Simplify hir::PathSegment

compiler/rustc_ast_lowering/src/expr.rs

@@ -1776,12 +1776,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
         binding: hir::HirId,
         attrs: AttrVec,
     ) -> hir::Expr<'hir> {
+        let hir_id = self.next_id();
+        let res = Res::Local(binding);
         let expr_path = hir::ExprKind::Path(hir::QPath::Resolved(
             None,
             self.arena.alloc(hir::Path {
                 span: self.lower_span(span),
-                res: Res::Local(binding),
-                segments: arena_vec![self; hir::PathSegment::from_ident(ident)],
+                res,
+                segments: arena_vec![self; hir::PathSegment::new(ident, hir_id, res)],
             }),
         ));
 

compiler/rustc_ast_lowering/src/index.rs

@@ -246,9 +246,7 @@ impl<'a, 'hir> Visitor<'hir> for NodeCollector<'a, 'hir> {
     }
 
     fn visit_path_segment(&mut self, path_span: Span, path_segment: &'hir PathSegment<'hir>) {
-        if let Some(hir_id) = path_segment.hir_id {
-            self.insert(path_span, hir_id, Node::PathSegment(path_segment));
-        }
+        self.insert(path_span, path_segment.hir_id, Node::PathSegment(path_segment));
         intravisit::walk_path_segment(self, path_span, path_segment);
     }
 

compiler/rustc_ast_lowering/src/item.rs

@@ -1431,10 +1431,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
             GenericParamKind::Const { .. } => None,
             GenericParamKind::Type { .. } => {
                 let def_id = self.local_def_id(id).to_def_id();
+                let hir_id = self.next_id();
+                let res = Res::Def(DefKind::TyParam, def_id);
                 let ty_path = self.arena.alloc(hir::Path {
                     span: param_span,
-                    res: Res::Def(DefKind::TyParam, def_id),
-                    segments: self.arena.alloc_from_iter([hir::PathSegment::from_ident(ident)]),
+                    res,
+                    segments: self
+                        .arena
+                        .alloc_from_iter([hir::PathSegment::new(ident, hir_id, res)]),
                 });
                 let ty_id = self.next_id();
                 let bounded_ty =

compiler/rustc_ast_lowering/src/lib.rs

@@ -1260,14 +1260,17 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 return self.lower_path_ty(t, qself, path, ParamMode::Explicit, itctx);
             }
             TyKind::ImplicitSelf => {
+                let hir_id = self.lower_node_id(t.id);
                 let res = self.expect_full_res(t.id);
                 let res = self.lower_res(res);
                 hir::TyKind::Path(hir::QPath::Resolved(
                     None,
                     self.arena.alloc(hir::Path {
                         res,
-                        segments: arena_vec![self; hir::PathSegment::from_ident(
-                            Ident::with_dummy_span(kw::SelfUpper)
+                        segments: arena_vec![self; hir::PathSegment::new(
+                            Ident::with_dummy_span(kw::SelfUpper),
+                            hir_id,
+                            res
                         )],
                         span: self.lower_span(t.span),
                     }),
@@ -2193,12 +2196,15 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             hir::PredicateOrigin::ImplTrait,
         );
 
+        let hir_id = self.next_id();
+        let res = Res::Def(DefKind::TyParam, def_id.to_def_id());
         let ty = hir::TyKind::Path(hir::QPath::Resolved(
             None,
             self.arena.alloc(hir::Path {
                 span: self.lower_span(span),
-                res: Res::Def(DefKind::TyParam, def_id.to_def_id()),
-                segments: arena_vec![self; hir::PathSegment::from_ident(self.lower_ident(ident))],
+                res,
+                segments:
+                    arena_vec![self; hir::PathSegment::new(self.lower_ident(ident), hir_id, res)],
             }),
         ));
 

