Python: Get rid of some get...Object methods

This frees `Class.qll`, `Exprs.qll`, and `Function.qll` from the
clutches of points-to. For the somewhat complicated setup with
`getLiteralObject` (an abstract method), I opted for a slightly ugly but
workable solution of just defining a predicate on `ImmutableLiteral`
that inlines each predicate body, special-cased to the specific instance
to which it applies.

python/ql/lib/LegacyPointsTo.qll

@@ -221,3 +221,66 @@ class ModuleWithPointsTo extends Module {
 
   override string getAQlClass() { none() }
 }
+
+/**
+ * An extension of `Function` that provides points-to related methods.
+ */
+class FunctionWithPointsTo extends Function {
+  /** Gets the FunctionObject corresponding to this function */
+  FunctionObject getFunctionObject() { result.getOrigin() = this.getDefinition() }
+
+  override string getAQlClass() { none() }
+}
+
+/**
+ * An extension of `Class` that provides points-to related methods.
+ */
+class ClassWithPointsTo extends Class {
+  /** Gets the ClassObject corresponding to this class */
+  ClassObject getClassObject() { result.getOrigin() = this.getParent() }
+
+  override string getAQlClass() { none() }
+}
+
+Object getLiteralObject(ImmutableLiteral l) {
+  l instanceof IntegerLiteral and
+  (
+    py_cobjecttypes(result, theIntType()) and py_cobjectnames(result, l.(Num).getN())
+    or
+    py_cobjecttypes(result, theLongType()) and py_cobjectnames(result, l.(Num).getN())
+  )
+  or
+  l instanceof FloatLiteral and
+  py_cobjecttypes(result, theFloatType()) and
+  py_cobjectnames(result, l.(Num).getN())
+  or
+  l instanceof ImaginaryLiteral and
+  py_cobjecttypes(result, theComplexType()) and
+  py_cobjectnames(result, l.(Num).getN())
+  or
+  l instanceof NegativeIntegerLiteral and
+  (
+    (py_cobjecttypes(result, theIntType()) or py_cobjecttypes(result, theLongType())) and
+    py_cobjectnames(result, "-" + l.(UnaryExpr).getOperand().(IntegerLiteral).getN())
+  )
+  or
+  l instanceof Bytes and
+  py_cobjecttypes(result, theBytesType()) and
+  py_cobjectnames(result, l.(Bytes).quotedString())
+  or
+  l instanceof Unicode and
+  py_cobjecttypes(result, theUnicodeType()) and
+  py_cobjectnames(result, l.(Unicode).quotedString())
+  or
+  l instanceof True and
+  name_consts(l, "True") and
+  result = theTrueObject()
+  or
+  l instanceof False and
+  name_consts(l, "False") and
+  result = theFalseObject()
+  or
+  l instanceof None and
+  name_consts(l, "None") and
+  result = theNoneObject()
+}

python/ql/lib/semmle/python/Class.qll

@@ -141,9 +141,6 @@ class Class extends Class_, Scope, AstNode {
   /** Gets the metaclass expression */
   Expr getMetaClass() { result = this.getParent().getMetaClass() }
 
-  /** Gets the ClassObject corresponding to this class */
-  ClassObject getClassObject() { result.getOrigin() = this.getParent() }
-
   /** Gets the nth base of this class definition. */
   Expr getBase(int index) { result = this.getParent().getBase(index) }
 

python/ql/lib/semmle/python/Exprs.qll

@@ -240,17 +240,12 @@ class Bytes extends StringLiteral {
   /* syntax: b"hello" */
   Bytes() { not this.isUnicode() }
 
-  override Object getLiteralObject() {
-    py_cobjecttypes(result, theBytesType()) and
-    py_cobjectnames(result, this.quotedString())
-  }
-
   /**
    * The extractor puts quotes into the name of each string (to prevent "0" clashing with 0).
    * The following predicate help us match up a string/byte literals in the source
    * which the equivalent object.
    */
-  private string quotedString() {
+  string quotedString() {
     exists(string b_unquoted | b_unquoted = this.getS() | result = "b'" + b_unquoted + "'")
   }
 }
@@ -266,8 +261,6 @@ class Ellipsis extends Ellipsis_ {
  * Consists of string (both unicode and byte) literals and numeric literals.
  */
 abstract class ImmutableLiteral extends Expr {
-  abstract Object getLiteralObject();
-
   abstract boolean booleanValue();
 }
 
@@ -292,12 +285,6 @@ class IntegerLiteral extends Num {
 
   override string toString() { result = "IntegerLiteral" }
 
-  override Object getLiteralObject() {
-    py_cobjecttypes(result, theIntType()) and py_cobjectnames(result, this.getN())
-    or
-    py_cobjecttypes(result, theLongType()) and py_cobjectnames(result, this.getN())
-  }
-
   override boolean booleanValue() {
     this.getValue() = 0 and result = false
     or
@@ -317,10 +304,6 @@ class FloatLiteral extends Num {
 
   override string toString() { result = "FloatLiteral" }
 
-  override Object getLiteralObject() {
-    py_cobjecttypes(result, theFloatType()) and py_cobjectnames(result, this.getN())
-  }
-
   override boolean booleanValue() {
     this.getValue() = 0.0 and result = false
     or
@@ -343,10 +326,6 @@ class ImaginaryLiteral extends Num {
 
   override string toString() { result = "ImaginaryLiteral" }
 
-  override Object getLiteralObject() {
-    py_cobjecttypes(result, theComplexType()) and py_cobjectnames(result, this.getN())
-  }
-
   override boolean booleanValue() {
     this.getValue() = 0.0 and result = false
     or
@@ -365,11 +344,6 @@ class NegativeIntegerLiteral extends ImmutableLiteral, UnaryExpr {
 
   override boolean booleanValue() { result = this.getOperand().(IntegerLiteral).booleanValue() }
 
