Auto merge of #148817 - Zalathar:rollup-tf5ti2m, r=Zalathar

Rollup of 15 pull requests

Successful merges:

 - #141470 (Add new `function_casts_as_integer` lint)
 - #143619 (`c_variadic`: Add future-incompatibility warning for `...` arguments without a pattern outside of `extern` blocks)
 - #146495 (rustdoc: Erase `#![doc(document_private_items)]`)
 - #147771 (Rename `*exact_{div,shr,shl}` to `*{div,shr,shl}_exact`)
 - #147833 (rustdoc-json: move `target` to `json::conversions`)
 - #147955 (compiletest: Migrate `TestProps` directive handling to a system of named handlers)
 - #148480 (Add `Steal::risky_hack_borrow_mut`)
 - #148506 (Special case detecting `'static` lifetime requirement coming from `-> Box<dyn Trait>`)
 - #148508 (Provide more context when mutably borrowing an imutably borrowed value)
 - #148530 (update the bootstrap readme)
 - #148608 (Add test for --test-builder success path)
 - #148636 (bootstrap: respect `build.python` on macOS)
 - #148639 (test(rustdoc): move tests into jump-to-def)
 - #148647 (Check unsafety for non-macro attributes in `validate_attr`)
 - #148667 (a few small clippy fixes)

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

compiler/rustc_ast_lowering/src/index.rs

@@ -125,9 +125,9 @@ impl<'a, 'hir> NodeCollector<'a, 'hir> {
 }
 
 impl<'a, 'hir> Visitor<'hir> for NodeCollector<'a, 'hir> {
-    /// Because we want to track parent items and so forth, enable
-    /// deep walking so that we walk nested items in the context of
-    /// their outer items.
+    // Because we want to track parent items and so forth, enable
+    // deep walking so that we walk nested items in the context of
+    // their outer items.
 
     fn visit_nested_item(&mut self, item: ItemId) {
         debug!("visit_nested_item: {:?}", item);

compiler/rustc_attr_parsing/src/validate_attr.rs

@@ -209,7 +209,7 @@ pub fn check_attribute_safety(
 
         // - Normal builtin attribute
         // - Writing `#[unsafe(..)]` is not permitted on normal builtin attributes
-        (Some(AttributeSafety::Normal), Safety::Unsafe(unsafe_span)) => {
+        (None | Some(AttributeSafety::Normal), Safety::Unsafe(unsafe_span)) => {
             psess.dcx().emit_err(errors::InvalidAttrUnsafe {
                 span: unsafe_span,
                 name: attr_item.path.clone(),
@@ -218,15 +218,10 @@ pub fn check_attribute_safety(
 
         // - Normal builtin attribute
         // - No explicit `#[unsafe(..)]` written.
-        (Some(AttributeSafety::Normal), Safety::Default) => {
+        (None | Some(AttributeSafety::Normal), Safety::Default) => {
             // OK
         }
 
-        // - Non-builtin attribute
-        (None, Safety::Unsafe(_) | Safety::Default) => {
-            // OK (not checked here)
-        }
-
         (
             Some(AttributeSafety::Unsafe { .. } | AttributeSafety::Normal) | None,
             Safety::Safe(..),

compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -213,7 +213,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
             AccessKind::Mutate => {
                 err = self.cannot_assign(span, &(item_msg + &reason));
                 act = "assign";
-                acted_on = "written";
+                acted_on = "written to";
                 span
             }
             AccessKind::MutableBorrow => {
@@ -518,8 +518,8 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                         err.span_label(
                             span,
                             format!(
-                                "`{name}` is a `{pointer_sigil}` {pointer_desc}, \
-                                 so the data it refers to cannot be {acted_on}",
+                                "`{name}` is a `{pointer_sigil}` {pointer_desc}, so it cannot be \
+                                 {acted_on}",
                             ),
                         );
 
@@ -542,7 +542,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 self.expected_fn_found_fn_mut_call(&mut err, span, act);
             }
 
