wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
List(61,93,58)
List(61,93,58)
Correct.
Scala
function foo(): void {{ return 87; }}
function foo(): number {{ return 87; }}
Return type mismatch.
TypeScript
if (result = 20) {{}}
if (result == 20) {{}}
Use ==.
Kotlin
User.save();
User.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
match x {{ 1 => {{}} }}
match x {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
#footer {{ color: green; }}
#footer {{ color: green; }}
Correct.
CSS
<a href='https://test.org' target='_blank'>
<a href='https://test.org' target='_blank' rel='noopener'>
Add rel for security.
HTML
let item = 60;
let item = 60;
Correct.
JavaScript
let foo: number = 'message';
let foo: string = 'message';
Fix type.
TypeScript
class Child Base:
class Child(Base):
Inheritance uses parentheses.
Python
<user><name>result</name><name>86</name></user
<user><name>result</name><name>86</name></user>
Add closing >.
XML
if bar > 3 print('message')
if bar > 3: print('message')
Colon missing after if.
Python
$count = 99; if ($count = 99) {{}}
$count = 99; if ($count == 99) {{}}
Use ==.
PHP
<input type='text' value='info'>
<input type='text' value='info' name='name'>
Add name attribute.
HTML
console.log('info'
console.log('info')
Close parenthesis.
JavaScript
if [ $c = 11 ]; then
if [ "$c" = 11 ]; then
Quote variable.
Shell
fn test() -> i32 {{ 62 }}
fn test() -> i32 {{ 62 }}
Correct.
Rust
data.forEach(function(index) {{ console.log(index); }})
data.forEach((index) => {{ console.log(index); }})
Arrow functions are cleaner.
JavaScript
if (count = 30)
if (count == 30)
Use ==.
Scala
if foo = 68
if foo == 68
Use ==.
Ruby
'test' + 51
'test' + str(51)
Can't add int to string.
Python
switch(index){{ case 56: break; }}
switch(index){{ case 56: break; default: break; }}
Add default case.
Java
val == '48'
val === 48
Use strict equality.
JavaScript
const obj:Person = {{name:'result'}};
const obj:Person = {{name:'result', age:52}};
Add missing property.
TypeScript
let a: Int = 'info'
let a: String = 'info'
Fix type.
Swift
data[57]
if (length(data) >= 57) data[57]
Check length.
R
{{'name':69, 'status' 9}}
{{'name':69, 'status':9}}
Colon missing.
Python
if (item) console.log('yes') else console.log('no')
if (item) console.log('yes'); else console.log('no');
Missing semicolon.
JavaScript
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
print 'hello'
print 'hello';
Add semicolon.
Perl
fmt.Println 'hello'
fmt.Println('hello')
Missing parentheses.
Go
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
let msg = String::from("hello"); let borrow=&msg; msg.push_str("!");
let mut msg = String::from("hello"); let borrow=&msg; println!("{{}}", borrow); msg.push_str("!");
Cannot mutate while borrowed.
Rust
<br></br>
<br>
Self-closing.
HTML
else print('value')
else: print('value')
Colon after else.
Python
.Person {{ color: blue; }}
.Person {{ color: blue; }}
Correct.
CSS
p {{ color: #333 }}
p {{ color: #333; }}
Add semicolon.
CSS
echo test world
echo 'test world'
Quote to prevent splitting.
Shell
if (bar = 37) {}
if (bar == 37) {}
Use ==.
Dart
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
SELECT * FROM products WHRE id=78;
SELECT * FROM products WHERE id=78;
Fix WHERE.
SQL
for i=1,42 do print(i) end
for i=1,42 do print(i) end
Correct.
Lua
if (bar = 100)
if (bar == 100)
Use ==.
C++
WHERE name = '85'
WHERE name = 85
Don't quote integer.
SQL
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
void main() {{ print('result') }}
void main() {{ print('result'); }}
Add semicolon.
Dart
var x int
var x int
Correct.
Go
my @arr = (10,25,12);
my @arr = (10,25,12);
Correct.
