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sx/examples/issue-0012.sx
2026-03-05 16:20:36 +02:00

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// issue-0012: Pattern match expression with mixed null/concrete arms
//
// A match expression with both `null` arms and concrete struct value arms
// should produce an optional type (?T) and correctly wrap non-null values.
#import "modules/std.sx";
HAlignment :: enum { leading; center; trailing; }
VAlignment :: enum { top; center; bottom; }
Alignment :: struct { h: HAlignment; v: VAlignment; }
ALIGN_CENTER :: Alignment.{ h = .center, v = .center };
ALIGN_TOP :: Alignment.{ h = .center, v = .top };
ALIGN_BOTTOM :: Alignment.{ h = .center, v = .bottom };
ALIGN_LEADING :: Alignment.{ h = .leading, v = .center };
ALIGN_TRAILING :: Alignment.{ h = .trailing, v = .center };
ALIGN_TOP_LEADING :: Alignment.{ h = .leading, v = .top };
ALIGN_TOP_TRAILING :: Alignment.{ h = .trailing, v = .top };
ALIGN_BOTTOM_LEADING :: Alignment.{ h = .leading, v = .bottom };
ALIGN_BOTTOM_TRAILING :: Alignment.{ h = .trailing, v = .bottom };
Zone :: enum {
floating;
fill;
center;
top;
bottom;
left;
right;
top_left;
top_right;
bottom_left;
bottom_right;
}
// Match expression as implicit return with mixed null/concrete arms
zone_to_alignment :: (zone: Zone) -> ?Alignment {
if zone == {
case .floating: null;
case .fill: ALIGN_CENTER;
case .center: ALIGN_CENTER;
case .top: ALIGN_TOP;
case .bottom: ALIGN_BOTTOM;
case .left: ALIGN_LEADING;
case .right: ALIGN_TRAILING;
case .top_left: ALIGN_TOP_LEADING;
case .top_right: ALIGN_TOP_TRAILING;
case .bottom_left: ALIGN_BOTTOM_LEADING;
case .bottom_right: ALIGN_BOTTOM_TRAILING;
}
}
// Side-effect match inside a function returning bool — must NOT be
// affected by optional inference (no null arms here)
NodeType :: enum { rect; text; image; }
process_node :: (t: NodeType) -> bool {
if t == {
case .rect: { out("rect\n"); }
case .text: { out("text\n"); }
case .image: { out("image\n"); }
}
true;
}
main :: () -> void {
// Test null arm
r0 := zone_to_alignment(.floating);
if a := r0 { print("BUG: floating should be null, got h={}\n", xx a.h); }
else { out("ok: floating is null\n"); }
// Test concrete arms
r1 := zone_to_alignment(.left);
if a := r1 { print("ok: left h={}\n", xx a.h); }
else { out("BUG: left returned null\n"); }
r2 := zone_to_alignment(.center);
if a := r2 { print("ok: center h={}\n", xx a.h); }
else { out("BUG: center returned null\n"); }
r3 := zone_to_alignment(.top_right);
if a := r3 { print("ok: top_right h={} v={}\n", xx a.h, xx a.v); }
else { out("BUG: top_right returned null\n"); }
// Test side-effect match (no null arms) still works
process_node(.rect);
process_node(.text);
}