-  override Object getLiteralObject() {
-    (py_cobjecttypes(result, theIntType()) or py_cobjecttypes(result, theLongType())) and
-    py_cobjectnames(result, "-" + this.getOperand().(IntegerLiteral).getN())
-  }
-
   /**
    * Gets the (integer) value of this constant. Will not return a result if the value does not fit into
    * a 32 bit signed value
@@ -385,11 +359,6 @@ class Unicode extends StringLiteral {
   /* syntax: "hello" */
   Unicode() { this.isUnicode() }
 
-  override Object getLiteralObject() {
-    py_cobjecttypes(result, theUnicodeType()) and
-    py_cobjectnames(result, this.quotedString())
-  }
-
   /**
    * Gets the quoted representation fo this string.
    *
@@ -593,12 +562,10 @@ class StringLiteral extends Str_, ImmutableLiteral {
     this.getText() != "" and result = true
   }
 
-  override Object getLiteralObject() { none() }
-
   override string toString() { result = "StringLiteral" }
 }
 
-private predicate name_consts(Name_ n, string id) {
+predicate name_consts(Name_ n, string id) {
   exists(Variable v | py_variables(v, n) and id = v.getId() |
     id = "True" or id = "False" or id = "None"
   )
@@ -627,8 +594,6 @@ class True extends BooleanLiteral {
   /* syntax: True */
   True() { name_consts(this, "True") }
 
-  override Object getLiteralObject() { name_consts(this, "True") and result = theTrueObject() }
-
   override boolean booleanValue() { result = true }
 }
 
@@ -637,8 +602,6 @@ class False extends BooleanLiteral {
   /* syntax: False */
   False() { name_consts(this, "False") }
 
-  override Object getLiteralObject() { name_consts(this, "False") and result = theFalseObject() }
-
   override boolean booleanValue() { result = false }
 }
 
@@ -647,8 +610,6 @@ class None extends NameConstant {
   /* syntax: None */
   None() { name_consts(this, "None") }
 
-  override Object getLiteralObject() { name_consts(this, "None") and result = theNoneObject() }
-
   override boolean booleanValue() { result = false }
 }
 

python/ql/lib/semmle/python/Function.qll

@@ -87,9 +87,6 @@ class Function extends Function_, Scope, AstNode {
   /** Gets the metrics for this function */
   FunctionMetrics getMetrics() { result = this }
 
-  /** Gets the FunctionObject corresponding to this function */
-  FunctionObject getFunctionObject() { result.getOrigin() = this.getDefinition() }
-
   /**
    * Whether this function is a procedure, that is, it has no explicit return statement and always returns None.
    * Note that generator and async functions are not procedures as they return generators and coroutines respectively.

python/ql/lib/semmle/python/types/ClassObject.qll

@@ -89,7 +89,7 @@ class ClassObject extends Object {
   }
 
   /** Gets the scope associated with this class, if it is not a builtin class */
-  Class getPyClass() { result.getClassObject() = this }
+  ClassWithPointsTo getPyClass() { result.getClassObject() = this }
 
   /** Returns an attribute declared on this class (not on a super-class) */
   Object declaredAttribute(string name) {

python/ql/test/2/extractor-tests/normalise/Numbers.ql

@@ -7,10 +7,11 @@
  */
 
 import python
+private import LegacyPointsTo
 
 from NumericObject n
 where
-  exists(IntegerLiteral i | i.getLiteralObject() = n |
+  exists(IntegerLiteral i | getLiteralObject(i) = n |
     i.getEnclosingModule().getFile().getShortName() = "test.py"
   )
 select n.toString(), n.repr()

python/ql/test/2/library-tests/objects/Literals.ql

@@ -1,5 +1,6 @@
 /* Test that there are no literals that do not have a corresponding object. */
 import python
+private import LegacyPointsTo
 
 string repr(Expr e) {
   result = e.(Num).getN() or
@@ -8,5 +9,5 @@ string repr(Expr e) {
 }
 
 from ImmutableLiteral l
-where not exists(l.getLiteralObject())
+where not exists(getLiteralObject(l))
 select l.getLocation().getStartLine(), repr(l)

python/ql/test/library-tests/objects/Literals.ql

@@ -1,5 +1,6 @@
 /* Test that there are no literals that do not have a corresponding object. */
 import python
+private import LegacyPointsTo
 
 string repr(Expr e) {
   result = e.(Num).getN() or
@@ -8,5 +9,5 @@ string repr(Expr e) {
 }
 
 from ImmutableLiteral l
-where not exists(l.getLiteralObject())
+where not exists(getLiteralObject(l))
 select l.getLocation().getStartLine(), repr(l)