Python (pruning): Refactor a bit and all comments for clarity.

markshannon · markshannon · commit a3d50e88cdba · 2019-06-13T17:42:53.000+01:00
diff --git a/python/ql/src/semmle/python/Exprs.qll b/python/ql/src/semmle/python/Exprs.qll
@@ -466,9 +466,9 @@ class NegativeIntegerLiteral extends ImmutableLiteral, UnaryExpr {
     }
 
     override Object getLiteralObject() {
-        py_cobjecttypes(result, theIntType()) and py_cobjectnames(result, "-" + this.getOperand().(IntegerLiteral).getN())
-        or
-        py_cobjecttypes(result, theLongType()) and py_cobjectnames(result, "-" + this.getOperand().(IntegerLiteral).getN())
+        (py_cobjecttypes(result, theIntType()) or  py_cobjecttypes(result, theLongType()))
+        and
+        py_cobjectnames(result, "-" + this.getOperand().(IntegerLiteral).getN())
     }
 
 }
diff --git a/python/ql/src/semmle/python/Pruning.qll b/python/ql/src/semmle/python/Pruning.qll
@@ -190,7 +190,7 @@ module Pruner {
          * same variable.
          * For example `x > 0` implies that `not bool(x)` is `False`.
          */
-        abstract predicate impliesFalse(Constraint other);
+        abstract predicate contradicts(Constraint other);
 
     }
 
@@ -279,13 +279,14 @@ module Pruner {
             value = this.booleanValue()
         }
 
-        override predicate impliesFalse(Constraint other) {
+        override predicate contradicts(Constraint other) {
             other.constrainsVariableToBe(this.booleanValue().booleanNot())
         }
 
     }
 
-    /** A constraint that the variable is None `(var is None) is True` or not None `(var is None) is False` */
+    /** A constraint that the variable is None `(var is None) is True` or not None `(var is None) is False`.
+     * This includes the `is not` operator, `x is not None` being equivalent to `not x is None` */
     class IsNone extends Constraint, TIsNone {
 
         private boolean isNone() {
@@ -306,7 +307,7 @@ module Pruner {
             value = false and this.isNone() = true
         }
 
-        override predicate impliesFalse(Constraint other) {
+        override predicate contradicts(Constraint other) {
             other = TIsNone(this.isNone().booleanNot())
             or
             this.isNone() = true and other = TTruthy(true)
@@ -351,7 +352,7 @@ module Pruner {
             )
         }
 
-        override predicate impliesFalse(Constraint other) {
+        override predicate contradicts(Constraint other) {
             exists(boolean b |
                 this.constrainsVariableToBe(b) and other.constrainsVariableToBe(b.booleanNot())
             )
@@ -481,7 +482,7 @@ module Pruner {
         module_import(asgn, var) and result = true
     }
 
-    /** Gets the constraint on `var` resulting from the an assignment in `asgn` */
+    /** Gets the constraint on `var` resulting from the assignment in `asgn` */
     Constraint constraintFromAssignment(SsaVariable var, UnprunedBasicBlock asgn) {
         exists(CompareOp op, int k |
             int_assignment(asgn.getANode(), var, op, k) and
@@ -536,7 +537,7 @@ module Pruner {
     predicate unreachableEdge(UnprunedBasicBlock pred, UnprunedBasicBlock succ) {
         exists(Constraint pre, Constraint cond |
             controllingConditions(pred, succ, pre, cond) and
-            impliesFalse(pre, cond)
+            contradicts(pre, cond)
         )
         or
         unreachableBB(pred) and succ = pred.getASuccessor()
@@ -545,8 +546,8 @@ module Pruner {
     }
 
     /* Helper for `unreachableEdge` */
-    private predicate impliesFalse(Constraint a, Constraint b) {
-        a.impliesFalse(b) or
+    private predicate contradicts(Constraint a, Constraint b) {
+        a.contradicts(b) or
         a.(ConstrainedByConstant).minValue() > b.(ConstrainedByConstant).maxValue() or
         a.(ConstrainedByConstant).maxValue() < b.(ConstrainedByConstant).minValue()
     }

