builtin: fix map.clear() not resetting map's metas and keys blocks (fix

#22139)

vlib/builtin/map.v

@@ -317,6 +317,10 @@ pub fn (mut m map) clear() {
 	m.len = 0
 	m.even_index = 0
 	m.key_values.len = 0
+	m.key_values.deletes = 0
+	unsafe { free(m.key_values.all_deleted) }
+	unsafe { vmemset(m.key_values.keys, 0, m.key_values.key_bytes * m.key_values.cap) }
+	unsafe { vmemset(m.metas, 0, sizeof(u32) * (m.even_index + 2 + m.extra_metas)) }
 }
 
 @[inline]

vlib/builtin/map_issue_22139_clear_test.v

@@ -0,0 +1,59 @@
+fn test_map_clear_done_several_times() {
+	mut ints := map[int]int{}
+
+	ints[5] = 5
+	dump(ints.len)
+	assert ints.len == 1
+
+	ints.clear()
+	dump(ints.len)
+	assert ints.len == 0
+
+	ints[5] = 3
+	dump(ints.len)
+	assert ints.len == 1
+
+	ints.clear()
+	dump(ints.len)
+	assert ints.len == 0
+
+	ints[5] = 123
+	dump(ints.len)
+	assert ints.len == 1
+}
+
+fn test_map_clear_in_loop_metas_should_be_cleared_too() {
+	mut ints := map[int]int{}
+	for i in 0 .. 100 {
+		ints[i] = i * 123
+		ints.clear()
+		assert ints.len == 0
+		// dump(ints)
+		ints[i] = i
+		// dump(ints)
+		assert ints.len == 1
+		ints[1000 + i] = 1000 * i
+		assert ints.len == 2
+	}
+}
+
+fn test_map_clear_in_loop_delete_keys() {
+	mut ints := map[int]int{}
+	for i in 0 .. 100 {
+		ints[i] = i * 123
+		ints[i + 2] = i
+		ints.delete(i)
+		ints.delete(i + 1)
+		ints.delete(i + 2)
+		ints.delete(i + 3)
+		ints.delete(i + 4)
+		ints.clear()
+		assert ints.len == 0
+		// dump(ints)
+		ints[i] = 5
+		// dump(ints)
+		assert ints.len == 1
+		ints[1000 + i] = 1000 * i
+		assert ints.len == 2
+	}
+}