Auto merge of #62935 - Centril:rollup-hzj9att, r=Centril

Rollup of 10 pull requests

Successful merges:

 - #62641 (Regenerate character tables for Unicode 12.1)
 - #62716 (state also in the intro that UnsafeCell has no effect on &mut)
 - #62738 (Remove uses of mem::uninitialized from std::sys::cloudabi)
 - #62772 (Suggest trait bound on type parameter when it is unconstrained)
 - #62890 (Normalize use of backticks in compiler messages for libsyntax/*)
 - #62905 (Normalize use of backticks in compiler messages for doc)
 - #62916 (Add test `self-in-enum-definition`)
 - #62917 (Always emit trailing slash error)
 - #62926 (Fix typo in mem::uninitialized doc)
 - #62927 (use PanicMessage in MIR, kill InterpError::description)

Failed merges:

r? @ghost

Author: bors

Diff for: src/doc/rustc/src/lints/index.md

@@ -19,7 +19,7 @@ warning: unused variable: `x`
 2 |     let x = 5;
   |         ^
   |
-  = note: #[warn(unused_variables)] on by default
+  = note: `#[warn(unused_variables)]` on by default
   = note: to avoid this warning, consider using `_x` instead
 ```
 

Diff for: src/doc/rustc/src/lints/levels.md

@@ -53,7 +53,7 @@ warning: unused variable: `x`
 2 |     let x = 5;
   |         ^
   |
-  = note: #[warn(unused_variables)] on by default
+  = note: `#[warn(unused_variables)]` on by default
   = note: to avoid this warning, consider using `_x` instead
 ```
 
@@ -76,7 +76,7 @@ error: bitshift exceeds the type's number of bits
 2 |     100u8 << 10;
   |     ^^^^^^^^^^^
   |
-  = note: #[deny(exceeding_bitshifts)] on by default
+  = note: `#[deny(exceeding_bitshifts)]` on by default
 ```
 
 What's the difference between an error from a lint and a regular old error?
@@ -236,7 +236,7 @@ warning: bitshift exceeds the type's number of bits
 2 |     100u8 << 10;
   |     ^^^^^^^^^^^
   |
-  = note: #[warn(exceeding_bitshifts)] on by default
+  = note: `#[warn(exceeding_bitshifts)]` on by default
 
 warning: this expression will panic at run-time
  --> lib.rs:2:5

Diff for: src/doc/rustc/src/lints/listing/allowed-by-default.md

@@ -165,7 +165,7 @@ pub struct Foo;
 When set to 'deny', this will produce:
 
 ```text
-error: type does not implement `fmt::Debug`; consider adding #[derive(Debug)] or a manual implementation
+error: type does not implement `fmt::Debug`; consider adding `#[derive(Debug)]` or a manual implementation
  --> src/main.rs:3:1
   |
 3 | pub struct Foo;

Diff for: src/doc/rustc/src/lints/listing/deny-by-default.md

@@ -40,7 +40,7 @@ error: defaults for type parameters are only allowed in `struct`, `enum`, `type`
 4 | fn foo<T=i32>(t: T) {}
   |        ^
   |
-  = note: #[deny(invalid_type_param_default)] on by default
+  = note: `#[deny(invalid_type_param_default)]` on by default
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
 ```
@@ -74,7 +74,7 @@ error: private struct constructors are not usable through re-exports in outer mo
 5 |         ::S;
   |         ^^^
   |
-  = note: #[deny(legacy_constructor_visibility)] on by default
+  = note: `#[deny(legacy_constructor_visibility)]` on by default
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #39207 <https://github.com/rust-lang/rust/issues/39207>
 ```
@@ -84,9 +84,9 @@ error: private struct constructors are not usable through re-exports in outer mo
 
 The legacy_directory_ownership warning is issued when
 
-* There is a non-inline module with a #[path] attribute (e.g. #[path = "foo.rs"] mod bar;),
+* There is a non-inline module with a `#[path]` attribute (e.g. `#[path = "foo.rs"] mod bar;`),
 * The module's file ("foo.rs" in the above example) is not named "mod.rs", and
-* The module's file contains a non-inline child module without a #[path] attribute.
+* The module's file contains a non-inline child module without a `#[path]` attribute.
 
