AST: add begin expressions

ql/src/codeql_ruby/ast/Statement.qll

@@ -36,7 +36,21 @@ class EmptyStmt extends Stmt, @token_empty_statement {
 }
 
 /**
- * An `BEGIN` block.
+ * A `begin` statement.
+ * ```rb
+ * begin
+ *  puts "hello world"
+ * end
+ * ```
+ */
+class BeginExpr extends BodyStatement, @begin {
+  final override Begin::Range range;
+
+  final override string getAPrimaryQlClass() { result = "BeginExpr" }
+}
+
+/**
+ * A `BEGIN` block.
  * ```rb
  * BEGIN { puts "starting ..." }
  * ```

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

@@ -90,16 +90,6 @@ module ParenthesizedExpr {
   }
 }
 
-module BeginBlock {
-  class Range extends StmtSequence::Range, @begin_block {
-    final override Generated::BeginBlock generated;
-
-    final override Stmt getStmt(int n) { result = generated.getChild(n) }
-
-    final override string toString() { result = "BEGIN { ... }" }
-  }
-}
-
 module ThenExpr {
   class Range extends StmtSequence::Range, @then {
     final override Generated::Then generated;

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

@@ -17,6 +17,26 @@ module EmptyStmt {
   }
 }
 
+module Begin {
+  class Range extends BodyStatement::Range, @begin {
+    final override Generated::Begin generated;
+
+    final override Generated::AstNode getChild(int n) { result = generated.getChild(n) }
+
+    final override string toString() { result = "begin ... " }
+  }
+}
+
+module BeginBlock {
+  class Range extends StmtSequence::Range, @begin_block {
+    final override Generated::BeginBlock generated;
+
+    final override Stmt getStmt(int n) { result = generated.getChild(n) }
+
+    final override string toString() { result = "BEGIN { ... }" }
+  }
+}
+
 module EndBlock {
   class Range extends StmtSequence::Range, @end_block {
     final override Generated::EndBlock generated;