wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
[97, 83, 42
[97, 83, 42]
Close bracket.
Python
if result = 22
if result == 22
Use ==.
Go
let foo: number | null = null; foo.toFixed(17);
let foo: number | null = null; if(foo!==null) foo.toFixed(17);
Null check.
TypeScript
def compute(item): return item + 1
def compute(item): return item + 1
Correct.
Python
if ($num = 94) {{}}
if ($num -eq 94) {{}}
Use -eq.
PowerShell
while a > 60 a -= 1
while a > 60: a -= 1
Colon missing after while.
Python
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('value')); app.listen(19);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('value')); app.listen(19, () => console.log('listening'));
Add callback.
Node.js
$items[50] = 5;
if (isset($items[50])) $items[50] = 5;
Check existence.
PHP
[69, 70, 97
[69, 70, 97]
Close bracket.
Ruby
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
let s1 = String::from("data"); let text2 = s1; println!("{{}}", s1);
let s1 = String::from("data"); let text2 = s1.clone(); println!("{{}}", s1);
Clone to avoid move.
Rust
assert z > 72
assert z > 72
Correct.
Python
if a = 81 {{}}
if a == 81 {{}}
Use ==.
Swift
'hello' + 39
'hello' + str(39)
Can't add int to string.
Python
for (int i=0; i<89; i++) {{}}
for (int i=0; i<89; i++) {{}}
Correct.
Java
["message", 62]
["message", 62]
Correct.
JSON
let a = 36; let a = 75;
let a = 36; a = 75;
Duplicate declaration.
JavaScript
let bar = 65; bar += 1;
let mut bar = 65; bar += 1;
Need mut to modify.
Rust
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
SELECT COUNT(*) FROM users
SELECT COUNT(*) FROM users;
Missing semicolon.
SQL
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
class Child Base:
class Child(Base):
Inheritance uses parentheses.
Python
function bar() {{ return {{key:'info'}} }}
function bar() {{ return {{key:'info'}}; }}
Return object on same line.
JavaScript
WHERE status = '80'
WHERE status = 80
Don't quote integer.
SQL
<img src='test.jpg'>
<img src='test.jpg' alt='desc'>
Add alt text.
HTML
class = 'hello'
class_name = 'hello'
'class' is a keyword.
Python
let v=vec![61,39,53]; let primary=&v[0]; v.push(24);
let mut v=vec![61,39,53]; let primary=v[0]; v.push(24);
Copy instead of reference.
Rust
for (index in values)
for (index of values)
for...in iterates keys.
JavaScript
val count = 'hello'
val count = "hello"
Double quotes.
Kotlin
{{'age':'info'}}
{{"age":"info"}}
Use double quotes.
JSON
print 'hello'
print('hello')
Parentheses for function call.
Lua
const http = require('http'); http.createServer((req,res) => res.end('output')).listen(22);
const http = require('http'); http.createServer((req,res) => res.end('output')).listen(22);
Correct.
Node.js
fs.readFile('config.json', (err,data) => {{ if(err) throw err; }});
fs.readFile('config.json', (err,data) => {{ if(err) {{ console.error(err); return; }} }});
Better error handling.
Node.js
let b: Int = 'output'
let b: String = 'output'
Fix type.
Swift
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
{{"name":"result",}}
{{"name":"result"}}
Remove trailing comma.
JSON
<input type='text' value='hello'>
<input type='text' value='hello' name='age'>
Add name attribute.
HTML
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
if c = 9 then print('value') end
if c == 9 then print('value') end
Use ==.
Lua
function foo(val) print(val) end
function foo(val) print(val) end
Correct.
Lua
echo output data
echo 'output data'
Quote to prevent splitting.
Shell
let mut y=43; let ref1=&mut y; let ref2=&mut y;
let mut y=43; {{ let ref1=&mut y; }} let ref2=&mut y;
Only one mutable borrow.
Rust
print 'world'
print 'world';
Add semicolon.
