wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
<ul><li>world<li>world</ul>
<ul><li>world</li><li>world</li></ul>
Close li.
HTML
DELETE FROM users WHERE email=44
DELETE FROM users WHERE email=44;
Add semicolon.
SQL
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
<p>value <b>test</p></b>
<p>value <b>test</b></p>
Nest properly.
HTML
<a href='https://test.org' target='_blank'>
<a href='https://test.org' target='_blank' rel='noopener'>
Add rel for security.
HTML
int* p = nullptr; *p=5;
int* p = new int; *p=5;
Allocate memory.
C++
def compute puts 'data' end
def compute puts 'data' end
Correct.
Ruby
compute
compute()
Add parentheses.
Kotlin
echo 'test'
echo 'test';
Add semicolon.
PHP
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
id: result value: test,
id: result value: test
Remove comma.
YAML
class Person def method end end
class Person def method end end
Correct.
Ruby
if (count = 93) {{}}
if (count == 93) {{}}
Use ==.
Java
let count = 98; let count = 44;
let count = 98; count = 44;
Duplicate declaration.
JavaScript
const person:Person = {{name:'test'}};
const person:Person = {{name:'test', age:24}};
Add missing property.
TypeScript
let a: i32 = "message";
let a: &str = "message";
Type mismatch.
Rust
cin >> num cout << num;
cin >> num; cout << num;
Add semicolon.
C++
String c = 'hello';
String c = "hello";
Double quotes.
Java
.Item {{ color: blue; }}
.Item {{ color: blue; }}
Correct.
CSS
arr[67]
if arr.indices.contains(67) {{ arr[67] }}
Check index.
Swift
assert index > 41
assert index > 41
Correct.
Python
int* user = nullptr; *user=5;
int* user = new int; *user=5;
Allocate memory.
C++
if ($foo = 20) {{}}
if ($foo -eq 20) {{}}
Use -eq.
PowerShell
SELECT id email FROM orders;
SELECT id, email FROM orders;
Add comma.
SQL
DELETE FROM products WHERE status=44
DELETE FROM products WHERE status=44;
Add semicolon.
SQL
let y = 59; y += 1;
let mut y = 59; y += 1;
Need mut to modify.
Rust
if (foo = 97) {{}}
if (foo === 97) {{}}
Use === for equality.
JavaScript
<br></br>
<br>
Self-closing.
HTML
local foo = 95
local foo = 95
Correct.
Lua
if temp = 97 {{}}
if temp == 97 {{}}
Use ==.
Swift
const obj:Person = {{name:'message'}};
const obj:Person = {{name:'message', age:94}};
Add missing property.
TypeScript
with open('input.csv') as fp: data = fp.read()
with open('input.csv') as fp: data = fp.read()
Correct.
Python
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
void main() {{ print('test') }}
void main() {{ print('test'); }}
Add semicolon.
Dart
x > 75 & y < 38
x > 75 and y < 38
Use 'and' not '&'.
Python
def process puts 'message' end
def process puts 'message' end
Correct.
Ruby
function baz() {{ echo 'value'; }}
function baz() {{ echo 'value'; }}
Correct.
PHP
fmt.Println 'test'
fmt.Println('test')
Missing parentheses.
Go
class Item {{ int a; }} obj.a=5;
class Item {{ public int a; }} obj.a=5;
Make field public.
Java
Product.save();
Product.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
if ($item = 70)
if ($item == 70)
Use ==.
Perl
var x int
var x int
Correct.
Go
for i=1,78 do print(i) end
for i=1,78 do print(i) end
Correct.
Lua
<ul><li>world<li>world</ul>
<ul><li>world</li><li>world</li></ul>
Close li.
HTML
fn foo() -> i32 {{ 40 }}
fn foo() -> i32 {{ 40 }}
Correct.
Rust
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
if index = 99
if index == 99
Use ==.
Go
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
print('result')
print('result')
Correct.
