cgen: fix array sort error (#11046)

vlib/builtin/array_test.v

@@ -897,6 +897,24 @@ fn test_i64_sort() {
 	assert f[6] == 79
 }
 
+fn test_a_b_paras_sort() {
+	mut arr_i := [1, 3, 2]
+	arr_i.sort(a < b)
+	println(arr_i)
+	assert arr_i == [1, 2, 3]
+	arr_i.sort(b < a)
+	println(arr_i)
+	assert arr_i == [3, 2, 1]
+
+	mut arr_f := [1.1, 3.3, 2.2]
+	arr_f.sort(a < b)
+	println(arr_f)
+	assert arr_f == [1.1, 2.2, 3.3]
+	arr_f.sort(b < a)
+	println(arr_f)
+	assert arr_f == [3.3, 2.2, 1.1]
+}
+
 /*
 fn test_for_last() {
 	numbers := [1, 2, 3, 4]

vlib/v/gen/c/array.v

@@ -286,10 +286,16 @@ fn (mut g Gen) gen_array_sort(node ast.CallExpr) {
 				g.definitions.writeln('\tif (${styp}__lt(*b, *a)) { return -1; } else { return 1; }}')
 			} else {
 				field_type := g.typ(infix_expr.left_type)
+				left_name := '$infix_expr.left'
 				left_expr_str := g.expr_string(infix_expr.left)
 				right_expr_str := g.expr_string(infix_expr.right)
-				g.definitions.writeln('\t$field_type a_ = $left_expr_str;')
-				g.definitions.writeln('\t$field_type b_ = $right_expr_str;')
+				if left_name.starts_with('a') {
+					g.definitions.writeln('\t$field_type a_ = $left_expr_str;')
+					g.definitions.writeln('\t$field_type b_ = $right_expr_str;')
+				} else {
+					g.definitions.writeln('\t$field_type a_ = $right_expr_str;')
+					g.definitions.writeln('\t$field_type b_ = $left_expr_str;')
+				}
 				mut op1, mut op2 := '', ''
 				if infix_expr.left_type == ast.string_type {
 					if is_reverse {