AST: add Self class

ql/src/codeql_ruby/ast/Expr.qll

@@ -12,6 +12,18 @@ class Expr extends Stmt {
   Expr() { this = range }
 }
 
+/**
+ * A reference to the current object. For example:
+ * - `self == other`
+ * - `self.method_name`
+ * - `def self.method_name ... end`
+ */
+class Self extends Expr, @token_self {
+  override Self::Range range;
+
+  final override string getAPrimaryQlClass() { result = "Self" }
+}
+
 /**
  * A literal.
  *

ql/src/codeql_ruby/ast/internal/AST.qll

@@ -47,8 +47,6 @@ module AstNode {
       or
       this instanceof Generated::BareString
       or
-      this instanceof Generated::Self
-      or
       this instanceof Generated::Float
       or
       this instanceof Generated::Superclass

ql/src/codeql_ruby/ast/internal/Expr.qll

@@ -6,6 +6,14 @@ module Expr {
   abstract class Range extends Stmt::Range { }
 }
 
+module Self {
+  class Range extends Expr::Range, @token_self {
+    final override Generated::Self generated;
+
+    final override string toString() { result = "self" }
+  }
+}
+
 module Literal {
   abstract class Range extends Expr::Range {
     abstract string getValueText();