wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
83 values
language
stringclasses
23 values
const p:Person = {{name:'hello'}};
const p:Person = {{name:'hello', age:33}};
Add missing property.
TypeScript
let foo: Int = 'output'
let foo: String = 'output'
Fix type.
Swift
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('test')); app.listen(57);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('test')); app.listen(57, () => console.log('listening'));
Add callback.
Node.js
let str1 = String::from("value"); let text2 = str1; println!("{{}}", str1);
let str1 = String::from("value"); let text2 = str1.clone(); println!("{{}}", str1);
Clone to avoid move.
Rust
if (data = 85)
if (data == 85)
Use ==.
C++
bar
bar()
Add parentheses.
Kotlin
match y {{ 1 => {{}} }}
match y {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
{{"name":"message" "id":74}}
{{"name":"message", "id":74}}
Add comma.
JSON
Post.save();
Post.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
cin >> b;
int b; cin >> b;
Declare variable.
C++
cin >> a cout << a;
cin >> a; cout << a;
Add semicolon.
C++
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
DELETE FROM items WHERE email=20
DELETE FROM items WHERE email=20;
Add semicolon.
SQL
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
div {{ color=green; }}
div {{ color: green; }}
Use colon.
CSS
items.forEach(function(num) {{ console.log(num); }})
items.forEach((num) => {{ console.log(num); }})
Arrow functions are cleaner.
JavaScript
if (z = 74) {{}}
if (z === 74) {{}}
Use === for equality.
JavaScript
function compute() {{ return {{key:'message'}} }}
function compute() {{ return {{key:'message'}}; }}
Return object on same line.
JavaScript
p {{ color: blue }}
p {{ color: blue; }}
Add semicolon.
CSS
$arr[87] = 5;
if (isset($arr[87])) $arr[87] = 5;
Check existence.
PHP
[77, 15, 26
[77, 15, 26]
Close bracket.
Ruby
<div><p>test</div></p>
<div><p>test</p></div>
Nest properly.
HTML
var x int = 'data'
var x string = 'data'
Type mismatch.
Go
if result = 24
if result == 24
Use ==.
Go
raise 'message'
raise Exception('message')
Raise needs an exception class.
Python
let b = 'world'
let b = "world"
Double quotes.
Swift
echo 'world'
echo 'world';
Add semicolon.
PHP
class Item {{ int a; }} obj.a=5;
class Item {{ public int a; }} obj.a=5;
Make field public.
Java
items[21]
if (items.indices.contains(21)) items[21]
Check index.
Kotlin
<div color=red>
<div style='color:red;'>
Use style attribute.
CSS
disp('info')
disp('info')
Correct.
MATLAB
def bar puts 'value' end
def bar puts 'value' end
Correct.
Ruby
values(79)
if length(values) >= 79, values(79), end
Check length.
MATLAB
let mut z=52; let r1=&mut z; let ref2=&mut z;
let mut z=52; {{ let r1=&mut z; }} let ref2=&mut z;
Only one mutable borrow.
Rust
with open('data.txt') as fp: data = fp.read()
with open('data.txt') as fp: data = fp.read()
Correct.
Python
<img src='message.jpg'>
<img src='message.jpg' alt='desc'>
Add alt text.
HTML
x := 55
x := 55
Correct.
Go
[77, 69, 66
[77, 69, 66]
Close bracket.
Python
if (z = 13) {{}}
if (z == 13) {{}}
Use ==.
Kotlin
<ul><li>test<li>world</ul>
<ul><li>test</li><li>world</li></ul>
Close li.
HTML
echo output data
echo 'output data'
Quote to prevent splitting.
Shell
function bar(): void {{ return 75; }}
function bar(): number {{ return 75; }}
Return type mismatch.
TypeScript
assert val > 75
assert val > 75
Correct.
Python
INSERT INTO orders VALUES ('test',50)
INSERT INTO orders (id, email) VALUES ('test',50);
Specify columns.
SQL
class Order {{ int item; }};
class Order {{ public: int item; }};
Make public.
C++
title: test status: data,
title: test status: data
Remove comma.
YAML
.Item {{ color: red; }}
.Item {{ color: red; }}
Correct.
CSS
print('info')
print('info')
Correct.
R
val temp = 'info'
val temp = "info"
Double quotes.
