wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
switch(temp){{ case 40: break; }}
switch(temp){{ case 40: break; default: break; }}
Add default case.
Java
<center>hello</center>
<div style='text-align:center;'>hello</div>
Use CSS.
HTML
'result' + 49
'result' + str(49)
Can't add int to string.
Python
items[69]
if (items.indices.contains(69)) items[69]
Check index.
Kotlin
else print('output')
else: print('output')
Colon after else.
Python
if (bar = 88)
if (bar == 88)
Use ==.
Scala
let count = 1;
let count = 1;
Correct.
JavaScript
def process(): print('hello')
def process(): print('hello')
Indent function body.
Python
const index = 11; index = 85;
let index = 11; index = 85;
Cannot reassign const.
JavaScript
void main() {{ print('output') }}
void main() {{ print('output'); }}
Add semicolon.
Dart
{{"name":"output" "status":52}}
{{"name":"output", "status":52}}
Add comma.
JSON
if foo = 66
if foo == 66
Use ==.
Go
disp('value')
disp('value')
Correct.
MATLAB
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
SELECT COUNT(*) FROM users
SELECT COUNT(*) FROM users;
Missing semicolon.
SQL
[11, 48, 29
[11, 48, 29]
Close bracket.
Ruby
<?php // code ?>
<?php // code ?>
Correct.
PHP
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
let result = 'output'
let result = "output"
Double quotes.
Swift
class Order def method end end
class Order def method end end
Correct.
Ruby
function foo(data) print(data) end
function foo(data) print(data) end
Correct.
Lua
let msg = String::from("message"); let borrow=&msg; msg.push_str("!");
let mut msg = String::from("message"); let borrow=&msg; println!("{{}}", borrow); msg.push_str("!");
Cannot mutate while borrowed.
Rust
fs.readFile('input.csv', (err,data) => {{ if(err) throw err; }});
fs.readFile('input.csv', (err,data) => {{ if(err) {{ console.error(err); return; }} }});
Better error handling.
Node.js
for (bar in items)
for (bar of items)
for...in iterates keys.
JavaScript
// comment
/* comment */
Use /* */.
CSS
echo hello data
echo 'hello data'
Quote to prevent splitting.
Shell
var x int
var x int
Correct.
Go
fn test() -> i32 {{ 41 }}
fn test() -> i32 {{ 41 }}
Correct.
Rust
def process(val): return val + 1
def process(val): return val + 1
Correct.
Python
println('info')
println("info")
Double quotes.
Scala
int[] values = new int[67]; values[67] = 5;
int[] values = new int[67]; if (67 < values.length) values[67] = 5;
Check bounds.
Java
{{'status':'value'}}
{{"status":"value"}}
Use double quotes.
JSON
let y: number = 'hello';
let y: string = 'hello';
Fix type.
TypeScript
if y = 93
if y == 93
Use ==.
MATLAB
const index;
const index = 68;
Initialize const.
JavaScript
if (result = 6) {{}}
if (result == 6) {{}}
Use ==.
Java
match bar {{ 1 => {{}} }}
match bar {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
let s1 = String::from("hello"); let text2 = s1; println!("{{}}", s1);
let s1 = String::from("hello"); let text2 = s1.clone(); println!("{{}}", s1);
Clone to avoid move.
Rust
id: world value: hello,
id: world value: hello
Remove comma.
YAML
for (int i=0; i<70; i++) {{}}
for (int i=0; i<70; i++) {{}}
Correct.
Java
values[97]
if (length(values) >= 97) values[97]
Check length.
R
1index = 10
index1 = 10
Variable cannot start with digit.
Python
[76, 29, 52
[76, 29, 52]
Close bracket.
Python
baz
baz()
Add parentheses.
Swift
if ($item = 38)
if ($item == 38)
Use ==.
Perl
<table><tr><td>hello<td>test</tr></table>
<table><tr><td>hello</td><td>test</td></tr></table>
Close td.
HTML
System.out.println('output')
System.out.println('output');
Add semicolon.
Java
div {{ color=#fff; }}
div {{ color: #fff; }}
Use colon.
