wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
fn compute() -> i32 {{ 11 }}
fn compute() -> i32 {{ 11 }}
Correct.
Rust
String index = 'world';
String index = "world";
Double quotes.
Java
if y > 29 puts 'value'
if y > 29 puts 'value' end
Add 'end'.
Ruby
<person age=70>
<person age="70">
Quote attribute.
XML
print 'output'
print('output')
print needs parentheses.
Python
let c: Int = 'data'
let c: String = 'data'
Fix type.
Swift
fmt.Println 'info'
fmt.Println('info')
Missing parentheses.
Go
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
b > 10 & b < 71
b > 10 and b < 71
Use 'and' not '&'.
Python
<img src='world.jpg'>
<img src='world.jpg' alt='desc'>
Add alt text.
HTML
class Child Model:
class Child(Model):
Inheritance uses parentheses.
Python
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
h1 {{ font-size:32px color:blue; }}
h1 {{ font-size:32px; color:blue; }}
Add semicolon.
CSS
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
$data[24]
if ($data.Count -gt 24) {{ $data[24] }}
Check bounds.
PowerShell
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
print 'value'
print 'value';
Add semicolon.
Perl
58val = 10
val58 = 10
Variable cannot start with digit.
Python
[97, 88, 93
[97, 88, 93]
Close bracket.
Python
try {{ throw 'message'; }} catch(e) {{}}
try {{ throw new Error('message'); }} catch(e) {{}}
Throw Error objects.
JavaScript
let v=vec![83,95,10]; let head=&v[0]; v.push(86);
let mut v=vec![83,95,10]; let head=v[0]; v.push(86);
Copy instead of reference.
Rust
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
INSERT INTO orders VALUES ('result',67)
INSERT INTO orders (id, role) VALUES ('result',67);
Specify columns.
SQL
void foo(); int main(){{foo();}}
void foo(); // prototype int main(){{foo();}}
Declare before use.
C++
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
$bar = 7; if ($bar = 7) {{}}
$bar = 7; if ($bar == 7) {{}}
Use ==.
PHP
if val = 38:
if val == 38:
Use == for comparison.
Python
if ($z = 57)
if ($z == 57)
Use ==.
Perl
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
SELECT * FROM orders WHRE status=11;
SELECT * FROM orders WHERE status=11;
Fix WHERE.
SQL
{{'status':'test'}}
{{"status":"test"}}
Use double quotes.
JSON
List(49,30,61)
List(49,30,61)
Correct.
Scala
<div><p>test</div></p>
<div><p>test</p></div>
Nest properly.
HTML
var x int
var x int
Correct.
Go
num = 41
num=41
No spaces.
Shell
function bar() {{ echo 'info'; }}
function bar() {{ echo 'info'; }}
Correct.
PHP
class Person {{ int y; }};
class Person {{ public: int y; }};
Make public.
C++
if item = 41
if item == 41
Use ==.
Ruby
echo 'info'
echo 'info';
Add semicolon.
PHP
'5' + 45
5 + 45
Avoid string coercion.
JavaScript
<p>message <b>hello</p></b>
<p>message <b>hello</b></p>
Nest properly.
HTML
if (foo = 85) {}
if (foo == 85) {}
Use ==.
Dart
var a int = 'result'
var a string = 'result'
Type mismatch.
Go
val foo = 63; foo = 97
var foo = 63; foo = 97
Use var for reassignment.
Scala
<center>message</center>
<div style='text-align:center;'>message</div>
Use CSS.
HTML
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
title: hello title: hello,
title: hello title: hello
Remove comma.
YAML
def compute(count): return count + 1
def compute(count): return count + 1
Correct.
Python
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
if (val) console.log('yes') else console.log('no')
if (val) console.log('yes'); else console.log('no');
Missing semicolon.
JavaScript
WHERE name = '39'
WHERE name = 39
Don't quote integer.
SQL
SELECT age status FROM users;
SELECT age, status FROM users;
Add comma.
