Auto merge of #101228 - nnethercote:simplify-hir-PathSegment, r=petrochenkov

Simplify `hir::PathSegment`

r? `@petrochenkov`

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);
     }