3c738695dc
Erasing a type to a protocol when it conforms only via a free function (not an explicit impl P for T) built a vtable of unreachable thunks -> SIGABRT on first dispatch, with no diagnostic. Per specs.md erasure is impl-driven, not structural, so the erasure was never valid. Add a conformance gate (firstUnimplementedMethod in buildProtocolValue, src/ir/lower/protocol.zig): emit a located diagnostic when a protocol method has no reachable impl, or when an impl method introduces its own type params (signature mismatch — it bails lazyLowerFunction and would reach the unreachable thunk). A std.debug.panic tripwire guards the diagnostics==null path so a non-conforming erasure can never silently ship as undef. Gate<->thunk equivalence verified bidirectional. Regressions: protocols/0419 (positive struct-field dispatch), diagnostics/1197 (no-impl) + 1198 (generic-method signature mismatch). Updated memory/0808 (it erased a non-conforming type that never dispatched). Verified by 3+1 adversarial reviews, suite 788/0. Filed adjacent bug 0178 (protocol impl method type-mismatch silent miscompile).
21 lines
914 B
Plaintext
21 lines
914 B
Plaintext
// Erasing a concrete type to a protocol it does NOT `impl`-ement is a hard
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// error, not a silent SIGABRT. Regression (issue 0176): a plain free function
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// `speak :: (self: *Dog)` with a matching receiver does NOT satisfy the
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// protocol — protocol erasure is impl-driven, not structural (specs.md
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// §"Storage and protocol conformance"). Before the fix, erasure built a vtable
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// of unreachable thunks and `h.s.speak()` aborted with exit 133 and no output;
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// now it reports a clear diagnostic at the erasure site and exits 1.
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#import "modules/std.sx";
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Speaker :: protocol { speak :: (self: *Self) -> i64; }
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Dog :: struct { n: i64 = 0; }
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speak :: (self: *Dog) -> i64 { return self.n; } // free fn — NOT an impl
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Holder :: struct { s: Speaker; b: i64 = 0; }
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main :: () {
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d := Dog.{ n = 42 };
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h : Holder = .{ s = d, b = 5 }; // <- 'Dog' does not implement 'Speaker'
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print("{}\n", h.s.speak());
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}
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