Open two file with nest "with" statement causes a core dumped

[xiaxinmeng]

In a input stream of a file 'fill-in', we open the second file 'fileout', codon crashes.

test.py:

with open('filein') as input:
    with open('fileout') as input:
        pass

Reproduce: codon/codon-linux-x86_64/codon-deploy/bin/codon' run -release test.py

Crash message:

IOError: file filein could not be opened

Raised from: std.internal.file.File.__init__:2
codon/codon-linux-x86_64/codon-deploy/lib/codon/stdlib/internal/file.codon:17:13

Backtrace:
  [0x7ff88b9daaac] GCC_except_table58 at codon/codon-linux-x86_64/codon-deploy/lib/codon/stdlib/internal/file.codon:17:13
  [0x7ff88b9dab2b] GCC_except_table58 at codon/codon-linux-x86_64/codon-deploy/lib/codon/stdlib/internal/file.codon:238:23
  [0x7ff88b9df003] GCC_except_table58 at test.py:237:33
Aborted (core dumped)

Environment: codon: v0.15.5 on Feb 6 Ubuntu 18.04

[elisbyberi]

@xiaxinmeng If the "filein" and/or "fileout" file is missing, it will result in an error, which is the expected behavior. Furthermore, it appears that both files are being opened with the same name, "input".