Different list comprehension variable will share same place of variable

[Shylock-Hg]

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Describe the bug (required)

return [i in e where i > 1] Union return [i in e where i > 1]

The first list comprehension expression will share variable e in same place, because we don't provide mechanism for inner variable, and put inner variable to global too.
And #4498 change global unique list comprehension variables to be same.

Your Environments (required)

• OS: uname -a
• Compiler: g++ --version or clang++ --version
• CPU: lscpu
• Commit id (e.g. a3ffc7d8)

How To Reproduce(required)

Steps to reproduce the behavior:

1. Step 1
2. Step 2
3. Step 3

Expected behavior

Additional context