Rollup of 6 pull requests

compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -575,7 +575,8 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                         // ---------- place
                         self.err.multipart_suggestions(
                             format!(
-                                "to modify a `{}`, use `.get_mut()`, `.insert()` or the entry API",
+                                "use `.insert()` to insert a value into a `{}`, `.get_mut()` \
+                                to modify it, or the entry API for more flexibility",
                                 self.ty,
                             ),
                             vec![
@@ -592,16 +593,17 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                                     (rv.span.shrink_to_hi(), ")".to_string()),
                                 ],
                                 vec![
-                                    // val.get_mut(index).map(|v| { *v = rv; });
+                                    // if let Some(v) = val.get_mut(index) { *v = rv; }
+                                    (val.span.shrink_to_lo(), "if let Some(val) = ".to_string()),
                                     (
                                         val.span.shrink_to_hi().with_hi(index.span.lo()),
                                         ".get_mut(".to_string(),
                                     ),
                                     (
                                         index.span.shrink_to_hi().with_hi(place.span.hi()),
-                                        ").map(|val| { *val".to_string(),
+                                        ") { *val".to_string(),
                                     ),
-                                    (rv.span.shrink_to_hi(), "; })".to_string()),
+                                    (rv.span.shrink_to_hi(), "; }".to_string()),
                                 ],
                                 vec![
                                     // let x = val.entry(index).or_insert(rv);
@@ -622,21 +624,22 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                         self.suggested = true;
                     } else if let hir::ExprKind::MethodCall(_path, receiver, _, sp) = expr.kind
                         && let hir::ExprKind::Index(val, index, _) = receiver.kind
-                        && expr.span == self.assign_span
+                        && receiver.span == self.assign_span
                     {
                         // val[index].path(args..);
                         self.err.multipart_suggestion(
                             format!("to modify a `{}` use `.get_mut()`", self.ty),
                             vec![
+                                (val.span.shrink_to_lo(), "if let Some(val) = ".to_string()),
                                 (
                                     val.span.shrink_to_hi().with_hi(index.span.lo()),
                                     ".get_mut(".to_string(),
                                 ),
                                 (
                                     index.span.shrink_to_hi().with_hi(receiver.span.hi()),
-                                    ").map(|val| val".to_string(),
+                                    ") { val".to_string(),
                                 ),
-                                (sp.shrink_to_hi(), ")".to_string()),
+                                (sp.shrink_to_hi(), "; }".to_string()),
                             ],
                             Applicability::MachineApplicable,
                         );

compiler/rustc_builtin_macros/messages.ftl

@@ -197,6 +197,8 @@ builtin_macros_format_redundant_args = redundant {$n ->
 
 builtin_macros_format_remove_raw_ident = remove the `r#`
 
+builtin_macros_format_reorder_format_parameter = did you mean `{$replacement}`?
+
 builtin_macros_format_requires_string = requires at least a format string argument
 
 builtin_macros_format_string_invalid = invalid format string: {$desc}

compiler/rustc_builtin_macros/src/errors.rs

@@ -618,6 +618,17 @@ pub(crate) enum InvalidFormatStringSuggestion {
         #[primary_span]
         span: Span,
     },
+    #[suggestion(
+        builtin_macros_format_reorder_format_parameter,
+        code = "{replacement}",
+        style = "verbose",
+        applicability = "machine-applicable"
+    )]
+    ReorderFormatParameter {
+        #[primary_span]
+        span: Span,
+        replacement: String,
+    },
 }
 
 #[derive(Diagnostic)]

compiler/rustc_builtin_macros/src/format.rs

@@ -321,6 +321,13 @@ fn make_format_args(
                     e.sugg_ = Some(errors::InvalidFormatStringSuggestion::RemoveRawIdent { span })
                 }
             }
+            parse::Suggestion::ReorderFormatParameter(span, replacement) => {
+                let span = fmt_span.from_inner(InnerSpan::new(span.start, span.end));
+                e.sugg_ = Some(errors::InvalidFormatStringSuggestion::ReorderFormatParameter {
+                    span,
+                    replacement,
+                });
+            }
         }
         let guar = ecx.dcx().emit_err(e);
         return ExpandResult::Ready(Err(guar));

compiler/rustc_driver_impl/src/signal_handler.rs

@@ -2,7 +2,7 @@
 //! Primarily used to extract a backtrace from stack overflow
 
 use std::alloc::{Layout, alloc};
-use std::{fmt, mem, ptr};
+use std::{fmt, mem, ptr, slice};
 
 use rustc_interface::util::{DEFAULT_STACK_SIZE, STACK_SIZE};
 
@@ -35,20 +35,22 @@ macro raw_errln($tokens:tt) {
 }
 
 /// Signal handler installed for SIGSEGV
-// FIXME(static_mut_refs): Do not allow `static_mut_refs` lint
-#[allow(static_mut_refs)]
-extern "C" fn print_stack_trace(_: libc::c_int) {
+///
+/// # Safety
+///
+/// Caller must ensure that this function is not re-entered.
+unsafe 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
-    // in incredibly undesirable and unexpected ways due to e.g. the allocator deadlocking
-    static mut STACK_TRACE: [*mut libc::c_void; MAX_FRAMES] = [ptr::null_mut(); MAX_FRAMES];
     let stack = unsafe {
+        // Reserve data segment so we don't have to malloc in a signal handler, which might fail
+        // in incredibly undesirable and unexpected ways due to e.g. the allocator deadlocking
+        static mut STACK_TRACE: [*mut libc::c_void; MAX_FRAMES] = [ptr::null_mut(); MAX_FRAMES];
         // Collect return addresses
-        let depth = libc::backtrace(STACK_TRACE.as_mut_ptr(), MAX_FRAMES as i32);
+        let depth = libc::backtrace(&raw mut STACK_TRACE as _, MAX_FRAMES as i32);
         if depth == 0 {
             return;
         }
-        &STACK_TRACE.as_slice()[0..(depth as _)]
+        slice::from_raw_parts(&raw const STACK_TRACE as _, depth as _)
     };
 
