Rollup merge of #68692 - jyn514:vec-from-array, r=LukasKalbertodt

impl From<[T; N]> for Vec<T>

Closes https://github.com/rust-lang/rust/issues/67963

src/liballoc/vec.rs

+// ignore-tidy-filelength
 //! A contiguous growable array type with heap-allocated contents, written
 //! `Vec<T>`.
 //!
@@ -2398,6 +2399,21 @@ fn from(s: &mut [T]) -> Vec<T> {
     }
 }
 
+#[stable(feature = "vec_from_array", since = "1.44.0")]
+impl<T, const N: usize> From<[T; N]> for Vec<T>
+where
+    [T; N]: LengthAtMost32,
+{
+    #[cfg(not(test))]
+    fn from(s: [T; N]) -> Vec<T> {
+        <[T]>::into_vec(box s)
+    }
+    #[cfg(test)]
+    fn from(s: [T; N]) -> Vec<T> {
+        crate::slice::into_vec(box s)
+    }
+}
+
 #[stable(feature = "vec_from_cow_slice", since = "1.14.0")]
 impl<'a, T> From<Cow<'a, [T]>> for Vec<T>
 where

src/test/ui/const-generics/array-impls/alloc-traits-impls-length-32.rs

@@ -14,6 +14,10 @@
     Vec::<A>::new()
 }
 
+pub fn yes_array_into_vec<T>() -> Vec<T> {
+    [].into()
+}
+
 use std::collections::VecDeque;
 
 pub fn yes_vecdeque_partial_eq_array<A, B>() -> impl PartialEq<[B; 32]>

src/test/ui/const-generics/array-impls/alloc-types-no-impls-length-33.rs

@@ -2,6 +2,11 @@
 
 use std::{convert::TryFrom, rc::Rc, sync::Arc};
 
+pub fn no_vec() {
+    let v: Vec<_> = [0; 33].into();
+    //~^ ERROR arrays only have std trait implementations for lengths 0..=32
+}
+
 pub fn no_box() {
     let boxed_slice = Box::new([0; 33]) as Box<[i32]>;
     let boxed_array = <Box<[i32; 33]>>::try_from(boxed_slice);

src/test/ui/const-generics/array-impls/alloc-types-no-impls-length-33.stderr

+error[E0277]: arrays only have std trait implementations for lengths 0..=32
+  --> $DIR/alloc-types-no-impls-length-33.rs:6:29
+   |
+LL |     let v: Vec<_> = [0; 33].into();
+   |                             ^^^^ the trait `std::array::LengthAtMost32` is not implemented for `[{integer}; 33]`
+   |
+   = note: required because of the requirements on the impl of `std::convert::From<[{integer}; 33]>` for `std::vec::Vec<{integer}>`
+   = note: required because of the requirements on the impl of `std::convert::Into<std::vec::Vec<{integer}>>` for `[{integer}; 33]`
+
 error[E0277]: the trait bound `std::boxed::Box<[i32; 33]>: std::convert::From<std::boxed::Box<[i32]>>` is not satisfied
-  --> $DIR/alloc-types-no-impls-length-33.rs:7:23
+  --> $DIR/alloc-types-no-impls-length-33.rs:12:23
    |
 LL |     let boxed_array = <Box<[i32; 33]>>::try_from(boxed_slice);
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::convert::From<std::boxed::Box<[i32]>>` is not implemented for `std::boxed::Box<[i32; 33]>`
@@ -14,7 +23,7 @@ LL |     let boxed_array = <Box<[i32; 33]>>::try_from(boxed_slice);
    = note: required because of the requirements on the impl of `std::convert::TryFrom<std::boxed::Box<[i32]>>` for `std::boxed::Box<[i32; 33]>`
 
