25 lines
943 B
Rust
25 lines
943 B
Rust
// Here, `f` is a function that takes a pointer `x` and a function
|
|
// `g`, where `g` requires its argument `y` to be in the same region
|
|
// that `x` is in.
|
|
fn has_same_region(f: fn(x: &a.int, g: fn(y: &a.int))) {
|
|
// Somewhat counterintuitively, this fails because, in
|
|
// `wants_two_regions`, the `g` argument needs to be able to
|
|
// accept any region. That is, the type that `has_same_region`
|
|
// expects is *not* a subtype of the type that `wants_two_regions`
|
|
// expects.
|
|
wants_two_regions(f); //~ ERROR mismatched types
|
|
}
|
|
|
|
fn wants_two_regions(_f: fn(x: &int, g: fn(y: &int))) {
|
|
// Suppose we were to write code here that passed some arbitrary
|
|
// &int and some arbitrary fn(&int) to whatever's passed in as _f.
|
|
// This would be fine as far as the type annotation on the formal
|
|
// parameter _f goes, but if _f were `f` we'd be in trouble since
|
|
// `f` can't handle those arguments.
|
|
}
|
|
|
|
fn main() {
|
|
}
|
|
|
|
|