     // Just a stack trace is cryptic. Explain what we're doing.

compiler/rustc_lint/src/default_could_be_derived.rs

@@ -1,9 +1,11 @@
 use rustc_data_structures::fx::FxHashMap;
-use rustc_errors::Diag;
+use rustc_errors::{Applicability, Diag};
 use rustc_hir as hir;
 use rustc_middle::ty;
+use rustc_middle::ty::TyCtxt;
 use rustc_session::{declare_lint, impl_lint_pass};
 use rustc_span::Symbol;
+use rustc_span::def_id::DefId;
 use rustc_span::symbol::sym;
 
 use crate::{LateContext, LateLintPass};
@@ -149,13 +151,16 @@ impl<'tcx> LateLintPass<'tcx> for DefaultCouldBeDerived {
         let hir_id = cx.tcx.local_def_id_to_hir_id(local);
         let hir::Node::Item(item) = cx.tcx.hir_node(hir_id) else { return };
         cx.tcx.node_span_lint(DEFAULT_OVERRIDES_DEFAULT_FIELDS, hir_id, item.span, |diag| {
-            mk_lint(diag, orig_fields, fields);
+            mk_lint(cx.tcx, diag, type_def_id, parent, orig_fields, fields);
         });
     }
 }
 
 fn mk_lint(
+    tcx: TyCtxt<'_>,
     diag: &mut Diag<'_, ()>,
+    type_def_id: DefId,
+    impl_def_id: DefId,
     orig_fields: FxHashMap<Symbol, &hir::FieldDef<'_>>,
     fields: &[hir::ExprField<'_>],
 ) {
@@ -175,11 +180,24 @@ fn mk_lint(
         }
     }
 
-    diag.help(if removed_all_fields {
-        "to avoid divergence in behavior between `Struct { .. }` and \
-         `<Struct as Default>::default()`, derive the `Default`"
+    if removed_all_fields {
+        let msg = "to avoid divergence in behavior between `Struct { .. }` and \
+                   `<Struct as Default>::default()`, derive the `Default`";
+        if let Some(hir::Node::Item(impl_)) = tcx.hir().get_if_local(impl_def_id) {
+            diag.multipart_suggestion_verbose(
+                msg,
+                vec![
+                    (tcx.def_span(type_def_id).shrink_to_lo(), "#[derive(Default)] ".to_string()),
+                    (impl_.span, String::new()),
+                ],
+                Applicability::MachineApplicable,
+            );
+        } else {
+            diag.help(msg);
+        }
     } else {
-        "use the default values in the `impl` with `Struct { mandatory_field, .. }` to avoid them \
-         diverging over time"
-    });
+        let msg = "use the default values in the `impl` with `Struct { mandatory_field, .. }` to \
+                   avoid them diverging over time";
+        diag.help(msg);
+    }
 }

compiler/rustc_parse_format/src/lib.rs

@@ -221,6 +221,11 @@ pub enum Suggestion {
     /// Remove `r#` from identifier:
     /// `format!("{r#foo}")` -> `format!("{foo}")`
     RemoveRawIdent(InnerSpan),
+    /// Reorder format parameter:
+    /// `format!("{foo:?#}")` -> `format!("{foo:#?}")`
+    /// `format!("{foo:?x}")` -> `format!("{foo:x?}")`
+    /// `format!("{foo:?X}")` -> `format!("{foo:X?}")`
+    ReorderFormatParameter(InnerSpan, string::String),
 }
 
 /// The parser structure for interpreting the input format string. This is
@@ -731,6 +736,12 @@ impl<'a> Parser<'a> {
             }
         } else if self.consume('?') {
             spec.ty = "?";
+            if let Some(&(_, maybe)) = self.cur.peek() {
+                match maybe {
+                    '#' | 'x' | 'X' => self.suggest_format_parameter(maybe),
+                    _ => (),
+                }
+            }
         } else {
             spec.ty = self.word();
             if !spec.ty.is_empty() {
@@ -932,6 +943,30 @@ impl<'a> Parser<'a> {
             }
         }
     }
+
+    fn suggest_format_parameter(&mut self, c: char) {
+        let replacement = match c {
+            '#' => "#?",
+            'x' => "x?",
+            'X' => "X?",
+            _ => return,
+        };
+        let Some(pos) = self.consume_pos(c) else {
+            return;
+        };
+
+        let span = self.span(pos - 1, pos + 1);
+        let pos = self.to_span_index(pos);
+
+        self.errors.insert(0, ParseError {
+            description: format!("expected `}}`, found `{c}`"),
+            note: None,
+            label: "expected `'}'`".into(),
+            span: pos.to(pos),
+            secondary_label: None,
+            suggestion: Suggestion::ReorderFormatParameter(span, format!("{replacement}")),
+        })
+    }
 }
 
 /// Finds the indices of all characters that have been processed and differ between the actual