-            PlaceRef { local: _, projection: [.., ProjectionElem::Deref] } => {
+            PlaceRef { local, projection: [.., ProjectionElem::Deref] } => {
                 err.span_label(span, format!("cannot {act}"));
 
                 match opt_source {
@@ -559,11 +559,36 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                         ));
                         self.suggest_map_index_mut_alternatives(ty, &mut err, span);
                     }
-                    _ => (),
+                    _ => {
+                        let local = &self.body.local_decls[local];
+                        match local.local_info() {
+                            LocalInfo::StaticRef { def_id, .. } => {
+                                let span = self.infcx.tcx.def_span(def_id);
+                                err.span_label(span, format!("this `static` cannot be {acted_on}"));
+                            }
+                            LocalInfo::ConstRef { def_id } => {
+                                let span = self.infcx.tcx.def_span(def_id);
+                                err.span_label(span, format!("this `const` cannot be {acted_on}"));
+                            }
+                            LocalInfo::BlockTailTemp(_) | LocalInfo::Boring
+                                if !local.source_info.span.overlaps(span) =>
+                            {
+                                err.span_label(
+                                    local.source_info.span,
+                                    format!("this cannot be {acted_on}"),
+                                );
+                            }
+                            _ => {}
+                        }
+                    }
                 }
             }
 
-            _ => {
+            PlaceRef { local, .. } => {
+                let local = &self.body.local_decls[local];
+                if !local.source_info.span.overlaps(span) {
+                    err.span_label(local.source_info.span, format!("this cannot be {acted_on}"));
+                }
                 err.span_label(span, format!("cannot {act}"));
             }
         }

compiler/rustc_data_structures/src/steal.rs

@@ -1,5 +1,5 @@
 use crate::stable_hasher::{HashStable, StableHasher};
-use crate::sync::{MappedReadGuard, ReadGuard, RwLock};
+use crate::sync::{MappedReadGuard, MappedWriteGuard, ReadGuard, RwLock, WriteGuard};
 
 /// The `Steal` struct is intended to used as the value for a query.
 /// Specifically, we sometimes have queries (*cough* MIR *cough*)
@@ -40,9 +40,17 @@ impl<T> Steal<T> {
         ReadGuard::map(borrow, |opt| opt.as_ref().unwrap())
     }
 
+    /// An escape hatch for rustc drivers to mutate `Steal` caches.
+    ///
+    /// Use at your own risk. This can badly break incremental compilation
+    /// and anything else that relies on the immutability of query caches.
     #[track_caller]
-    pub fn get_mut(&mut self) -> &mut T {
-        self.value.get_mut().as_mut().expect("attempt to read from stolen value")
+    pub fn risky_hack_borrow_mut(&self) -> MappedWriteGuard<'_, T> {
+        let borrow = self.value.borrow_mut();
+        if borrow.is_none() {
+            panic!("attempted to read from stolen value: {}", std::any::type_name::<T>());
+        }
+        WriteGuard::map(borrow, |opt| opt.as_mut().unwrap())
     }
 
     #[track_caller]

compiler/rustc_driver_impl/src/signal_handler.rs

@@ -152,7 +152,8 @@ pub(super) fn install() {
         libc::sigaltstack(&alt_stack, ptr::null_mut());
 
         let mut sa: libc::sigaction = mem::zeroed();
-        sa.sa_sigaction = print_stack_trace as libc::sighandler_t;
+        sa.sa_sigaction =
+            print_stack_trace as unsafe extern "C" fn(libc::c_int) as libc::sighandler_t;
         sa.sa_flags = libc::SA_NODEFER | libc::SA_RESETHAND | libc::SA_ONSTACK;
         libc::sigemptyset(&mut sa.sa_mask);
         for (signum, _signame) in KILL_SIGNALS {

compiler/rustc_errors/src/emitter.rs

@@ -2322,11 +2322,6 @@ impl HumanEmitter {
                 show_code_change
             {
                 for part in parts {
-                    let snippet = if let Ok(snippet) = sm.span_to_snippet(part.span) {
-                        snippet
-                    } else {
-                        String::new()
-                    };
                     let span_start_pos = sm.lookup_char_pos(part.span.lo()).col_display;
                     let span_end_pos = sm.lookup_char_pos(part.span.hi()).col_display;
 
