ast: fix the registration of fixed arrays, when size_expr is a const (fix #23946) (#23949)

Author: felipensp

vlib/v/ast/table.v

@@ -991,7 +991,7 @@ pub fn (t &Table) array_fixed_name(elem_type Type, size int, size_expr Expr) str
 	ptr := if elem_type.is_ptr() { '&'.repeat(elem_type.nr_muls()) } else { '' }
 	opt := if elem_type.has_flag(.option) { '?' } else { '' }
 	res := if elem_type.has_flag(.result) { '!' } else { '' }
-	size_str := if size_expr is EmptyExpr || size != 987654321 {
+	size_str := if size_expr is EmptyExpr || size !in [0, 987654321] {
 		size.str()
 	} else {
 		size_expr.str()

vlib/v/tests/consts/const_fixed_array_test.v

@@ -0,0 +1,33 @@
+module main
+
+const c_u16_size = sizeof(u16)
+const c_u32_size = sizeof(u32)
+
+pub enum DataKind as u8 {
+	u8_array
+}
+
+union U16Bytes {
+	value u16
+	bytes [c_u16_size]u8
+}
+
+union U32Bytes {
+	value u32
+	bytes [c_u32_size]u8
+}
+
+fn test_main() {
+	kind := DataKind.u8_array
+	match kind {
+		.u8_array {
+			buf_4u8 := [c_u32_size]u8{}
+			w := U32Bytes{
+				bytes: buf_4u8
+			}
+			unsafe {
+				assert w.bytes.len == c_u32_size
+			}
+		}
+	}
+}