296c809d85
A `v, err := failable()` destructure now binds the value slot(s) "live
only where `err` is proven absent". Reading `v` where the compiler cannot
prove `err == null` is a compile error.
New diagnostic-only Pass 1e (`checkErrorFlow` in ir/lower.zig): a
structured, path-sensitive walk over each main-file function body. A
proven-null set is threaded across branches and joined by intersection
at each `if`'s merge. Proof shapes recognized:
- `if !err { … v … }` (proven inside the guard)
- `if err { return/raise } … v` (proven on the fall-through)
- `if err { … } else { … v … }` (proven in the else branch)
- `!err and <reads v>` (short-circuit refinement)
Error-set tag compares (`if err == error.X`) prove nothing about
absence — they narrow the tag only. Nested lambdas are analyzed as their
own boundaries. Library modules are trusted (skipped).
Migrated the canon value-failable examples (1011/1012/1018/1044) to read
their value slots under `if !err` guards — output unchanged. New
regressions: 1046 (every proof shape compiles + runs, exit 210) and 1047
(unproven reads rejected, exit 1).
Gates: zig build, zig build test, run_examples.sh -> 338 passed, 0 failed.
36 lines
1.1 KiB
Plaintext
36 lines
1.1 KiB
Plaintext
// Rejection counterpart to 1046 (ERR step E1.8). Reading a failable's value slot
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// where its error is NOT proven absent is a compile error. Two unproven shapes:
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//
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// (A) reading the value inside the `if err { … }` error path itself
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// (B) reading the value after a bare tag-compare (`if err == error.X`), which
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// narrows the tag but proves nothing about absence
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//
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// Each read is rejected with the E1.8 diagnostic; the program never runs (exit 1).
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#import "modules/std.sx";
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E :: error { Bad }
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parse :: (n: s32) -> (s32, !E) {
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if n < 0 { raise error.Bad; }
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return n * 10;
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}
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// (A) the read sits on the error path — `err` is present here, not absent.
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bad_a :: () -> s32 {
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v, err := parse(5);
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if err { return v; } // REJECTED: err present on this path
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return 0;
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}
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// (B) a tag-compare narrows which error, but does not prove there is none.
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bad_b :: () -> s32 {
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v, err := parse(5);
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if err == error.Bad { return 1; }
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return v; // REJECTED: err not proven absent
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}
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main :: () -> s32 {
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return bad_a() + bad_b();
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}
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