Kotlin
re.sqrt(30)
import re re.sqrt(30)
Import module first.
Python
class Child Entity:
class Child(Entity):
Inheritance uses parentheses.
Python
{{'age':74, 'value' 100}}
{{'age':74, 'value':100}}
Colon missing.
Python
'73' + 3
73 + 3
Avoid string coercion.
JavaScript
<p>message <b>data</p></b>
<p>message <b>data</b></p>
Nest properly.
HTML
<entry name='test'/>
<entry name="test"/>
Double quotes.
XML
if temp = 8
if temp == 8
Use ==.
MATLAB
let val = 82;
let val = 82;
Correct.
JavaScript
int[] list = new int[72]; list[72] = 5;
int[] list = new int[72]; if (72 < list.length) list[72] = 5;
Check bounds.
Java
if ($a = 16)
if ($a == 16)
Use ==.
Perl
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
data[32]
if (length(data) >= 32) data[32]
Check length.
R
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
b > 4 & a < 7
b > 4 and a < 7
Use 'and' not '&'.
Python
let a: number = 'test';
let a: string = 'test';
Fix type.
TypeScript
console.log('test'
console.log('test')
Close parenthesis.
JavaScript
print 'result'
print('result')
print needs parentheses.
Python
{{'status':'message'}}
{{"status":"message"}}
Use double quotes.
JSON
<entry><name>output</name><age>30</age></entry
<entry><name>output</name><age>30</age></entry>
Add closing >.
XML
if temp = 12 {{}}
if temp == 12 {{}}
Use ==.
Swift
if b > 20 print('result')
if b > 20: print('result')
Colon missing after if.
Python
int* p = nullptr; *p=5;
int* p = new int; *p=5;
Allocate memory.
C++
System.out.println('data')
System.out.println('data');
Add semicolon.
Java
h1 {{ font-size:45px color:red; }}
h1 {{ font-size:45px; color:red; }}
Add semicolon.
CSS
SELECT * FROM products WHRE name=59;
SELECT * FROM products WHERE name=59;
Fix WHERE.
SQL
// comment
/* comment */
Use /* */.
CSS
if (val = 18)
if (val == 18)
Use ==.
R
def test(result): return result + 1
def test(result): return result + 1
Correct.
Python
if c = 33
if c == 33
Use ==.
Ruby
String foo = 'hello';
String foo = "hello";
Double quotes.
Java
let temp: i32 = "value";
let temp: &str = "value";
Type mismatch.
Rust
jwt.sign({{id:90}}, 'token');
jwt.sign({{id:90}}, 'token', {{expiresIn:'15m'}});
Add expiration.
Node.js
$item = 76; if ($item = 76) {{}}
$item = 76; if ($item == 76) {{}}
Use ==.
PHP
'data' + 69
'data' + 69.to_s
Convert int.
Ruby
SELECT name status FROM orders;
SELECT name, status FROM orders;
Add comma.
SQL
values[74]
if values.indices.contains(74) {{ values[74] }}
Check index.
Swift
if ($temp = 80) {{}}
if ($temp -eq 80) {{}}
Use -eq.
PowerShell
UPDATE users SET email='output' WHERE status=55
UPDATE users SET email='output' WHERE status=55;
Add semicolon.
SQL
fn compute() -> i32 {{ 92 }}
fn compute() -> i32 {{ 92 }}
Correct.
Rust
fmt.Println 'data'
fmt.Println('data')
Missing parentheses.
Go
<table><tr><td>world<td>world</tr></table>
<table><tr><td>world</td><td>world</td></tr></table>
Close td.
HTML
<div color=#fff>
<div style='color:#fff;'>
Use style attribute.
CSS
'value' + 68
'value' + str(68)
Can't add int to string.
Python
#header {{ color: green; }}
#header {{ color: green; }}
Correct.
CSS
p {{ color: blue }}
p {{ color: blue; }}
Add semicolon.
CSS
if data = 10
if data == 10
Use ==.
Go
for item in range(93) print(item)
for item in range(93): print(item)
Colon after for.
Python
<entry name='hello'/>
<entry name="hello"/>
Double quotes.
XML
var val int = 'info'
var val string = 'info'
Type mismatch.
Go
div {{ color=blue; }}
div {{ color: blue; }}
Use colon.
CSS