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).
47 lines
1.7 KiB
Plaintext
47 lines
1.7 KiB
Plaintext
// Generic value-carrying failable functions (`($T) -> (T, !E)`) whose body ends in
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// a trailing success EXPRESSION (no explicit `return`) must set the success
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// error slot to 0 — the caller's `catch` must NOT fire and the value must be
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// intact across instantiations (i64 / string / struct), and `or` must yield the
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// real value not the fallback.
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// Regression (issue 0190): `lowerGenericInstance` hand-rolled a body-return
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// (coerceToType+ret) that missed the value-failable success routing, leaving
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// the error-tag slot uninitialized → phantom catch on success / value
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// corruption for generic instantiations.
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#import "modules/std.sx";
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E :: error { Bad }
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Point :: struct { x: i64; y: i64; }
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// Generic trailing-expression success — instantiated at i64 / string / struct.
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gen :: ($T: Type, v: T) -> (T, !E) { v }
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// Generic that RAISES — the caller's catch must still fire.
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gfail :: ($T: Type, v: T, bad: bool) -> (T, !E) {
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if bad { raise error.Bad; }
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v
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}
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main :: () -> i32 {
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a := gen(i64, 42) catch (e) { print("PHANTOM i64\n"); return 1; };
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print("i64: {}\n", a);
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s := gen(string, "hello") catch (e) { print("PHANTOM string\n"); return 1; };
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print("string: {}\n", s);
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p := gen(Point, Point.{ x = 3, y = 4 }) catch (e) { print("PHANTOM struct\n"); return 1; };
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print("struct: ({},{})\n", p.x, p.y);
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// `or`-form on success must yield the real value, not the fallback.
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o := gen(i64, 7) or 999;
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print("or: {}\n", o);
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// A generic that raises still propagates to the caller's catch.
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gfail(i64, 0, true) catch (e) {
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print("raise caught\n");
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return 0;
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};
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print("UNEXPECTED no error\n");
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return 1;
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}
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