Rollup merge of rust-lang#102889 - petrochenkov:partres, r=cjgillot

rustc_hir: Less error-prone methods for accessing `PartialRes` resolution

Author: matthiaskrgr

compiler/rustc_ast_lowering/src/asm.rs

@@ -205,13 +205,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         let static_def_id = self
                             .resolver
                             .get_partial_res(sym.id)
-                            .filter(|res| res.unresolved_segments() == 0)
-                            .and_then(|res| {
-                                if let Res::Def(DefKind::Static(_), def_id) = res.base_res() {
-                                    Some(def_id)
-                                } else {
-                                    None
-                                }
+                            .and_then(|res| res.full_res())
+                            .and_then(|res| match res {
+                                Res::Def(DefKind::Static(_), def_id) => Some(def_id),
+                                _ => None,
                             });
 
                         if let Some(def_id) = static_def_id {

compiler/rustc_ast_lowering/src/expr.rs

@@ -1044,9 +1044,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         if let ExprKind::Path(qself, path) = &expr.kind {
             // Does the path resolve to something disallowed in a tuple struct/variant pattern?
             if let Some(partial_res) = self.resolver.get_partial_res(expr.id) {
-                if partial_res.unresolved_segments() == 0
-                    && !partial_res.base_res().expected_in_tuple_struct_pat()
-                {
+                if let Some(res) = partial_res.full_res() && !res.expected_in_tuple_struct_pat() {
                     return None;
                 }
             }
@@ -1066,9 +1064,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         if let ExprKind::Path(qself, path) = &expr.kind {
             // Does the path resolve to something disallowed in a unit struct/variant pattern?
             if let Some(partial_res) = self.resolver.get_partial_res(expr.id) {
-                if partial_res.unresolved_segments() == 0
-                    && !partial_res.base_res().expected_in_unit_struct_pat()
-                {
+                if let Some(res) = partial_res.full_res() && !res.expected_in_unit_struct_pat() {
                     return None;
                 }
             }

compiler/rustc_ast_lowering/src/item.rs

@@ -947,7 +947,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 }
                 AssocItemKind::MacCall(..) => unimplemented!(),
             },
-            trait_item_def_id: self.resolver.get_partial_res(i.id).map(|r| r.base_res().def_id()),
+            trait_item_def_id: self
+                .resolver
+                .get_partial_res(i.id)
+                .map(|r| r.expect_full_res().def_id()),
         }
     }
 
@@ -1349,9 +1352,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 match self
                     .resolver
                     .get_partial_res(bound_pred.bounded_ty.id)
-                    .map(|d| (d.base_res(), d.unresolved_segments()))
+                    .and_then(|r| r.full_res())
                 {
-                    Some((Res::Def(DefKind::TyParam, def_id), 0))
+                    Some(Res::Def(DefKind::TyParam, def_id))
                         if bound_pred.bound_generic_params.is_empty() =>
                     {
                         generics

compiler/rustc_ast_lowering/src/lib.rs

@@ -175,12 +175,7 @@ impl ResolverAstLoweringExt for ResolverAstLowering {
                 return None;
             }
 
-            let partial_res = self.partial_res_map.get(&expr.id)?;
-            if partial_res.unresolved_segments() != 0 {
-                return None;
-            }
-
-            if let Res::Def(DefKind::Fn, def_id) = partial_res.base_res() {
+            if let Res::Def(DefKind::Fn, def_id) = self.partial_res_map.get(&expr.id)?.full_res()? {
                 // We only support cross-crate argument rewriting. Uses
                 // within the same crate should be updated to use the new
                 // const generics style.
@@ -753,12 +748,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     }
 
     fn expect_full_res(&mut self, id: NodeId) -> Res<NodeId> {
-        self.resolver.get_partial_res(id).map_or(Res::Err, |pr| {
-            if pr.unresolved_segments() != 0 {
-                panic!("path not fully resolved: {:?}", pr);
-            }
-            pr.base_res()
-        })
+        self.resolver.get_partial_res(id).map_or(Res::Err, |pr| pr.expect_full_res())
     }
 