compiler/rustc_ast_lowering/src/pat.rs

@@ -254,14 +254,18 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     lower_sub(self),
                 )
             }
-            Some(res) => hir::PatKind::Path(hir::QPath::Resolved(
-                None,
-                self.arena.alloc(hir::Path {
-                    span: self.lower_span(ident.span),
-                    res: self.lower_res(res),
-                    segments: arena_vec![self; hir::PathSegment::from_ident(self.lower_ident(ident))],
-                }),
-            )),
+            Some(res) => {
+                let hir_id = self.next_id();
+                let res = self.lower_res(res);
+                hir::PatKind::Path(hir::QPath::Resolved(
+                    None,
+                    self.arena.alloc(hir::Path {
+                        span: self.lower_span(ident.span),
+                        res,
+                        segments: arena_vec![self; hir::PathSegment::new(self.lower_ident(ident), hir_id, res)],
+                    }),
+            ))
+            }
         }
     }
 

compiler/rustc_ast_lowering/src/path.rs

@@ -250,16 +250,16 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         }
 
         let res = self.expect_full_res(segment.id);
-        let id = self.lower_node_id(segment.id);
+        let hir_id = self.lower_node_id(segment.id);
         debug!(
             "lower_path_segment: ident={:?} original-id={:?} new-id={:?}",
-            segment.ident, segment.id, id,
+            segment.ident, segment.id, hir_id,
         );
 
         hir::PathSegment {
             ident: self.lower_ident(segment.ident),
-            hir_id: Some(id),
-            res: Some(self.lower_res(res)),
+            hir_id,
+            res: self.lower_res(res),
             infer_args,
             args: if generic_args.is_empty() && generic_args.span.is_empty() {
                 None

compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -935,10 +935,11 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 _,
             ) = hir_map.body(fn_body_id).value.kind
             {
-                let opt_suggestions = path_segment
-                    .hir_id
-                    .map(|path_hir_id| self.infcx.tcx.typeck(path_hir_id.owner))
-                    .and_then(|typeck| typeck.type_dependent_def_id(*hir_id))
+                let opt_suggestions = self
+                    .infcx
+                    .tcx
+                    .typeck(path_segment.hir_id.owner)
+                    .type_dependent_def_id(*hir_id)
                     .and_then(|def_id| self.infcx.tcx.impl_of_method(def_id))
                     .map(|def_id| self.infcx.tcx.associated_items(def_id))
                     .map(|assoc_items| {

compiler/rustc_hir/src/def.rs

@@ -308,6 +308,7 @@ pub enum Res<Id = hir::HirId> {
     ///
     /// **Belongs to the type namespace.**
     PrimTy(hir::PrimTy),
+
     /// The `Self` type, optionally with the [`DefId`] of the trait it belongs to and
     /// optionally with the [`DefId`] of the item introducing the `Self` type alias.
     ///
@@ -355,7 +356,8 @@ pub enum Res<Id = hir::HirId> {
     /// const fn baz<T>() -> usize { 10 }
     /// ```
     /// We do however allow `Self` in repeat expression even if it is generic to not break code
-    /// which already works on stable while causing the `const_evaluatable_unchecked` future compat lint:
+    /// which already works on stable while causing the `const_evaluatable_unchecked` future compat
+    /// lint:
     /// ```
     /// fn foo<T>() {
     ///     let _bar = [1_u8; std::mem::size_of::<*mut T>()];
@@ -370,6 +372,7 @@ pub enum Res<Id = hir::HirId> {
         /// from mentioning generics (i.e. when used in an anonymous constant).
         alias_to: Option<(DefId, bool)>,
     },
+
     /// A tool attribute module; e.g., the `rustfmt` in `#[rustfmt::skip]`.
     ///
     /// **Belongs to the type namespace.**
@@ -383,6 +386,7 @@ pub enum Res<Id = hir::HirId> {
     ///
     /// *See also [`Res::SelfTy`].*
     SelfCtor(DefId),
+
     /// A local variable or function parameter.
     ///
     /// **Belongs to the value namespace.**

compiler/rustc_hir/src/hir.rs

@@ -202,13 +202,8 @@ impl Path<'_> {
 pub struct PathSegment<'hir> {
     /// The identifier portion of this path segment.
     pub ident: Ident,
-    // `id` and `res` are optional. We currently only use these in save-analysis,
-    // any path segments without these will not have save-analysis info and
-    // therefore will not have 'jump to def' in IDEs, but otherwise will not be
-    // affected. (In general, we don't bother to get the defs for synthesized
-    // segments, only for segments which have come from the AST).
-    pub hir_id: Option<HirId>,
-    pub res: Option<Res>,
+    pub hir_id: HirId,
+    pub res: Res,
 
