Rollup of 7 pull requests

compiler/rustc_driver_impl/src/signal_handler.rs

@@ -34,6 +34,8 @@ macro raw_errln($tokens:tt) {
 }
 
 /// Signal handler installed for SIGSEGV
+// FIXME(obeis): Use `SyncUnsafeCell` instead of allowing `static_mut_refs` lint
+#[allow(static_mut_refs)]
 extern "C" fn print_stack_trace(_: libc::c_int) {
     const MAX_FRAMES: usize = 256;
     // Reserve data segment so we don't have to malloc in a signal handler, which might fail

compiler/rustc_hir_analysis/messages.ftl

@@ -463,24 +463,20 @@ hir_analysis_start_not_target_feature = `#[start]` function is not allowed to ha
 hir_analysis_start_not_track_caller = `#[start]` function is not allowed to be `#[track_caller]`
     .label = `#[start]` function is not allowed to be `#[track_caller]`
 
-hir_analysis_static_mut_ref = creating a {$shared} reference to a mutable static
-    .label = {$shared} reference to mutable static
-    .note = {$shared ->
-        [shared] this shared reference has lifetime `'static`, but if the static ever gets mutated, or a mutable reference is created, then any further use of this shared reference is Undefined Behavior
-        *[mutable] this mutable reference has lifetime `'static`, but if the static gets accessed (read or written) by any other means, or any other reference is created, then any further use of this mutable reference is Undefined Behavior
-    }
+hir_analysis_static_mut_ref = creating a {$shared_label}reference to a mutable static
+    .label = {$shared_label}reference to mutable static
+    .shared_note = shared references to mutable statics are dangerous since if there's any kind of mutation of, or mutable reference created for, that static while the reference lives, that's undefined behavior
+    .mut_note = mutable references to mutable statics are dangerous since if there's any other pointer used or reference created for that static while the reference lives, that's undefined behavior
     .suggestion = use `addr_of!` instead to create a raw pointer
     .suggestion_mut = use `addr_of_mut!` instead to create a raw pointer
 
-hir_analysis_static_mut_refs_lint = creating a {$shared} reference to mutable static is discouraged
-    .label = {$shared} reference to mutable static
+hir_analysis_static_mut_refs_lint = creating a {$shared_label}reference to mutable static is discouraged
+    .label = {$shared_label}reference to mutable static
     .suggestion = use `addr_of!` instead to create a raw pointer
     .suggestion_mut = use `addr_of_mut!` instead to create a raw pointer
     .note = this will be a hard error in the 2024 edition
-    .why_note = {$shared ->
-        [shared] this shared reference has lifetime `'static`, but if the static ever gets mutated, or a mutable reference is created, then any further use of this shared reference is Undefined Behavior
-        *[mutable] this mutable reference has lifetime `'static`, but if the static gets accessed (read or written) by any other means, or any other reference is created, then any further use of this mutable reference is Undefined Behavior
-    }
+    .shared_note = shared references to mutable statics are dangerous since if there's any kind of mutation of, or mutable reference created for, that static while the reference lives, that's undefined behavior
+    .mut_note = mutable references to mutable statics are dangerous since if there's any other pointer used or reference created for that static while the reference lives, that's undefined behavior
 
 hir_analysis_static_specialize = cannot specialize on `'static` lifetime
 

compiler/rustc_hir_analysis/src/check/errs.rs

@@ -1,60 +1,113 @@
 use rustc_hir as hir;
 use rustc_lint_defs::builtin::STATIC_MUT_REFS;
-use rustc_middle::ty::{Mutability, TyCtxt};
+use rustc_middle::ty::{Mutability, TyCtxt, TyKind};
 use rustc_span::Span;
 
 use crate::errors;
 