     fn expect_full_res_from_use(&mut self, id: NodeId) -> impl Iterator<Item = Res<NodeId>> {
@@ -1138,8 +1128,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     // type and value namespaces. If we resolved the path in the value namespace, we
                     // transform it into a generic const argument.
                     TyKind::Path(ref qself, ref path) => {
-                        if let Some(partial_res) = self.resolver.get_partial_res(ty.id) {
-                            let res = partial_res.base_res();
+                        if let Some(res) = self
+                            .resolver
+                            .get_partial_res(ty.id)
+                            .and_then(|partial_res| partial_res.full_res())
+                        {
                             if !res.matches_ns(Namespace::TypeNS) {
                                 debug!(
                                     "lower_generic_arg: Lowering type argument as const argument: {:?}",
@@ -1206,8 +1199,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         // by `ty_path`.
         if qself.is_none()
             && let Some(partial_res) = self.resolver.get_partial_res(t.id)
-            && partial_res.unresolved_segments() == 0
-            && let Res::Def(DefKind::Trait | DefKind::TraitAlias, _) = partial_res.base_res()
+            && let Some(Res::Def(DefKind::Trait | DefKind::TraitAlias, _)) = partial_res.full_res()
         {
             let (bounds, lifetime_bound) = self.with_dyn_type_scope(true, |this| {
                 let poly_trait_ref = this.ast_arena.ptr.alloc(PolyTraitRef {

compiler/rustc_ast_lowering/src/pat.rs

@@ -239,7 +239,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         ident: Ident,
         lower_sub: impl FnOnce(&mut Self) -> Option<&'hir hir::Pat<'hir>>,
     ) -> hir::PatKind<'hir> {
-        match self.resolver.get_partial_res(p.id).map(|d| d.base_res()) {
+        match self.resolver.get_partial_res(p.id).map(|d| d.expect_full_res()) {
             // `None` can occur in body-less function signatures
             res @ (None | Some(Res::Local(_))) => {
                 let canonical_id = match res {

compiler/rustc_ast_lowering/src/path.rs

@@ -29,11 +29,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
         let partial_res =
             self.resolver.get_partial_res(id).unwrap_or_else(|| PartialRes::new(Res::Err));
+        let base_res = partial_res.base_res();
+        let unresolved_segments = partial_res.unresolved_segments();
 
         let path_span_lo = p.span.shrink_to_lo();
-        let proj_start = p.segments.len() - partial_res.unresolved_segments();
+        let proj_start = p.segments.len() - unresolved_segments;
         let path = self.arena.alloc(hir::Path {
-            res: self.lower_res(partial_res.base_res()),
+            res: self.lower_res(base_res),
             segments: self.arena.alloc_from_iter(p.segments[..proj_start].iter().enumerate().map(
                 |(i, segment)| {
                     let param_mode = match (qself_position, param_mode) {
@@ -46,7 +48,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         _ => param_mode,
                     };
 
-                    let parenthesized_generic_args = match partial_res.base_res() {
+                    let parenthesized_generic_args = match base_res {
                         // `a::b::Trait(Args)`
                         Res::Def(DefKind::Trait, _) if i + 1 == proj_start => {
                             ParenthesizedGenericArgs::Ok
@@ -83,7 +85,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
         // Simple case, either no projections, or only fully-qualified.
         // E.g., `std::mem::size_of` or `<I as Iterator>::Item`.
-        if partial_res.unresolved_segments() == 0 {
+        if unresolved_segments == 0 {
             return hir::QPath::Resolved(qself, path);
         }
 

compiler/rustc_hir/src/def.rs

@@ -464,6 +464,16 @@ impl PartialRes {
     pub fn unresolved_segments(&self) -> usize {
         self.unresolved_segments
     }
+
+    #[inline]
+    pub fn full_res(&self) -> Option<Res<NodeId>> {
+        (self.unresolved_segments == 0).then_some(self.base_res)
+    }
+
+    #[inline]
+    pub fn expect_full_res(&self) -> Res<NodeId> {
+        self.full_res().expect("unexpected unresolved segments")
+    }
 }
 
 /// Different kinds of symbols can coexist even if they share the same textual name.

