg; } return x; }), -1));
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return 0;
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}
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