When left side is expanded but become invalid, the expansion result in the AST leaking for the user, for example:
```
iex(1)> __ENV__.line.foo
{{:., [line: 1], [1, :foo]}, [line: 1], []}
```
This checks the expanded left to ensure that it's safe
When left side is expanded but become invalid, the expansion result in the AST leaking for the user, for example:
```
iex(1)> __ENV__.line.foo
{{:., [line: 1], [1, :foo]}, [line: 1], []}
```
This checks the expanded left to ensure that it's safe