 /// Check for shared or mutable references of `static mut` inside expression
-pub fn maybe_expr_static_mut(tcx: TyCtxt<'_>, expr: hir::Expr<'_>) {
-    let span = expr.span;
-    let hir_id = expr.hir_id;
-    if let hir::ExprKind::AddrOf(borrow_kind, m, expr) = expr.kind
-        && matches!(borrow_kind, hir::BorrowKind::Ref)
-        && path_if_static_mut(expr)
-    {
-        handle_static_mut_ref(
-            tcx,
-            span,
-            span.with_hi(expr.span.lo()),
-            span.shrink_to_hi(),
-            span.edition().at_least_rust_2024(),
-            m,
-            hir_id,
-        );
+pub fn maybe_expr_static_mut(tcx: TyCtxt<'_>, expr: &hir::Expr<'_>) {
+    let err_span = expr.span;
+    let lint_level_hir_id = expr.hir_id;
+    match expr.kind {
+        hir::ExprKind::AddrOf(borrow_kind, m, ex)
+            if matches!(borrow_kind, hir::BorrowKind::Ref)
+                && let Some(err_span) = path_is_static_mut(ex, err_span) =>
+        {
+            handle_static_mut_ref(
+                tcx,
+                err_span,
+                err_span.with_hi(ex.span.lo()),
+                err_span.shrink_to_hi(),
+                err_span.edition().at_least_rust_2024(),
+                Some(m),
+                lint_level_hir_id,
+                !expr.span.from_expansion(),
+            );
+        }
+        hir::ExprKind::Index(expr, _, _)
+            if let Some(err_span) = path_is_static_mut(expr, err_span) =>
+        {
+            handle_static_mut_ref(
+                tcx,
+                err_span,
+                err_span.with_hi(expr.span.lo()),
+                err_span.shrink_to_hi(),
+                err_span.edition().at_least_rust_2024(),
+                None,
+                lint_level_hir_id,
+                false,
+            );
+        }
+        _ => {}
     }
 }
 
 /// Check for shared or mutable references of `static mut` inside statement
-pub fn maybe_stmt_static_mut(tcx: TyCtxt<'_>, stmt: hir::Stmt<'_>) {
+pub fn maybe_stmt_static_mut(tcx: TyCtxt<'_>, stmt: &hir::Stmt<'_>) {
     if let hir::StmtKind::Let(loc) = stmt.kind
         && let hir::PatKind::Binding(ba, _, _, _) = loc.pat.kind
         && let hir::ByRef::Yes(rmutbl) = ba.0
         && let Some(init) = loc.init
-        && path_if_static_mut(init)
+        && let Some(err_span) = path_is_static_mut(init, init.span)
     {
         handle_static_mut_ref(
             tcx,
-            init.span,
-            init.span.shrink_to_lo(),
-            init.span.shrink_to_hi(),
+            err_span,
+            err_span.shrink_to_lo(),
+            err_span.shrink_to_hi(),
             loc.span.edition().at_least_rust_2024(),
-            rmutbl,
+            Some(rmutbl),
             stmt.hir_id,
+            false,
+        );
+    }
+}
+
+/// Check if method call takes shared or mutable references of `static mut`
+#[allow(rustc::usage_of_ty_tykind)]
+pub fn maybe_method_static_mut(tcx: TyCtxt<'_>, expr: &hir::Expr<'_>) {
+    if let hir::ExprKind::MethodCall(_, e, _, _) = expr.kind
+        && let Some(err_span) = path_is_static_mut(e, expr.span)
+        && let typeck = tcx.typeck(expr.hir_id.owner)
+        && let Some(method_def_id) = typeck.type_dependent_def_id(expr.hir_id)
+        && let inputs = tcx.fn_sig(method_def_id).skip_binder().inputs().skip_binder()
+        && !inputs.is_empty()
+        && inputs[0].is_ref()
+    {
+        let m = if let TyKind::Ref(_, _, m) = inputs[0].kind() { *m } else { Mutability::Not };
+
+        handle_static_mut_ref(
+            tcx,
+            err_span,
+            err_span.shrink_to_lo(),
+            err_span.shrink_to_hi(),
+            err_span.edition().at_least_rust_2024(),
+            Some(m),
+            expr.hir_id,
+            false,
         );
     }
 }
 
-fn path_if_static_mut(expr: &hir::Expr<'_>) -> bool {
+fn path_is_static_mut(mut expr: &hir::Expr<'_>, mut err_span: Span) -> Option<Span> {
+    if err_span.from_expansion() {
+        err_span = expr.span;
+    }
+
+    while let hir::ExprKind::Field(e, _) = expr.kind {
+        expr = e;
+    }
+
     if let hir::ExprKind::Path(qpath) = expr.kind
         && let hir::QPath::Resolved(_, path) = qpath
         && let hir::def::Res::Def(def_kind, _) = path.res
         && let hir::def::DefKind::Static { safety: _, mutability: Mutability::Mut, nested: false } =
             def_kind
     {
-        return true;
+        return Some(err_span);
     }
-    false
+    None
 }
 
