Reject mutable externally implementable statics

compiler/rustc_builtin_macros/src/eii.rs

@@ -1,7 +1,8 @@
 use rustc_ast::token::{Delimiter, TokenKind};
 use rustc_ast::tokenstream::{DelimSpacing, DelimSpan, Spacing, TokenStream, TokenTree};
 use rustc_ast::{
-    Attribute, DUMMY_NODE_ID, EiiDecl, EiiImpl, ItemKind, MetaItem, Path, StmtKind, Visibility, ast,
+    Attribute, DUMMY_NODE_ID, EiiDecl, EiiImpl, ItemKind, MetaItem, Mutability, Path, StmtKind,
+    Visibility, ast,
 };
 use rustc_ast_pretty::pprust::path_to_string;
 use rustc_expand::base::{Annotatable, ExtCtxt};
@@ -11,7 +12,7 @@
 use crate::errors::{
     EiiExternTargetExpectedList, EiiExternTargetExpectedMacro, EiiExternTargetExpectedUnsafe,
     EiiMacroExpectedMaxOneArgument, EiiOnlyOnce, EiiSharedMacroInStatementPosition,
-    EiiSharedMacroTarget, EiiStaticArgumentRequired, EiiStaticDefault,
+    EiiSharedMacroTarget, EiiStaticArgumentRequired, EiiStaticDefault, EiiStaticMutable,
 };
 
 /// ```rust
@@ -100,6 +101,15 @@ fn eii_(
                 });
                 return vec![];
             }
+
+            // Mut statics are currently not supported
+            if stat.mutability == Mutability::Mut {
+                ecx.dcx().emit_err(EiiStaticMutable {
+                    span: eii_attr_span,
+                    name: path_to_string(&meta_item.path),
+                });
+            }
+
             (item.span, stat.ident)
         }
         _ => {

compiler/rustc_builtin_macros/src/errors.rs

@@ -1140,6 +1140,14 @@ pub(crate) struct EiiStaticArgumentRequired {
     pub name: String,
 }
 
+#[derive(Diagnostic)]
+#[diag("`#[{$name}]` cannot be used on mutable statics")]
+pub(crate) struct EiiStaticMutable {
+    #[primary_span]
+    pub span: Span,
+    pub name: String,
+}
+
 #[derive(Diagnostic)]
 #[diag("`#[{$name}]` can only be used on functions inside a module")]
 pub(crate) struct EiiSharedMacroInStatementPosition {

tests/ui/eii/static/mismatch_mut.rs

@@ -5,6 +5,7 @@
 #![feature(extern_item_impls)]
 
 #[eii(hello)]
+//~^ ERROR `#[eii]` cannot be used on mutable statics
 static mut HELLO: u64;
 
 #[hello]

tests/ui/eii/static/mismatch_mut.stderr

@@ -1,8 +1,14 @@
+error: `#[eii]` cannot be used on mutable statics
+  --> $DIR/mismatch_mut.rs:7:1
+   |
+LL | #[eii(hello)]
+   | ^^^^^^^^^^^^^
+
 error: mutability does not match with the definition of`#[hello]`
-  --> $DIR/mismatch_mut.rs:10:1
+  --> $DIR/mismatch_mut.rs:11:1
    |
 LL | #[hello]
    | ^^^^^^^^
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 

tests/ui/eii/static/mismatch_mut2.rs

@@ -0,0 +1,21 @@
+//@ ignore-backends: gcc
+// FIXME: linking on windows (specifically mingw) not yet supported, see tracking issue #125418
+//@ ignore-windows
+// Tests whether EIIs work on statics
+#![feature(extern_item_impls)]
+
+#[eii(hello)]
+static HELLO: u64;
+
+#[hello]
+//~^ ERROR mutability does not match with the definition of`#[hello]`
+static mut HELLO_IMPL: u64 = 5;
+
+// what you would write:
+fn main() {
+    // directly
+    println!("{}", unsafe { HELLO_IMPL });
+
+    // through the alias
+    println!("{HELLO}");
+}

tests/ui/eii/static/mismatch_mut2.stderr

@@ -0,0 +1,8 @@
+error: mutability does not match with the definition of`#[hello]`
+  --> $DIR/mismatch_mut2.rs:10:1
+   |
+LL | #[hello]
+   | ^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/eii/static/mismatch_safety.rs

@@ -5,7 +5,7 @@
 #![feature(extern_item_impls)]
 
 #[eii(hello)]
-unsafe static mut HELLO: u64;
+unsafe static HELLO: u64;
 
 #[hello]
 //~^ ERROR safety does not match with the definition of`#[hello]`

tests/ui/eii/static/mismatch_safety2.rs

@@ -0,0 +1,21 @@
+//@ ignore-backends: gcc
+// FIXME: linking on windows (specifically mingw) not yet supported, see tracking issue #125418
+//@ ignore-windows
+// Tests whether EIIs work on statics
+#![feature(extern_item_impls)]
+
+#[eii(hello)]
+static HELLO: u64;
+
+#[hello]
+unsafe static HELLO_IMPL: u64 = 5;
+//~^ ERROR static items cannot be declared with `unsafe` safety qualifier outside of `extern` block
+
+// what you would write:
+fn main() {
+    // directly
+    println!("{HELLO_IMPL}");
+
+    // through the alias
+    println!("{}", unsafe { HELLO });
+}

tests/ui/eii/static/mismatch_safety2.stderr

@@ -0,0 +1,8 @@
+error: static items cannot be declared with `unsafe` safety qualifier outside of `extern` block
+  --> $DIR/mismatch_safety2.rs:11:1
+   |
+LL | unsafe static HELLO_IMPL: u64 = 5;
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/eii/static/mut.rs

@@ -1,5 +1,3 @@
-//@ run-pass
-//@ check-run-results
 //@ ignore-backends: gcc
 // FIXME: linking on windows (specifically mingw) not yet supported, see tracking issue #125418
 //@ ignore-windows
@@ -7,6 +5,7 @@
 #![feature(extern_item_impls)]
 
 #[eii(hello)]
+//~^ ERROR `#[eii]` cannot be used on mutable statics
 static mut HELLO: u64;
 
 #[hello]

tests/ui/eii/static/mut.stderr

@@ -0,0 +1,8 @@
+error: `#[eii]` cannot be used on mutable statics
+  --> $DIR/mut.rs:7:1
+   |
+LL | #[eii(hello)]
+   | ^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+