From c7af2c21d122289b3235e4ac32bdada54c8c260c Mon Sep 17 00:00:00 2001
From: Swastik Baranwal <swstkbaranwal@gmail.com>
Date: Fri, 26 Apr 2024 18:50:21 +0530
Subject: [PATCH]  builtin.string: fix `is_upper` and `is_lower` with numbers
 (#21357)

---
 vlib/builtin/string.v      | 6 ++++++
 vlib/builtin/string_test.v | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git a/vlib/builtin/string.v b/vlib/builtin/string.v
index 5ea321c6752d89..0494be2a62a546 100644
--- a/vlib/builtin/string.v
+++ b/vlib/builtin/string.v
@@ -1524,6 +1524,9 @@ pub fn (s string) to_lower() string {
 // Example: assert 'hello developer'.is_lower() == true
 @[direct_array_access]
 pub fn (s string) is_lower() bool {
+	if s[0].is_digit() {
+		return false
+	}
 	for i in 0 .. s.len {
 		if s[i] >= `A` && s[i] <= `Z` {
 			return false
@@ -1555,6 +1558,9 @@ pub fn (s string) to_upper() string {
 // Example: assert 'HELLO V'.is_upper() == true
 @[direct_array_access]
 pub fn (s string) is_upper() bool {
+	if s[0].is_digit() {
+		return false
+	}
 	for i in 0 .. s.len {
 		if s[i] >= `a` && s[i] <= `z` {
 			return false
diff --git a/vlib/builtin/string_test.v b/vlib/builtin/string_test.v
index 82a0ce8ff99e9d..c0427e4c6f2ce6 100644
--- a/vlib/builtin/string_test.v
+++ b/vlib/builtin/string_test.v
@@ -1013,6 +1013,9 @@ fn test_lower() {
 	assert s.to_lower() == 'hi'
 	assert 'aloha!'[0] == `a`
 	assert 'aloha!'[5] == `!`
+	s = '123'
+	assert !s.is_lower()
+	assert s.to_lower() == '123'
 }
 
 fn test_upper() {
@@ -1033,6 +1036,9 @@ fn test_upper() {
 	s = 'HI'
 	assert s.is_upper()
 	assert s.to_upper() == 'HI'
+	s = '123'
+	assert !s.is_upper()
+	assert s.to_upper() == '123'
 }
 
 fn test_capitalize() {