Rollup of 8 pull requests

compiler/rustc_builtin_macros/src/asm.rs

@@ -700,11 +700,11 @@ fn expand_preparsed_asm(ecx: &mut ExtCtxt<'_>, args: AsmArgs) -> Option<ast::Inl
                                 Some(idx)
                             }
                         }
-                        parse::ArgumentNamed(name) => match args.named_args.get(&name) {
+                        parse::ArgumentNamed(name, span) => match args.named_args.get(&name) {
                             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(template_span.from_inner(span), &msg).emit();
                                 None
                             }
                         },

compiler/rustc_builtin_macros/src/format.rs

@@ -11,7 +11,7 @@ use rustc_errors::{pluralize, Applicability, DiagnosticBuilder};
 use rustc_expand::base::{self, *};
 use rustc_parse_format as parse;
 use rustc_span::symbol::{sym, Ident, Symbol};
-use rustc_span::{MultiSpan, Span};
+use rustc_span::{InnerSpan, MultiSpan, Span};
 use smallvec::SmallVec;
 
 use std::borrow::Cow;
@@ -26,7 +26,7 @@ enum ArgumentType {
 enum Position {
     Exact(usize),
     Capture(usize),
-    Named(Symbol),
+    Named(Symbol, InnerSpan),
 }
 
 struct Context<'a, 'b> {
@@ -247,13 +247,13 @@ impl<'a, 'b> Context<'a, 'b> {
         match *p {
             parse::String(_) => {}
             parse::NextArgument(ref mut arg) => {
-                if let parse::ArgumentNamed(s) = arg.position {
+                if let parse::ArgumentNamed(s, _) = arg.position {
                     arg.position = parse::ArgumentIs(lookup(s));
                 }
-                if let parse::CountIsName(s) = arg.format.width {
+                if let parse::CountIsName(s, _) = arg.format.width {
                     arg.format.width = parse::CountIsParam(lookup(s));
                 }
-                if let parse::CountIsName(s) = arg.format.precision {
+                if let parse::CountIsName(s, _) = arg.format.precision {
                     arg.format.precision = parse::CountIsParam(lookup(s));
                 }
             }
@@ -276,7 +276,7 @@ impl<'a, 'b> Context<'a, 'b> {
                 // it's written second, so it should come after width/precision.
                 let pos = match arg.position {
                     parse::ArgumentIs(i) | parse::ArgumentImplicitlyIs(i) => Exact(i),
-                    parse::ArgumentNamed(s) => Named(s),
+                    parse::ArgumentNamed(s, span) => Named(s, span),
                 };
 
                 let ty = Placeholder(match arg.format.ty {
@@ -346,8 +346,8 @@ impl<'a, 'b> Context<'a, 'b> {
             parse::CountIsParam(i) => {
                 self.verify_arg_type(Exact(i), Count);
             }
-            parse::CountIsName(s) => {
-                self.verify_arg_type(Named(s), Count);
+            parse::CountIsName(s, span) => {
+                self.verify_arg_type(Named(s, span), Count);
             }
         }
     }
@@ -533,7 +533,7 @@ impl<'a, 'b> Context<'a, 'b> {
                 }
             }
 
-            Named(name) => {
+            Named(name, span) => {
                 match self.names.get(&name) {
                     Some(&idx) => {
                         // Treat as positional arg.
@@ -548,7 +548,7 @@ impl<'a, 'b> Context<'a, 'b> {
                             self.arg_types.push(Vec::new());
                             self.arg_unique_types.push(Vec::new());
                             let span = if self.is_literal {
-                                *self.arg_spans.get(self.curpiece).unwrap_or(&self.fmtsp)
+                                self.fmtsp.from_inner(span)
                             } else {
                                 self.fmtsp
                             };
@@ -559,7 +559,7 @@ impl<'a, 'b> Context<'a, 'b> {
                         } else {
                             let msg = format!("there is no argument named `{}`", name);
                             let sp = if self.is_literal {
-                                *self.arg_spans.get(self.curpiece).unwrap_or(&self.fmtsp)
+                                self.fmtsp.from_inner(span)
                             } else {
                                 self.fmtsp
                             };
@@ -629,7 +629,7 @@ impl<'a, 'b> Context<'a, 'b> {
             }
             parse::CountImplied => count(sym::Implied, None),
             // should never be the case, names are already resolved
-            parse::CountIsName(_) => panic!("should never happen"),
+            parse::CountIsName(..) => panic!("should never happen"),
         }
     }
 
