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).
28 lines
1.2 KiB
Plaintext
28 lines
1.2 KiB
Plaintext
// A closure VALUE (a pre-bound variable) cannot be passed into a bare
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// function-pointer slot `(...) -> ...` (ERR E5.1). The bare ABI calls
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// `fn_ptr(ctx, args)` with no env channel, so a closure's environment can't be
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// carried — passing one is unsound (drops env / shifts args / segfaults on a
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// capturing closure). Only a closure LITERAL crosses this boundary (lowerLambda
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// emits a static adapter); a variable is rejected with a pointer to the idiom.
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//
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// The fix for these is either to pass the literal directly, or to type the
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// parameter `Closure(...)` so the environment is carried (the idiomatic form).
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#import "modules/std.sx";
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E :: error { Z }
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bare :: (cb: (i64) -> i64, n: i64) -> i64 { return cb(n); }
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baref :: (cb: (i64) -> (i64, !E), n: i64) -> i64 { return cb(n) catch (e) -1; }
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main :: () -> i32 {
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inc := closure((x: i64) -> i64 => x + 1); // capture-free closure var
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base := 100;
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add := closure((x: i64) -> i64 => x + base); // CAPTURING closure var
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_ := bare(inc, 9); // reject: closure value → bare slot
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_ := baref(inc, 9); // reject: also the ∅-widening crossing
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_ := bare(add, 9); // reject: capturing closure → bare slot
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return 0;
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}
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