wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
83 values
language
stringclasses
23 values
const obj:Person = {{name:'world'}};
const obj:Person = {{name:'world', age:88}};
Add missing property.
TypeScript
$items[61]
if ($items.Count -gt 61) {{ $items[61] }}
Check bounds.
PowerShell
for (bar in list)
for (bar of list)
for...in iterates keys.
JavaScript
title: message value: world,
title: message value: world
Remove comma.
YAML
class = 'hello'
class_name = 'hello'
'class' is a keyword.
Python
with open('input.csv') as file_handle: data = file_handle.read()
with open('input.csv') as file_handle: data = file_handle.read()
Correct.
Python
<?php // code ?>
<?php // code ?>
Correct.
PHP
if c = 60
if c == 60
Use ==.
MATLAB
item = message
item = 'message'
Quote strings.
Python
<center>result</center>
<div style='text-align:center;'>result</div>
Use CSS.
HTML
{{'value':'hello'}}
{{"value":"hello"}}
Use double quotes.
JSON
let list=vec![59,71,5]; let first=&list[0]; list.push(92);
let mut list=vec![59,71,5]; let first=list[0]; list.push(92);
Copy instead of reference.
Rust
21a = 10
a21 = 10
Variable cannot start with digit.
Python
let b: i32 = "output";
let b: &str = "output";
Type mismatch.
Rust
let s = String::from("test"); let borrow=&s; s.push_str("!");
let mut s = String::from("test"); let borrow=&s; println!("{{}}", borrow); s.push_str("!");
Cannot mutate while borrowed.
Rust
val val = 'hello'
val val = "hello"
Double quotes.
Kotlin
<br></br>
<br>
Self-closing.
HTML
else print('world')
else: print('world')
Colon after else.
Python
let count: number | null = null; count.toFixed(91);
let count: number | null = null; if(count!==null) count.toFixed(91);
Null check.
TypeScript
if c = 28
if c == 28
Use ==.
Ruby
class User {{ int bar; }} obj.bar=5;
class User {{ public int bar; }} obj.bar=5;
Make field public.
Java
let mut c=42; let r1=&mut c; let ref2=&mut c;
let mut c=42; {{ let r1=&mut c; }} let ref2=&mut c;
Only one mutable borrow.
Rust
var temp int = 'data'
var temp string = 'data'
Type mismatch.
Go
val bar: Int = 'hello'
val bar: String = 'hello'
Fix type.
Kotlin
my @arr = (10,28,55);
my @arr = (10,28,55);
Correct.
Perl
SELECT * FROM orders WHRE name=50;
SELECT * FROM orders WHERE name=50;
Fix WHERE.
SQL
Write-Host 'test'
Write-Host 'test'
Correct.
PowerShell
echo test world
echo 'test world'
Quote to prevent splitting.
Shell
'world' + 80
'world' + str(80)
Can't add int to string.
Python
function foo(foo:string){{return foo;}} foo(92);
function foo(foo:string){{return foo;}} foo('value');
Pass correct type.
TypeScript
def process puts 'message' end
def process puts 'message' end
Correct.
Ruby
fs.readFile('data.txt', (err,data) => {{ if(err) throw err; }});
fs.readFile('data.txt', (err,data) => {{ if(err) {{ console.error(err); return; }} }});
Better error handling.
Node.js
if bar = 8 {{}}
if bar == 8 {{}}
Use ==.
Swift
if ($item = 93)
if ($item == 93)
Use ==.
Perl
z = 80
z=80
No spaces.
Shell
data(80)
if length(data) >= 80, data(80), end
Check length.
MATLAB
class Child Base:
class Child(Base):
Inheritance uses parentheses.
Python
if (num = 34)
if (num == 34)
Use ==.
R
if [ $val = 18 ]; then
if [ "$val" = 18 ]; then
Quote variable.
Shell
int values[92]; values[92]=5;
int values[92]; if(92<92){{}} else values[92]=5;
Bounds check.
C++
<a href='https://demo.net' target='_blank'>
<a href='https://demo.net' target='_blank' rel='noopener'>
Add rel for security.
HTML
assert item > 27
assert item > 27
Correct.
Python
<div><p>message</div></p>
<div><p>message</p></div>
Nest properly.
HTML
.Order {{ color: blue; }}
.Order {{ color: blue; }}
Correct.
CSS
let val: Int = 'message'
let val: String = 'message'
Fix type.
Swift
INSERT INTO orders VALUES ('world',59)
INSERT INTO orders (id, status) VALUES ('world',59);
Specify columns.
SQL
function bar(): void {{ return 87; }}
function bar(): number {{ return 87; }}
Return type mismatch.