@@ -2402,7 +2397,7 @@ impl HumanEmitter {
                         // LL - REMOVED <- row_num - 2 - (newlines - first_i - 1)
                         // LL + NEWER
                         //    |         <- row_num
-
+                        let snippet = sm.span_to_snippet(part.span).unwrap_or_default();
                         let newlines = snippet.lines().count();
                         if newlines > 0 && row_num > newlines {
                             // Account for removals where the part being removed spans multiple

compiler/rustc_expand/src/expand.rs

@@ -886,9 +886,6 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                         }
                     }
                 } else if let SyntaxExtensionKind::NonMacroAttr = ext {
-                    if let ast::Safety::Unsafe(span) = attr.get_normal_item().unsafety {
-                        self.cx.dcx().span_err(span, "unnecessary `unsafe` on safe attribute");
-                    }
                     // `-Zmacro-stats` ignores these because they don't do any real expansion.
                     self.cx.expanded_inert_attrs.mark(&attr);
                     item.visit_attrs(|attrs| attrs.insert(pos, attr));

compiler/rustc_hir_analysis/src/variance/terms.rs

@@ -44,7 +44,7 @@ impl<'a> fmt::Debug for VarianceTerm<'a> {
     }
 }
 
-/// The first pass over the crate simply builds up the set of inferreds.
+// The first pass over the crate simply builds up the set of inferreds.
 
 pub(crate) struct TermsContext<'a, 'tcx> {
     pub tcx: TyCtxt<'tcx>,

compiler/rustc_lint/messages.ftl

@@ -265,6 +265,9 @@ lint_forgetting_copy_types = calls to `std::mem::forget` with a value that imple
 lint_forgetting_references = calls to `std::mem::forget` with a reference instead of an owned value does nothing
     .label = argument has type `{$arg_ty}`
 
+lint_function_casts_as_integer = direct cast of function item into an integer
+    .cast_as_fn = first cast to a pointer `as *const ()`
+
 lint_hidden_glob_reexport = private item shadows public glob re-export
     .note_glob_reexport = the name `{$name}` in the {$namespace} namespace is supposed to be publicly re-exported here
     .note_private_item = but the private item here shadows it

compiler/rustc_lint/src/function_cast_as_integer.rs

@@ -0,0 +1,63 @@
+use rustc_hir as hir;
+use rustc_middle::ty;
+use rustc_session::{declare_lint, declare_lint_pass};
+use rustc_span::BytePos;
+
+use crate::lints::{FunctionCastsAsIntegerDiag, FunctionCastsAsIntegerSugg};
+use crate::{LateContext, LateLintPass};
+
+declare_lint! {
+    /// The `function_casts_as_integer` lint detects cases where a function item is cast
+    /// to an integer.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// fn foo() {}
+    /// let x = foo as usize;
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// When casting a function item to an integer, it implicitly creates a
+    /// function pointer that will in turn be cast to an integer. By making
+    /// it explicit, it improves readability of the code and prevents bugs.
+    pub FUNCTION_CASTS_AS_INTEGER,
+    Warn,
+    "casting a function into an integer",
+}
+
+declare_lint_pass!(
+    /// Lint for casts of functions into integers.
+    FunctionCastsAsInteger => [FUNCTION_CASTS_AS_INTEGER]
+);
+
+impl<'tcx> LateLintPass<'tcx> for FunctionCastsAsInteger {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
+        let hir::ExprKind::Cast(cast_from_expr, cast_to_expr) = expr.kind else { return };
+        let cast_to_ty = cx.typeck_results().expr_ty(expr);
+        // Casting to a function (pointer?), so all good.
+        //
+        // Normally, only casts to integers is possible, but if it ever changed, this condition
+        // will likely need to be updated.
+        if matches!(cast_to_ty.kind(), ty::FnDef(..) | ty::FnPtr(..) | ty::RawPtr(..)) {
+            return;
+        }
+        let cast_from_ty = cx.typeck_results().expr_ty(cast_from_expr);
+        if matches!(cast_from_ty.kind(), ty::FnDef(..)) {
+            cx.tcx.emit_node_span_lint(
+                FUNCTION_CASTS_AS_INTEGER,
+                expr.hir_id,
+                cast_to_expr.span.with_lo(cast_from_expr.span.hi() + BytePos(1)),
+                FunctionCastsAsIntegerDiag {
+                    sugg: FunctionCastsAsIntegerSugg {
+                        suggestion: cast_from_expr.span.shrink_to_hi(),
+                        cast_to_ty,
+                    },
+                },
+            );
+        }
+    }
+}