wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
String name = 'result';
String name = 'result';
Correct.
Dart
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
System.out.println('world')
System.out.println('world');
Add semicolon.
Java
.Order {{ color: green; }}
.Order {{ color: green; }}
Correct.
CSS
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
if ($b = 42)
if ($b == 42)
Use ==.
Perl
{{'id':'output'}}
{{"id":"output"}}
Use double quotes.
JSON
val num: Int = 'world'
val num: String = 'world'
Fix type.
Kotlin
Order.save();
Order.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
function handle() {{ echo 'value'; }}
function handle() {{ echo 'value'; }}
Correct.
PHP
Write-Host 'data'
Write-Host 'data'
Correct.
PowerShell
let data = 'test'
let data = "test"
Double quotes.
Swift
INSERT INTO orders VALUES ('hello',34)
INSERT INTO orders (id, email) VALUES ('hello',34);
Specify columns.
SQL
num == '8'
num === 8
Use strict equality.
JavaScript
let text = String::from("world"); let r=&text; text.push_str("!");
let mut text = String::from("world"); let r=&text; println!("{{}}", r); text.push_str("!");
Cannot mutate while borrowed.
Rust
with open('log.txt') as fp: data = fp.read()
with open('log.txt') as fp: data = fp.read()
Correct.
Python
println('test')
println("test")
Double quotes.
Scala
print 'result'
print('result')
print needs parentheses.
Python
for (count in list)
for (count of list)
for...in iterates keys.
JavaScript
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
if index > 15 print('message')
if index > 15: print('message')
Colon missing after if.
Python
if item = 93
if item == 93
Use ==.
Ruby
p {{ color: green }}
p {{ color: green; }}
Add semicolon.
CSS
data[26]
if (data.indices.contains(26)) data[26]
Check index.
Kotlin
{{"name":"world" "id":92}}
{{"name":"world", "id":92}}
Add comma.
JSON
6result = 10
result6 = 10
Variable cannot start with digit.
Python
random.sqrt(1)
import random random.sqrt(1)
Import module first.
Python
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
<div><p>hello</div></p>
<div><p>hello</p></div>
Nest properly.
HTML
<hr></hr>
<hr>
Self-closing.
HTML
{{'title':59, 'name' 44}}
{{'title':59, 'name':44}}
Colon missing.
Python
function render(): void {{ return 47; }}
function render(): number {{ return 47; }}
Return type mismatch.
TypeScript
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
if (count = 34)
if (count == 34)
Use ==.
Scala
<person age=55>
<person age="55">
Quote attribute.
XML
def render(): print('value')
def render(): print('value')
Indent function body.
Python
let temp: Int = 'data'
let temp: String = 'data'
Fix type.
Swift
object Item {{ def main(args: Array[String]) = println("data") }}
object Item {{ def main(args: Array[String]): Unit = println("data") }}
Add return type Unit.
Scala
if x = 56 {{}}
if x == 56 {{}}
Use ==.
Swift
for (int i=0; i<65; i++) {{}}
for (int i=0; i<65; i++) {{}}
Correct.
Java
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
if ($data = 87)
if ($data == 87)
Use ==.
Perl
if b = 66:
if b == 66:
Use == for comparison.
Python
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
val item = 'message'
val item = "message"
Double quotes.
Kotlin
const a = 47; a = 83;
let a = 47; a = 83;
Cannot reassign const.
JavaScript
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
$foo = 91; if ($foo = 91) {{}}
$foo = 91; if ($foo == 91) {{}}
Use ==.
PHP
if num > 67 print('output')
if num > 67: print('output')
Colon missing after if.
Python
let foo: number | null = null; foo.toFixed(82);
let foo: number | null = null; if(foo!==null) foo.toFixed(82);
Null check.
TypeScript
if num = 26
if num == 26
Use ==.
Ruby
class Person {{ int bar; }};
class Person {{ public: int bar; }};
Make public.
C++
val count: Int = 'result'
val count: String = 'result'
Fix type.