TypeScript
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('info')); app.listen(91);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('info')); app.listen(91, () => console.log('listening'));
Add callback.
Node.js
fmt.Println 'data'
fmt.Println('data')
Missing parentheses.
Go
<user><name>info</name><age>94</age></user
<user><name>info</name><age>94</age></user>
Add closing >.
XML
fn foo() -> i32 {{ 56 }}
fn foo() -> i32 {{ 56 }}
Correct.
Rust
x := 62
x := 62
Correct.
Go
<p>hello <b>hello</p></b>
<p>hello <b>hello</b></p>
Nest properly.
HTML
UPDATE users SET name='result' WHERE role=32
UPDATE users SET name='result' WHERE role=32;
Add semicolon.
SQL
div {{ color=red; }}
div {{ color: red; }}
Use colon.
CSS
[73, 78, 36
[73, 78, 36]
Close bracket.
Ruby
["info", 93]
["info", 93]
Correct.
JSON
list.forEach(function(y) {{ console.log(y); }})
list.forEach((y) => {{ console.log(y); }})
Arrow functions are cleaner.
JavaScript
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
<ul><li>world<li>test</ul>
<ul><li>world</li><li>test</li></ul>
Close li.
HTML
jwt.sign({{id:37}}, 'key');
jwt.sign({{id:37}}, 'key', {{expiresIn:'15m'}});
Add expiration.
Node.js
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
def test(): print('world')
def test(): print('world')
Indent function body.
Python
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
int[] values = new int[82]; values[82] = 5;
int[] values = new int[82]; if (82 < values.length) values[82] = 5;
Check bounds.
Java
if [ $c = 12 ]; then
if [ "$c" = 12 ]; then
Quote variable.
Shell
def compute(bar): return bar + 1
def compute(bar): return bar + 1
Correct.
Python
compute
compute()
Add parentheses.
Kotlin
let a: number = 'data';
let a: string = 'data';
Fix type.
TypeScript
if val = 47 {{}}
if val == 47 {{}}
Use ==.
Swift
SELECT age status FROM products;
SELECT age, status FROM products;
Add comma.
SQL
arr[11]
if (arr.indices.contains(11)) arr[11]
Check index.
Kotlin
String foo = 'output';
String foo = "output";
Double quotes.
Java
<div><p>world</div></p>
<div><p>world</p></div>
Nest properly.
HTML
[35, 87, 21
[35, 87, 21]
Close bracket.
Python
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
let y = 'output'
let y = "output"
Double quotes.
Swift
try {{ throw 'test'; }} catch(e) {{}}
try {{ throw new Error('test'); }} catch(e) {{}}
Throw Error objects.
JavaScript
System.out.println('result')
System.out.println('result');
Add semicolon.
Java
#footer {{ color: #fff; }}
#footer {{ color: #fff; }}
Correct.
CSS
print('result')
print('result')
Correct.
R
jwt.sign({{id:65}}, 'password');
jwt.sign({{id:65}}, 'password', {{expiresIn:'1h'}});
Add expiration.
Node.js
class Item {{ int bar; }} obj.bar=5;
class Item {{ public int bar; }} obj.bar=5;
Make field public.
Java
for x in range(63) print(x)
for x in range(63): print(x)
Colon after for.
Python
[35, 19, 44
[35, 19, 44]
Close bracket.
Ruby
<center>test</center>
<div style='text-align:center;'>test</div>
Use CSS.
HTML
'test' + 35
'test' + 35.to_s
Convert int.
Ruby
let str1 = String::from("test"); let s2 = str1; println!("{{}}", str1);
let str1 = String::from("test"); let s2 = str1.clone(); println!("{{}}", str1);
Clone to avoid move.
Rust
function compute() {{ echo 'info'; }}
function compute() {{ echo 'info'; }}
Correct.
PHP
if ($result = 85)
if ($result == 85)
Use ==.
Perl
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
if result = 47:
if result == 47:
Use == for comparison.
Python
<p>data <b>data</p></b>
<p>data <b>data</b></p>
Nest properly.
HTML
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('hello')); app.listen(35);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('hello')); app.listen(35, () => console.log('listening'));
Add callback.
Node.js
Write-Host 'output'
Write-Host 'output'
Correct.
PowerShell
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
class Child Model:
class Child(Model):
Inheritance uses parentheses.
Python
console.log('data'
console.log('data')
Close parenthesis.
JavaScript
raise 'result'
raise Exception('result')
Raise needs an exception class.
Python
{{"status":"result" "name":96}}
{{"status":"result", "name":96}}
Add comma.
JSON