Auto merge of #29580 - alexbool:smart-pointer-conversion, r=alexcrichton
Sometimes when writing generic code you want to abstract over owning/pointer type so that calling code isn't restricted by one concrete owning/pointer type. This commit makes possible such code: ```rust fn i_will_work_with_arc<T: Into<Arc<MyTy>>>(t: T) { let the_arc = t.into(); // Do something } i_will_work_with_arc(MyTy::new()); i_will_work_with_arc(Box::new(MyTy::new())); let arc_that_i_already_have = Arc::new(MyTy::new()); i_will_work_with_arc(arc_that_i_already_have); ``` Please note that this patch doesn't work with DSTs. Also to mention, I made those impls stable, and I don't know whether they should be actually stable from the beginning. Please tell me if this should be feature-gated.
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commit
99093b79f1
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@ -87,6 +87,7 @@ use core::ptr::{self, Shared};
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use core::marker::Unsize;
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use core::hash::{Hash, Hasher};
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use core::{usize, isize};
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use core::convert::From;
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use heap::deallocate;
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const MAX_REFCOUNT: usize = (isize::MAX) as usize;
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@ -896,6 +897,13 @@ impl<T: ?Sized + Hash> Hash for Arc<T> {
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}
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}
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#[stable(feature = "from_for_ptrs", since = "1.6.0")]
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impl<T> From<T> for Arc<T> {
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fn from(t: T) -> Self {
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Arc::new(t)
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}
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}
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#[cfg(test)]
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mod tests {
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use std::clone::Clone;
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@ -910,6 +918,7 @@ mod tests {
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use std::vec::Vec;
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use super::{Arc, Weak};
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use std::sync::Mutex;
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use std::convert::From;
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struct Canary(*mut atomic::AtomicUsize);
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@ -1139,6 +1148,13 @@ mod tests {
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drop(x);
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assert!(y.upgrade().is_none());
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}
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#[test]
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fn test_from_owned() {
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let foo = 123;
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let foo_arc = Arc::from(foo);
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assert!(123 == *foo_arc);
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}
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}
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impl<T: ?Sized> borrow::Borrow<T> for Arc<T> {
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@ -67,6 +67,7 @@ use core::ops::{CoerceUnsized, Deref, DerefMut};
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use core::ops::{Placer, Boxed, Place, InPlace, BoxPlace};
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use core::ptr::{self, Unique};
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use core::raw::TraitObject;
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use core::convert::From;
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/// A value that represents the heap. This is the default place that the `box`
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/// keyword allocates into when no place is supplied.
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@ -373,6 +374,13 @@ impl<T: ?Sized + Hash> Hash for Box<T> {
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}
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}
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#[stable(feature = "from_for_ptrs", since = "1.6.0")]
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impl<T> From<T> for Box<T> {
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fn from(t: T) -> Self {
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Box::new(t)
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}
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}
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impl Box<Any> {
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#[inline]
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#[stable(feature = "rust1", since = "1.0.0")]
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@ -169,6 +169,7 @@ use core::ops::Deref;
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#[cfg(not(stage0))]
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use core::ops::CoerceUnsized;
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use core::ptr::{self, Shared};
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use core::convert::From;
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use heap::deallocate;
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@ -701,6 +702,13 @@ impl<T> fmt::Pointer for Rc<T> {
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}
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}
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#[stable(feature = "from_for_ptrs", since = "1.6.0")]
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impl<T> From<T> for Rc<T> {
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fn from(t: T) -> Self {
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Rc::new(t)
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}
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}
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/// A weak version of `Rc<T>`.
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///
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/// Weak references do not count when determining if the inner value should be
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@ -906,6 +914,7 @@ mod tests {
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use std::result::Result::{Err, Ok};
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use std::mem::drop;
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use std::clone::Clone;
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use std::convert::From;
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#[test]
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fn test_clone() {
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@ -1108,6 +1117,13 @@ mod tests {
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let foo: Rc<[i32]> = Rc::new([1, 2, 3]);
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assert_eq!(foo, foo.clone());
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}
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#[test]
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fn test_from_owned() {
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let foo = 123;
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let foo_rc = Rc::from(foo);
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assert!(123 == *foo_rc);
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}
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}
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impl<T: ?Sized> borrow::Borrow<T> for Rc<T> {
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