Operator grouping with string inside a function triggers a syntax error

[0liv1er]

Concatenating the result of an operator group (...) together with a string inside a function triggers a syntax error.

function f(s) {
        return s
}
BEGIN{
        foo = ""
        print f("hello"(foo=="bar" ? "world" : ""))
        print f("hello" (foo=="bar" ? "world" : ""))
        print f((foo=="bar" ? "world" : "")"hello")
}

Note that the error is triggered only if there is no space between the string and the grouping operator, and the string is first.