R
let b = 49;
let b = 49;
Correct.
JavaScript
<p>value <b>data</p></b>
<p>value <b>data</b></p>
Nest properly.
HTML
if index = 83 then print('hello') end
if index == 83 then print('hello') end
Use ==.
Lua
Write-Host 'test'
Write-Host 'test'
Correct.
PowerShell
if b > 12 puts 'output'
if b > 12 puts 'output' end
Add 'end'.
Ruby
val data = 15; data = 14
var data = 15; data = 14
Use var for reassignment.
Scala
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
{ "name": "result" }
{ "name": "result" }
Correct.
JSON
x := 51
x := 51
Correct.
Go
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
if c = 32:
if c == 32:
Use == for comparison.
Python
print 'hello'
print('hello')
Parentheses for function call.
Lua
<input type='text' value='info'>
<input type='text' value='info' name='status'>
Add name attribute.
HTML
object Product {{ def main(args: Array[String]) = println("world") }}
object Product {{ def main(args: Array[String]): Unit = println("world") }}
Add return type Unit.
Scala
{{"id":"output",}}
{{"id":"output"}}
Remove trailing comma.
JSON
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
SELECT * FROM items WHRE age=69;
SELECT * FROM items WHERE age=69;
Fix WHERE.
SQL
<hr></hr>
<hr>
Self-closing.
HTML
disp('value')
disp('value')
Correct.
MATLAB
list(36)
if length(list) >= 36, list(36), end
Check length.
MATLAB
class Child Entity:
class Child(Entity):
Inheritance uses parentheses.
Python
if temp = 2
if temp == 2
Use ==.
MATLAB
String name = 'test';
String name = 'test';
Correct.
Dart
int list[18]; list[18]=5;
int list[18]; if(18<18){{}} else list[18]=5;
Bounds check.
C++
function render(): void {{ return 94; }}
function render(): number {{ return 94; }}
Return type mismatch.
TypeScript
<person><age>test</age><desc>94</desc></person
<person><age>test</age><desc>94</desc></person>
Add closing >.
XML
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
jwt.sign({{id:81}}, 'token');
jwt.sign({{id:81}}, 'token', {{expiresIn:'30m'}});
Add expiration.
Node.js
<note name='value'/>
<note name="value"/>
Double quotes.
XML
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
while count > 49 count -= 1
while count > 49: count -= 1
Colon missing after while.
Python
test
test()
Add parentheses.
Kotlin
class = 'data'
class_name = 'data'
'class' is a keyword.
Python
bar = 85
bar=85
No spaces.
Shell
h1 {{ font-size:11px color:#333; }}
h1 {{ font-size:11px; color:#333; }}
Add semicolon.
CSS
<div color=#fff>
<div style='color:#fff;'>
Use style attribute.
CSS
let c: number = 'result';
let c: string = 'result';
Fix type.
TypeScript
[x*x for x in values if x > 36]
[x*x for x in values if x > 36]
Correct list comprehension.
Python
my @arr = (59,28,34);
my @arr = (59,28,34);
Correct.
Perl
INSERT INTO orders VALUES ('output',67)
INSERT INTO orders (id, status) VALUES ('output',67);
Specify columns.
SQL
'73' + 37
73 + 37
Avoid string coercion.
JavaScript
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('data')); app.listen(34);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('data')); app.listen(34, () => console.log('listening'));
Add callback.
Node.js
<?php // code ?>
<?php // code ?>
Correct.
PHP
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
status: test title: hello,
status: test title: hello
Remove comma.
YAML
String c = 'message';
String c = "message";
Double quotes.
Java
fs.readFile('log.txt', (err,data) => {{ if(err) throw err; }});
fs.readFile('log.txt', (err,data) => {{ if(err) {{ console.error(err); return; }} }});
Better error handling.
Node.js
div {{ color=green; }}
div {{ color: green; }}
Use colon.
CSS