Given a function foo() that returns an array, you can write
foo()[1] = 42;
and the compiler accepts it.
but
(foo() as Array<Number>)[1] = 42;
is a parser error.
And so is
(foo())[1] = 42;
...: no viable alternative at input '(foo())[1]='
There doesn't seem to be any reason not to support either of these, since they would compile to the exact same bytecode.
