function isScope( node ) {
	return (
		// Function scopes:
		node.type === 'FunctionExpression' ||
		node.type === 'FunctionDeclaration' ||
		node.type === 'ArrowFunctionExpression' ||

		// Global scope:
		node.type === 'Program'
	);
}
Tests whether an AST node defines a scope.

@private
@param {Node} node - AST node
@returns {boolean} boolean indicating whether an AST node defines a scope