Guards: Refactor EqualityTest interface.

java/ql/lib/semmle/code/java/controlflow/Guards.qll

@@ -294,27 +294,23 @@ private module GuardsInput implements SharedGuards::InputSig<Location> {
     equals.getNumberOfParameters() = 2
   }
 
-  class EqualityTest extends Expr {
-    EqualityTest() {
-      this instanceof J::EqualityTest or
-      this.(MethodCall).getMethod() instanceof EqualsMethod or
-      objectsEquals(this.(MethodCall).getMethod())
-    }
-
-    Expr getAnOperand() {
-      result = this.(J::EqualityTest).getAnOperand()
-      or
-      result = this.(MethodCall).getAnArgument()
-      or
-      this.(MethodCall).getMethod() instanceof EqualsMethod and
-      result = this.(MethodCall).getQualifier()
-    }
-
-    boolean polarity() {
-      result = this.(J::EqualityTest).polarity()
+  pragma[nomagic]
+  predicate equalityTest(Expr eqtest, Expr left, Expr right, boolean polarity) {
+    exists(EqualityTest eq | eq = eqtest |
+      eq.getLeftOperand() = left and
+      eq.getRightOperand() = right and
+      eq.polarity() = polarity
+    )
+    or
+    exists(MethodCall call | call = eqtest and polarity = true |
+      call.getMethod() instanceof EqualsMethod and
+      call.getQualifier() = left and
+      call.getAnArgument() = right
       or
-      result = true and not this instanceof J::EqualityTest
-    }
+      objectsEquals(call.getMethod()) and
+      call.getArgument(0) = left and
+      call.getArgument(1) = right
+    )
   }
 
   class ConditionalExpr extends Expr instanceof J::ConditionalExpr {

shared/controlflow/codeql/controlflow/Guards.qll

@@ -188,13 +188,12 @@ signature module InputSig<LocationSig Location> {
     Expr getEqualChildExpr();
   }
 
-  class EqualityTest extends Expr {
-    /** Gets an operand of this expression. */
-    Expr getAnOperand();
-
-    /** Gets a boolean indicating whether this test is equality (true) or inequality (false). */
-    boolean polarity();
-  }
+  /**
+   * Holds if `eqtest` is an equality or inequality test between `left` and
+   * `right`. The `polarity` indicates whether this is an equality test (true)
+   * or inequality test (false).
+   */
+  predicate equalityTest(Expr eqtest, Expr left, Expr right, boolean polarity);
 
   class ConditionalExpr extends Expr {
     /** Gets the condition of this expression. */
@@ -351,12 +350,10 @@ module Make<LocationSig Location, InputSig<Location> Input> {
     c.nonMatchEdge(bb1, bb2)
   }
 
-  pragma[nomagic]
-  private predicate eqtestHasOperands(EqualityTest eqtest, Expr e1, Expr e2, boolean polarity) {
-    eqtest.getAnOperand() = e1 and
-    eqtest.getAnOperand() = e2 and
-    e1 != e2 and
-    eqtest.polarity() = polarity
+  private predicate equalityTestSymmetric(Expr eqtest, Expr e1, Expr e2, boolean eqval) {
+    equalityTest(eqtest, e1, e2, eqval)
+    or
+    equalityTest(eqtest, e2, e1, eqval)
   }
 
   private predicate constcaseEquality(PreGuard g, Expr e1, ConstantExpr e2) {
@@ -424,7 +421,7 @@ module Make<LocationSig Location, InputSig<Location> Input> {
      * to `eqval`.
      */
     predicate isEquality(Expr e1, Expr e2, boolean eqval) {
-      eqtestHasOperands(this, e1, e2, eqval)
+      equalityTestSymmetric(this, e1, e2, eqval)
       or
       constcaseEquality(this, e1, e2) and eqval = true
       or
@@ -466,7 +463,7 @@ module Make<LocationSig Location, InputSig<Location> Input> {
     )
     or
     exists(NonNullExpr nonnull |
-      eqtestHasOperands(g1, g2, nonnull, v1.asBooleanValue()) and
+      equalityTestSymmetric(g1, g2, nonnull, v1.asBooleanValue()) and
       v2.isNonNullValue()
     )
     or
@@ -589,7 +586,7 @@ module Make<LocationSig Location, InputSig<Location> Input> {
     private predicate guardChecksEqualVars(
       Guard guard, SsaDefinition v1, SsaDefinition v2, boolean branch
     ) {
-      eqtestHasOperands(guard, v1.getARead(), v2.getARead(), branch)
+      equalityTestSymmetric(guard, v1.getARead(), v2.getARead(), branch)
     }
 
     private predicate guardReadsSsaVar(Guard guard, SsaDefinition def) {
@@ -773,7 +770,7 @@ module Make<LocationSig Location, InputSig<Location> Input> {
       or
       exists(Expr nonnull |
         exprHasValue(nonnull, v2) and
-        eqtestHasOperands(g1, g2, nonnull, v1.asBooleanValue()) and
+        equalityTestSymmetric(g1, g2, nonnull, v1.asBooleanValue()) and
         v2.isNonNullValue()
       )
     }