 The warning can be fixed by renaming the parent module to "mod.rs" and moving
 it into its own directory if appropriate.
@@ -139,7 +139,7 @@ const FOO: i32 = 5;
 This will produce:
 
 ```text
-error: const items should never be #[no_mangle]
+error: const items should never be `#[no_mangle]`
  --> src/main.rs:3:1
   |
 3 | const FOO: i32 = 5;
@@ -187,7 +187,7 @@ error: parenthesized parameters may only be used with a trait
 2 |   let x = 5 as usize();
   |                     ^^
   |
-  = note: #[deny(parenthesized_params_in_types_and_modules)] on by default
+  = note: `#[deny(parenthesized_params_in_types_and_modules)]` on by default
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #42238 <https://github.com/rust-lang/rust/issues/42238>
 ```

Diff for: src/doc/rustc/src/lints/listing/warn-by-default.md

@@ -90,7 +90,7 @@ warning: floating-point literals cannot be used in patterns
 4 |         5.0 => {},
   |         ^^^
   |
-  = note: #[warn(illegal_floating_point_literal_pattern)] on by default
+  = note: `#[warn(illegal_floating_point_literal_pattern)]` on by default
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #41620 <https://github.com/rust-lang/rust/issues/41620>
 ```
@@ -109,7 +109,7 @@ extern "C" {
 This will produce:
 
 ```text
-warning: found struct without foreign-function-safe representation annotation in foreign module, consider adding a #[repr(C)] attribute to the type
+warning: found struct without foreign-function-safe representation annotation in foreign module, consider adding a `#[repr(C)]` attribute to the type
  --> src/main.rs:2:20
   |
 2 |     static STATIC: String;
@@ -146,7 +146,7 @@ warning: cannot specify lifetime arguments explicitly if late bound lifetime par
 8 |     S.late::<'static>(&0, &0);
   |              ^^^^^^^
   |
-  = note: #[warn(late_bound_lifetime_arguments)] on by default
+  = note: `#[warn(late_bound_lifetime_arguments)]` on by default
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #42868 <https://github.com/rust-lang/rust/issues/42868>
 ```
@@ -327,7 +327,7 @@ warning: patterns aren't allowed in methods without bodies
 2 |     fn foo(mut arg: u8);
   |            ^^^^^^^
   |
-  = note: #[warn(patterns_in_fns_without_body)] on by default
+  = note: `#[warn(patterns_in_fns_without_body)]` on by default
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #35203 <https://github.com/rust-lang/rust/issues/35203>
 ```
@@ -406,7 +406,7 @@ fn foo() {}
 This will produce:
 
 ```text
-warning: function is marked #[no_mangle], but not exported
+warning: function is marked `#[no_mangle]`, but not exported
  --> src/main.rs:2:1
   |
 2 | fn foo() {}
@@ -433,7 +433,7 @@ static X: i32 = 4;
 This will produce:
 
 ```text
-warning: static is marked #[no_mangle], but not exported
+warning: static is marked `#[no_mangle]`, but not exported
  --> src/main.rs:2:1
   |
 2 | static X: i32 = 4;
@@ -496,7 +496,7 @@ warning: borrow of packed field requires unsafe function or block (error E0133)
 11 |     let y = &x.data.0;
    |             ^^^^^^^^^
    |
-   = note: #[warn(safe_packed_borrows)] on by default
+   = note: `#[warn(safe_packed_borrows)]` on by default
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #46043 <https://github.com/rust-lang/rust/issues/46043>
 ```
@@ -542,7 +542,7 @@ warning: bounds on generic parameters are not enforced in type aliases
 2 | type SendVec<T: Send> = Vec<T>;
   |                 ^^^^
   |
-  = note: #[warn(type_alias_bounds)] on by default
+  = note: `#[warn(type_alias_bounds)]` on by default
   = help: the bound will not be checked when the type alias is used, and should be removed
 ```
 