 error[E0277]: the trait bound `std::boxed::Box<[i32; 33]>: std::convert::TryFrom<std::boxed::Box<[i32]>>` is not satisfied
-  --> $DIR/alloc-types-no-impls-length-33.rs:7:23
+  --> $DIR/alloc-types-no-impls-length-33.rs:12:23
    |
 LL |     let boxed_array = <Box<[i32; 33]>>::try_from(boxed_slice);
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::convert::TryFrom<std::boxed::Box<[i32]>>` is not implemented for `std::boxed::Box<[i32; 33]>`
@@ -23,7 +32,7 @@ LL |     let boxed_array = <Box<[i32; 33]>>::try_from(boxed_slice);
              <std::boxed::Box<[T; _]> as std::convert::TryFrom<std::boxed::Box<[T]>>>
 
 error[E0277]: the trait bound `std::rc::Rc<[i32; 33]>: std::convert::From<std::rc::Rc<[i32]>>` is not satisfied
-  --> $DIR/alloc-types-no-impls-length-33.rs:14:23
+  --> $DIR/alloc-types-no-impls-length-33.rs:19:23
    |
 LL |     let boxed_array = <Rc<[i32; 33]>>::try_from(boxed_slice);
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::convert::From<std::rc::Rc<[i32]>>` is not implemented for `std::rc::Rc<[i32; 33]>`
@@ -38,7 +47,7 @@ LL |     let boxed_array = <Rc<[i32; 33]>>::try_from(boxed_slice);
    = note: required because of the requirements on the impl of `std::convert::TryFrom<std::rc::Rc<[i32]>>` for `std::rc::Rc<[i32; 33]>`
 
 error[E0277]: the trait bound `std::rc::Rc<[i32; 33]>: std::convert::TryFrom<std::rc::Rc<[i32]>>` is not satisfied
-  --> $DIR/alloc-types-no-impls-length-33.rs:14:23
+  --> $DIR/alloc-types-no-impls-length-33.rs:19:23
    |
 LL |     let boxed_array = <Rc<[i32; 33]>>::try_from(boxed_slice);
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::convert::TryFrom<std::rc::Rc<[i32]>>` is not implemented for `std::rc::Rc<[i32; 33]>`
@@ -47,7 +56,7 @@ LL |     let boxed_array = <Rc<[i32; 33]>>::try_from(boxed_slice);
              <std::rc::Rc<[T; _]> as std::convert::TryFrom<std::rc::Rc<[T]>>>
 
 error[E0277]: the trait bound `std::sync::Arc<[i32; 33]>: std::convert::From<std::sync::Arc<[i32]>>` is not satisfied
-  --> $DIR/alloc-types-no-impls-length-33.rs:21:23
+  --> $DIR/alloc-types-no-impls-length-33.rs:26:23
    |
 LL |     let boxed_array = <Arc<[i32; 33]>>::try_from(boxed_slice);
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::convert::From<std::sync::Arc<[i32]>>` is not implemented for `std::sync::Arc<[i32; 33]>`
@@ -62,7 +71,7 @@ LL |     let boxed_array = <Arc<[i32; 33]>>::try_from(boxed_slice);
    = note: required because of the requirements on the impl of `std::convert::TryFrom<std::sync::Arc<[i32]>>` for `std::sync::Arc<[i32; 33]>`
 
 error[E0277]: the trait bound `std::sync::Arc<[i32; 33]>: std::convert::TryFrom<std::sync::Arc<[i32]>>` is not satisfied
-  --> $DIR/alloc-types-no-impls-length-33.rs:21:23
+  --> $DIR/alloc-types-no-impls-length-33.rs:26:23
    |
 LL |     let boxed_array = <Arc<[i32; 33]>>::try_from(boxed_slice);
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::convert::TryFrom<std::sync::Arc<[i32]>>` is not implemented for `std::sync::Arc<[i32; 33]>`
@@ -70,6 +79,6 @@ LL |     let boxed_array = <Arc<[i32; 33]>>::try_from(boxed_slice);
    = help: the following implementations were found:
              <std::sync::Arc<[T; _]> as std::convert::TryFrom<std::sync::Arc<[T]>>>
 
-error: aborting due to 6 previous errors
+error: aborting due to 7 previous errors
 
 For more information about this error, try `rustc --explain E0277`.