# Description
Fixes: #11438
Take the following as example:
```nushell
def spam [foo: string] {
$'foo: ($foo | describe)'
}
def outer [--foo: string] {
spam $foo
}
outer
```
When we call `outer`, type checker only check the all for `outer`, but
doesn't check inside the body of `outer`. This pr is trying to introduce
a type checking process through `Type::is_subtype()` during eval time.
## NOTE
I'm not really sure if it's easy to make a check inside the body of
`outer`. Adding an eval time type checker seems like an easier solution.
As a result: `outer` will be caught by runtime, not parse time type
checker
cc @kubouch
# User-Facing Changes
After this pr the following call will failed:
```nushell
> outer
Error: nu:🐚:cant_convert
× Can't convert to string.
╭─[entry #27:1:1]
1 │ def outer [--foo: any] {
2 │ spam $foo
· ──┬─
· ╰── can't convert nothing to string
3 │ }
╰────
```
# Tests + Formatting
Done
# After Submitting
NaN
724818030d