a049e2940c
The consumer side of the error-channel tuple ABI. A value-carrying `-> (T, !E)`
failable can now be consumed by `try` and `catch` (not just destructured).
Single-value; multi-value `-> (T1, T2, !)` consumers bail (E2).
- lowerTry: a value-carrying callee returns `{v, err}`. Extract `err`
(tuple_get field 1), branch; on success the try value is `tuple_get(field 0)`,
on error propagate via emitErrorReturn (pure caller → `ret(tag)`;
value-carrying caller → `ret {undef..., tag}`). Widening now runs for
value-carrying callees too. Retires the two value-carrying bails.
- lowerCatch: a value-carrying LHS merges through a block-param phi — the
success edge feeds `tuple_get(field 0)`, the handler edge feeds the body's
value (coerced to the success type). runCatchBody factors the bound-tag body
lowering (force_block_value for the value case). Pure-failable catch
unchanged.
- A non-diverging value-carrying catch body that yields no value is now a
clean diagnostic ("`catch` body must produce a value … or diverge") instead
of coercing `void` into a bad ref / failing LLVM verification — caught by an
adversarial review of the lowering.
Tests: examples/229-value-failable-consume.sx (try in value-carrying + pure
callers, catch block/bare/match-body/diverging bodies; exit 32),
examples/230-value-failable-reject.sx (void catch body rejected; exit 1).
Gates: zig build, zig build test, 268/268 examples.
62 lines
2.1 KiB
Plaintext
62 lines
2.1 KiB
Plaintext
// Consuming value-carrying failables with `try` and `catch` (ERR step E2.1b —
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// the consumer side of the error-channel tuple ABI). `try f()` on a
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// `-> (T, !E)` callee binds the value slot on success and propagates the error
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// on failure (a pure-failable caller returns the tag; a value-carrying caller
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// returns `{undef, tag}`). `f() catch e BODY` yields the value slot on success
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// or the handler body's value on failure, merged through a block parameter.
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// The producer side is `examples/228-value-failable.sx`.
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#import "modules/std.sx";
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E :: error { Bad, Empty }
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parse :: (n: s32) -> (s32, !E) {
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if n < 0 { raise error.Bad; }
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if n == 0 { raise error.Empty; }
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return n * 2;
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}
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// value-carrying `try` in a value-carrying caller — propagates {undef, tag}.
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inc :: (n: s32) -> (s32, !E) {
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v := try parse(n);
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return v + 1;
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}
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// value-carrying `try` in a pure-failable caller — propagates the tag.
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relay :: (n: s32) -> !E {
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v := try parse(n);
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if v < 0 { raise error.Bad; }
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return;
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}
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// value-carrying `catch`, bare-expression fallback.
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safe :: (n: s32) -> s32 {
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return parse(n) catch e 0;
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}
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// value-carrying `catch`, match-body value.
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classify :: (n: s32) -> s32 {
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return parse(n) catch e == {
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case .Bad: 1;
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case .Empty: 2;
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else: 3;
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};
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}
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main :: () -> s32 {
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r : s32 = 0;
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a, ea := inc(5); // parse(5)=10 → v=10 → 11
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if ea == error.Bad { r = r + 100; } // false
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r = r + a; // +11
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b, eb := inc(-1); // parse(-1)=Bad → propagate {undef, Bad}
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if eb == error.Bad { r = r + 4; } // true → +4
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er := relay(3); // parse(3)=6 ok → relay ok
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if er == error.Bad { r = r + 50; } // false
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r = r + safe(7); // parse(7)=14 → +14
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r = r + safe(-1); // Bad → catch → 0
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r = r + classify(-1); // Bad → 1
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r = r + classify(0); // Empty → 2
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print("consume result: {}\n", r); // 11+4+14+0+1+2 = 32
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return r;
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}
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