Rollup of 22 pull requests

.mailmap

@@ -246,6 +246,7 @@ Philipp Brüschweiler <[email protected]> <[email protected]>
 Philipp Krones <[email protected]> flip1995 <[email protected]>
 Philipp Krones <[email protected]> <[email protected]>
 Philipp Matthias Schäfer <[email protected]>
+pierwill <[email protected]> <[email protected]>
 Przemysław Wesołek <[email protected]> Przemek Wesołek <[email protected]>
 Rafael Ávila de Espíndola <[email protected]> Rafael Avila de Espindola <espindola@dream.(none)>
 Ralph Giles <[email protected]> Ralph Giles <[email protected]>

compiler/rustc_ast/src/util/literal.rs

@@ -57,7 +57,7 @@ impl LitKind {
                 // string in the token.
                 let s = symbol.as_str();
                 let symbol =
-                    if s.contains(&['\\', '\r'][..]) {
+                    if s.contains(&['\\', '\r']) {
                         let mut buf = String::with_capacity(s.len());
                         let mut error = Ok(());
                         unescape_literal(&s, Mode::Str, &mut |_, unescaped_char| {

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -347,7 +347,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
 
                     if let Some(modifiers) = nested_meta.value_str() {
                         for modifier in modifiers.as_str().split(',') {
-                            if let Some(modifier) = modifier.strip_prefix(&['+', '-'][..]) {
+                            if let Some(modifier) = modifier.strip_prefix(&['+', '-']) {
                                 macro_rules! gate_modifier { ($($name:literal => $feature:ident)*) => {
                                     $(if modifier == $name {
                                         let msg = concat!("`#[link(modifiers=\"", $name, "\")]` is unstable");
@@ -383,7 +383,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
             }
 
             ast::ItemKind::Fn(..) => {
-                if self.sess.contains_name(&i.attrs[..], sym::start) {
+                if self.sess.contains_name(&i.attrs, sym::start) {
                     gate_feature_post!(
                         &self,
                         start,
@@ -396,7 +396,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
             }
 
             ast::ItemKind::Struct(..) => {
-                for attr in self.sess.filter_by_name(&i.attrs[..], sym::repr) {
+                for attr in self.sess.filter_by_name(&i.attrs, sym::repr) {
                     for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
                         if item.has_name(sym::simd) {
                             gate_feature_post!(

