Refer to u8 by absolute path in expansion of thread_local

[dtolnay]

The standard library's thread_local! macro previously referred to u8 just as u8, resolving to whatever u8 existed in the type namespace at the call site. This PR replaces those with $crate::primitive::u8 which always refers to std::primitive::u8 regardless of what's in scope at the call site. Unambiguously naming primitives inside macro-generated code is the reason that std::primitive was introduced in the first place.

Here is the error message prior to this PR ⬇️

error[E0308]: mismatched types
 --> src/main.rs:6:1
  |
6 | / std::thread_local! {
7 | |     pub static A: i32 = f();
8 | |     pub static B: i32 = const { 0 };
9 | | }
  | |_^ expected struct `u8`, found integer
  |
  = note: this error originates in the macro `$crate::__thread_local_inner` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0308]: mismatched types
 --> src/main.rs:6:1
  |
6 | / std::thread_local! {
7 | |     pub static A: i32 = f();
8 | |     pub static B: i32 = const { 0 };
9 | | }
  | | ^
  | | |
  | |_expected struct `u8`, found integer
  |   this expression has type `u8`
  |
  = note: this error originates in the macro `$crate::__thread_local_inner` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0308]: mismatched types
 --> src/main.rs:6:1
  |
6 | / std::thread_local! {
7 | |     pub static A: i32 = f();
8 | |     pub static B: i32 = const { 0 };
9 | | }
  | |_^ expected `u8`, found struct `u8`
  |
  = note: expected raw pointer `*mut u8` (`u8`)
             found raw pointer `*mut u8` (struct `u8`)
  = note: this error originates in the macro `$crate::__thread_local_inner` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0308]: mismatched types
 --> src/main.rs:6:1
  |
6 | / std::thread_local! {
7 | |     pub static A: i32 = f();
8 | |     pub static B: i32 = const { 0 };
9 | | }
  | |_^ expected `u8`, found struct `u8`
  |
  = note: expected fn pointer `unsafe extern "C" fn(*mut u8)`
                found fn item `unsafe extern "C" fn(*mut u8) {destroy}`
  = note: this error originates in the macro `$crate::__thread_local_inner` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0308]: mismatched types
 --> src/main.rs:6:1
  |
6 | / std::thread_local! {
7 | |     pub static A: i32 = f();
8 | |     pub static B: i32 = const { 0 };
9 | | }
  | | ^
  | | |
  | |_expected struct `u8`, found integer
  |   expected due to this type
  |
  = note: this error originates in the macro `$crate::__thread_local_inner` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0369]: binary operation `==` cannot be applied to type `u8`
 --> src/main.rs:6:1
  |
6 | / std::thread_local! {
7 | |     pub static A: i32 = f();
8 | |     pub static B: i32 = const { 0 };
9 | | }
  | | ^
  | | |
  | |_u8
  |   {integer}
  |
note: an implementation of `PartialEq<_>` might be missing for `u8`
 --> src/main.rs:4:1
  |
4 | struct u8;
  | ^^^^^^^^^^ must implement `PartialEq<_>`
  = note: this error originates in the macro `$crate::assert_eq` (in Nightly builds, run with -Z macro-backtrace for more info)
help: consider annotating `u8` with `#[derive(PartialEq)]`
  |
4 | #[derive(PartialEq)]
  |

error[E0277]: `u8` doesn't implement `Debug`
 --> src/main.rs:6:1
  |
6 | / std::thread_local! {
7 | |     pub static A: i32 = f();
8 | |     pub static B: i32 = const { 0 };
9 | | }
  | |_^ `u8` cannot be formatted using `{:?}`
  |
  = help: the trait `Debug` is not implemented for `u8`
  = note: add `#[derive(Debug)]` to `u8` or manually `impl Debug for u8`
  = note: this error originates in the macro `$crate::assert_eq` (in Nightly builds, run with -Z macro-backtrace for more info)

[rust-highfive]

r? @yaahc

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[Dylan-DPC]

@bors r+ rollup

[bors]

📌 Commit d93af61 has been approved by Dylan-DPC