goType errorMedium

UTF-8 multi-byte rune indexing error

Time: 0:00

BugFind the bug and fix the code

What it should do

Extract the first character of a string as a clean string representation. Example: extractFirstRune("世界") -> "世"

What happens instead

Indexing returns single byte 0xe4 instead of full unicode rune 世

package main

import "fmt"

func extractFirstRune(s string) string {
	if len(s) == 0 {
		return ""
	}
	// Indexing returns a uint8 raw byte
	return string(s[0])
}

func main() {
	fmt.Println(extractFirstRune("世界"))
}

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

⏱️0:00

Hints

🏆 0 hints = Flawless Solve

Think & Test Cooldown

2:00 remaining

Take a moment to read the bug symptom and trace the code with Run & Check before unlocking Hint 1.

Hint 2

Unlocks after Hint 1

Hint 3

Unlocks after Hint 2

This bug belongs to the type errors pattern

Totals that concatenate, sorts that put 10 before 9, comparisons that refuse to run.

Learn the type errors pattern Step through your own code

<iframe src="https://trybughunt.com/embed/8922572e-fbcd-4952-a193-165c66f9a017" title="Debugging challenge: UTF-8 multi-byte rune indexing error" width="100%" height="580" loading="lazy" style="border:1px solid #d4d4d8;border-radius:12px;max-width:760px"></iframe> <p style="font-size:14px">Debugging challenge from <a href="https://trybughunt.com/challenges/8922572e-fbcd-4952-a193-165c66f9a017">TryBugHunt</a></p>

package main import "fmt" func extractFirstRune(s string) string { if len(s) == 0 { return "" } // Indexing returns a uint8 raw byte return string(s[0]) } func main() { fmt.Println(extractFirstRune("世界")) }

UTF-8 multi-byte rune indexing error

What it should do

What happens instead

More type errors to practise

UTF-8 multi-byte rune indexing error

What it should do

What happens instead

More type errors to practise