7a9db03bcc
declare now takes the type's NAME — `declare(name) -> Type` — because the
compiler needs it at compile time to register the forward type, which is
what makes self-reference resolve. EnumInfo drops `name` (it lives on
declare now); define completes the handle's body in place (the slot is
already named).
Self-reference mechanism (evalComptimeType): before lowering a comptime
type expression, preregisterForwardTypes scans it (and a called ctor fn's
body) for `declare("Name")` calls and registers each as an empty forward
nominal type AND binds it as a type alias. The alias is essential: a
`Name :: ctor()` decl makes `Name` a const_decl author, so a `*Name`
self-reference resolves through the forward-ALIAS path
(type_aliases_by_source), which a bare findByName registration doesn't
satisfy. With both in place `*Name` resolves to the forward slot at lower
time; the interp's declare returns that same slot; define fills it.
List :: make_list();
make_list :: () -> Type {
h := declare("List");
return define(h, .enum(.{ variants = .[
EnumVariant.{ name = "cons", payload = *List },
EnumVariant.{ name = "nil", payload = void } ] }));
}
Verified: cons/nil construct + match (direct and through the pointer),
multi-node list traversal via a recursive `count(*List)`. meta.sx
RecvResult/TryResult + examples 0614/0615/0617 updated to declare(name);
full suite green (673).
35 lines
1.2 KiB
Plaintext
35 lines
1.2 KiB
Plaintext
// Comptime type construction — identity: a type-fn that builds a type with
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// `define(declare("Box"), ...)` must memoize by the instantiation's mangled name, so
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// `Box(i64)` resolved at two INDEPENDENT sites (here: a return type and a
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// parameter type) is ONE `TypeId`. A value built at one site is therefore
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// assignable / matchable at the other — nominal identity. If the minted result
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// were not registered under the mangled instantiation name, the two sites would
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// mint distinct types and `consume(build())` would be a type error.
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#import "modules/std.sx";
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#import "modules/std/meta.sx";
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Box :: ($T: Type) -> Type {
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return define(declare("Box"), .enum(.{ variants = .[
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EnumVariant.{ name = "some", payload = T },
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EnumVariant.{ name = "none", payload = void },
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] }));
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}
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build :: () -> Box(i64) { // site A resolves Box(i64)
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return Box(i64).some(7);
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}
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consume :: (b: Box(i64)) { // site B resolves Box(i64) independently
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if b == {
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case .some: (n) { print("some {}\n", n); }
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case .none: { print("none\n"); }
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}
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}
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main :: () -> i32 {
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consume(build()); // typechecks ONLY if site A == site B
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b : Box(i64) = .none;
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consume(b);
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return 0;
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}
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