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November 1, 2019 06:52
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rust deref
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struct X { val: i32 } | |
impl std::ops::Deref for X { | |
type Target = i32; | |
fn deref(&self) -> &i32 { &self.val } | |
} | |
trait M { fn m(self); } | |
impl M for i32 { fn m(self) { println!("i32::m()"); } } | |
impl M for X { fn m(self) { println!("X::m()"); } } | |
impl<'a> M for &'a X { fn m(self) { println!("&X::m()"); } } | |
impl<'a, 'b> M for &'a &'b X { fn m(self) { println!("&&X::m()"); } } | |
impl<'a, 'b, 'c> M for &'a &'b &'c X { fn m(self) { println!("&&&X::m()"); } } | |
trait RefM { fn refm(&self); } | |
impl RefM for i32 { fn refm(&self) { println!("i32::refm()"); } } | |
impl RefM for X { fn refm(&self) { println!("X::refm()"); } } | |
impl<'a> RefM for &'a X { fn refm(&self) { println!("&X::refm()"); } } | |
impl<'a, 'b> RefM for &'a &'b X { fn refm(&self) { println!("&&X::refm()"); } } | |
impl<'a, 'b, 'c> RefM for &'a &'b &'c X { fn refm(&self) { println!("&&&X::refm()"); } } | |
struct Y { val: i32 } | |
impl std::ops::Deref for Y { | |
type Target = i32; | |
fn deref(&self) -> &i32 { &self.val } | |
} | |
struct Z { val: Y } | |
impl std::ops::Deref for Z { | |
type Target = Y; | |
fn deref(&self) -> &Y { &self.val } | |
} | |
#[derive(Clone)] | |
struct A; | |
//impl std::marker::Clone for A {} | |
impl std::marker::Copy for A {} | |
impl M for A { fn m(self) { println!("A::m()"); } } | |
impl<'a, 'b, 'c> M for &'a &'b &'c A { fn m(self) { println!("&&&A::m()"); } } | |
impl RefM for A { fn refm(&self) { println!("A::refm()"); } } | |
impl<'a, 'b, 'c> RefM for &'a &'b &'c A { fn refm(&self) { println!("&&&A::refm()"); } } | |
fn main() { | |
// I'll use @ to denote left side of the dot operator | |
(*X{val:42}).m(); // i32::refm() , self == @ | |
X{val:42}.m(); // X::m() , self == @ | |
(&X{val:42}).m(); // &X::m() , self == @ | |
(&&X{val:42}).m(); // &&X::m() , self == @ | |
(&&&X{val:42}).m(); // &&&X:m() , self == @ | |
(&&&&X{val:42}).m(); // &&&X::m() , self == *@ | |
(&&&&&X{val:42}).m(); // &&&X::m() , self == **@ | |
println!(""); | |
(*X{val:42}).refm(); // i32::refm() , self == @ | |
X{val:42}.refm(); // X::refm() , self == @ | |
(&X{val:42}).refm(); // X::refm() , self == *@ | |
(&&X{val:42}).refm(); // &X::refm() , self == *@ | |
(&&&X{val:42}).refm(); // &&X::refm() , self == *@ | |
(&&&&X{val:42}).refm(); // &&&X::refm(), self == *@ | |
(&&&&&X{val:42}).refm(); // &&&X::refm(), self == **@ | |
println!(""); | |
Y{val:42}.refm(); // i32::refm() , self == *@ | |
Z{val:Y{val:42}}.refm(); // i32::refm() , self == **@ | |
println!(""); | |
A.m(); // A::m() , self == @ | |
// without the Copy trait, (&A).m() would be a compilation error: | |
// cannot move out of borrowed content | |
println!(""); | |
(&A).m(); // A::m() , self == *@ | |
(&&A).m(); // &&&A::m() , self == &@ | |
(&&&A).m(); // &&&A::m() , self == @ | |
A.refm(); // A::refm() , self == @ | |
(&A).refm(); // A::refm() , self == *@ | |
(&&A).refm(); // A::refm() , self == **@ | |
(&&&A).refm(); // &&&A::refm(), self == @ | |
} |
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