wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
<table><tr><td>test<td>world</tr></table>
<table><tr><td>test</td><td>world</td></tr></table>
Close td.
HTML
$values[8] = 5;
if (isset($values[8])) $values[8] = 5;
Check existence.
PHP
const person:Person = {{name:'world'}};
const person:Person = {{name:'world', age:85}};
Add missing property.
TypeScript
<p>world <b>hello</p></b>
<p>world <b>hello</b></p>
Nest properly.
HTML
int* user = nullptr; *user=5;
int* user = new int; *user=5;
Allocate memory.
C++
my @arr = (26,18,16);
my @arr = (26,18,16);
Correct.
Perl
class = 'value'
class_name = 'value'
'class' is a keyword.
Python
{{"value":"value" "age":99}}
{{"value":"value", "age":99}}
Add comma.
JSON
if (y = 3) {{}}
if (y === 3) {{}}
Use === for equality.
JavaScript
if ($z = 85)
if ($z == 85)
Use ==.
Perl
div {{ color=red; }}
div {{ color: red; }}
Use colon.
CSS
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
// comment
/* comment */
Use /* */.
CSS
int list[82]; list[82]=5;
int list[82]; if(82<82){{}} else list[82]=5;
Bounds check.
C++
{{'title':1, 'age' 89}}
{{'title':1, 'age':89}}
Colon missing.
Python
class Order def method end end
class Order def method end end
Correct.
Ruby
if foo = 25:
if foo == 25:
Use == for comparison.
Python
for z in range(27) print(z)
for z in range(27): print(z)
Colon after for.
Python
var x int
var x int
Correct.
Go
let v=vec![69,1,38]; let head=&v[0]; v.push(51);
let mut v=vec![69,1,38]; let head=v[0]; v.push(51);
Copy instead of reference.
Rust
function handle(x) print(x) end
function handle(x) print(x) end
Correct.
Lua
Product.save();
Product.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
if (temp = 15)
if (temp == 15)
Use ==.
Scala
if [ $y = 73 ]; then
if [ "$y" = 73 ]; then
Quote variable.
Shell
{{'age':28, 'value' 2}}
{{'age':28, 'value':2}}
Colon missing.
Python
function process() {{ return {{key:'info'}} }}
function process() {{ return {{key:'info'}}; }}
Return object on same line.
JavaScript
jwt.sign({{id:36}}, 'token');
jwt.sign({{id:36}}, 'token', {{expiresIn:'2h'}});
Add expiration.
Node.js
'test' + 40
'test' + 40.to_s
Convert int.
Ruby
let index = 'message'
let index = "message"
Double quotes.
Swift
function bar(): void {{ return 54; }}
function bar(): number {{ return 54; }}
Return type mismatch.
TypeScript
const obj:Person = {{name:'message'}};
const obj:Person = {{name:'message', age:38}};
Add missing property.
TypeScript
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
b == '92'
b === 92
Use strict equality.
JavaScript
<a href='https://example.com' target='_blank'>
<a href='https://example.com' target='_blank' rel='noopener'>
Add rel for security.
HTML
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
arr[39]
if (length(arr) >= 39) arr[39]
Check length.
R
for i=1,21 do print(i) end
for i=1,21 do print(i) end
Correct.
Lua
switch(temp){{ case 66: break; }}
switch(temp){{ case 66: break; default: break; }}
Add default case.
Java
val foo = 12; foo = 11
var foo = 12; foo = 11
Use var for reassignment.
Scala
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
print 'hello'
print('hello')
Parentheses for function call.
Lua
[38, 21, 76
[38, 21, 76]
Close bracket.
Python
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
<ul><li>test<li>data</ul>
<ul><li>test</li><li>data</li></ul>
Close li.
HTML
if ($data = 17)
if ($data == 17)
Use ==.
Perl
Write-Host 'data'
Write-Host 'data'
Correct.
PowerShell
if (item = 41)
if (item == 41)
Use ==.
C++
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
while read line; do echo $line; done < input.csv
while read line; do echo $line; done < input.csv
Correct.
