wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
.Person {{ color: red; }}
.Person {{ color: red; }}
Correct.
CSS
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
value: test status: test,
value: test status: test
Remove comma.
YAML
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
<center>output</center>
<div style='text-align:center;'>output</div>
Use CSS.
HTML
fmt.Println 'test'
fmt.Println('test')
Missing parentheses.
Go
<input type='text' value='output'>
<input type='text' value='output' name='id'>
Add name attribute.
HTML
if (y = 100)
if (y == 100)
Use ==.
R
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
println('value')
println("value")
Double quotes.
Scala
void bar(); int main(){{bar();}}
void bar(); // prototype int main(){{bar();}}
Declare before use.
C++
#header {{ color: #333; }}
#header {{ color: #333; }}
Correct.
CSS
System.out.println('hello')
System.out.println('hello');
Add semicolon.
Java
disp('world')
disp('world')
Correct.
MATLAB
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
if item = 8
if item == 8
Use ==.
Go
<a href='https://example.com' target='_blank'>
<a href='https://example.com' target='_blank' rel='noopener'>
Add rel for security.
HTML
int[] values = new int[44]; values[44] = 5;
int[] values = new int[44]; if (44 < values.length) values[44] = 5;
Check bounds.
Java
SELECT age email FROM items;
SELECT age, email FROM items;
Add comma.
SQL
int list[38]; list[38]=5;
int list[38]; if(38<38){{}} else list[38]=5;
Bounds check.
C++
JOIN profiles ON items.id = profiles.id
JOIN profiles ON items.id = profiles.id
Correct.
SQL
let x = 6; x += 1;
let mut x = 6; x += 1;
Need mut to modify.
Rust
UPDATE items SET email='info' WHERE email=6
UPDATE items SET email='info' WHERE email=6;
Add semicolon.
SQL
INSERT INTO orders VALUES ('value',65)
INSERT INTO orders (age, role) VALUES ('value',65);
Specify columns.
SQL
while read line; do echo $line; done < config.json
while read line; do echo $line; done < config.json
Correct.
Shell
var x = 79;
var x = 79;
Correct.
Dart
<p>info <b>data</p></b>
<p>info <b>data</b></p>
Nest properly.
HTML
raise 'world'
raise Exception('world')
Raise needs an exception class.
Python
let index = 'message'
let index = "message"
Double quotes.
Swift
for (int i=0; i<69; i++) {{}}
for (int i=0; i<69; i++) {{}}
Correct.
Java
Write-Host 'message'
Write-Host 'message'
Correct.
PowerShell
{ "name": "data" }
{ "name": "data" }
Correct.
JSON
let data: number = 'value';
let data: string = 'value';
Fix type.
TypeScript
yield a
yield a
Correct yield.
Python
'message' + 79
'message' + 79.to_s
Convert int.
Ruby
print('data')
print('data')
Correct.
R
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
int item = 'test';
String item = 'test';
Type mismatch.
Dart
for (num in list)
for (num of list)
for...in iterates keys.
JavaScript
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
let y = 54; let y = 10;
let y = 54; y = 10;
Duplicate declaration.
JavaScript
var x int
var x int
Correct.
Go
[74, 8, 74
[74, 8, 74]
Close bracket.
Python
'86' + 74
86 + 74
Avoid string coercion.
JavaScript
'result' + 83
'result' + str(83)
Can't add int to string.
Python
function test(bar:string){{return bar;}} test(71);
function test(bar:string){{return bar;}} test('data');
Pass correct type.
TypeScript
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
class Person {{ int bar; }};
class Person {{ public: int bar; }};
Make public.
C++
function compute() {{ return {{key:'result'}} }}
function compute() {{ return {{key:'result'}}; }}
Return object on same line.
JavaScript
if (z = 62) {{}}
if (z === 62) {{}}
Use === for equality.
JavaScript
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
p {{ color: green }}
p {{ color: green; }}
Add semicolon.
CSS
if item = 97 then print('message') end
if item == 97 then print('message') end
Use ==.
Lua
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
data[24]
if (data.indices.contains(24)) data[24]
Check index.
Kotlin
data[38]
if (length(data) >= 38) data[38]
Check length.
R
DELETE FROM items WHERE status=93
DELETE FROM items WHERE status=93;
Add semicolon.
SQL
// comment
/* comment */
Use /* */.
CSS
class Order {{ int item; }} obj.item=5;
class Order {{ public int item; }} obj.item=5;
Make field public.
Java
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
for b in range(44) print(b)
for b in range(44): print(b)
Colon after for.
Python
var b int = 'hello'
var b string = 'hello'
Type mismatch.
Go
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
{{'status':11, 'value' 89}}
{{'status':11, 'value':89}}
Colon missing.
Python
if result = 32 {{}}
if result == 32 {{}}
Use ==.
Swift
let x: number | null = null; x.toFixed(33);
let x: number | null = null; if(x!==null) x.toFixed(33);
Null check.
TypeScript
if bar = 61:
if bar == 61:
Use == for comparison.
Python
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
else print('data')
else: print('data')
Colon after else.
Python
let index = 'output'
let index = "output"
Double quotes.
Swift
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
function process(result:string){{return result;}} process(30);
function process(result:string){{return result;}} process('message');
Pass correct type.
TypeScript
[82, 60, 96
[82, 60, 96]
Close bracket.
Python
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
class Person {{ int result; }} obj.result=5;
class Person {{ public int result; }} obj.result=5;
Make field public.
Java
y > 88 & a < 72
y > 88 and a < 72
Use 'and' not '&'.
Python
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
if (c = 8)
if (c == 8)
Use ==.
Scala
class User {{ int index; }};
class User {{ public: int index; }};
Make public.
C++
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
$arr[27]
if ($arr.Count -gt 27) {{ $arr[27] }}
Check bounds.
PowerShell
if num > 1 print('output')
if num > 1: print('output')
Colon missing after if.
Python
// comment
/* comment */
Use /* */.
CSS
SELECT COUNT(*) FROM users
SELECT COUNT(*) FROM users;
Missing semicolon.
SQL
let msg = String::from("world"); let ref=&msg; msg.push_str("!");
let mut msg = String::from("world"); let ref=&msg; println!("{{}}", ref); msg.push_str("!");
Cannot mutate while borrowed.
Rust
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
while read line; do echo $line; done < input.csv
while read line; do echo $line; done < input.csv
Correct.
Shell
cin >> c;
int c; cin >> c;
Declare variable.
C++
<center>result</center>
<div style='text-align:center;'>result</div>
Use CSS.
HTML
x := 82
x := 82
Correct.
Go
object Person {{ def main(args: Array[String]) = println("world") }}
object Person {{ def main(args: Array[String]): Unit = println("world") }}
Add return type Unit.
Scala
raise 'message'
raise Exception('message')
Raise needs an exception class.
Python
fn foo() -> i32 {{ 82 }}
fn foo() -> i32 {{ 82 }}
Correct.
Rust
'data' + 49
'data' + 49.to_s
Convert int.
Ruby
if (c = 53)
if (c == 53)
Use ==.
R
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
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
let x = 77;
let x = 77;
Correct.
JavaScript
while num > 46 num -= 1
while num > 46: num -= 1
Colon missing after while.
Python
p {{ color: blue }}
p {{ color: blue; }}
Add semicolon.
CSS