@@ -567,7 +567,7 @@ warning: type annotations needed
 4 |     if data.is_null() {}
   |             ^^^^^^^
   |
-  = note: #[warn(tyvar_behind_raw_pointer)] on by default
+  = note: `#[warn(tyvar_behind_raw_pointer)]` on by default
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in the 2018 edition!
   = note: for more information, see issue #46906 <https://github.com/rust-lang/rust/issues/46906>
 ```
@@ -787,7 +787,7 @@ warning: doc comment not used by rustdoc
 
 ## unused-features
 
-This lint detects unused or unknown features found in crate-level #[feature] directives.
+This lint detects unused or unknown features found in crate-level `#[feature]` directives.
 To fix this, simply remove the feature flag.
 
 ## unused-imports
@@ -839,7 +839,7 @@ warning: unused macro definition
 
 ## unused-must-use
 
-This lint detects unused result of a type flagged as #[must_use]. Some
+This lint detects unused result of a type flagged as `#[must_use]`. Some
 example code that triggers this lint:
 
 ```rust

Diff for: src/libcore/cell.rs

@@ -1412,8 +1412,9 @@ impl<T: ?Sized + fmt::Display> fmt::Display for RefMut<'_, T> {
 /// If you have a reference `&SomeStruct`, then normally in Rust all fields of `SomeStruct` are
 /// immutable. The compiler makes optimizations based on the knowledge that `&T` is not mutably
 /// aliased or mutated, and that `&mut T` is unique. `UnsafeCell<T>` is the only core language
-/// feature to work around this restriction. All other types that allow internal mutability, such as
-/// `Cell<T>` and `RefCell<T>`, use `UnsafeCell` to wrap their internal data.
+/// feature to work around the restriction that `&T` may not be mutated. All other types that
+/// allow internal mutability, such as `Cell<T>` and `RefCell<T>`, use `UnsafeCell` to wrap their
+/// internal data. There is *no* legal way to obtain aliasing `&mut`, not even with `UnsafeCell<T>`.
 ///
 /// The `UnsafeCell` API itself is technically very simple: it gives you a raw pointer `*mut T` to
 /// its contents. It is up to _you_ as the abstraction designer to use that raw pointer correctly.

Diff for: src/libcore/mem/mod.rs

@@ -456,7 +456,7 @@ pub unsafe fn zeroed<T>() -> T {
 /// Bypasses Rust's normal memory-initialization checks by pretending to
 /// produce a value of type `T`, while doing nothing at all.
 ///
-/// **This functon is deprecated.** Use [`MaybeUninit<T>`] instead.
+/// **This function is deprecated.** Use [`MaybeUninit<T>`] instead.
 ///
 /// The reason for deprecation is that the function basically cannot be used
 /// correctly: [the Rust compiler assumes][inv] that values are properly initialized.

Diff for: src/libcore/unicode/printable.py

@@ -111,17 +111,17 @@ def compress_normal(normal):
     return compressed
 
 def print_singletons(uppers, lowers, uppersname, lowersname):
-    print("const {}: &'static [(u8, u8)] = &[".format(uppersname))
+    print("const {}: &[(u8, u8)] = &[".format(uppersname))
     for u, c in uppers:
         print("    ({:#04x}, {}),".format(u, c))
     print("];")
-    print("const {}: &'static [u8] = &[".format(lowersname))
+    print("const {}: &[u8] = &[".format(lowersname))
     for i in range(0, len(lowers), 8):
         print("    {}".format(" ".join("{:#04x},".format(l) for l in lowers[i:i+8])))
     print("];")
 
 def print_normal(normal, normalname):
-    print("const {}: &'static [u8] = &[".format(normalname))
+    print("const {}: &[u8] = &[".format(normalname))
     for v in normal:
         print("    {}".format(" ".join("{:#04x},".format(i) for i in v)))
     print("];")