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Python: Fix logic in pruning for tests like 'x != 0' as that does not imply that 'x is None' is false.

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This commit is contained in:
Mark Shannon
2019-06-13 17:26:43 +01:00
parent f975b8b87d
commit e1fb1d27a1
1 changed files with 2 additions and 4 deletions
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6
python/ql/src/semmle/python/Pruning.qll
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@@ -181,7 +181,7 @@ module Pruner {
abstract Constraint invert();
/** Holds if this constraint constrains the "truthiness" of the variable.
* That is, for a variable `var` constrainted by this constraint
* That is, for a variable `var` constrained by this constraint
* `bool(var) is value`
*/
abstract predicate constrainsVariableToBe(boolean value);
@@ -341,8 +341,6 @@ module Pruner {
value = true and (
this.getOp() = eq() and this.intValue() != 0
or
this.getOp() = ne() and this.intValue() = 0
or
this.getOp() = lt() and this.intValue() <= 0
or
this.getOp() = le() and this.intValue() < 0
@@ -355,7 +353,7 @@ module Pruner {
override predicate impliesFalse(Constraint other) {
exists(boolean b |
this.constrainsVariableToBe(b) and other = TTruthy(b.booleanNot())
this.constrainsVariableToBe(b) and other.constrainsVariableToBe(b.booleanNot())
)
or
this.getOp() = eq() and other = TIsNone(true)