Shell
try {{ throw 'data'; }} catch(e) {{}}
try {{ throw new Error('data'); }} catch(e) {{}}
Throw Error objects.
JavaScript
26temp = 10
temp26 = 10
Variable cannot start with digit.
Python
<p>result <b>world</p></b>
<p>result <b>world</b></p>
Nest properly.
HTML
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
<br></br>
<br>
Self-closing.
HTML
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
bar
bar()
Add parentheses.
Kotlin
if index > 8 puts 'value'
if index > 8 puts 'value' end
Add 'end'.
Ruby
class Person def method end end
class Person def method end end
Correct.
Ruby
print('output')
print('output')
Correct.
R
if index = 84 then print('message') end
if index == 84 then print('message') end
Use ==.
Lua
// comment
/* comment */
Use /* */.
CSS
<person age=90>
<person age="90">
Quote attribute.
XML
const x;
const x = 15;
Initialize const.
JavaScript
while z > 58 z -= 1
while z > 58: z -= 1
Colon missing after while.
Python
if (a = 4)
if (a == 4)
Use ==.
R
let y: number | null = null; y.toFixed(39);
let y: number | null = null; if(y!==null) y.toFixed(39);
Null check.
TypeScript
'39' + 54
39 + 54
Avoid string coercion.
JavaScript
UPDATE users SET id='world' WHERE email=57
UPDATE users SET id='world' WHERE email=57;
Add semicolon.
SQL
int values[77]; values[77]=5;
int values[77]; if(77<77){{}} else values[77]=5;
Bounds check.
C++
<note><desc>info</desc><desc>35</desc></note
<note><desc>info</desc><desc>35</desc></note>
Add closing >.
XML
class = 'world'
class_name = 'world'
'class' is a keyword.
Python
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
INSERT INTO products VALUES ('output',55)
INSERT INTO products (age, email) VALUES ('output',55);
Specify columns.
SQL
local count = 41
local count = 41
Correct.
Lua
int b = 'world';
String b = 'world';
Type mismatch.
Dart
JOIN orders ON orders.id = orders.age
JOIN orders ON orders.id = orders.age
Correct.
SQL
yield result
yield result
Correct yield.
Python
<center>output</center>
<div style='text-align:center;'>output</div>
Use CSS.
HTML
fn handle() -> i32 {{ 19 }}
fn handle() -> i32 {{ 19 }}
Correct.
Rust
<div color=red>
<div style='color:red;'>
Use style attribute.
CSS
my @arr = (43,22,20);
my @arr = (43,22,20);
Correct.
Perl
{{"age":"result",}}
{{"age":"result"}}
Remove trailing comma.
JSON
const index = 80; index = 64;
let index = 80; index = 64;
Cannot reassign const.
JavaScript
<input type='text' value='test'>
<input type='text' value='test' name='status'>
Add name attribute.
HTML
let mut result=63; let r1=&mut result; let ref2=&mut result;
let mut result=63; {{ let r1=&mut result; }} let ref2=&mut result;
Only one mutable borrow.
Rust
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
function foo(count:string){{return count;}} foo(3);
function foo(count:string){{return count;}} foo('info');
Pass correct type.
TypeScript
<user name='world'/>
<user name="world"/>
Double quotes.
XML
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
def test(foo): return foo + 1
def test(foo): return foo + 1
Correct.
Python
{{'value':'hello'}}
{{"value":"hello"}}
Use double quotes.
JSON
$items[16] = 5;
if (isset($items[16])) $items[16] = 5;
Check existence.
PHP
if result = 15
if result == 15
Use ==.
MATLAB
items[42]
if items.indices.contains(42) {{ items[42] }}
Check index.
Swift
[x*x for x in items if x > 22]
[x*x for x in items if x > 22]
Correct list comprehension.
Python
let b: number = 'test';
let b: string = 'test';
Fix type.
TypeScript
assert bar > 80
assert bar > 80
Correct.
Python
<hr></hr>
<hr>
Self-closing.
HTML
.Order {{ color: blue; }}
.Order {{ color: blue; }}
Correct.
CSS
$list[25]
if ($list.Count -gt 25) {{ $list[25] }}
Check bounds.
PowerShell