Rollup merge of #56916 - oli-obk:static_mut_beta_regression, r=davidtwco

Fix mutable references in `static mut`

fixes #56903

7 files changed, 68 insertions, 5 deletions

diff --git a/src/test/ui/consts/static_mut_containing_mut_ref.rs b/src/test/ui/consts/static_mut_containing_mut_ref.rs
new file mode 100644
index 00000000000..27e1a111163
--- /dev/null
+++ b/src/test/ui/consts/static_mut_containing_mut_ref.rs
@@ -0,0 +1,7 @@
+// compile-pass
+
+static mut STDERR_BUFFER_SPACE: [u8; 42] = [0u8; 42];
+
+pub static mut STDERR_BUFFER: *mut [u8] = unsafe { &mut STDERR_BUFFER_SPACE };
+
+fn main() {}
diff --git a/src/test/ui/consts/static_mut_containing_mut_ref2.rs b/src/test/ui/consts/static_mut_containing_mut_ref2.rs
new file mode 100644
index 00000000000..4180b1e295a
--- /dev/null
+++ b/src/test/ui/consts/static_mut_containing_mut_ref2.rs
@@ -0,0 +1,9 @@
+#![feature(const_let)]
+
+static mut STDERR_BUFFER_SPACE: u8 = 0;
+
+pub static mut STDERR_BUFFER: () = unsafe { *(&mut STDERR_BUFFER_SPACE) = 42; };
+//~^ ERROR references in statics may only refer to immutable values
+//~| ERROR static contains unimplemented expression type
+
+fn main() {}
diff --git a/src/test/ui/consts/static_mut_containing_mut_ref2.stderr b/src/test/ui/consts/static_mut_containing_mut_ref2.stderr
new file mode 100644
index 00000000000..f0ae1545056
--- /dev/null
+++ b/src/test/ui/consts/static_mut_containing_mut_ref2.stderr
@@ -0,0 +1,16 @@
+error[E0017]: references in statics may only refer to immutable values
+  --> $DIR/static_mut_containing_mut_ref2.rs:5:46
+   |
+LL | pub static mut STDERR_BUFFER: () = unsafe { *(&mut STDERR_BUFFER_SPACE) = 42; };
+   |                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^ statics require immutable values
+
+error[E0019]: static contains unimplemented expression type
+  --> $DIR/static_mut_containing_mut_ref2.rs:5:45
+   |
+LL | pub static mut STDERR_BUFFER: () = unsafe { *(&mut STDERR_BUFFER_SPACE) = 42; };
+   |                                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
+Some errors occurred: E0017, E0019.
+For more information about an error, try `rustc --explain E0017`.
diff --git a/src/test/ui/consts/static_mut_containing_mut_ref3.rs b/src/test/ui/consts/static_mut_containing_mut_ref3.rs
new file mode 100644
index 00000000000..0bc7faa9afd
--- /dev/null
+++ b/src/test/ui/consts/static_mut_containing_mut_ref3.rs
@@ -0,0 +1,8 @@
+#![feature(const_let)]
+
+static mut FOO: (u8, u8) = (42, 43);
+
+static mut BAR: () = unsafe { FOO.0 = 99; };
+//~^ ERROR could not evaluate static initializer
+
+fn main() {}
diff --git a/src/test/ui/consts/static_mut_containing_mut_ref3.stderr b/src/test/ui/consts/static_mut_containing_mut_ref3.stderr
new file mode 100644
index 00000000000..cae53c6fee9
--- /dev/null
+++ b/src/test/ui/consts/static_mut_containing_mut_ref3.stderr
@@ -0,0 +1,9 @@
+error[E0080]: could not evaluate static initializer
+  --> $DIR/static_mut_containing_mut_ref3.rs:5:31
+   |
+LL | static mut BAR: () = unsafe { FOO.0 = 99; };
+   |                               ^^^^^^^^^^ tried to modify a static's initial value from another static's initializer
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0080`.
diff --git a/src/test/ui/write-to-static-mut-in-static.rs b/src/test/ui/write-to-static-mut-in-static.rs
index 191f09b54ee..983b5d48e60 100644
--- a/src/test/ui/write-to-static-mut-in-static.rs
+++ b/src/test/ui/write-to-static-mut-in-static.rs
@@ -12,10 +12,10 @@
 
 pub static mut A: u32 = 0;
 pub static mut B: () = unsafe { A = 1; };
-//~^ ERROR cannot mutate statics in the initializer of another static
+//~^ ERROR could not evaluate static initializer
 
 pub static mut C: u32 = unsafe { C = 1; 0 };
-//~^ ERROR cannot mutate statics in the initializer of another static
+//~^ ERROR cycle detected
 
 pub static D: u32 = D;
 
diff --git a/src/test/ui/write-to-static-mut-in-static.stderr b/src/test/ui/write-to-static-mut-in-static.stderr
index 673a71b4642..335f849fb24 100644
--- a/src/test/ui/write-to-static-mut-in-static.stderr
+++ b/src/test/ui/write-to-static-mut-in-static.stderr
@@ -1,14 +1,28 @@
-error: cannot mutate statics in the initializer of another static
+error[E0080]: could not evaluate static initializer
   --> $DIR/write-to-static-mut-in-static.rs:14:33
    |
 LL | pub static mut B: () = unsafe { A = 1; };
-   |                                 ^^^^^
+   |                                 ^^^^^ tried to modify a static's initial value from another static's initializer
 
-error: cannot mutate statics in the initializer of another static
+error[E0391]: cycle detected when const-evaluating `C`
   --> $DIR/write-to-static-mut-in-static.rs:17:34
    |
 LL | pub static mut C: u32 = unsafe { C = 1; 0 };
    |                                  ^^^^^
+   |
+note: ...which requires const-evaluating `C`...
+  --> $DIR/write-to-static-mut-in-static.rs:17:1
+   |
+LL | pub static mut C: u32 = unsafe { C = 1; 0 };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: ...which again requires const-evaluating `C`, completing the cycle
+note: cycle used when const-evaluating + checking `C`
+  --> $DIR/write-to-static-mut-in-static.rs:17:1
+   |
+LL | pub static mut C: u32 = unsafe { C = 1; 0 };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 2 previous errors
 
+Some errors occurred: E0080, E0391.
+For more information about an error, try `rustc --explain E0080`.