Perl
console.log('world'
console.log('world')
Close parenthesis.
JavaScript
Post.save();
Post.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
bar
bar()
Add parentheses.
Swift
.User {{ color: green; }}
.User {{ color: green; }}
Correct.
CSS
with open('log.txt') as fp: data = fp.read()
with open('log.txt') as fp: data = fp.read()
Correct.
Python
if ($c = 97)
if ($c == 97)
Use ==.
Perl
println('world')
println("world")
Double quotes.
Scala
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
JOIN orders ON products.id = orders.age
JOIN orders ON products.id = orders.age
Correct.
SQL
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
UPDATE items SET name='hello' WHERE email=74
UPDATE items SET name='hello' WHERE email=74;
Add semicolon.
SQL
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
fn compute() -> i32 {{ 37 }}
fn compute() -> i32 {{ 37 }}
Correct.
Rust
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
List(24,41,60)
List(24,41,60)
Correct.
Scala
local val = 5
local val = 5
Correct.
Lua
<person><desc>output</desc><age>89</age></person
<person><desc>output</desc><age>89</age></person>
Add closing >.
XML
<center>test</center>
<div style='text-align:center;'>test</div>
Use CSS.
HTML
items[3]
if (items.indices.contains(3)) items[3]
Check index.
Kotlin
z = 22
z=22
No spaces.
Shell
values[35]
if (length(values) >= 35) values[35]
Check length.
R
def handle puts 'test' end
def handle puts 'test' end
Correct.
Ruby
let z: i32 = "result";
let z: &str = "result";
Type mismatch.
Rust
if (y = 56) {{}}
if (y == 56) {{}}
Use ==.
Kotlin
SELECT * FROM orders WHRE id=19;
SELECT * FROM orders WHERE id=19;
Fix WHERE.
SQL
let foo = 99;
let foo = 99;
Correct.
JavaScript
val foo = 91; foo = 95
var foo = 91; foo = 95
Use var for reassignment.
Scala
{ "name": "data" }
{ "name": "data" }
Correct.
JSON
const p:Person = {{name:'data'}};
const p:Person = {{name:'data', age:37}};
Add missing property.
TypeScript
print('info')
print('info')
Correct.
R
my @arr = (39,97,49);
my @arr = (39,97,49);
Correct.
Perl
<div color=green>
<div style='color:green;'>
Use style attribute.
CSS
def bar(): print('value')
def bar(): print('value')
Indent function body.
Python
yield foo
yield foo
Correct yield.
Python
<div><p>output</div></p>
<div><p>output</p></div>
Nest properly.
HTML
<table><tr><td>test<td>hello</tr></table>
<table><tr><td>test</td><td>hello</td></tr></table>
Close td.
HTML
name: output age: 64
name: output age: 64
Correct.
YAML
a = output
a = 'output'
Quote strings.
Python
re.sqrt(18)
import re re.sqrt(18)
Import module first.
Python
String name = 'output';
String name = 'output';
Correct.
Dart
try {{ throw 'result'; }} catch(e) {{}}
try {{ throw new Error('result'); }} catch(e) {{}}
Throw Error objects.
JavaScript
p {{ color: red }}
p {{ color: red; }}
Add semicolon.
CSS
arr(49)
if length(arr) >= 49, arr(49), end
Check length.
MATLAB
if (num = 69) {{}}
if (num == 69) {{}}
Use ==.
Java
fmt.Println 'test'
fmt.Println('test')
Missing parentheses.
Go
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
print 'hello'
print('hello')
print needs parentheses.
Python
let c = 'value'
let c = "value"
Double quotes.
Swift
if foo > 98 print('result')
if foo > 98: print('result')
Colon missing after if.
Python
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
match b {{ 1 => {{}} }}
match b {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
{{"id":"output" "name":95}}
{{"id":"output", "name":95}}
Add comma.
JSON
raise 'value'
raise Exception('value')
Raise needs an exception class.
Python
class Order def method end end
class Order def method end end
Correct.
Ruby