Kotlin
title: hello title: test,
title: hello title: test
Remove comma.
YAML
jwt.sign({{id:90}}, 'token');
jwt.sign({{id:90}}, 'token', {{expiresIn:'30m'}});
Add expiration.
Node.js
if (index = 44) {}
if (index == 44) {}
Use ==.
Dart
<table><tr><td>test<td>world</tr></table>
<table><tr><td>test</td><td>world</td></tr></table>
Close td.
HTML
const http = require('http'); http.createServer((req,res) => res.end('value')).listen(90);
const http = require('http'); http.createServer((req,res) => res.end('value')).listen(90);
Correct.
Node.js
list[44]
if list.indices.contains(44) {{ list[44] }}
Check index.
Swift
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
const temp;
const temp = 12;
Initialize const.
JavaScript
var x = 53;
var x = 53;
Correct.
Dart
<input type='text' value='data'>
<input type='text' value='data' name='id'>
Add name attribute.
HTML
for i=1,36 do print(i) end
for i=1,36 do print(i) end
Correct.
Lua
<?php // code ?>
<?php // code ?>
Correct.
PHP
if (a = 91) {{}}
if (a == 91) {{}}
Use ==.
Java
let a = 'test'
let a = "test"
Double quotes.
Swift
let mut data=52; let r1=&mut data; let r2=&mut data;
let mut data=52; {{ let r1=&mut data; }} let r2=&mut data;
Only one mutable borrow.
Rust
function handle() {{ echo 'data'; }}
function handle() {{ echo 'data'; }}
Correct.
PHP
function render() {{ return {{key:'test'}} }}
function render() {{ return {{key:'test'}}; }}
Return object on same line.
JavaScript
[36, 55, 84
[36, 55, 84]
Close bracket.
Ruby
<div><p>data</div></p>
<div><p>data</p></div>
Nest properly.
HTML
Post.save();
Post.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
10result = 10
result10 = 10
Variable cannot start with digit.
Python
SELECT age role FROM orders;
SELECT age, role FROM orders;
Add comma.
SQL
yield temp
yield temp
Correct yield.
Python
let text = String::from("result"); let r=&text; text.push_str("!");
let mut text = String::from("result"); let r=&text; println!("{{}}", r); text.push_str("!");
Cannot mutate while borrowed.
Rust
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
if (item = 80)
if (item == 80)
Use ==.
Scala
def process(x): return x + 1
def process(x): return x + 1
Correct.
Python
<center>world</center>
<div style='text-align:center;'>world</div>
Use CSS.
HTML
function baz(count) print(count) end
function baz(count) print(count) end
Correct.
Lua
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
fmt.Println 'world'
fmt.Println('world')
Missing parentheses.
Go
def foo(): print('data')
def foo(): print('data')
Indent function body.
Python
<a href='https://example.com' target='_blank'>
<a href='https://example.com' target='_blank' rel='noopener'>
Add rel for security.
HTML
function baz(): void {{ return 94; }}
function baz(): number {{ return 94; }}
Return type mismatch.
TypeScript
String a = 'message';
String a = "message";
Double quotes.
Java
void main() {{ print('data') }}
void main() {{ print('data'); }}
Add semicolon.
Dart
class = 'value'
class_name = 'value'
'class' is a keyword.
Python
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('hello')); app.listen(91);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('hello')); app.listen(91, () => console.log('listening'));
Add callback.
Node.js
print('world')
print('world')
Correct.
R
class Child Model:
class Child(Model):
Inheritance uses parentheses.
Python
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
WHERE status = '5'
WHERE status = 5
Don't quote integer.
SQL
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
fn foo() -> i32 {{ 34 }}
fn foo() -> i32 {{ 34 }}
Correct.
Rust
$values[23] = 5;
if (isset($values[23])) $values[23] = 5;
Check existence.
PHP
while a > 65 a -= 1
while a > 65: a -= 1
Colon missing after while.
Python