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -326,7 +326,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                     }
                     PathResult::Module(..) => Err(VisResolutionError::ModuleOnly(path.span)),
                     PathResult::NonModule(partial_res) => {
-                        expected_found_error(partial_res.base_res())
+                        expected_found_error(partial_res.expect_full_res())
                     }
                     PathResult::Failed { span, label, suggestion, .. } => {
                         Err(VisResolutionError::FailedToResolve(span, label, suggestion))

compiler/rustc_resolve/src/late.rs

@@ -641,8 +641,7 @@ impl<'a: 'ast, 'ast> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast> {
                 // Check whether we should interpret this as a bare trait object.
                 if qself.is_none()
                     && let Some(partial_res) = self.r.partial_res_map.get(&ty.id)
-                    && partial_res.unresolved_segments() == 0
-                    && let Res::Def(DefKind::Trait | DefKind::TraitAlias, _) = partial_res.base_res()
+                    && let Some(Res::Def(DefKind::Trait | DefKind::TraitAlias, _)) = partial_res.full_res()
                 {
                     // This path is actually a bare trait object.  In case of a bare `Fn`-trait
                     // object with anonymous lifetimes, we need this rib to correctly place the
@@ -1929,7 +1928,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                 match ty.kind {
                     TyKind::ImplicitSelf => true,
                     TyKind::Path(None, _) => {
-                        let path_res = self.r.partial_res_map[&ty.id].base_res();
+                        let path_res = self.r.partial_res_map[&ty.id].expect_full_res();
                         if let Res::SelfTyParam { .. } | Res::SelfTyAlias { .. } = path_res {
                             return true;
                         }
@@ -1970,7 +1969,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                     None
                 }
             })
-            .map(|res| res.base_res())
+            .map(|res| res.expect_full_res())
             .filter(|res| {
                 // Permit the types that unambiguously always
                 // result in the same type constructor being used
@@ -2530,7 +2529,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                 Finalize::new(trait_ref.ref_id, trait_ref.path.span),
             );
             self.diagnostic_metadata.currently_processing_impl_trait = None;
-            if let Some(def_id) = res.base_res().opt_def_id() {
+            if let Some(def_id) = res.expect_full_res().opt_def_id() {
                 new_id = Some(def_id);
                 new_val = Some((self.r.expect_module(def_id), trait_ref.clone()));
             }
@@ -2886,7 +2885,10 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
     }
 
     fn is_base_res_local(&self, nid: NodeId) -> bool {
-        matches!(self.r.partial_res_map.get(&nid).map(|res| res.base_res()), Some(Res::Local(..)))
+        matches!(
+            self.r.partial_res_map.get(&nid).map(|res| res.expect_full_res()),
+            Some(Res::Local(..))
+        )
     }
 
     /// Checks that all of the arms in an or-pattern have exactly the
@@ -3373,12 +3375,11 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
             source.defer_to_typeck(),
             finalize,
         ) {
-            Ok(Some(partial_res)) if partial_res.unresolved_segments() == 0 => {
-                if source.is_expected(partial_res.base_res()) || partial_res.base_res() == Res::Err
-                {
+            Ok(Some(partial_res)) if let Some(res) = partial_res.full_res() => {
+                if source.is_expected(res) || res == Res::Err {
                     partial_res
                 } else {
-                    report_errors(self, Some(partial_res.base_res()))
+                    report_errors(self, Some(res))
                 }
             }
 
@@ -3586,20 +3587,21 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
         };
 
         if path.len() > 1
-            && result.base_res() != Res::Err
+            && let Some(res) = result.full_res()
+            && res != Res::Err
             && path[0].ident.name != kw::PathRoot
             && path[0].ident.name != kw::DollarCrate
         {
             let unqualified_result = {
                 match self.resolve_path(&[*path.last().unwrap()], Some(ns), None) {
-                    PathResult::NonModule(path_res) => path_res.base_res(),
+                    PathResult::NonModule(path_res) => path_res.expect_full_res(),
                     PathResult::Module(ModuleOrUniformRoot::Module(module)) => {
                         module.res().unwrap()
                     }
                     _ => return Ok(Some(result)),
                 }
             };
-            if result.base_res() == unqualified_result {
+            if res == unqualified_result {
                 let lint = lint::builtin::UNUSED_QUALIFICATIONS;
                 self.r.lint_buffer.buffer_lint(
                     lint,