Perl
if ($bar = 41) {{}}
if ($bar -eq 41) {{}}
Use -eq.
PowerShell
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
DELETE FROM users WHERE name=36
DELETE FROM users WHERE name=36;
Add semicolon.
SQL
let s1 = String::from("world"); let text2 = s1; println!("{{}}", s1);
let s1 = String::from("world"); let text2 = s1.clone(); println!("{{}}", s1);
Clone to avoid move.
Rust
let result = 'result'
let result = "result"
Double quotes.
Swift
int* p = nullptr; *p=5;
int* p = new int; *p=5;
Allocate memory.
C++
print 'hello'
print('hello')
print needs parentheses.
Python
assert b > 37
assert b > 37
Correct.
Python
let count = 20; let count = 24;
let count = 20; count = 24;
Duplicate declaration.
JavaScript
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
SELECT age email FROM users;
SELECT age, email FROM users;
Add comma.
SQL
<div color=green>
<div style='color:green;'>
Use style attribute.
CSS
b = output
b = 'output'
Quote strings.
Python
$items[52]
if ($items.Count -gt 52) {{ $items[52] }}
Check bounds.
PowerShell
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
UPDATE items SET name='info' WHERE role=2
UPDATE items SET name='info' WHERE role=2;
Add semicolon.
SQL
{{"status":"test" "title":24}}
{{"status":"test", "title":24}}
Add comma.
JSON
{{"status":"output",}}
{{"status":"output"}}
Remove trailing comma.
JSON
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
if ($z = 91) {{}}
if ($z -eq 91) {{}}
Use -eq.
PowerShell
name: info age: 41
name: info age: 41
Correct.
YAML
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
if ($bar = 29)
if ($bar == 29)
Use ==.
Perl
int[] values = new int[21]; values[21] = 5;
int[] values = new int[21]; if (21 < values.length) values[21] = 5;
Check bounds.
Java
def test(c): return c + 1
def test(c): return c + 1
Correct.
Python
<p>info <b>world</p></b>
<p>info <b>world</b></p>
Nest properly.
HTML
print 'hello'
print('hello')
Parentheses for function call.
Lua
h1 {{ font-size:23px color:#333; }}
h1 {{ font-size:23px; color:#333; }}
Add semicolon.
CSS
for b in range(87) print(b)
for b in range(87): print(b)
Colon after for.
Python
int index = 'test';
String index = 'test';
Type mismatch.
Dart
while a > 62 a -= 1
while a > 62: a -= 1
Colon missing after while.
Python
jwt.sign({{id:67}}, 'key');
jwt.sign({{id:67}}, 'key', {{expiresIn:'1h'}});
Add expiration.
Node.js
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
'result' + 1
'result' + str(1)
Can't add int to string.
Python
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
print('test')
print('test')
Correct.
R
list(90)
if length(list) >= 90, list(90), end
Check length.
MATLAB
[x*x for x in values if x > 1]
[x*x for x in values if x > 1]
Correct list comprehension.
Python
data[77]
if data.indices.contains(77) {{ data[77] }}
Check index.
Swift
if [ $data = 60 ]; then
if [ "$data" = 60 ]; then
Quote variable.
Shell
SELECT COUNT(*) FROM users
SELECT COUNT(*) FROM users;
Missing semicolon.
SQL
function render() {{ return {{key:'output'}} }}
function render() {{ return {{key:'output'}}; }}
Return object on same line.
JavaScript
function baz(val) print(val) end
function baz(val) print(val) end
Correct.
Lua
[34, 16, 5
[34, 16, 5]
Close bracket.
Ruby
let result: i32 = "value";
let result: &str = "value";
Type mismatch.
Rust
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
<input type='text' value='result'>
<input type='text' value='result' name='title'>
Add name attribute.
HTML
["data", 62]
["data", 62]
Correct.
JSON
class = 'test'
class_name = 'test'
'class' is a keyword.
Python
for i=1,93 do print(i) end
for i=1,93 do print(i) end
Correct.
Lua
foo = 37
foo=37
No spaces.
Shell