Files
sx/examples/0212-generics-array-arg-slice-param.sx
agra 309f48e1b5 fix(0126): array args bind []$T generic params; uninferrable type params diagnose at the call
extractTypeParam's slice arm only extracted from slice-typed args, so
first(a) with a : [3]s64 at first :: (xs: []$T) -> T left T unbound
and the mono body reached LLVM emission carrying the .unresolved
sentinel (panic). The arm now also extracts from array args via the
array's element type — mirroring the array→slice promotion concrete
slice params already perform; the existing arg coercion handles the
rest.

lowerGenericCall additionally diagnoses any still-uninferrable TYPE
param at the call site instead of monomorphizing unbound — the
deliberate string-at-[]$T gap used to hit the same sentinel panic and
now errors with a source-located message. Comptime value params
($N: u32) and ..$Ts packs bind through their own dispatch and stay
exempt.

Regressions: examples/0212-generics-array-arg-slice-param.sx (scalar /
u8 / struct elements + the slice spelling) and
examples/1168-diagnostics-generic-param-uninferrable.sx (string arg
diagnostic) — both failed pre-fix.
2026-06-12 08:31:45 +03:00

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// An ARRAY argument at a generic slice param (`xs: []$T`) binds T from
// the array's element type — the same array→slice promotion concrete
// slice params perform — for scalar and struct elements, with the
// return-position `T` resolving to the element type. The slice
// spelling keeps working unchanged.
//
// Regression (issue 0126): the binding extractor only accepted slice
// args, so `first(a)` left T unbound and the monomorphized body
// reached LLVM emission with the `.unresolved` sentinel (panic).
#import "modules/std.sx";
P :: struct { x: s64; y: s64; }
first :: (xs: []$T) -> T {
return xs[0];
}
last :: (xs: []$T) -> T {
return xs[xs.len - 1];
}
main :: () -> s32 {
a : [3]s64 = ---;
a[0] = 7; a[1] = 8; a[2] = 9;
print("{}\n", first(a));
print("{}\n", last(a));
bs : [4]u8 = ---;
bs[0] = 5; bs[1] = 6; bs[2] = 7; bs[3] = 8;
print("{}\n", last(bs));
ps : [2]P = ---;
ps[0] = .{ x = 1, y = 2 };
ps[1] = .{ x = 3, y = 4 };
print("{}\n", first(ps).y);
s : []s64 = a;
print("{}\n", first(s));
return 0;
}