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -968,11 +968,10 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
             let Some(partial_res) = self.r.partial_res_map.get(&bounded_ty.id) else {
                 return false;
             };
-            if !(matches!(
-                partial_res.base_res(),
-                hir::def::Res::Def(hir::def::DefKind::AssocTy, _)
-            ) && partial_res.unresolved_segments() == 0)
-            {
+            if !matches!(
+                partial_res.full_res(),
+                Some(hir::def::Res::Def(hir::def::DefKind::AssocTy, _))
+            ) {
                 return false;
             }
             (ty, position, path)
@@ -986,11 +985,10 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
             let Some(partial_res) = self.r.partial_res_map.get(&peeled_ty.id) else {
                 return false;
             };
-            if !(matches!(
-                partial_res.base_res(),
-                hir::def::Res::Def(hir::def::DefKind::TyParam, _)
-            ) && partial_res.unresolved_segments() == 0)
-            {
+            if !matches!(
+                partial_res.full_res(),
+                Some(hir::def::Res::Def(hir::def::DefKind::TyParam, _))
+            ) {
                 return false;
             }
             if let (
@@ -1518,20 +1516,14 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
             {
                 // Look for a field with the same name in the current self_type.
                 if let Some(resolution) = self.r.partial_res_map.get(&node_id) {
-                    match resolution.base_res() {
-                        Res::Def(DefKind::Struct | DefKind::Union, did)
-                            if resolution.unresolved_segments() == 0 =>
-                        {
-                            if let Some(field_names) = self.r.field_names.get(&did) {
-                                if field_names
-                                    .iter()
-                                    .any(|&field_name| ident.name == field_name.node)
-                                {
-                                    return Some(AssocSuggestion::Field);
-                                }
+                    if let Some(Res::Def(DefKind::Struct | DefKind::Union, did)) =
+                        resolution.full_res()
+                    {
+                        if let Some(field_names) = self.r.field_names.get(&did) {
+                            if field_names.iter().any(|&field_name| ident.name == field_name.node) {
+                                return Some(AssocSuggestion::Field);
                             }
                         }
-                        _ => {}
                     }
                 }
             }

compiler/rustc_resolve/src/lib.rs

@@ -1883,12 +1883,10 @@ impl<'a> Resolver<'a> {
 
         match self.maybe_resolve_path(&segments, Some(ns), &parent_scope) {
             PathResult::Module(ModuleOrUniformRoot::Module(module)) => Some(module.res().unwrap()),
-            PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
-                Some(path_res.base_res())
+            PathResult::NonModule(path_res) => path_res.full_res(),
+            PathResult::Module(ModuleOrUniformRoot::ExternPrelude) | PathResult::Failed { .. } => {
+                None
             }
-            PathResult::Module(ModuleOrUniformRoot::ExternPrelude)
-            | PathResult::NonModule(..)
-            | PathResult::Failed { .. } => None,
             PathResult::Module(..) | PathResult::Indeterminate => unreachable!(),
         }
     }
@@ -1939,12 +1937,8 @@ impl<'a> Resolver<'a> {
                 return None;
             }
 
-            let partial_res = self.partial_res_map.get(&expr.id)?;
-            if partial_res.unresolved_segments() != 0 {
-                return None;
-            }
-
-            if let Res::Def(def::DefKind::Fn, def_id) = partial_res.base_res() {
+            let res = self.partial_res_map.get(&expr.id)?.full_res()?;
+            if let Res::Def(def::DefKind::Fn, def_id) = res {
                 // We only support cross-crate argument rewriting. Uses
                 // within the same crate should be updated to use the new
                 // const generics style.

compiler/rustc_resolve/src/macros.rs

@@ -590,9 +590,7 @@ impl<'a> Resolver<'a> {
 
         let res = if path.len() > 1 {
             let res = match self.maybe_resolve_path(&path, Some(MacroNS), parent_scope) {
-                PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
-                    Ok(path_res.base_res())
-                }
+                PathResult::NonModule(path_res) if let Some(res) = path_res.full_res() => Ok(res),
                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
                 PathResult::NonModule(..)
                 | PathResult::Indeterminate
@@ -692,9 +690,8 @@ impl<'a> Resolver<'a> {
                 Some(Finalize::new(ast::CRATE_NODE_ID, path_span)),
                 None,
             ) {
-                PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
-                    let res = path_res.base_res();
-                    check_consistency(self, &path, path_span, kind, initial_res, res);
+                PathResult::NonModule(path_res) if let Some(res) = path_res.full_res() => {
+                    check_consistency(self, &path, path_span, kind, initial_res, res)
                 }
                 path_res @ PathResult::NonModule(..) | path_res @ PathResult::Failed { .. } => {
                     let (span, label) = if let PathResult::Failed { span, label, .. } = path_res {