Auto merge of #48171 - FraGag:doc-copy-clone-impls, r=nikomatsakis

Better document the implementors of Clone and Copy

There are two parts to this change. The first part is a change to the compiler and to the standard library (specifically, libcore) to allow implementations of `Clone` and `Copy` to be written for a subset of builtin types. By adding these implementations to libcore, they now show up in the documentation. This is a [breaking-change] for users of `#![no_core]`, because they will now have to supply their own copy of the implementations of `Clone` and `Copy` that were added in libcore.

The second part is purely a documentation change to document the other implementors of `Clone` and `Copy` that cannot be described in Rust code (yet) and are thus provided by the compiler.

Fixes #25893

4 files changed, 53 insertions, 23 deletions

diff --git a/src/test/ui/coherence-impls-copy.rs b/src/test/ui/coherence-impls-copy.rs
index 51f43d27c34..f48790d1f40 100644
--- a/src/test/ui/coherence-impls-copy.rs
+++ b/src/test/ui/coherence-impls-copy.rs
@@ -12,6 +12,10 @@
 
 use std::marker::Copy;
 
+impl Copy for i32 {}
+//~^ ERROR conflicting implementations of trait `std::marker::Copy` for type `i32`:
+//~| ERROR only traits defined in the current crate can be implemented for arbitrary types
+
 enum TestE {
   A
 }
@@ -35,14 +39,14 @@ impl Copy for (MyType, MyType) {}
 //~| ERROR only traits defined in the current crate can be implemented for arbitrary types
 
 impl Copy for &'static NotSync {}
-//~^ ERROR the trait `Copy` may not be implemented for this type
+//~^ ERROR conflicting implementations of trait `std::marker::Copy` for type `&NotSync`:
 
 impl Copy for [MyType] {}
 //~^ ERROR the trait `Copy` may not be implemented for this type
 //~| ERROR only traits defined in the current crate can be implemented for arbitrary types
 
 impl Copy for &'static [NotSync] {}
-//~^ ERROR the trait `Copy` may not be implemented for this type
+//~^ ERROR conflicting implementations of trait `std::marker::Copy` for type `&[NotSync]`:
 //~| ERROR only traits defined in the current crate can be implemented for arbitrary types
 
 fn main() {
diff --git a/src/test/ui/coherence-impls-copy.stderr b/src/test/ui/coherence-impls-copy.stderr
index 5f9b0c62df2..24e7e85b1a9 100644
--- a/src/test/ui/coherence-impls-copy.stderr
+++ b/src/test/ui/coherence-impls-copy.stderr
@@ -1,35 +1,61 @@
-error[E0206]: the trait `Copy` may not be implemented for this type
-  --> $DIR/coherence-impls-copy.rs:29:15
+error[E0119]: conflicting implementations of trait `std::marker::Copy` for type `i32`:
+  --> $DIR/coherence-impls-copy.rs:15:1
    |
-LL | impl Copy for &'static mut MyType {}
-   |               ^^^^^^^^^^^^^^^^^^^ type is not a structure or enumeration
+LL | impl Copy for i32 {}
+   | ^^^^^^^^^^^^^^^^^
+   |
+   = note: conflicting implementation in crate `core`:
+           - impl std::marker::Copy for i32;
+
+error[E0119]: conflicting implementations of trait `std::marker::Copy` for type `&NotSync`:
+  --> $DIR/coherence-impls-copy.rs:41:1
+   |
+LL | impl Copy for &'static NotSync {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: conflicting implementation in crate `core`:
+           - impl<'a, T> std::marker::Copy for &'a T
+             where T: ?Sized;
+
+error[E0119]: conflicting implementations of trait `std::marker::Copy` for type `&[NotSync]`:
+  --> $DIR/coherence-impls-copy.rs:48:1
+   |
+LL | impl Copy for &'static [NotSync] {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: conflicting implementation in crate `core`:
+           - impl<'a, T> std::marker::Copy for &'a T
+             where T: ?Sized;
 
 error[E0206]: the trait `Copy` may not be implemented for this type
   --> $DIR/coherence-impls-copy.rs:33:15
    |
-LL | impl Copy for (MyType, MyType) {}
-   |               ^^^^^^^^^^^^^^^^ type is not a structure or enumeration
+LL | impl Copy for &'static mut MyType {}
+   |               ^^^^^^^^^^^^^^^^^^^ type is not a structure or enumeration
 