 fn handle_static_mut_ref(
@@ -63,27 +116,37 @@ fn handle_static_mut_ref(
     lo: Span,
     hi: Span,
     e2024: bool,
-    mutable: Mutability,
-    hir_id: hir::HirId,
+    mutable: Option<Mutability>,
+    lint_level_hir_id: hir::HirId,
+    suggest_addr_of: bool,
 ) {
+    let (shared_label, shared_note, mut_note, sugg) = match mutable {
+        Some(Mutability::Mut) => {
+            let sugg =
+                if suggest_addr_of { Some(errors::MutRefSugg::Mut { lo, hi }) } else { None };
+            ("mutable ", false, true, sugg)
+        }
+        Some(Mutability::Not) => {
+            let sugg =
+                if suggest_addr_of { Some(errors::MutRefSugg::Shared { lo, hi }) } else { None };
+            ("shared ", true, false, sugg)
+        }
+        None => ("", true, true, None),
+    };
     if e2024 {
-        let (sugg, shared) = if mutable == Mutability::Mut {
-            (errors::MutRefSugg::Mut { lo, hi }, "mutable")
-        } else {
-            (errors::MutRefSugg::Shared { lo, hi }, "shared")
-        };
-        tcx.dcx().emit_err(errors::StaticMutRef { span, sugg, shared });
+        tcx.dcx().emit_err(errors::StaticMutRef {
+            span,
+            sugg,
+            shared_label,
+            shared_note,
+            mut_note,
+        });
     } else {
-        let (sugg, shared) = if mutable == Mutability::Mut {
-            (errors::MutRefSugg::Mut { lo, hi }, "mutable")
-        } else {
-            (errors::MutRefSugg::Shared { lo, hi }, "shared")
-        };
         tcx.emit_node_span_lint(
             STATIC_MUT_REFS,
-            hir_id,
+            lint_level_hir_id,
             span,
-            errors::RefOfMutStatic { span, sugg, shared },
+            errors::RefOfMutStatic { span, sugg, shared_label, shared_note, mut_note },
         );
     }
 }

compiler/rustc_hir_analysis/src/check/mod.rs

@@ -66,7 +66,7 @@ mod check;
 mod compare_impl_item;
 pub mod dropck;
 mod entry;
-mod errs;
+pub mod errs;
 pub mod intrinsic;
 pub mod intrinsicck;
 mod region;

compiler/rustc_hir_analysis/src/check/region.rs

@@ -228,7 +228,7 @@ fn resolve_stmt<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, stmt: &'tcx h
     let stmt_id = stmt.hir_id.local_id;
     debug!("resolve_stmt(stmt.id={:?})", stmt_id);
 
-    maybe_stmt_static_mut(visitor.tcx, *stmt);
+    maybe_stmt_static_mut(visitor.tcx, stmt);
 
     // Every statement will clean up the temporaries created during
     // execution of that statement. Therefore each statement has an
@@ -248,7 +248,7 @@ fn resolve_stmt<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, stmt: &'tcx h
 fn resolve_expr<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
     debug!("resolve_expr - pre-increment {} expr = {:?}", visitor.expr_and_pat_count, expr);
 
-    maybe_expr_static_mut(visitor.tcx, *expr);
+    maybe_expr_static_mut(visitor.tcx, expr);
 
     let prev_cx = visitor.cx;
     visitor.enter_node_scope_with_dtor(expr.hir_id.local_id);

compiler/rustc_hir_analysis/src/collect.rs

@@ -43,6 +43,7 @@ use std::cell::Cell;
 use std::iter;
 use std::ops::Bound;
 
+use crate::check::errs::maybe_method_static_mut;
 use crate::check::intrinsic::intrinsic_operation_unsafety;
 use crate::errors;
 use crate::hir_ty_lowering::{HirTyLowerer, RegionInferReason};
@@ -324,6 +325,7 @@ impl<'tcx> Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
             // depends on typecheck and would therefore hide
             // any further errors in case one typeck fails.
         }
+        maybe_method_static_mut(self.tcx, expr);
         intravisit::walk_expr(self, expr);
     }
 

compiler/rustc_hir_analysis/src/errors.rs

@@ -1502,14 +1502,17 @@ pub struct OnlyCurrentTraitsPointerSugg<'a> {
 
 #[derive(Diagnostic)]
 #[diag(hir_analysis_static_mut_ref, code = E0796)]
-#[note]
 pub struct StaticMutRef<'a> {
     #[primary_span]
     #[label]
     pub span: Span,
     #[subdiagnostic]
-    pub sugg: MutRefSugg,
-    pub shared: &'a str,
+    pub sugg: Option<MutRefSugg>,
+    pub shared_label: &'a str,
+    #[note(hir_analysis_shared_note)]
+    pub shared_note: bool,
+    #[note(hir_analysis_mut_note)]
+    pub mut_note: bool,
 }
 