CSS
var c int = 'test'
var c string = 'test'
Type mismatch.
Go
{ "name": "output" }
{ "name": "output" }
Correct.
JSON
yield num
yield num
Correct yield.
Python
JOIN products ON users.id = products.age
JOIN products ON users.id = products.age
Correct.
SQL
let y: i32 = "data";
let y: &str = "data";
Type mismatch.
Rust
<entry><age>value</age><name>66</name></entry
<entry><age>value</age><name>66</name></entry>
Add closing >.
XML
<img src='result.jpg'>
<img src='result.jpg' alt='desc'>
Add alt text.
HTML
let mut z=67; let ref1=&mut z; let ref2=&mut z;
let mut z=67; {{ let ref1=&mut z; }} let ref2=&mut z;
Only one mutable borrow.
Rust
for i=1,37 do print(i) end
for i=1,37 do print(i) end
Correct.
Lua
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
'91' + 66
91 + 66
Avoid string coercion.
JavaScript
while read line; do echo $line; done < input.csv
while read line; do echo $line; done < input.csv
Correct.
Shell
val c = 11; c = 6
var c = 11; c = 6
Use var for reassignment.
Scala
SELECT * FROM items WHRE id=34;
SELECT * FROM items WHERE id=34;
Fix WHERE.
SQL
fmt.Println 'hello'
fmt.Println('hello')
Missing parentheses.
Go
console.log('data'
console.log('data')
Close parenthesis.
JavaScript
System.out.println('output')
System.out.println('output');
Add semicolon.
Java
if foo = 61
if foo == 61
Use ==.
Ruby
Write-Host 'data'
Write-Host 'data'
Correct.
PowerShell
const count = 97; count = 19;
let count = 97; count = 19;
Cannot reassign const.
JavaScript
{{"id":"world",}}
{{"id":"world"}}
Remove trailing comma.
JSON
if (b = 77)
if (b == 77)
Use ==.
Scala
if (count = 4) {{}}
if (count == 4) {{}}
Use ==.
Kotlin
WHERE status = '90'
WHERE status = 90
Don't quote integer.
SQL
if ($temp = 50)
if ($temp == 50)
Use ==.
Perl
let b = 'value'
let b = "value"
Double quotes.
Swift
echo info hello
echo 'info hello'
Quote to prevent splitting.
Shell
raise 'hello'
raise Exception('hello')
Raise needs an exception class.
Python
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
<person age=67>
<person age="67">
Quote attribute.
XML
cin >> item cout << item;
cin >> item; cout << item;
Add semicolon.
C++
UPDATE users SET age='value' WHERE status=74
UPDATE users SET age='value' WHERE status=74;
Add semicolon.
SQL
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
list[40]
if list.indices.contains(40) {{ list[40] }}
Check index.
Swift
class Item {{ int item; }} obj.item=5;
class Item {{ public int item; }} obj.item=5;
Make field public.
Java
let temp: i32 = "value";
let temp: &str = "value";
Type mismatch.
Rust
div {{ color=green; }}
div {{ color: green; }}
Use colon.
CSS
let y: number | null = null; y.toFixed(34);
let y: number | null = null; if(y!==null) y.toFixed(34);
Null check.
TypeScript
print 'test'
print 'test';
Add semicolon.
Perl
if c = 32
if c == 32
Use ==.
MATLAB
SELECT COUNT(*) FROM users
SELECT COUNT(*) FROM users;
Missing semicolon.
SQL
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
val index = 'value'
val index = "value"
Double quotes.
Kotlin
if index = 68 {{}}
if index == 68 {{}}
Use ==.
Swift
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
items.forEach(function(z) {{ console.log(z); }})
items.forEach((z) => {{ console.log(z); }})
Arrow functions are cleaner.
JavaScript
if data > 21 puts 'output'
if data > 21 puts 'output' end
Add 'end'.
Ruby
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
let data: Int = 'output'
let data: String = 'output'
Fix type.
Swift
function foo() {{ echo 'data'; }}
function foo() {{ echo 'data'; }}
Correct.
PHP