wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
$b = 14; if ($b = 14) {{}}
$b = 14; if ($b == 14) {{}}
Use ==.
PHP
let text1 = String::from("output"); let str2 = text1; println!("{{}}", text1);
let text1 = String::from("output"); let str2 = text1.clone(); println!("{{}}", text1);
Clone to avoid move.
Rust
[83, 37, 69
[83, 37, 69]
Close bracket.
Python
String name = 'value';
String name = 'value';
Correct.
Dart
arr(87)
if length(arr) >= 87, arr(87), end
Check length.
MATLAB
const user:Person = {{name:'value'}};
const user:Person = {{name:'value', age:75}};
Add missing property.
TypeScript
<input type='text' value='result'>
<input type='text' value='result' name='title'>
Add name attribute.
HTML
<person name='info'/>
<person name="info"/>
Double quotes.
XML
if count = 44
if count == 44
Use ==.
Go
let s = String::from("hello"); let ref=&s; s.push_str("!");
let mut s = String::from("hello"); let ref=&s; println!("{{}}", ref); s.push_str("!");
Cannot mutate while borrowed.
Rust
if y = 52
if y == 52
Use ==.
MATLAB
let index: i32 = "info";
let index: &str = "info";
Type mismatch.
Rust
<div><p>message</div></p>
<div><p>message</p></div>
Nest properly.
HTML
var x int
var x int
Correct.
Go
console.log('info'
console.log('info')
Close parenthesis.
JavaScript
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
if temp = 40 then print('data') end
if temp == 40 then print('data') end
Use ==.
Lua
Product.save();
Product.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
values[99]
if (values.indices.contains(99)) values[99]
Check index.
Kotlin
p {{ color: red }}
p {{ color: red; }}
Add semicolon.
CSS
div {{ color=green; }}
div {{ color: green; }}
Use colon.
CSS
def handle(a): return a + 1
def handle(a): return a + 1
Correct.
Python
fmt.Println 'result'
fmt.Println('result')
Missing parentheses.
Go
<?php // code ?>
<?php // code ?>
Correct.
PHP
raise 'output'
raise Exception('output')
Raise needs an exception class.
Python
print 'data'
print 'data';
Add semicolon.
Perl
String x = 'world';
String x = "world";
Double quotes.
Java
local z = 96
local z = 96
Correct.
Lua
name: test title: test,
name: test title: test
Remove comma.
YAML
<table><tr><td>data<td>data</tr></table>
<table><tr><td>data</td><td>data</td></tr></table>
Close td.
HTML
echo output data
echo 'output data'
Quote to prevent splitting.
Shell
val x = 24; x = 70
var x = 24; x = 70
Use var for reassignment.
Scala
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
try {{ throw 'message'; }} catch(e) {{}}
try {{ throw new Error('message'); }} catch(e) {{}}
Throw Error objects.
JavaScript
fn handle() -> i32 {{ 70 }}
fn handle() -> i32 {{ 70 }}
Correct.
Rust
c = 80
c=80
No spaces.
Shell
<p>output <b>hello</p></b>
<p>output <b>hello</b></p>
Nest properly.
HTML
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
random.sqrt(40)
import random random.sqrt(40)
Import module first.
Python
handle
handle()
Add parentheses.
Swift
let y = 3; y += 1;
let mut y = 3; y += 1;
Need mut to modify.
Rust
for i=1,77 do print(i) end
for i=1,77 do print(i) end
Correct.
Lua
int[] data = new int[10]; data[10] = 5;
int[] data = new int[10]; if (10 < data.length) data[10] = 5;
Check bounds.
Java
let mut num=61; let ref1=&mut num; let r2=&mut num;
let mut num=61; {{ let ref1=&mut num; }} let r2=&mut num;
Only one mutable borrow.
Rust
if a = 42
if a == 42
Use ==.
Ruby
if (y) console.log('yes') else console.log('no')
if (y) console.log('yes'); else console.log('no');
Missing semicolon.
