# Description
Fixes: #10450
This pr differentiating between `--x: bool` and `--x`
Here are examples which demostrate difference between them:
```nushell
def a [--x: bool] { $x };
a --x # not allowed, you need to parse a value to the flag.
a # it's allowed, and the value of `$x` is false, which behaves the same to `def a [--x] { $x }; a`
```
For boolean flag with default value, it works a little bit different to
#10450 mentioned:
```nushell
def foo [--option: bool = false] { $option }
foo # output false
foo --option # not allowed, you need to parse a value to the flag.
foo --option true # output true
```
# User-Facing Changes
After the pr, the following code is not allowed:
```nushell
def a [--x: bool] { $x }; a --x
```
Instead, you have to pass a value to flag `--x` like `a --x false`. But
bare flag works in the same way as before.
## Update: one more breaking change to help on #7260
```
def foo [--option: bool] { $option == null }
foo
```
After the pr, if we don't use a boolean flag, the value will be `null`
instead of `true`. Because here `--option: bool` is treated as a flag
rather than a switch
---------
Co-authored-by: amtoine <stevan.antoine@gmail.com>
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