 error[E0206]: the trait `Copy` may not be implemented for this type
   --> $DIR/coherence-impls-copy.rs:37:15
    |
-LL | impl Copy for &'static NotSync {}
+LL | impl Copy for (MyType, MyType) {}
    |               ^^^^^^^^^^^^^^^^ type is not a structure or enumeration
 
 error[E0206]: the trait `Copy` may not be implemented for this type
-  --> $DIR/coherence-impls-copy.rs:40:15
+  --> $DIR/coherence-impls-copy.rs:44:15
    |
 LL | impl Copy for [MyType] {}
    |               ^^^^^^^^ type is not a structure or enumeration
 
-error[E0206]: the trait `Copy` may not be implemented for this type
-  --> $DIR/coherence-impls-copy.rs:44:15
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/coherence-impls-copy.rs:15:1
    |
-LL | impl Copy for &'static [NotSync] {}
-   |               ^^^^^^^^^^^^^^^^^^ type is not a structure or enumeration
+LL | impl Copy for i32 {}
+   | ^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
+   |
+   = note: the impl does not reference any types defined in this crate
+   = note: define and implement a trait or new type instead
 
 error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
-  --> $DIR/coherence-impls-copy.rs:33:1
+  --> $DIR/coherence-impls-copy.rs:37:1
    |
 LL | impl Copy for (MyType, MyType) {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
@@ -38,7 +64,7 @@ LL | impl Copy for (MyType, MyType) {}
    = note: define and implement a trait or new type instead
 
 error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
-  --> $DIR/coherence-impls-copy.rs:40:1
+  --> $DIR/coherence-impls-copy.rs:44:1
    |
 LL | impl Copy for [MyType] {}
    | ^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
@@ -47,7 +73,7 @@ LL | impl Copy for [MyType] {}
    = note: define and implement a trait or new type instead
 
 error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
-  --> $DIR/coherence-impls-copy.rs:44:1
+  --> $DIR/coherence-impls-copy.rs:48:1
    |
 LL | impl Copy for &'static [NotSync] {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl doesn't use types inside crate
@@ -55,7 +81,7 @@ LL | impl Copy for &'static [NotSync] {}
    = note: the impl does not reference any types defined in this crate
    = note: define and implement a trait or new type instead
 
-error: aborting due to 8 previous errors
+error: aborting due to 10 previous errors
 
-Some errors occurred: E0117, E0206.
+Some errors occurred: E0117, E0119, E0206.
 For more information about an error, try `rustc --explain E0117`.
diff --git a/src/test/ui/error-codes/E0206.rs b/src/test/ui/error-codes/E0206.rs
index da0370b301b..9b3d1b351dd 100644
--- a/src/test/ui/error-codes/E0206.rs
+++ b/src/test/ui/error-codes/E0206.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-type Foo = i32;
+type Foo = [u8; 256];
 
 impl Copy for Foo { }
 //~^ ERROR the trait `Copy` may not be implemented for this type
@@ -17,7 +17,7 @@ impl Copy for Foo { }
 #[derive(Copy, Clone)]
 struct Bar;
 
-impl Copy for &'static Bar { }
+impl Copy for &'static mut Bar { }
 //~^ ERROR the trait `Copy` may not be implemented for this type
 
 fn main() {
diff --git a/src/test/ui/error-codes/E0206.stderr b/src/test/ui/error-codes/E0206.stderr
index bbc0da2248f..f2c23b0767a 100644
--- a/src/test/ui/error-codes/E0206.stderr
+++ b/src/test/ui/error-codes/E0206.stderr
@@ -7,8 +7,8 @@ LL | impl Copy for Foo { }
 error[E0206]: the trait `Copy` may not be implemented for this type
   --> $DIR/E0206.rs:20:15
    |
-LL | impl Copy for &'static Bar { }
-   |               ^^^^^^^^^^^^ type is not a structure or enumeration
+LL | impl Copy for &'static mut Bar { }
+   |               ^^^^^^^^^^^^^^^^ type is not a structure or enumeration
 
 error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
   --> $DIR/E0206.rs:13:1