Original file line number	Diff line number	Diff line change
`@@ -466,9 +466,9 @@ class NegativeIntegerLiteral extends ImmutableLiteral, UnaryExpr {`
`466`	`466`	`}`
`467`	`467`
`468`	`468`	`override Object getLiteralObject() {`
`469`		`- py_cobjecttypes(result, theIntType()) and py_cobjectnames(result, "-" + this.getOperand().(IntegerLiteral).getN())`
`470`		`- or`
`471`		`- py_cobjecttypes(result, theLongType()) and py_cobjectnames(result, "-" + this.getOperand().(IntegerLiteral).getN())`
	`469`	`+ (py_cobjecttypes(result, theIntType()) or py_cobjecttypes(result, theLongType()))`
	`470`	`+ and`
	`471`	`+ py_cobjectnames(result, "-" + this.getOperand().(IntegerLiteral).getN())`
`472`	`472`	`}`
`473`	`473`
`474`	`474`	`}`
Original file line number	Diff line number	Diff line change
`@@ -190,7 +190,7 @@ module Pruner {`
`190`	`190`	`* same variable.`
`191`	`191`	* For example `x > 0` implies that `not bool(x)` is `False`.
`192`	`192`	`*/`
`193`		`- abstract predicate impliesFalse(Constraint other);`
	`193`	`+ abstract predicate contradicts(Constraint other);`
`194`	`194`
`195`	`195`	`}`
`196`	`196`
`@@ -279,13 +279,14 @@ module Pruner {`
`279`	`279`	`value = this.booleanValue()`
`280`	`280`	`}`
`281`	`281`
`282`		`- override predicate impliesFalse(Constraint other) {`
	`282`	`+ override predicate contradicts(Constraint other) {`
`283`	`283`	`other.constrainsVariableToBe(this.booleanValue().booleanNot())`
`284`	`284`	`}`
`285`	`285`
`286`	`286`	`}`
`287`	`287`
`288`		- /** A constraint that the variable is None `(var is None) is True` or not None `(var is None) is False` */
	`288`	+ /** A constraint that the variable is None `(var is None) is True` or not None `(var is None) is False`.
	`289`	+ * This includes the `is not` operator, `x is not None` being equivalent to `not x is None` */
`289`	`290`	`class IsNone extends Constraint, TIsNone {`
`290`	`291`
`291`	`292`	`private boolean isNone() {`
`@@ -306,7 +307,7 @@ module Pruner {`
`306`	`307`	`value = false and this.isNone() = true`
`307`	`308`	`}`
`308`	`309`
`309`		`- override predicate impliesFalse(Constraint other) {`
	`310`	`+ override predicate contradicts(Constraint other) {`
`310`	`311`	`other = TIsNone(this.isNone().booleanNot())`
`311`	`312`	`or`
`312`	`313`	`this.isNone() = true and other = TTruthy(true)`
`@@ -351,7 +352,7 @@ module Pruner {`
`351`	`352`	`)`
`352`	`353`	`}`
`353`	`354`
`354`		`- override predicate impliesFalse(Constraint other) {`
	`355`	`+ override predicate contradicts(Constraint other) {`
`355`	`356`	`exists(boolean b \|`
`356`	`357`	`this.constrainsVariableToBe(b) and other.constrainsVariableToBe(b.booleanNot())`
`357`	`358`	`)`
`@@ -481,7 +482,7 @@ module Pruner {`
`481`	`482`	`module_import(asgn, var) and result = true`
`482`	`483`	`}`
`483`	`484`
`484`		- /** Gets the constraint on `var` resulting from the an assignment in `asgn` */
	`485`	+ /** Gets the constraint on `var` resulting from the assignment in `asgn` */
`485`	`486`	`Constraint constraintFromAssignment(SsaVariable var, UnprunedBasicBlock asgn) {`
`486`	`487`	`exists(CompareOp op, int k \|`
`487`	`488`	`int_assignment(asgn.getANode(), var, op, k) and`
`@@ -536,7 +537,7 @@ module Pruner {`
`536`	`537`	`predicate unreachableEdge(UnprunedBasicBlock pred, UnprunedBasicBlock succ) {`
`537`	`538`	`exists(Constraint pre, Constraint cond \|`
`538`	`539`	`controllingConditions(pred, succ, pre, cond) and`
`539`		`- impliesFalse(pre, cond)`
	`540`	`+ contradicts(pre, cond)`
`540`	`541`	`)`
`541`	`542`	`or`
`542`	`543`	`unreachableBB(pred) and succ = pred.getASuccessor()`
`@@ -545,8 +546,8 @@ module Pruner {`
`545`	`546`	`}`
`546`	`547`
`547`	`548`	/* Helper for `unreachableEdge` */
`548`		`- private predicate impliesFalse(Constraint a, Constraint b) {`
`549`		`- a.impliesFalse(b) or`
	`549`	`+ private predicate contradicts(Constraint a, Constraint b) {`
	`550`	`+ a.contradicts(b) or`
`550`	`551`	`a.(ConstrainedByConstant).minValue() > b.(ConstrainedByConstant).maxValue() or`
`551`	`552`	`a.(ConstrainedByConstant).maxValue() < b.(ConstrainedByConstant).minValue()`
`552`	`553`	`}`