Rollup merge of #62735 - petrochenkov:galloc, r=alexcrichton

Turn `#[global_allocator]` into a regular attribute macro

It was a 99% macro with exception of some diagnostic details.

As a result of the change, `#[global_allocator]` now works in nested modules and even in nameless blocks.

Fixes https://github.com/rust-lang/rust/issues/44113
Fixes https://github.com/rust-lang/rust/issues/58072

src/test/ui/allocator-submodule.rs

@@ -1,28 +0,0 @@
-// Tests that it is possible to create a global allocator in a submodule, rather than in the crate
-// root.
-
-extern crate alloc;
-
-use std::{
-    alloc::{GlobalAlloc, Layout},
-    ptr,
-};
-
-struct MyAlloc;
-
-unsafe impl GlobalAlloc for MyAlloc {
-    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
-        ptr::null_mut()
-    }
-
-    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {}
-}
-
-mod submod {
-    use super::MyAlloc;
-
-    #[global_allocator]
-    static MY_HEAP: MyAlloc = MyAlloc; //~ ERROR global_allocator
-}
-
-fn main() {}

src/test/ui/allocator-submodule.stderr

@@ -1,8 +0,0 @@
-error: `global_allocator` cannot be used in submodules
-  --> $DIR/allocator-submodule.rs:25:5
-   |
-LL |     static MY_HEAP: MyAlloc = MyAlloc;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to previous error
-

src/test/ui/allocator/allocator-args.rs

@@ -0,0 +1,13 @@
+use std::alloc::{GlobalAlloc, Layout};
+
+struct A;
+
+unsafe impl GlobalAlloc for A {
+    unsafe fn alloc(&self, _: Layout) -> *mut u8 { panic!() }
+    unsafe fn dealloc(&self, _: *mut u8, _: Layout) { panic!() }
+}
+
+#[global_allocator(malloc)] //~ ERROR malformed `global_allocator` attribute input
+static S: A = A;
+
+fn main() {}

src/test/ui/allocator/allocator-args.stderr

@@ -0,0 +1,8 @@
+error: malformed `global_allocator` attribute input
+  --> $DIR/allocator-args.rs:10:1
+   |
+LL | #[global_allocator(malloc)]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: must be of the form: `#[global_allocator]`
+
+error: aborting due to previous error
+

src/test/ui/allocator/two-allocators.rs

@@ -4,6 +4,6 @@ use std::alloc::System;
 static A: System = System;
 #[global_allocator]
 static B: System = System;
-//~^ ERROR: cannot define more than one `#[global_allocator]`
+//~^ ERROR: cannot define multiple global allocators
 
 fn main() {}

src/test/ui/allocator/two-allocators.stderr

@@ -1,8 +1,14 @@
-error: cannot define more than one `#[global_allocator]`
+error: cannot define multiple global allocators
   --> $DIR/two-allocators.rs:6:1
    |
 LL | static B: System = System;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: the previous global allocator is defined here
+  --> $DIR/two-allocators.rs:4:1
+   |
+LL | static A: System = System;
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/feature-gate/issue-43106-gating-of-bench.stderr

@@ -1,3 +1,13 @@
+warning: attribute must be of the form `#[bench]`
+  --> $DIR/issue-43106-gating-of-bench.rs:15:1
+   |
+LL | #![bench                   = "4100"]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(ill_formed_attribute_input)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #57571 <https://github.com/rust-lang/rust/issues/57571>
+
 error[E0601]: `main` function not found in crate `issue_43106_gating_of_bench`
    |
    = note: consider adding a `main` function to `$DIR/issue-43106-gating-of-bench.rs`

src/test/ui/feature-gate/issue-43106-gating-of-test.stderr

@@ -1,3 +1,13 @@
+warning: attribute must be of the form `#[test]`
+  --> $DIR/issue-43106-gating-of-test.rs:10:1
+   |
+LL | #![test                    = "4200"]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(ill_formed_attribute_input)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #57571 <https://github.com/rust-lang/rust/issues/57571>
+
 error[E0601]: `main` function not found in crate `issue_43106_gating_of_test`
    |
    = note: consider adding a `main` function to `$DIR/issue-43106-gating-of-test.rs`