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -499,7 +499,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
             ast::MetaItemKind::List(ref items) => {
                 self.print_path(&item.path, false, 0);
                 self.popen();
-                self.commasep(Consistent, &items[..], |s, i| s.print_meta_list_item(i));
+                self.commasep(Consistent, &items, |s, i| s.print_meta_list_item(i));
                 self.pclose();
             }
         }
@@ -997,7 +997,7 @@ impl<'a> State<'a> {
             }
             ast::TyKind::Tup(ref elts) => {
                 self.popen();
-                self.commasep(Inconsistent, &elts[..], |s, ty| s.print_type(ty));
+                self.commasep(Inconsistent, &elts, |s, ty| s.print_type(ty));
                 if elts.len() == 1 {
                     self.word(",");
                 }
@@ -1017,10 +1017,10 @@ impl<'a> State<'a> {
             ast::TyKind::Path(Some(ref qself), ref path) => self.print_qpath(path, qself, false),
             ast::TyKind::TraitObject(ref bounds, syntax) => {
                 let prefix = if syntax == ast::TraitObjectSyntax::Dyn { "dyn" } else { "" };
-                self.print_type_bounds(prefix, &bounds[..]);
+                self.print_type_bounds(prefix, &bounds);
             }
             ast::TyKind::ImplTrait(_, ref bounds) => {
-                self.print_type_bounds("impl", &bounds[..]);
+                self.print_type_bounds("impl", &bounds);
             }
             ast::TyKind::Array(ref ty, ref length) => {
                 self.word("[");
@@ -1339,7 +1339,7 @@ impl<'a> State<'a> {
                         real_bounds.push(b.clone());
                     }
                 }
-                self.print_type_bounds(":", &real_bounds[..]);
+                self.print_type_bounds(":", &real_bounds);
                 self.print_where_clause(&generics.where_clause);
                 self.word(" ");
                 self.bopen();
@@ -1368,7 +1368,7 @@ impl<'a> State<'a> {
                     }
                 }
                 self.nbsp();
-                self.print_type_bounds("=", &real_bounds[..]);
+                self.print_type_bounds("=", &real_bounds);
                 self.print_where_clause(&generics.where_clause);
                 self.word(";");
             }
@@ -1960,10 +1960,10 @@ impl<'a> State<'a> {
                 self.print_expr_tup(exprs);
             }
             ast::ExprKind::Call(ref func, ref args) => {
-                self.print_expr_call(func, &args[..]);
+                self.print_expr_call(func, &args);
             }
             ast::ExprKind::MethodCall(ref segment, ref args, _) => {
-                self.print_expr_method_call(segment, &args[..]);
+                self.print_expr_method_call(segment, &args);
             }
             ast::ExprKind::Binary(op, ref lhs, ref rhs) => {
                 self.print_expr_binary(op, lhs, rhs);
@@ -2440,11 +2440,11 @@ impl<'a> State<'a> {
                     self.print_path(path, true, 0);
                 }
                 self.popen();
-                self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(p));
+                self.commasep(Inconsistent, &elts, |s, p| s.print_pat(p));
                 self.pclose();
             }
             PatKind::Or(ref pats) => {
-                self.strsep("|", true, Inconsistent, &pats[..], |s, p| s.print_pat(p));
+                self.strsep("|", true, Inconsistent, &pats, |s, p| s.print_pat(p));
             }
             PatKind::Path(None, ref path) => {
                 self.print_path(path, true, 0);
@@ -2462,7 +2462,7 @@ impl<'a> State<'a> {
                 self.word_space("{");
                 self.commasep_cmnt(
                     Consistent,
-                    &fields[..],
+                    &fields,
                     |s, f| {
                         s.cbox(INDENT_UNIT);
                         if !f.is_shorthand {
@@ -2485,7 +2485,7 @@ impl<'a> State<'a> {
             }
             PatKind::Tuple(ref elts) => {
                 self.popen();
-                self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(p));
+                self.commasep(Inconsistent, &elts, |s, p| s.print_pat(p));
                 if elts.len() == 1 {
                     self.word(",");
                 }
@@ -2527,7 +2527,7 @@ impl<'a> State<'a> {
             }
             PatKind::Slice(ref elts) => {
                 self.word("[");
-                self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(p));
+                self.commasep(Inconsistent, &elts, |s, p| s.print_pat(p));
                 self.word("]");
             }
             PatKind::Rest => self.word(".."),
@@ -2836,7 +2836,7 @@ impl<'a> State<'a> {
                     self.print_path(&tree.prefix, false, 0);
                     self.word("::{");
                 }
-                self.commasep(Inconsistent, &items[..], |this, &(ref tree, _)| {
+                self.commasep(Inconsistent, &items, |this, &(ref tree, _)| {
                     this.print_use_tree(tree)
                 });
                 self.word("}");

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -15,16 +15,18 @@ use rustc_span::symbol::sym;
 use rustc_span::{BytePos, MultiSpan, Span, DUMMY_SP};
 use rustc_trait_selection::infer::InferCtxtExt;
 
+use crate::borrow_set::TwoPhaseActivation;
 use crate::borrowck_errors;
 
+use crate::diagnostics::find_all_local_uses;
 use crate::{
     borrow_set::BorrowData, diagnostics::Instance, prefixes::IsPrefixOf,
     InitializationRequiringAction, MirBorrowckCtxt, PrefixSet, WriteKind,
 };
 
 use super::{
-    explain_borrow::BorrowExplanation, FnSelfUseKind, IncludingDowncast, RegionName,
-    RegionNameSource, UseSpans,
+    explain_borrow::{BorrowExplanation, LaterUseKind},
+    FnSelfUseKind, IncludingDowncast, RegionName, RegionNameSource, UseSpans,
 };
 
