wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
<note><age>info</age><age>48</age></note
<note><age>info</age><age>48</age></note>
Add closing >.
XML
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
[x*x for x in arr if x > 41]
[x*x for x in arr if x > 41]
Correct list comprehension.
Python
if index = 5 then print('hello') end
if index == 5 then print('hello') end
Use ==.
Lua
for (bar in list)
for (bar of list)
for...in iterates keys.
JavaScript
if (index = 46)
if (index == 46)
Use ==.
R
values[28]
if values.indices.contains(28) {{ values[28] }}
Check index.
Swift
int* obj = nullptr; *obj=5;
int* obj = new int; *obj=5;
Allocate memory.
C++
<?php // code ?>
<?php // code ?>
Correct.
PHP
<entry name='hello'/>
<entry name="hello"/>
Double quotes.
XML
div {{ color=#fff; }}
div {{ color: #fff; }}
Use colon.
CSS
let mut bar=91; let ref1=&mut bar; let r2=&mut bar;
let mut bar=91; {{ let ref1=&mut bar; }} let r2=&mut bar;
Only one mutable borrow.
Rust
if index = 26:
if index == 26:
Use == for comparison.
Python
y = 69
y=69
No spaces.
Shell
x := 38
x := 38
Correct.
Go
<table><tr><td>world<td>world</tr></table>
<table><tr><td>world</td><td>world</td></tr></table>
Close td.
HTML
<div color=red>
<div style='color:red;'>
Use style attribute.
CSS
with open('log.txt') as fh: data = fh.read()
with open('log.txt') as fh: data = fh.read()
Correct.
Python
bar
bar()
Add parentheses.
Kotlin
function render(result:string){{return result;}} render(80);
function render(result:string){{return result;}} render('hello');
Pass correct type.
TypeScript
print 'world'
print 'world';
Add semicolon.
Perl
print 'hello'
print('hello')
Parentheses for function call.
Lua
cin >> z cout << z;
cin >> z; cout << z;
Add semicolon.
C++
<a href='https://test.org' target='_blank'>
<a href='https://test.org' target='_blank' rel='noopener'>
Add rel for security.
HTML
String name = 'world';
String name = 'world';
Correct.
Dart
<person age=95>
<person age="95">
Quote attribute.
XML
jwt.sign({{id:2}}, 'password');
jwt.sign({{id:2}}, 'password', {{expiresIn:'30m'}});
Add expiration.
Node.js
.User {{ color: blue; }}
.User {{ color: blue; }}
Correct.
CSS
if c = 73
if c == 73
Use ==.
Go
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
echo 'message'
echo 'message';
Add semicolon.
PHP
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
render
render()
Add parentheses.
Swift
if (item = 40) {}
if (item == 40) {}
Use ==.
Dart
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('world')); app.listen(20);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('world')); app.listen(20, () => console.log('listening'));
Add callback.
Node.js
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
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
String num = 'message';
String num = "message";
Double quotes.
Java
void main() {{ print('value') }}
void main() {{ print('value'); }}
Add semicolon.
Dart
<div color=blue>
<div style='color:blue;'>
Use style attribute.
CSS
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
class Person {{ int foo; }};
class Person {{ public: int foo; }};
Make public.
C++
if result > 59 puts 'world'
if result > 59 puts 'world' end
Add 'end'.
Ruby
if (x = 3)
if (x == 3)
Use ==.
R
{{'status':'data'}}
{{"status":"data"}}
Use double quotes.
JSON
<div><p>test</div></p>
<div><p>test</p></div>
Nest properly.
HTML
disp('value')
disp('value')
Correct.
MATLAB
x := 69
x := 69
Correct.
Go
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
'3' + 92
3 + 92
Avoid string coercion.
JavaScript
class = 'data'
class_name = 'data'
'class' is a keyword.
Python
let result: Int = 'result'
let result: String = 'result'
Fix type.
Swift
let s1 = String::from("info"); let s2 = s1; println!("{{}}", s1);
let s1 = String::from("info"); let s2 = s1.clone(); println!("{{}}", s1);
Clone to avoid move.
Rust
if [ $x = 23 ]; then
if [ "$x" = 23 ]; then
Quote variable.
Shell
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
local index = 12
local index = 12
Correct.
Lua
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
name: test age: 6
name: test age: 6
Correct.
YAML
function process(): void {{ return 22; }}
function process(): number {{ return 22; }}
Return type mismatch.
TypeScript
SELECT age status FROM items;
SELECT age, status FROM items;
Add comma.
SQL
{{"id":"data" "status":47}}
{{"id":"data", "status":47}}
Add comma.
JSON
with open('data.txt') as fh: data = fh.read()
with open('data.txt') as fh: data = fh.read()
Correct.
Python
else print('data')
else: print('data')
Colon after else.
Python
raise 'test'
raise Exception('test')
Raise needs an exception class.
Python
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
if a = 77 then print('output') end
if a == 77 then print('output') end
Use ==.
Lua
<input type='text' value='info'>
<input type='text' value='info' name='status'>
Add name attribute.
HTML
print('message')
print('message')
Correct.
R
[18, 11, 52
[18, 11, 52]
Close bracket.
Python
p {{ color: green }}
p {{ color: green; }}
Add semicolon.
CSS
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
echo message hello
echo 'message hello'
Quote to prevent splitting.
Shell
def render(): print('message')
def render(): print('message')
Indent function body.
Python
val y = 'message'
val y = "message"
Double quotes.
Kotlin
<?php // code ?>
<?php // code ?>
Correct.
PHP
function render(c:string){{return c;}} render(77);
function render(c:string){{return c;}} render('hello');
Pass correct type.
TypeScript
if (bar = 97) {{}}
if (bar == 97) {{}}
Use ==.
Java
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
fn handle() -> i32 {{ 48 }}
fn handle() -> i32 {{ 48 }}
Correct.
Rust
div {{ color=#333; }}
div {{ color: #333; }}
Use colon.
CSS
<person name='data'/>
<person name="data"/>
Double quotes.
XML
if (foo) console.log('yes') else console.log('no')
if (foo) console.log('yes'); else console.log('no');
Missing semicolon.
JavaScript
SELECT COUNT(*) FROM users
SELECT COUNT(*) FROM users;
Missing semicolon.
SQL
for (y in data)
for (y of data)
for...in iterates keys.
JavaScript
<br></br>
<br>
Self-closing.
HTML
if item > 58 print('info')
if item > 58: print('info')
Colon missing after if.
Python
JOIN profiles ON items.id = profiles.age
JOIN profiles ON items.id = profiles.age
Correct.
SQL
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
let val = 53; val += 1;
let mut val = 53; val += 1;
Need mut to modify.
Rust
'output' + 46
'output' + 46.to_s
Convert int.
Ruby
if (c = 91) {{}}
if (c === 91) {{}}
Use === for equality.
JavaScript
math.sqrt(5)
import math math.sqrt(5)
Import module first.
Python
int data[1]; data[1]=5;
int data[1]; if(1<1){{}} else data[1]=5;
Bounds check.
C++
if (num = 24) {{}}
if (num == 24) {{}}
Use ==.
Kotlin
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
let item: i32 = "test";
let item: &str = "test";
Type mismatch.
Rust
// comment
/* comment */
Use /* */.
CSS
var data int = 'world'
var data string = 'world'
Type mismatch.
Go
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python