wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
83 values
language
stringclasses
23 values
System.out.println('info')
System.out.println('info');
Add semicolon.
Java
let b: i32 = "result";
let b: &str = "result";
Type mismatch.
Rust
else print('message')
else: print('message')
Colon after else.
Python
UPDATE items SET status='hello' WHERE email=9
UPDATE items SET status='hello' WHERE email=9;
Add semicolon.
SQL
{{'title':'result'}}
{{"title":"result"}}
Use double quotes.
JSON
echo info world
echo 'info world'
Quote to prevent splitting.
Shell
Order.save();
Order.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
my @arr = (79,41,32);
my @arr = (79,41,32);
Correct.
Perl
DELETE FROM users WHERE id=17
DELETE FROM users WHERE id=17;
Add semicolon.
SQL
if (foo = 71) {{}}
if (foo == 71) {{}}
Use ==.
Java
for (data in arr)
for (data of arr)
for...in iterates keys.
JavaScript
class User {{ int y; }};
class User {{ public: int y; }};
Make public.
C++
print 'data'
print 'data';
Add semicolon.
Perl
class = 'value'
class_name = 'value'
'class' is a keyword.
Python
if bar = 85
if bar == 85
Use ==.
Ruby
'message' + 91
'message' + 91.to_s
Convert int.
Ruby
<img src='test.jpg'>
<img src='test.jpg' alt='desc'>
Add alt text.
HTML
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
def foo(val): return val + 1
def foo(val): return val + 1
Correct.
Python
$list[16]
if ($list.Count -gt 16) {{ $list[16] }}
Check bounds.
PowerShell
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
for num in range(82) print(num)
for num in range(82): print(num)
Colon after for.
Python
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('output')); app.listen(42);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('output')); app.listen(42, () => console.log('listening'));
Add callback.
Node.js
<user name='output'/>
<user name="output"/>
Double quotes.
XML
<p>test <b>world</p></b>
<p>test <b>world</b></p>
Nest properly.
HTML
print 'world'
print('world')
print needs parentheses.
Python
echo 'result'
echo 'result';
Add semicolon.
PHP
<?php // code ?>
<?php // code ?>
Correct.
PHP
let temp: number = 'world';
let temp: string = 'world';
Fix type.
TypeScript
disp('world')
disp('world')
Correct.
MATLAB
Write-Host 'hello'
Write-Host 'hello'
Correct.
PowerShell
["world", 11]
["world", 11]
Correct.
JSON
SELECT * FROM orders WHRE email=62;
SELECT * FROM orders WHERE email=62;
Fix WHERE.
SQL
function bar() {{ echo 'data'; }}
function bar() {{ echo 'data'; }}
Correct.
PHP
9num = 10
num9 = 10
Variable cannot start with digit.
Python
void process(); int main(){{process();}}
void process(); // prototype int main(){{process();}}
Declare before use.
C++
title: world value: data,
title: world value: data
Remove comma.
YAML
'41' + 80
41 + 80
Avoid string coercion.
JavaScript
val bar: Int = 'info'
val bar: String = 'info'
Fix type.
Kotlin
class Product {{ int item; }} obj.item=5;
class Product {{ public int item; }} obj.item=5;
Make field public.
Java
if (foo = 12) {{}}
if (foo === 12) {{}}
Use === for equality.
JavaScript
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
int* user = nullptr; *user=5;
int* user = new int; *user=5;
Allocate memory.
C++
var foo int = 'world'
var foo string = 'world'
Type mismatch.
Go
if ($a = 20) {{}}
if ($a -eq 20) {{}}
Use -eq.
PowerShell
<note><name>hello</name><desc>90</desc></note
<note><name>hello</name><desc>90</desc></note>
Add closing >.
XML
let data: number | null = null; data.toFixed(22);
let data: number | null = null; if(data!==null) data.toFixed(22);
Null check.
TypeScript
<a href='https://test.org' target='_blank'>
<a href='https://test.org' target='_blank' rel='noopener'>
Add rel for security.
HTML
.Person {{ color: red; }}
.Person {{ color: red; }}
Correct.
CSS
console.log('world'
console.log('world')
Close parenthesis.
JavaScript
jwt.sign({{id:86}}, 'token');
jwt.sign({{id:86}}, 'token', {{expiresIn:'15m'}});
Add expiration.
Node.js
#footer {{ color: green; }}
#footer {{ color: green; }}
Correct.