     /// Type/lifetime parameters attached to this path. They come in
     /// two flavors: `Path<A,B,C>` and `Path(A,B) -> C`. Note that
@@ -226,12 +221,12 @@ pub struct PathSegment<'hir> {
 
 impl<'hir> PathSegment<'hir> {
     /// Converts an identifier to the corresponding segment.
-    pub fn from_ident(ident: Ident) -> PathSegment<'hir> {
-        PathSegment { ident, hir_id: None, res: None, infer_args: true, args: None }
+    pub fn new(ident: Ident, hir_id: HirId, res: Res) -> PathSegment<'hir> {
+        PathSegment { ident, hir_id, res, infer_args: true, args: None }
     }
 
     pub fn invalid() -> Self {
-        Self::from_ident(Ident::empty())
+        Self::new(Ident::empty(), HirId::INVALID, Res::Err)
     }
 
     pub fn args(&self) -> &GenericArgs<'hir> {

compiler/rustc_hir/src/hir_id.rs

@@ -20,6 +20,9 @@ pub struct HirId {
 }
 
 impl HirId {
+    /// Signal local id which should never be used.
+    pub const INVALID: HirId = HirId { owner: CRATE_DEF_ID, local_id: ItemLocalId::INVALID };
+
     #[inline]
     pub fn expect_owner(self) -> LocalDefId {
         assert_eq!(self.local_id.index(), 0);

compiler/rustc_hir/src/intravisit.rs

@@ -724,7 +724,7 @@ pub fn walk_path_segment<'v, V: Visitor<'v>>(
     segment: &'v PathSegment<'v>,
 ) {
     visitor.visit_ident(segment.ident);
-    walk_list!(visitor, visit_id, segment.hir_id);
+    visitor.visit_id(segment.hir_id);
     if let Some(ref args) = segment.args {
         visitor.visit_generic_args(path_span, args);
     }

compiler/rustc_hir_pretty/src/lib.rs

@@ -1189,7 +1189,7 @@ impl<'a> State<'a> {
 
         let generic_args = segment.args();
         if !generic_args.args.is_empty() || !generic_args.bindings.is_empty() {
-            self.print_generic_args(generic_args, segment.infer_args, true);
+            self.print_generic_args(generic_args, true);
         }
 
         self.print_call_post(base_args)
@@ -1592,15 +1592,15 @@ impl<'a> State<'a> {
             }
             if segment.ident.name != kw::PathRoot {
                 self.print_ident(segment.ident);
-                self.print_generic_args(segment.args(), segment.infer_args, colons_before_params);
+                self.print_generic_args(segment.args(), colons_before_params);
             }
         }
     }
 
     pub fn print_path_segment(&mut self, segment: &hir::PathSegment<'_>) {
         if segment.ident.name != kw::PathRoot {
             self.print_ident(segment.ident);
-            self.print_generic_args(segment.args(), segment.infer_args, false);
+            self.print_generic_args(segment.args(), false);
         }
     }
 
@@ -1619,23 +1619,15 @@ impl<'a> State<'a> {
                     }
                     if segment.ident.name != kw::PathRoot {
                         self.print_ident(segment.ident);
-                        self.print_generic_args(
-                            segment.args(),
-                            segment.infer_args,
-                            colons_before_params,
-                        );
+                        self.print_generic_args(segment.args(), colons_before_params);
                     }
                 }
 
                 self.word(">");
                 self.word("::");
                 let item_segment = path.segments.last().unwrap();
                 self.print_ident(item_segment.ident);
-                self.print_generic_args(
-                    item_segment.args(),
-                    item_segment.infer_args,
-                    colons_before_params,
-                )
+                self.print_generic_args(item_segment.args(), colons_before_params)
             }
             hir::QPath::TypeRelative(qself, item_segment) => {
                 // If we've got a compound-qualified-path, let's push an additional pair of angle
@@ -1651,11 +1643,7 @@ impl<'a> State<'a> {
 
                 self.word("::");
                 self.print_ident(item_segment.ident);
-                self.print_generic_args(
-                    item_segment.args(),
-                    item_segment.infer_args,
-                    colons_before_params,
-                )
+                self.print_generic_args(item_segment.args(), colons_before_params)
             }
             hir::QPath::LangItem(lang_item, span, _) => {
                 self.word("#[lang = \"");
@@ -1668,7 +1656,6 @@ impl<'a> State<'a> {
     fn print_generic_args(
         &mut self,
         generic_args: &hir::GenericArgs<'_>,
-        infer_args: bool,
         colons_before_params: bool,
     ) {
         if generic_args.parenthesized {
@@ -1715,13 +1702,6 @@ impl<'a> State<'a> {
                 );
             }
 