@@ -676,7 +676,7 @@ impl<'a, 'b> Context<'a, 'b> {
 
                         // should never be the case, because names are already
                         // resolved.
-                        parse::ArgumentNamed(_) => panic!("should never happen"),
+                        parse::ArgumentNamed(..) => panic!("should never happen"),
                     }
                 };
 

compiler/rustc_parse_format/src/lib.rs

@@ -95,7 +95,7 @@ pub enum Position {
     /// The argument is located at a specific index given in the format
     ArgumentIs(usize),
     /// The argument has a name.
-    ArgumentNamed(Symbol),
+    ArgumentNamed(Symbol, InnerSpan),
 }
 
 impl Position {
@@ -147,7 +147,7 @@ pub enum Count {
     /// The count is specified explicitly.
     CountIs(usize),
     /// The count is specified by the argument with the given name.
-    CountIsName(Symbol),
+    CountIsName(Symbol, InnerSpan),
     /// The count is specified by the argument at the given index.
     CountIsParam(usize),
     /// The count is implied and cannot be explicitly specified.
@@ -494,8 +494,11 @@ impl<'a> Parser<'a> {
             Some(ArgumentIs(i))
         } else {
             match self.cur.peek() {
-                Some(&(_, c)) if rustc_lexer::is_id_start(c) => {
-                    Some(ArgumentNamed(Symbol::intern(self.word())))
+                Some(&(start, c)) if rustc_lexer::is_id_start(c) => {
+                    let word = self.word();
+                    let end = start + word.len();
+                    let span = self.to_span_index(start).to(self.to_span_index(end));
+                    Some(ArgumentNamed(Symbol::intern(word), span))
                 }
 
                 // This is an `ArgumentNext`.
@@ -662,8 +665,9 @@ impl<'a> Parser<'a> {
             if word.is_empty() {
                 self.cur = tmp;
                 (CountImplied, None)
-            } else if self.consume('$') {
-                (CountIsName(Symbol::intern(word)), None)
+            } else if let Some(end) = self.consume_pos('$') {
+                let span = self.to_span_index(start + 1).to(self.to_span_index(end));
+                (CountIsName(Symbol::intern(word), span), None)
             } else {
                 self.cur = tmp;
                 (CountImplied, None)

compiler/rustc_parse_format/src/tests.rs

@@ -221,8 +221,8 @@ fn format_counts() {
                     fill: None,
                     align: AlignUnknown,
                     flags: 0,
-                    precision: CountIsName(Symbol::intern("b")),
-                    width: CountIsName(Symbol::intern("a")),
+                    precision: CountIsName(Symbol::intern("b"), InnerSpan::new(6, 7)),
+                    width: CountIsName(Symbol::intern("a"), InnerSpan::new(4, 4)),
                     precision_span: None,
                     width_span: None,
                     ty: "?",

compiler/rustc_trait_selection/src/traits/on_unimplemented.rs

@@ -309,23 +309,23 @@ impl<'tcx> OnUnimplementedFormatString {
                 Piece::String(_) => (), // Normal string, no need to check it
                 Piece::NextArgument(a) => match a.position {
                     // `{Self}` is allowed
-                    Position::ArgumentNamed(s) if s == kw::SelfUpper => (),
+                    Position::ArgumentNamed(s, _) if s == kw::SelfUpper => (),
                     // `{ThisTraitsName}` is allowed
-                    Position::ArgumentNamed(s) if s == name => (),
+                    Position::ArgumentNamed(s, _) if s == name => (),
                     // `{from_method}` is allowed
-                    Position::ArgumentNamed(s) if s == sym::from_method => (),
+                    Position::ArgumentNamed(s, _) if s == sym::from_method => (),
                     // `{from_desugaring}` is allowed
-                    Position::ArgumentNamed(s) if s == sym::from_desugaring => (),
+                    Position::ArgumentNamed(s, _) if s == sym::from_desugaring => (),
                     // `{ItemContext}` is allowed
-                    Position::ArgumentNamed(s) if s == sym::ItemContext => (),
+                    Position::ArgumentNamed(s, _) if s == sym::ItemContext => (),
                     // `{integral}` and `{integer}` and `{float}` are allowed
-                    Position::ArgumentNamed(s)
+                    Position::ArgumentNamed(s, _)
                         if s == sym::integral || s == sym::integer_ || s == sym::float =>
                     {
                         ()
                     }
                     // So is `{A}` if A is a type parameter
-                    Position::ArgumentNamed(s) => {
+                    Position::ArgumentNamed(s, _) => {
                         match generics.params.iter().find(|param| param.name == s) {
                             Some(_) => (),
                             None => {
@@ -392,7 +392,7 @@ impl<'tcx> OnUnimplementedFormatString {
             .map(|p| match p {
                 Piece::String(s) => s,
                 Piece::NextArgument(a) => match a.position {
-                    Position::ArgumentNamed(s) => match generic_map.get(&s) {
+                    Position::ArgumentNamed(s, _) => match generic_map.get(&s) {
                         Some(val) => val,
                         None if s == name => &trait_str,
                         None => {