 #[derive(Debug)]
@@ -768,9 +770,92 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             Some((issued_span, span)),
         );
 
+        self.suggest_using_local_if_applicable(
+            &mut err,
+            location,
+            (place, span),
+            gen_borrow_kind,
+            issued_borrow,
+            explanation,
+        );
+
         err
     }
 
+    #[instrument(level = "debug", skip(self, err))]
+    fn suggest_using_local_if_applicable(
+        &self,
+        err: &mut DiagnosticBuilder<'_>,
+        location: Location,
+        (place, span): (Place<'tcx>, Span),
+        gen_borrow_kind: BorrowKind,
+        issued_borrow: &BorrowData<'tcx>,
+        explanation: BorrowExplanation,
+    ) {
+        let used_in_call =
+            matches!(explanation, BorrowExplanation::UsedLater(LaterUseKind::Call, _call_span, _));
+        if !used_in_call {
+            debug!("not later used in call");
+            return;
+        }
+
+        let outer_call_loc =
+            if let TwoPhaseActivation::ActivatedAt(loc) = issued_borrow.activation_location {
+                loc
+            } else {
+                issued_borrow.reserve_location
+            };
+        let outer_call_stmt = self.body.stmt_at(outer_call_loc);
+
+        let inner_param_location = location;
+        let Some(inner_param_stmt) = self.body.stmt_at(inner_param_location).left() else {
+            debug!("`inner_param_location` {:?} is not for a statement", inner_param_location);
+            return;
+        };
+        let Some(&inner_param) = inner_param_stmt.kind.as_assign().map(|(p, _)| p) else {
+            debug!(
+                "`inner_param_location` {:?} is not for an assignment: {:?}",
+                inner_param_location, inner_param_stmt
+            );
+            return;
+        };
+        let inner_param_uses = find_all_local_uses::find(self.body, inner_param.local);
+        let Some((inner_call_loc,inner_call_term)) = inner_param_uses.into_iter().find_map(|loc| {
+            let Either::Right(term) = self.body.stmt_at(loc) else {
+                debug!("{:?} is a statement, so it can't be a call", loc);
+                return None;
+            };
+            let TerminatorKind::Call { args, .. } = &term.kind else {
+                debug!("not a call: {:?}", term);
+                return None;
+            };
+            debug!("checking call args for uses of inner_param: {:?}", args);
+            if args.contains(&Operand::Move(inner_param)) {
+                Some((loc,term))
+            } else {
+                None
+            }
+        }) else {
+            debug!("no uses of inner_param found as a by-move call arg");
+            return;
+        };
+        debug!("===> outer_call_loc = {:?}, inner_call_loc = {:?}", outer_call_loc, inner_call_loc);
+
+        let inner_call_span = inner_call_term.source_info.span;
+        let outer_call_span = outer_call_stmt.either(|s| s.source_info, |t| t.source_info).span;
+        if outer_call_span == inner_call_span || !outer_call_span.contains(inner_call_span) {
+            // FIXME: This stops the suggestion in some cases where it should be emitted.
+            //        Fix the spans for those cases so it's emitted correctly.
+            debug!(
+                "outer span {:?} does not strictly contain inner span {:?}",
+                outer_call_span, inner_call_span
+            );
+            return;
+        }
+        err.span_help(inner_call_span, "try adding a local storing this argument...");
+        err.span_help(outer_call_span, "...and then using that local as the argument to this call");
+    }
+
     fn suggest_split_at_mut_if_applicable(
         &self,
         err: &mut DiagnosticBuilder<'_>,

