void foo() {
    static struct Bar {
        uint doStuff() {
            return a;
        }
    }
}

D:\code\test.d(4): basic type expected, not struct
D:\code\test.d(4): no identifier for declarator int
D:\code\test.d(4): semicolon expected, not 'struct'

Before nested structs, one could declare a non-nested struct inside a function scope by simply omitting the static keyword.