Cannot store a closure using <'a> || lifetime syntax or inside generic types

[huonw]

struct Foo<'a> {
    x: <'a> ||
}
fn main() {}

store-closure.rs:2:7: 2:14 error: missing lifetime specifier
store-closure.rs:2     x: <'a> ||
                          ^~~~~~~

This & #11209 means that it is impossible to store closures inside another generic type e.g. an Option< closure >:

struct Foo<'a> {
    x: Option< <'a> ||>
}
fn main() {}

store-closure.rs:2:15: 2:22 error: missing lifetime specifier
store-closure.rs:2     x: Option< <'a> ||>
                                  ^~~~~~~

struct Foo<'a> {
    x: Option< 'a ||>
}
fn main() {}

store-closure.rs:2:18: 2:20 error: expected `,` or `>` after lifetime name, got: OROR
store-closure.rs:2     x: Option< 'a ||>
                                     ^~

[emberian]

cc @pcwalton