Fix an analyzer crash with multiple list comprehensions in py3 #447
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The crash was caused by selecting the wrong child symbol table for the list comprehension. Previously we were always selecting the first one in the list of subtables. This is wrong if there is more than 1 list comprehension, since each one gets its own subtable. This is works fine if the list comprehension only uses symbols defined within itself or symbols that are shared between it and the first list comprehension in the enclosing scope, since that will resolve to the same value. The specific error case we are fixing is when there is a list comprehension that is not the first one that references a symbol from the enclosing function scope that the first list comprehension does not reference. Both the symbol tables and the ListComp node are annotated with a line number attribute, by matching these up we can select the correct subtable to go with our list comprehension. This is still naive, but is better than what we had before. fixes aws#412
Codecov Report
@@ Coverage Diff @@
## master #447 +/- ##
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Coverage 93.6% 93.6%
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Files 18 18
Lines 2863 2863
Branches 375 375
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Hits 2680 2680
Misses 132 132
Partials 51 51
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jamesls
approved these changes
Jul 31, 2017
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The crash was caused by selecting the wrong child symbol table for the
list comprehension. Previously we were always selecting the first one in
the list of subtables. This is wrong if there is more than 1 list
comprehension, since each one gets its own subtable. This is works fine
if the list comprehension only uses symbols defined within itself or
symbols that are shared between it and the first list comprehension in
the enclosing scope, since that will resolve to the same value. The
specific error case we are fixing is when there is a list comprehension
that is not the first one that references a symbol from the enclosing
function scope that the first list comprehension does not reference.
Both the symbol tables and the ListComp node are annotated with a line
number attribute, by matching these up we can select the correct
subtable to go with our list comprehension. This is still naive, but is
better than what we had before.
fixes #412
cc @jamesls