Ruby: Make isCapturedAccess work with synthesized scopes

Author: hvitved

ruby/ql/lib/codeql/ruby/ast/Variable.qll

@@ -51,7 +51,7 @@ class LocalVariable extends Variable, TLocalVariable {
    *
    * `x` is a captured variable, whereas `y` is not.
    */
-  predicate isCaptured() { this.getAnAccess().isCapturedAccess() }
+  final predicate isCaptured() { this.getAnAccess().isCapturedAccess() }
 }
 
 /** A global variable. */
@@ -152,7 +152,7 @@ class LocalVariableAccess extends VariableAccess instanceof LocalVariableAccessI
    * the access to `x` in the first `puts x` is a captured access, while
    * the access to `x` in the second `puts x` is not.
    */
-  predicate isCapturedAccess() { isCapturedAccess(this) }
+  final predicate isCapturedAccess() { isCapturedAccess(this) }
 }
 
 /** An access to a local variable where the value is updated. */
@@ -200,10 +200,4 @@ class SelfVariableAccess extends LocalVariableAccess instanceof SelfVariableAcce
 }
 
 /** An access to the `self` variable where the value is read. */
-class SelfVariableReadAccess extends SelfVariableAccess, VariableReadAccess {
-  // We override the definition in `LocalVariableAccess` because it gives the
-  // wrong result for synthesised `self` variables.
-  override predicate isCapturedAccess() {
-    this.getVariable().getDeclaringScope() != this.getCfgScope()
-  }
-}
+class SelfVariableReadAccess extends SelfVariableAccess, VariableReadAccess { }