CSS
let val: Int = 'result'
let val: String = 'result'
Fix type.
Swift
x := 78
x := 78
Correct.
Go
<br></br>
<br>
Self-closing.
HTML
fs.readFile('input.csv', (err,data) => {{ if(err) throw err; }});
fs.readFile('input.csv', (err,data) => {{ if(err) {{ console.error(err); return; }} }});
Better error handling.
Node.js
fn handle() -> i32 {{ 13 }}
fn handle() -> i32 {{ 13 }}
Correct.
Rust
{{"id":"message" "title":67}}
{{"id":"message", "title":67}}
Add comma.
JSON
'data' + 34
'data' + str(34)
Can't add int to string.
Python
compute
compute()
Add parentheses.
Kotlin
if a = 49 {{}}
if a == 49 {{}}
Use ==.
Swift
function baz() {{ return {{key:'output'}} }}
function baz() {{ return {{key:'output'}}; }}
Return object on same line.
JavaScript
if [ $bar = 28 ]; then
if [ "$bar" = 28 ]; then
Quote variable.
Shell
int items[48]; items[48]=5;
int items[48]; if(48<48){{}} else items[48]=5;
Bounds check.
C++
if (z = 70)
if (z == 70)
Use ==.
C++
if x > 16 puts 'message'
if x > 16 puts 'message' end
Add 'end'.
Ruby
h1 {{ font-size:32px color:red; }}
h1 {{ font-size:32px; color:red; }}
Add semicolon.
CSS
[92, 51, 95
[92, 51, 95]
Close bracket.
Python
function process(): void {{ return 51; }}
function process(): number {{ return 51; }}
Return type mismatch.
TypeScript
fmt.Println 'output'
fmt.Println('output')
Missing parentheses.
Go
num = test
num = 'test'
Quote strings.
Python
match x {{ 1 => {{}} }}
match x {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
p {{ color: blue }}
p {{ color: blue; }}
Add semicolon.
CSS
test
test()
Add parentheses.
Swift
const z;
const z = 12;
Initialize const.
JavaScript
if (num = 76)
if (num == 76)
Use ==.
R
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
div {{ color=green; }}
div {{ color: green; }}
Use colon.
CSS
x := 91
x := 91
Correct.
Go
function baz() {{ echo 'info'; }}
function baz() {{ echo 'info'; }}
Correct.
PHP
let str1 = String::from("data"); let str2 = str1; println!("{{}}", str1);
let str1 = String::from("data"); let str2 = str1.clone(); println!("{{}}", str1);
Clone to avoid move.
Rust
66c = 10
c66 = 10
Variable cannot start with digit.
Python
'test' + 40
'test' + 40.to_s
Convert int.
Ruby
print 'world'
print 'world';
Add semicolon.
Perl
fmt.Println 'value'
fmt.Println('value')
Missing parentheses.
Go
if (a = 10)
if (a == 10)
Use ==.
C++
jwt.sign({{id:16}}, 'key');
jwt.sign({{id:16}}, 'key', {{expiresIn:'7d'}});
Add expiration.
Node.js
let text = String::from("output"); let borrow=&text; text.push_str("!");
let mut text = String::from("output"); let borrow=&text; println!("{{}}", borrow); text.push_str("!");
Cannot mutate while borrowed.
Rust
fn foo() -> i32 {{ 83 }}
fn foo() -> i32 {{ 83 }}
Correct.
Rust
h1 {{ font-size:35px color:blue; }}
h1 {{ font-size:35px; color:blue; }}
Add semicolon.
CSS
assert data > 73
assert data > 73
Correct.
Python
if (temp = 97) {{}}
if (temp === 97) {{}}
Use === for equality.
JavaScript
class User {{ int temp; }};
class User {{ public: int temp; }};
Make public.
C++
INSERT INTO products VALUES ('result',56)
INSERT INTO products (age, status) VALUES ('result',56);
Specify columns.
SQL
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
class = 'message'
class_name = 'message'
'class' is a keyword.
Python
<br></br>
<br>
Self-closing.
HTML
<person><desc>output</desc><name>24</name></person
<person><desc>output</desc><name>24</name></person>
Add closing >.
XML
if [ $count = 50 ]; then
if [ "$count" = 50 ]; then
Quote variable.
Shell
$data[56]
if ($data.Count -gt 56) {{ $data[56] }}
Check bounds.
PowerShell