ab572359ae
packVariadicCallArgs stored the raw concrete arg into a [N x P] array when the
element type was a protocol, so an 8-byte struct landed in a 16-byte {ctx,
vtable} slot -> garbage vtable -> Bus error on dispatch. Now, when the slice
element type is a protocol, each arg is xx-erased to the protocol value via
buildProtocolErasure (same impl-driven machinery as the xx cast). This makes
..xs: []P the runtime, protocol-erased counterpart to the comptime
heterogeneous pack ..xs: P (which stays comptime-only): xs[runtime_i].method()
now works in an ordinary loop.
specs.md: full variadic/pack form-comparison table (concrete-vs-erased,
comptime-vs-runtime). Regression: examples/202. Issue 0052 (FIXED). 237 green.
32 lines
1.1 KiB
Plaintext
32 lines
1.1 KiB
Plaintext
// Slice-of-protocol variadic `..xs: []P` — the RUNTIME counterpart to the
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// comptime pack `..xs: P`. Each trailing arg is `xx`-erased to a `P` protocol
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// value {ctx, vtable} and packed into a runtime `[]P`, so the elements can be
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// indexed by a RUNTIME index and dispatched through the protocol interface
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// (unlike a pack, which is comptime-only — see examples/163).
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//
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// This is the type-safe way to iterate a heterogeneous arg list at runtime:
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// concrete per-position types are erased to the constraint protocol.
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#import "modules/std.sx";
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Show :: protocol { show :: () -> string; }
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A :: struct { x: s64; }
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B :: struct { s: string; }
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impl Show for A { show :: (self: *A) -> string => "A"; }
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impl Show for B { show :: (self: *B) -> string => "B"; }
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// Runtime loop over a []Show: runtime index + protocol-method dispatch.
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each :: (..xs: []Show) -> void {
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i := 0;
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while i < xs.len {
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print("[{}]={}\n", i, xs[i].show());
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i = i + 1;
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}
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}
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main :: () -> s32 {
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each(A.{ x = 1 }, B.{ s = "hi" }, A.{ x = 3 }); // heterogeneous, erased to Show
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each(); // empty is fine (len 0)
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0;
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}
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