compiler/rustc_typeck/src/check/check.rs

@@ -382,10 +382,15 @@ fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: LocalDefId) -> b
                     tcx.sess,
                     field_span,
                     E0740,
-                    "unions may not contain fields that need dropping"
+                    "unions cannot contain fields that may need dropping"
+                )
+                .note(
+                    "a type is guaranteed not to need dropping \
+                    when it implements `Copy`, or when it is the special `ManuallyDrop<_>` type",
                 )
                 .multipart_suggestion_verbose(
-                    "wrap the type with `std::mem::ManuallyDrop` and ensure it is manually dropped",
+                    "when the type does not implement `Copy`, \
+                    wrap it inside a `ManuallyDrop<_>` and ensure it is manually dropped",
                     vec![
                         (ty_span.shrink_to_lo(), format!("std::mem::ManuallyDrop<")),
                         (ty_span.shrink_to_hi(), ">".into()),

compiler/rustc_typeck/src/check/method/suggest.rs

@@ -9,8 +9,10 @@ use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::{ExprKind, Node, QPath};
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
+use rustc_middle::traits::util::supertraits;
 use rustc_middle::ty::fast_reject::{simplify_type, SimplifyParams};
 use rustc_middle::ty::print::with_crate_prefix;
+use rustc_middle::ty::ToPolyTraitRef;
 use rustc_middle::ty::{self, DefIdTree, ToPredicate, Ty, TyCtxt, TypeFoldable};
 use rustc_span::lev_distance;
 use rustc_span::symbol::{kw, sym, Ident};
@@ -40,7 +42,19 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     Err(..) => return false,
                 };
 
+                // This conditional prevents us from asking to call errors and unresolved types.
+                // It might seem that we can use `predicate_must_hold_modulo_regions`,
+                // but since a Dummy binder is used to fill in the FnOnce trait's arguments,
+                // type resolution always gives a "maybe" here.
+                if self.autoderef(span, ty).any(|(ty, _)| {
+                    info!("check deref {:?} error", ty);
+                    matches!(ty.kind(), ty::Error(_) | ty::Infer(_))
+                }) {
+                    return false;
+                }
+
                 self.autoderef(span, ty).any(|(ty, _)| {
+                    info!("check deref {:?} impl FnOnce", ty);
                     self.probe(|_| {
                         let fn_once_substs = tcx.mk_substs_trait(
                             ty,
@@ -1196,26 +1210,40 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 Some(adt) if adt.did.is_local() => adt,
                 _ => continue,
             };
-            let can_derive = match self.tcx.get_diagnostic_name(trait_pred.def_id()) {
-                Some(sym::Default) => !adt.is_enum(),
-                Some(
+            if let Some(diagnostic_name) = self.tcx.get_diagnostic_name(trait_pred.def_id()) {
+                let can_derive = match diagnostic_name {
+                    sym::Default => !adt.is_enum(),
                     sym::Eq
                     | sym::PartialEq
                     | sym::Ord
                     | sym::PartialOrd
                     | sym::Clone
                     | sym::Copy
                     | sym::Hash
-                    | sym::Debug,
-                ) => true,
-                _ => false,
-            };
-            if can_derive {
-                derives.push((
-                    format!("{}", trait_pred.self_ty()),
-                    self.tcx.def_span(adt.did),
-                    format!("{}", trait_pred.trait_ref.print_only_trait_name()),
-                ));
+                    | sym::Debug => true,
+                    _ => false,
+                };
+                if can_derive {
+                    let self_name = trait_pred.self_ty().to_string();
+                    let self_span = self.tcx.def_span(adt.did);
+                    if let Some(poly_trait_ref) = pred.to_opt_poly_trait_pred() {
+                        for super_trait in supertraits(self.tcx, poly_trait_ref.to_poly_trait_ref())
+                        {
+                            if let Some(parent_diagnostic_name) =
+                                self.tcx.get_diagnostic_name(super_trait.def_id())
+                            {
+                                derives.push((
+                                    self_name.clone(),
+                                    self_span.clone(),
+                                    parent_diagnostic_name.to_string(),
+                                ));
+                            }
+                        }
+                    }
+                    derives.push((self_name, self_span, diagnostic_name.to_string()));
+                } else {
+                    traits.push(self.tcx.def_span(trait_pred.def_id()));
+                }
             } else {
                 traits.push(self.tcx.def_span(trait_pred.def_id()));
             }

