unified: Add a few more AST helper classes

unified/ql/lib/codeql/unified/internal/AstExtra.qll

@@ -5,6 +5,39 @@
 private import unified
 
 module Public {
+  /**
+   * A logical 'and' expression with short-circuiting.
+   */
+  class LogicalAndExpr extends BinaryExpr {
+    LogicalAndExpr() { this.getOperator().getValue() = "&&" }
+
+    Expr getAnOperand() { result = [this.getLeft(), this.getRight()] }
+  }
+
+  /**
+   * Declaration of a local or top-level variable.
+   */
+  class LocalVariableDeclaration extends VariableDeclaration {
+    private Block block;
+
+    LocalVariableDeclaration() { this = block.getStmt(_) }
+
+    /** Gets the block in which this variable is declared. */
+    Block getDeclaringBlock() { result = block }
+  }
+
+  /**
+   * Declaration of a local or top-level function.
+   */
+  class LocalFunctionDeclaration extends FunctionDeclaration {
+    private Block block;
+
+    LocalFunctionDeclaration() { this = block.getStmt(_) }
+
+    /** Gets the block in which this function is declared. */
+    Block getDeclaringBlock() { result = block }
+  }
+
   /**
    * A comment appearing in the source code.
    */