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
1.1 KiB
Plaintext
37 lines
1.1 KiB
Plaintext
// `!` on an error binding is the truthiness complement of `if e` (issue
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// 0129). Pre-fix, `!` lowered as a bitwise not, so a nonzero error tag
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// stayed nonzero and `if !e` held even on a SET error — with the success
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// value read as garbage. Integer operands get the same `!x ≡ x == 0`
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// semantics.
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#import "modules/std.sx";
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E :: error { Boom }
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f :: (fail: bool) -> (i64, !E) {
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if fail { raise error.Boom; }
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return 42;
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}
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main :: () -> i32 {
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// set error: `if e` holds, `if !e` must NOT
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v, e := f(true);
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took_e := false;
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if e { took_e = true; }
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if !e { print("BUG: !e held on a set error (v={})\n", v); return 1; }
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if !took_e { print("BUG: if e did not hold on a set error\n"); return 2; }
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// success: `if !e` holds and the value is real
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v2, e2 := f(false);
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if e2 { print("BUG: e2 set on success\n"); return 3; }
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if !e2 { print("ok: !e2 on success, v2={}\n", v2); }
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// integers: `!n` is `n == 0`, not a bit flip
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n := 7;
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if !n { print("BUG: !7 held\n"); return 4; }
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z := 0;
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if !z { print("ok: !0 holds\n"); }
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print("done\n");
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return 0;
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}
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