 #[derive(Subdiagnostic)]
@@ -1538,17 +1541,20 @@ pub enum MutRefSugg {
     },
 }
 
-// STATIC_MUT_REF lint
+// `STATIC_MUT_REF` lint
 #[derive(LintDiagnostic)]
 #[diag(hir_analysis_static_mut_refs_lint)]
 #[note]
-#[note(hir_analysis_why_note)]
 pub struct RefOfMutStatic<'a> {
     #[label]
     pub span: Span,
     #[subdiagnostic]
-    pub sugg: MutRefSugg,
-    pub shared: &'a str,
+    pub sugg: Option<MutRefSugg>,
+    pub shared_label: &'a str,
+    #[note(hir_analysis_shared_note)]
+    pub shared_note: bool,
+    #[note(hir_analysis_mut_note)]
+    pub mut_note: bool,
 }
 
 #[derive(Diagnostic)]

compiler/rustc_hir_typeck/src/closure.rs

@@ -18,7 +18,6 @@ use rustc_span::def_id::LocalDefId;
 use rustc_span::Span;
 use rustc_target::spec::abi::Abi;
 use rustc_trait_selection::error_reporting::traits::ArgKind;
-use rustc_trait_selection::error_reporting::traits::InferCtxtExt as _;
 use rustc_trait_selection::traits;
 use rustc_type_ir::ClosureKind;
 use std::iter;
@@ -734,13 +733,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             .map(|ty| ArgKind::from_expected_ty(*ty, None))
             .collect();
         let (closure_span, closure_arg_span, found_args) =
-            match self.get_fn_like_arguments(expr_map_node) {
+            match self.err_ctxt().get_fn_like_arguments(expr_map_node) {
                 Some((sp, arg_sp, args)) => (Some(sp), arg_sp, args),
                 None => (None, None, Vec::new()),
             };
         let expected_span =
             expected_sig.cause_span.unwrap_or_else(|| self.tcx.def_span(expr_def_id));
         let guar = self
+            .err_ctxt()
             .report_arg_count_mismatch(
                 expected_span,
                 closure_span,

compiler/rustc_infer/src/infer/mod.rs

@@ -755,18 +755,6 @@ impl<'tcx> InferCtxt<'tcx> {
             .collect()
     }
 
-    // FIXME(-Znext-solver): Get rid of this method, it's never correct. Either that,
-    // or we need to process the obligations.
-    pub fn can_eq_shallow<T>(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> bool
-    where
-        T: at::ToTrace<'tcx>,
-    {
-        let origin = &ObligationCause::dummy();
-        // We're only answering whether the types could be the same, and with
-        // opaque types, "they can be the same", via registering a hidden type.
-        self.probe(|_| self.at(origin, param_env).eq(DefineOpaqueTypes::Yes, a, b).is_ok())
-    }
-
     #[instrument(skip(self), level = "debug")]
     pub fn sub_regions(
         &self,

compiler/rustc_mir_build/src/check_unsafety.rs

@@ -466,6 +466,24 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
                     }
                 }
             }
+            ExprKind::AddressOf { arg, .. } => {
+                if let ExprKind::Scope { value: arg, .. } = self.thir[arg].kind
+                // THIR desugars UNSAFE_STATIC into *UNSAFE_STATIC_REF, where
+                // UNSAFE_STATIC_REF holds the addr of the UNSAFE_STATIC, so: take two steps
+                    && let ExprKind::Deref { arg } = self.thir[arg].kind
+                    // FIXME(workingjubiee): we lack a clear reason to reject ThreadLocalRef here,
+                    // but we also have no conclusive reason to allow it either!
+                    && let ExprKind::StaticRef { .. } = self.thir[arg].kind
+                {
+                    // A raw ref to a place expr, even an "unsafe static", is okay!
+                    // We short-circuit to not recursively traverse this expression.
+                    return;
+                    // note: const_mut_refs enables this code, and it currently remains unsafe:
+                    // static mut BYTE: u8 = 0;
+                    // static mut BYTE_PTR: *mut u8 = unsafe { addr_of_mut!(BYTE) };
+                    // static mut DEREF_BYTE_PTR: *mut u8 = unsafe { addr_of_mut!(*BYTE_PTR) };
+                }
+            }
             ExprKind::Deref { arg } => {
                 if let ExprKind::StaticRef { def_id, .. } | ExprKind::ThreadLocalRef(def_id) =
                     self.thir[arg].kind