-            // FIXME(eddyb): this would leak into error messages (e.g.,
-            // "non-exhaustive patterns: `Some::<..>(_)` not covered").
-            if infer_args && false {
-                start_or_comma(self);
-                self.word("..");
-            }
-
             for binding in generic_args.bindings {
                 start_or_comma(self);
                 self.print_type_binding(binding);
@@ -1735,7 +1715,7 @@ impl<'a> State<'a> {
 
     pub fn print_type_binding(&mut self, binding: &hir::TypeBinding<'_>) {
         self.print_ident(binding.ident);
-        self.print_generic_args(binding.gen_args, false, false);
+        self.print_generic_args(binding.gen_args, false);
         self.space();
         match binding.kind {
             hir::TypeBindingKind::Equality { ref term } => {

compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs

@@ -909,7 +909,7 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
                             None?
                         }
                         let substs = self.node_substs_opt(expr.hir_id)?;
-                        let span = tcx.hir().span(segment.hir_id?);
+                        let span = tcx.hir().span(segment.hir_id);
                         let insert_span = segment.ident.span.shrink_to_hi().with_hi(span.hi());
                         InsertableGenericArgs {
                             insert_span,
@@ -957,13 +957,13 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
         path.segments
             .iter()
             .filter_map(move |segment| {
-                let res = segment.res?;
+                let res = segment.res;
                 let generics_def_id = tcx.res_generics_def_id(res)?;
                 let generics = tcx.generics_of(generics_def_id);
                 if generics.has_impl_trait() {
                     return None;
                 }
-                let span = tcx.hir().span(segment.hir_id?);
+                let span = tcx.hir().span(segment.hir_id);
                 let insert_span = segment.ident.span.shrink_to_hi().with_hi(span.hi());
                 Some(InsertableGenericArgs {
                     insert_span,
@@ -996,7 +996,7 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
                     if !segment.infer_args || generics.has_impl_trait() {
                         None?;
                     }
-                    let span = tcx.hir().span(segment.hir_id?);
+                    let span = tcx.hir().span(segment.hir_id);
                     let insert_span = segment.ident.span.shrink_to_hi().with_hi(span.hi());
                     InsertableGenericArgs { insert_span, substs, generics_def_id: def_id, def_id }
                 };

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/trait_impl_difference.rs

@@ -154,16 +154,11 @@ impl<'tcx> Visitor<'tcx> for TypeParamSpanVisitor<'tcx> {
             }
             hir::TyKind::Path(hir::QPath::Resolved(None, path)) => match &path.segments {
                 [segment]
-                    if segment
-                        .res
-                        .map(|res| {
-                            matches!(
-                                res,
-                                Res::SelfTy { trait_: _, alias_to: _ }
-                                    | Res::Def(hir::def::DefKind::TyParam, _)
-                            )
-                        })
-                        .unwrap_or(false) =>
+                    if matches!(
+                        segment.res,
+                        Res::SelfTy { trait_: _, alias_to: _ }
+                            | Res::Def(hir::def::DefKind::TyParam, _)
+                    ) =>
                 {
                     self.types.push(path.span);
                 }

compiler/rustc_lint/src/internal.rs

@@ -118,8 +118,7 @@ impl<'tcx> LateLintPass<'tcx> for TyTyKind {
         _: rustc_hir::HirId,
     ) {
         if let Some(segment) = path.segments.iter().nth_back(1)
-        && let Some(res) = &segment.res
-        && lint_ty_kind_usage(cx, res)
+        && lint_ty_kind_usage(cx, &segment.res)
         {
             let span = path.span.with_hi(
                 segment.args.map_or(segment.ident.span, |a| a.span_ext).hi()