19bc644b11
A protocol-constrained pack element exposes only the constraint protocol's interface (the locked decision): `xs[i].<member>` is rejected unless `<member>` is one of the protocol's methods. `xs[i].v` (a concrete field of IntCell, not declared on Box) now errors, like a constrained generic — even though the substituted element is concretely an IntCell. monomorphizePackFn records the pack param's constraint protocol in a new `pack_constraint` map (pack-name → protocol); lowerFieldAccess checks it on an `xs[i]` (index_expr) base BEFORE substitution erases the "constrained to P" context. Protocol method calls (`xs[i].get()`) pass — the name is in the protocol. Regression: examples/195-pack-interface-only.sx.
23 lines
708 B
Plaintext
23 lines
708 B
Plaintext
// Feature 1 — a pack element exposes ONLY the constraint protocol's interface.
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// `xs[i].v` reaches a concrete field of IntCell that is not part of `Box`, so
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// it's rejected even though IntCell does have `v` — a pack element is viewed
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// through the protocol, like a constrained generic. (Protocol methods like
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// `get()` ARE callable; see examples 193/194.)
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#import "modules/std.sx";
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Box :: protocol(T: Type) {
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get :: () -> T;
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}
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IntCell :: struct { v: s64; }
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impl Box(s64) for IntCell { get :: (self: *IntCell) -> s64 => self.v; }
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leak :: (..xs: Box) -> s64 {
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return xs[0].v; // `v` is not part of Box — error
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}
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main :: () -> s32 {
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print("{}\n", leak(IntCell.{ v = 5 }));
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0;
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}
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