The type of a variable or parameter is narrowed in the following situations:
• In the true branch statement of an ‘if’ statement, the type of a variable or parameter is narrowed by any type guard in the ‘if’ condition when true, provided the if statement contains no assignments to the variable or parameter.
• In the false branch statement of an ‘if’ statement, the type of a variable or parameter is narrowed by any type guard in the ‘if’ condition when false, provided the if statement contains no assignments to the variable or parameter.