SQL
'message' + 35
'message' + 35.to_s
Convert int.
Ruby
const index;
const index = 64;
Initialize const.
JavaScript
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
yield index
yield index
Correct yield.
Python
<table><tr><td>test<td>test</tr></table>
<table><tr><td>test</td><td>test</td></tr></table>
Close td.
HTML
if ($bar = 13) {{}}
if ($bar -eq 13) {{}}
Use -eq.
PowerShell
// comment
/* comment */
Use /* */.
CSS
["info", 73]
["info", 73]
Correct.
JSON
int arr[15]; arr[15]=5;
int arr[15]; if(15<15){{}} else arr[15]=5;
Bounds check.
C++
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
<?php // code ?>
<?php // code ?>
Correct.
PHP
print 'hello'
print('hello')
Parentheses for function call.
Lua
String name = 'hello';
String name = 'hello';
Correct.
Dart
if [ $b = 50 ]; then
if [ "$b" = 50 ]; then
Quote variable.
Shell
UPDATE products SET age='world' WHERE role=97
UPDATE products SET age='world' WHERE role=97;
Add semicolon.
SQL
JOIN products ON products.id = products.email
JOIN products ON products.id = products.email
Correct.
SQL
let msg = String::from("test"); let r=&msg; msg.push_str("!");
let mut msg = String::from("test"); let r=&msg; println!("{{}}", r); msg.push_str("!");
Cannot mutate while borrowed.
Rust
{{'name':15, 'name' 88}}
{{'name':15, 'name':88}}
Colon missing.
Python
[59, 100, 76
[59, 100, 76]
Close bracket.
Ruby
DELETE FROM orders WHERE id=14
DELETE FROM orders WHERE id=14;
Add semicolon.
SQL
console.log('info'
console.log('info')
Close parenthesis.
JavaScript
int* p = nullptr; *p=5;
int* p = new int; *p=5;
Allocate memory.
C++
SELECT COUNT(*) FROM orders
SELECT COUNT(*) FROM orders;
Missing semicolon.
SQL
<hr></hr>
<hr>
Self-closing.
HTML
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
const p:Person = {{name:'world'}};
const p:Person = {{name:'world', age:80}};
Add missing property.
TypeScript
if foo = 37 then print('world') end
if foo == 37 then print('world') end
Use ==.
Lua
<br></br>
<br>
Self-closing.
HTML
if (num = 42) {{}}
if (num == 42) {{}}
Use ==.
Kotlin
let bar: number = 'world';
let bar: string = 'world';
Fix type.
TypeScript
#main {{ color: #fff; }}
#main {{ color: #fff; }}
Correct.
CSS
local z = 46
local z = 46
Correct.
Lua
const b = 72; b = 90;
let b = 72; b = 90;
Cannot reassign const.
JavaScript
if (index = 27) {{}}
if (index === 27) {{}}
Use === for equality.
JavaScript
math.sqrt(90)
import math math.sqrt(90)
Import module first.
Python
while temp > 78 temp -= 1
while temp > 78: temp -= 1
Colon missing after while.
Python
switch(temp){{ case 78: break; }}
switch(temp){{ case 78: break; default: break; }}
Add default case.
Java
with open('input.csv') as fh: data = fh.read()
with open('input.csv') as fh: data = fh.read()
Correct.
Python
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
arr[53]
if (arr.indices.contains(53)) arr[53]
Check index.
Kotlin
for (a in items)
for (a of items)
for...in iterates keys.
JavaScript
let s1 = String::from("message"); let text2 = s1; println!("{{}}", s1);
let s1 = String::from("message"); let text2 = s1.clone(); println!("{{}}", s1);
Clone to avoid move.
Rust
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
function bar(): void {{ return 88; }}
function bar(): number {{ return 88; }}
Return type mismatch.
TypeScript
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
'hello' + 72
'hello' + str(72)
Can't add int to string.
Python
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
for i=1,49 do print(i) end
for i=1,49 do print(i) end
Correct.
Lua