&+(_:_:)

Positional arguments are concatenated:

let arguments: StatementArguments = [1] &+ [2, 3]

// Prints [1, 2, 3]
print(arguments)

Named arguments are inserted or updated:

let arguments: StatementArguments = ["foo": 1] &+ ["bar": 2]

// Prints ["foo": 1, "bar": 2]
print(arguments)

If a named arguments is defined in both arguments, the right-hand side wins:

let arguments: StatementArguments = ["foo": 1] &+ ["foo": 2]

// Prints ["foo": 2]
print(arguments)

You can mix named and positional arguments (see the documentation of the StatementArguments type for more information about mixed arguments):

let arguments: StatementArguments = ["foo": 1] &+ [2, 3]
// Prints ["foo": 1, 2, 3]
print(arguments)