Rollup merge of #143092 - RalfJung:const-check-lifetime-ext, r=oli-obk

const checks for lifetime-extended temporaries: avoid 'top-level scope' terminology

This error recently got changed in https://github.com/rust-lang/rust/pull/140942 to use the terminology of "top-level scope", but after further discussion in https://github.com/rust-lang/reference/pull/1865 it seems the reference will not be using that terminology after all. So let's also remove it from the compiler again, and let's focus on what actually happens with these temporaries: their lifetime is extended until the end of the program.

r? ``@oli-obk`` ``@traviscross``

3 files changed, 19 insertions, 35 deletions

diff --git a/compiler/rustc_const_eval/messages.ftl b/compiler/rustc_const_eval/messages.ftl
index 671ae5975a7..2a2c3e6aee2 100644
--- a/compiler/rustc_const_eval/messages.ftl
+++ b/compiler/rustc_const_eval/messages.ftl
@@ -125,16 +125,11 @@ const_eval_incompatible_types =
     calling a function with argument of type {$callee_ty} passing data of type {$caller_ty}
 
 const_eval_interior_mutable_borrow_escaping =
-    interior mutable shared borrows of lifetime-extended temporaries in the top-level scope of a {const_eval_const_context} are not allowed
-    .label = this borrow of an interior mutable value refers to a lifetime-extended temporary
-    .help = to fix this, the value can be extracted to a separate `static` item and then referenced
-    .teach_note =
-        This creates a raw pointer to a temporary that has its lifetime extended to last for the entire program.
-        Lifetime-extended temporaries in constants and statics must be immutable.
-        This is to avoid accidentally creating shared mutable state.
-
-
-        If you really want global mutable state, try using an interior mutable `static` or a `static mut`.
+    interior mutable shared borrows of temporaries that have their lifetime extended until the end of the program are not allowed
+    .label = this borrow of an interior mutable value refers to such a temporary
+    .note = Temporaries in constants and statics can have their lifetime extended until the end of the program
+    .note2 = To avoid accidentally creating global mutable state, such temporaries must be immutable
+    .help = If you really want global mutable state, try replacing the temporary by an interior mutable `static` or a `static mut`
 
 const_eval_intern_kind = {$kind ->
     [static] static
@@ -215,14 +210,11 @@ const_eval_modified_global =
     modifying a static's initial value from another static's initializer
 
 const_eval_mutable_borrow_escaping =
-    mutable borrows of lifetime-extended temporaries in the top-level scope of a {const_eval_const_context} are not allowed
-    .teach_note =
-        This creates a reference to a temporary that has its lifetime extended to last for the entire program.
-        Lifetime-extended temporaries in constants and statics must be immutable.
-        This is to avoid accidentally creating shared mutable state.
-
-
-        If you really want global mutable state, try using an interior mutable `static` or a `static mut`.
+    mutable borrows of temporaries that have their lifetime extended until the end of the program are not allowed
+    .label = this mutable borrow refers to such a temporary
+    .note = Temporaries in constants and statics can have their lifetime extended until the end of the program
+    .note2 = To avoid accidentally creating global mutable state, such temporaries must be immutable
+    .help = If you really want global mutable state, try replacing the temporary by an interior mutable `static` or a `static mut`
 
 const_eval_mutable_ptr_in_final = encountered mutable pointer in final value of {const_eval_intern_kind}
 
diff --git a/compiler/rustc_const_eval/src/check_consts/ops.rs b/compiler/rustc_const_eval/src/check_consts/ops.rs
index b1e0ffd46c5..b2e0577cc82 100644
--- a/compiler/rustc_const_eval/src/check_consts/ops.rs
+++ b/compiler/rustc_const_eval/src/check_consts/ops.rs
@@ -567,12 +567,7 @@ impl<'tcx> NonConstOp<'tcx> for EscapingCellBorrow {
         DiagImportance::Secondary
     }
     fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> Diag<'tcx> {
-        ccx.dcx().create_err(errors::InteriorMutableBorrowEscaping {
-            span,
-            opt_help: matches!(ccx.const_kind(), hir::ConstContext::Static(_)),
-            kind: ccx.const_kind(),
-            teach: ccx.tcx.sess.teach(E0492),
-        })
+        ccx.dcx().create_err(errors::InteriorMutableBorrowEscaping { span, kind: ccx.const_kind() })
     }
 }
 
@@ -594,11 +589,7 @@ impl<'tcx> NonConstOp<'tcx> for EscapingMutBorrow {
     }
 
     fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> Diag<'tcx> {
-        ccx.dcx().create_err(errors::MutableBorrowEscaping {
-            span,
-            kind: ccx.const_kind(),
-            teach: ccx.tcx.sess.teach(E0764),
-        })
+        ccx.dcx().create_err(errors::MutableBorrowEscaping { span, kind: ccx.const_kind() })
     }
 }
 
diff --git a/compiler/rustc_const_eval/src/errors.rs b/compiler/rustc_const_eval/src/errors.rs
index b2c3103c34a..14abdd8c98c 100644
--- a/compiler/rustc_const_eval/src/errors.rs
+++ b/compiler/rustc_const_eval/src/errors.rs
@@ -151,12 +151,14 @@ pub(crate) struct UnmarkedIntrinsicExposed {
 
 #[derive(Diagnostic)]
 #[diag(const_eval_mutable_borrow_escaping, code = E0764)]
+#[note]
+#[note(const_eval_note2)]
+#[help]
 pub(crate) struct MutableBorrowEscaping {
     #[primary_span]
+    #[label]
     pub span: Span,
     pub kind: ConstContext,
-    #[note(const_eval_teach_note)]
-    pub teach: bool,
 }
 
 #[derive(Diagnostic)]
@@ -217,15 +219,14 @@ pub(crate) struct UnallowedInlineAsm {
 
 #[derive(Diagnostic)]
 #[diag(const_eval_interior_mutable_borrow_escaping, code = E0492)]
+#[note]
+#[note(const_eval_note2)]
+#[help]
 pub(crate) struct InteriorMutableBorrowEscaping {
     #[primary_span]
     #[label]
     pub span: Span,
-    #[help]
-    pub opt_help: bool,
     pub kind: ConstContext,
-    #[note(const_eval_teach_note)]
-    pub teach: bool,
 }
 
 #[derive(LintDiagnostic)]