compiler/rustc_typeck/src/check/pat.rs

@@ -2029,34 +2029,42 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 err.help("the semantics of slice patterns changed recently; see issue #62254");
             }
         } else if Autoderef::new(&self.infcx, self.param_env, self.body_id, span, expected_ty, span)
-            .any(|(ty, _)| matches!(ty.kind(), ty::Slice(..)))
+            .any(|(ty, _)| matches!(ty.kind(), ty::Slice(..) | ty::Array(..)))
         {
             if let (Some(span), true) = (ti.span, ti.origin_expr) {
                 if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
-                    let applicability = match self.resolve_vars_if_possible(ti.expected).kind() {
-                        ty::Adt(adt_def, _)
-                            if self.tcx.is_diagnostic_item(sym::Option, adt_def.did)
-                                || self.tcx.is_diagnostic_item(sym::Result, adt_def.did) =>
-                        {
-                            // Slicing won't work here, but `.as_deref()` might (issue #91328).
-                            err.span_suggestion(
-                                span,
-                                "consider using `as_deref` here",
-                                format!("{}.as_deref()", snippet),
-                                Applicability::MaybeIncorrect,
-                            );
-                            None
-                        }
-                        // FIXME: instead of checking for Vec only, we could check whether the
-                        // type implements `Deref<Target=X>`; see
-                        // https://github.com/rust-lang/rust/pull/91343#discussion_r761466979
-                        ty::Adt(adt_def, _)
-                            if self.tcx.is_diagnostic_item(sym::Vec, adt_def.did) =>
-                        {
-                            Some(Applicability::MachineApplicable)
+                    let applicability = Autoderef::new(
+                        &self.infcx,
+                        self.param_env,
+                        self.body_id,
+                        span,
+                        self.resolve_vars_if_possible(ti.expected),
+                        span,
+                    )
+                    .find_map(|(ty, _)| {
+                        match ty.kind() {
+                            ty::Adt(adt_def, _)
+                                if self.tcx.is_diagnostic_item(sym::Option, adt_def.did)
+                                    || self.tcx.is_diagnostic_item(sym::Result, adt_def.did) =>
+                            {
+                                // Slicing won't work here, but `.as_deref()` might (issue #91328).
+                                err.span_suggestion(
+                                    span,
+                                    "consider using `as_deref` here",
+                                    format!("{}.as_deref()", snippet),
+                                    Applicability::MaybeIncorrect,
+                                );
+                                Some(None)
+                            }
+
+                            ty::Slice(..) | ty::Array(..) => {
+                                Some(Some(Applicability::MachineApplicable))
+                            }
+
+                            _ => None,
                         }
-                        _ => Some(Applicability::MaybeIncorrect),
-                    };
+                    })
+                    .unwrap_or(Some(Applicability::MaybeIncorrect));
 
                     if let Some(applicability) = applicability {
                         err.span_suggestion(

library/alloc/src/collections/btree/map.rs

@@ -2052,6 +2052,8 @@ where
 
 #[stable(feature = "std_collections_from_array", since = "1.56.0")]
 impl<K: Ord, V, const N: usize> From<[(K, V); N]> for BTreeMap<K, V> {
+    /// Converts a `[(K, V); N]` into a `BTreeMap<(K, V)>`.
+    ///
     /// ```
     /// use std::collections::BTreeMap;
     ///

library/alloc/src/collections/btree/set.rs

@@ -1097,6 +1097,8 @@ impl<T: Ord> FromIterator<T> for BTreeSet<T> {
 
 #[stable(feature = "std_collections_from_array", since = "1.56.0")]
 impl<T: Ord, const N: usize> From<[T; N]> for BTreeSet<T> {
+    /// Converts a `[T; N]` into a `BTreeSet<T>`.
+    ///
     /// ```
     /// use std::collections::BTreeSet;
     ///