EssentialType: Merge binary operation implementations

EssentialBinaryArithmeticOperation and
EssentialBinaryBitwiseOperation only differ in their handling of
+ and - operations, so combine the two implementations to reduce
duplication.

In addition, change the characteristic predicate to an allow list.
This ensures we only capture the intended binary operations, and
exclude any others.

Author: lcartey

c/misra/src/codingstandards/c/misra/EssentialTypes.qll

@@ -286,11 +286,26 @@ class EssentialConditionalExpr extends EssentialExpr, ConditionalExpr {
   }
 }
 
-class EssentialBinaryArithmeticExpr extends EssentialExpr, BinaryArithmeticOperation {
-  EssentialBinaryArithmeticExpr() {
-    // GNU C extension has min/max which we can ignore
-    not this instanceof MinExpr and
-    not this instanceof MaxExpr
+/**
+ * A binary operation subject to usual conversions, with essential type behaviour as specified by D.7.9.
+ */
+class EssentialBinaryOperationSubjectToUsualConversions extends EssentialExpr, BinaryOperation {
+  EssentialBinaryOperationSubjectToUsualConversions() {
+    this instanceof MulExpr
+    or
+    this instanceof DivExpr
+    or
+    this instanceof RemExpr
+    or
+    this instanceof AddExpr
+    or
+    this instanceof SubExpr
+    or
+    this instanceof BitwiseAndExpr
+    or
+    this instanceof BitwiseOrExpr
+    or
+    this instanceof BitwiseXorExpr
   }
 
   override Type getEssentialType() {
@@ -353,51 +368,7 @@ class EssentialBinaryArithmeticExpr extends EssentialExpr, BinaryArithmeticOpera
   }
 }
 
-class EssentialBinaryBitwiseExpr extends EssentialExpr, BinaryBitwiseOperation {
-  EssentialBinaryBitwiseExpr() {
-    not this instanceof LShiftExpr and
-    not this instanceof RShiftExpr
-  }
-
-  override Type getEssentialType() {
-    exists(
-      Type leftEssentialType, Type rightEssentialType,
-      EssentialTypeCategory leftEssentialTypeCategory,
-      EssentialTypeCategory rightEssentialTypeCategory
-    |
-      leftEssentialType = getEssentialType(getLeftOperand()) and
-      rightEssentialType = getEssentialType(getRightOperand()) and
-      leftEssentialTypeCategory = getEssentialTypeCategory(leftEssentialType) and
-      rightEssentialTypeCategory = getEssentialTypeCategory(rightEssentialType)
-    |
-      if
-        leftEssentialTypeCategory = EssentiallySignedType() and
-        rightEssentialTypeCategory = EssentiallySignedType()
-      then
-        if exists(getValue())
-        then result = stlr(this)
-        else (
-          if leftEssentialType.getSize() > rightEssentialType.getSize()
-          then result = leftEssentialType
-          else result = rightEssentialType
-        )
-      else
-        if
-          leftEssentialTypeCategory = EssentiallyUnsignedType() and
-          rightEssentialTypeCategory = EssentiallyUnsignedType()
-        then
-          if exists(getValue())
-          then result = utlr(this)
-          else (
-            if leftEssentialType.getSize() > rightEssentialType.getSize()
-            then result = leftEssentialType
-            else result = rightEssentialType
-          )
-        else result = this.getStandardType()
-    )
-  }
-}
-
+// }
 /**
  * A named Enum type, as per D.5.
  */