rust/tests/run-pass/function_pointers.rs

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fn f() -> i32 {
42
}
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fn g(i: i32) -> i32 {
i*42
}
fn h(i: i32, j: i32) -> i32 {
j * i * 7
}
fn return_fn_ptr(f: fn() -> i32) -> fn() -> i32 {
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f
}
fn call_fn_ptr() -> i32 {
return_fn_ptr(f)()
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}
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fn indirect<F: Fn() -> i32>(f: F) -> i32 { f() }
fn indirect_mut<F: FnMut() -> i32>(mut f: F) -> i32 { f() }
fn indirect_once<F: FnOnce() -> i32>(f: F) -> i32 { f() }
fn indirect2<F: Fn(i32) -> i32>(f: F) -> i32 { f(10) }
fn indirect_mut2<F: FnMut(i32) -> i32>(mut f: F) -> i32 { f(10) }
fn indirect_once2<F: FnOnce(i32) -> i32>(f: F) -> i32 { f(10) }
fn indirect3<F: Fn(i32, i32) -> i32>(f: F) -> i32 { f(10, 3) }
fn indirect_mut3<F: FnMut(i32, i32) -> i32>(mut f: F) -> i32 { f(10, 3) }
fn indirect_once3<F: FnOnce(i32, i32) -> i32>(f: F) -> i32 { f(10, 3) }
fn main() {
assert_eq!(call_fn_ptr(), 42);
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assert_eq!(indirect(f), 42);
assert_eq!(indirect_mut(f), 42);
assert_eq!(indirect_once(f), 42);
assert_eq!(indirect2(g), 420);
assert_eq!(indirect_mut2(g), 420);
assert_eq!(indirect_once2(g), 420);
assert_eq!(indirect3(h), 210);
assert_eq!(indirect_mut3(h), 210);
assert_eq!(indirect_once3(h), 210);
let g = f as fn() -> i32;
assert!(return_fn_ptr(g) == g);
assert!(return_fn_ptr(g) as unsafe fn() -> i32 == g as fn() -> i32 as unsafe fn() -> i32);
assert!(return_fn_ptr(f) != f);
}