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# Description
Previously, only direcly-recursive calls were checked for recursion
depth. But most recursive calls in nushell are mutually recursive since
expressions like `for`, `where`, `try` and `do` all execute a separte
block.
```nushell
def f [] {
do { f }
}
```
Calling `f` would crash nushell with a stack overflow.
I think the only general way to prevent such a stack overflow is to
enforce a maximum call stack depth instead of only disallowing directly
recursive calls.
This commit also moves that logic into `eval_call()` instead of
`eval_block()` because the recursion limit is tracked in the `Stack`,
but not all blocks are evaluated in a new stack. Incrementing the
recursion depth of the caller's stack would permanently increment that
for all future calls.
Fixes #11667
# User-Facing Changes
Any function call can now fail with `recursion_limit_reached` instead of
just directly recursive calls. Mutually-recursive calls no longer crash
nushell.
# After Submitting
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nu-protocol
The nu-protocol crate holds the definitions of structs/traits that are used throughout Nushell. This gives us one way to expose them to many other crates, as well as make these definitions available to each other, without causing mutually recursive dependencies.