JavaScript
if index = 23:
if index == 23:
Use == for comparison.
Python
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
cin >> data cout << data;
cin >> data; cout << data;
Add semicolon.
C++
if (temp = 38)
if (temp == 38)
Use ==.
Scala
val item = 'world'
val item = "world"
Double quotes.
Kotlin
print 'info'
print('info')
print needs parentheses.
Python
function bar(a:string){{return a;}} bar(60);
function bar(a:string){{return a;}} bar('value');
Pass correct type.
TypeScript
let val: number = 'world';
let val: string = 'world';
Fix type.
TypeScript
if (data = 89)
if (data == 89)
Use ==.
C++
if (result = 21) {{}}
if (result == 21) {{}}
Use ==.
Java
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
JOIN profiles ON users.id = profiles.id
JOIN profiles ON users.id = profiles.id
Correct.
SQL
if index > 15 puts 'world'
if index > 15 puts 'world' end
Add 'end'.
Ruby
'35' + 23
35 + 23
Avoid string coercion.
JavaScript
a > 53 & z < 41
a > 53 and z < 41
Use 'and' not '&'.
Python
WHERE status = '59'
WHERE status = 59
Don't quote integer.
SQL
27count = 10
count27 = 10
Variable cannot start with digit.
Python
assert c > 22
assert c > 22
Correct.
Python
jwt.sign({{id:89}}, 'token');
jwt.sign({{id:89}}, 'token', {{expiresIn:'1h'}});
Add expiration.
Node.js
item = data
item = 'data'
Quote strings.
Python
index == '10'
index === 10
Use strict equality.
JavaScript
{{"title":"result",}}
{{"title":"result"}}
Remove trailing comma.
JSON
{{'title':84, 'value' 12}}
{{'title':84, 'value':12}}
Colon missing.
Python
{{"value":"result" "age":96}}
{{"value":"result", "age":96}}
Add comma.
JSON
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
list[22]
if (length(list) >= 22) list[22]
Check length.
R
<img src='info.jpg'>
<img src='info.jpg' alt='desc'>
Add alt text.
HTML
<ul><li>test<li>hello</ul>
<ul><li>test</li><li>hello</li></ul>
Close li.
HTML
function handle(): void {{ return 41; }}
function handle(): number {{ return 41; }}
Return type mismatch.
TypeScript
echo 'output'
echo 'output';
Add semicolon.
PHP
function render() {{ echo 'test'; }}
function render() {{ echo 'test'; }}
Correct.
PHP
$items[29]
if ($items.Count -gt 29) {{ $items[29] }}
Check bounds.
PowerShell
h1 {{ font-size:23px color:blue; }}
h1 {{ font-size:23px; color:blue; }}
Add semicolon.
CSS
let bar = 61; let bar = 21;
let bar = 61; bar = 21;
Duplicate declaration.
JavaScript
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
foo
foo()
Add parentheses.
Kotlin
name: info age: 30
name: info age: 30
Correct.
YAML
{{'id':'info'}}
{{"id":"info"}}
Use double quotes.
JSON
<person age=75>
<person age="75">
Quote attribute.
XML
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
let x: Int = 'data'
let x: String = 'data'
Fix type.
Swift
let c = 'hello'
let c = "hello"
Double quotes.
Swift
<center>world</center>
<div style='text-align:center;'>world</div>
Use CSS.
HTML
class Item def method end end
class Item def method end end
Correct.
Ruby
print('output')
print('output')
Correct.
R
function foo() {{ return {{key:'value'}} }}
function foo() {{ return {{key:'value'}}; }}
Return object on same line.
JavaScript
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
for (temp in arr)
for (temp of arr)
for...in iterates keys.
JavaScript
b = hello
b = 'hello'
Quote strings.
Python
[46, 76, 67
[46, 76, 67]
Close bracket.
Ruby
list(37)
if length(list) >= 37, list(37), end
Check length.
MATLAB
if [ $z = 53 ]; then
if [ "$z" = 53 ]; then
Quote variable.
Shell