compiler/rustc_borrowck/src/diagnostics/find_all_local_uses.rs

@@ -0,0 +1,26 @@
+use std::collections::BTreeSet;
+
+use rustc_middle::mir::visit::{PlaceContext, Visitor};
+use rustc_middle::mir::{Body, Local, Location};
+
+/// Find all uses of (including assignments to) a [`Local`].
+///
+/// Uses `BTreeSet` so output is deterministic.
+pub(super) fn find<'tcx>(body: &Body<'tcx>, local: Local) -> BTreeSet<Location> {
+    let mut visitor = AllLocalUsesVisitor { for_local: local, uses: BTreeSet::default() };
+    visitor.visit_body(body);
+    visitor.uses
+}
+
+struct AllLocalUsesVisitor {
+    for_local: Local,
+    uses: BTreeSet<Location>,
+}
+
+impl<'tcx> Visitor<'tcx> for AllLocalUsesVisitor {
+    fn visit_local(&mut self, local: &Local, _context: PlaceContext, location: Location) {
+        if *local == self.for_local {
+            self.uses.insert(location);
+        }
+    }
+}

compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -19,6 +19,7 @@ use rustc_target::abi::VariantIdx;
 use super::borrow_set::BorrowData;
 use super::MirBorrowckCtxt;
 
+mod find_all_local_uses;
 mod find_use;
 mod outlives_suggestion;
 mod region_name;

compiler/rustc_builtin_macros/src/asm.rs

@@ -712,7 +712,7 @@ fn expand_preparsed_asm(ecx: &mut ExtCtxt<'_>, args: AsmArgs) -> Option<ast::Inl
                             Some(&idx) => Some(idx),
                             None => {
                                 let msg = format!("there is no argument named `{}`", name);
-                                ecx.struct_span_err(span, &msg[..]).emit();
+                                ecx.struct_span_err(span, &msg).emit();
                                 None
                             }
                         },

compiler/rustc_builtin_macros/src/deriving/generic/mod.rs

@@ -766,17 +766,17 @@ impl<'a> TraitDef<'a> {
                         self,
                         struct_def,
                         type_ident,
-                        &self_args[..],
-                        &nonself_args[..],
+                        &self_args,
+                        &nonself_args,
                     )
                 } else {
                     method_def.expand_struct_method_body(
                         cx,
                         self,
                         struct_def,
                         type_ident,
-                        &self_args[..],
-                        &nonself_args[..],
+                        &self_args,
+                        &nonself_args,
                         use_temporaries,
                     )
                 };
@@ -815,8 +815,8 @@ impl<'a> TraitDef<'a> {
                         self,
                         enum_def,
                         type_ident,
-                        &self_args[..],
-                        &nonself_args[..],
+                        &self_args,
+                        &nonself_args,
                     )
                 } else {
                     method_def.expand_enum_method_body(
@@ -825,7 +825,7 @@ impl<'a> TraitDef<'a> {
                         enum_def,
                         type_ident,
                         self_args,
-                        &nonself_args[..],
+                        &nonself_args,
                     )
                 };
 
@@ -1217,7 +1217,7 @@ impl<'a> MethodDef<'a> {
         let vi_idents = self_arg_names
             .iter()
             .map(|name| {
-                let vi_suffix = format!("{}_vi", &name[..]);
+                let vi_suffix = format!("{}_vi", name);
                 Ident::from_str_and_span(&vi_suffix, span)
             })
             .collect::<Vec<Ident>>();
@@ -1226,7 +1226,7 @@ impl<'a> MethodDef<'a> {
         // delegated expression that handles the catch-all case,
         // using `__variants_tuple` to drive logic if necessary.
         let catch_all_substructure =
-            EnumNonMatchingCollapsed(self_arg_idents, &variants[..], &vi_idents[..]);
+            EnumNonMatchingCollapsed(self_arg_idents, &variants, &vi_idents);
 
         let first_fieldless = variants.iter().find(|v| v.data.fields().is_empty());
 
@@ -1261,7 +1261,7 @@ impl<'a> MethodDef<'a> {
                     idents
                 };
                 for self_arg_name in &self_arg_names[1..] {
-                    let (p, idents) = mk_self_pat(cx, &self_arg_name[..]);
+                    let (p, idents) = mk_self_pat(cx, &self_arg_name);
                     subpats.push(p);
                     self_pats_idents.push(idents);
                 }