builtin: add .hex() methods to the rune and char types too (#25635)

Author: spytheman

vlib/builtin/hex_test.v

@@ -0,0 +1,30 @@
+fn test_hex_methods_on_u8() {
+	assert u8(1).hex() == '01'
+	assert u8(` `).hex() == '20'
+	assert u8(255).hex() == 'ff'
+}
+
+fn test_hex_methods_on_byte() {
+	assert byte(1).hex() == '01'
+	assert byte(` `).hex() == '20'
+	assert byte(255).hex() == 'ff'
+}
+
+fn test_hex_methods_on_char() {
+	assert char(1).hex() == '01'
+	assert char(` `).hex() == '20'
+	assert char(255).hex() == 'ff'
+}
+
+fn test_hex_method_on_runes() {
+	assert ` `.hex() == '20'
+	assert `喂`.hex() == '5582'
+	// latin:
+	assert `A`.hex() == '41'
+	assert `Z`.hex() == '5a'
+	// cyrillic:
+	assert `Д`.hex() == '414'
+	assert `Я`.hex() == '42f'
+	// emojies:
+	assert `💣`.hex() == '1f4a3'
+}

vlib/builtin/int.v

@@ -340,6 +340,22 @@ pub fn (nn u8) hex() string {
 	return u64_to_hex(nn, 2)
 }
 
+// hex returns a hexadecimal representation of `c` (as an 8 bit unsigned number).
+// The output is zero padded for values below 16.
+// Example: assert char(`A`).hex() == '41'
+// Example: assert char(`Z`).hex() == '5a'
+// Example: assert char(` `).hex() == '20'
+pub fn (c char) hex() string {
+	return u8(c).hex()
+}
+
+// hex returns a hexadecimal representation of the rune `r` (as a 32 bit unsigned number).
+// Example: assert `A`.hex() == '41'
+// Example: assert `💣`.hex() == '1f4a3'
+pub fn (r rune) hex() string {
+	return u32(r).hex()
+}
+
 // hex returns the value of the `i8` as a hexadecimal `string`.
 // Note that the output is zero padded for values below 16.
 // Example: assert i8(8).hex() == '08'