Auto merge of rust-lang#89100 - petrochenkov:localbind, r=cjgillot

bors · bors · commit 6162529a0147 · 2021-10-20T07:21:01.000Z
resolve: Use `NameBinding` for local variables and generic parameters

`NameBinding` is a structure used for representing any name introduction (an item, or import, or even a built-in).
Except that local variables and generic parameters weren't represented as `NameBinding`s, for this reason they requires separate paths in name resolution code in several places.

This PR introduces `NameBinding`s for local variables as well and simplifies all the code working with them leaving only the `NameBinding` paths.
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
@@ -7,7 +7,7 @@
 
 use RibKind::*;
 
-use crate::{path_names_to_string, BindingError, CrateLint, LexicalScopeBinding};
+use crate::{path_names_to_string, BindingError, CrateLint, NameBinding, ToNameBinding};
 use crate::{Module, ModuleOrUniformRoot, ParentScope, PathResult};
 use crate::{ResolutionError, Resolver, Segment, UseError};
 
@@ -21,27 +21,22 @@ use rustc_hir::def::Namespace::{self, *};
 use rustc_hir::def::{self, CtorKind, DefKind, PartialRes, PerNS};
 use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX};
 use rustc_hir::{PrimTy, TraitCandidate};
-use rustc_middle::{bug, span_bug};
+use rustc_middle::{bug, span_bug, ty};
 use rustc_session::lint;
+use rustc_span::source_map::{respan, Spanned};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
-use rustc_span::Span;
+use rustc_span::{Span, DUMMY_SP};
 use smallvec::{smallvec, SmallVec};
+use tracing::debug;
 
-use rustc_span::source_map::{respan, Spanned};
 use std::collections::{hash_map::Entry, BTreeSet};
 use std::mem::{replace, take};
-use tracing::debug;
 
 mod diagnostics;
 crate mod lifetimes;
 
 type Res = def::Res<NodeId>;
 
-type IdentMap<T> = FxHashMap<Ident, T>;
-
-/// Map from the name in a pattern to its binding mode.
-type BindingMap = IdentMap<BindingInfo>;
-
 #[derive(Copy, Clone, Debug)]
 struct BindingInfo {
     span: Span,
@@ -172,8 +167,8 @@ impl RibKind<'_> {
 /// The resolution keeps a separate stack of ribs as it traverses the AST for each namespace. When
 /// resolving, the name is looked up from inside out.
 #[derive(Debug)]
-crate struct Rib<'a, R = Res> {
-    pub bindings: IdentMap<R>,
+crate struct Rib<'a, R = &'a NameBinding<'a>> {
+    pub bindings: FxHashMap<Ident, R>,
     pub kind: RibKind<'a>,
 }
 
@@ -567,12 +562,12 @@ impl<'a: 'ast, 'ast> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast> {
                 GenericParamKind::Type { .. } => {
                     forward_ty_ban_rib
                         .bindings
-                        .insert(Ident::with_dummy_span(param.ident.name), Res::Err);
+                        .insert(Ident::with_dummy_span(param.ident.name), self.r.dummy_binding);
                 }
                 GenericParamKind::Const { .. } => {
                     forward_const_ban_rib
                         .bindings
-                        .insert(Ident::with_dummy_span(param.ident.name), Res::Err);
+                        .insert(Ident::with_dummy_span(param.ident.name), self.r.dummy_binding);
                 }
                 GenericParamKind::Lifetime => {}
             }
@@ -589,7 +584,9 @@ impl<'a: 'ast, 'ast> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast> {
         // such as in the case of `trait Add<Rhs = Self>`.)
         if self.diagnostic_metadata.current_self_item.is_some() {
             // (`Some` if + only if we are in ADT's generics.)
-            forward_ty_ban_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), Res::Err);
+            forward_ty_ban_rib
+                .bindings
+                .insert(Ident::with_dummy_span(kw::SelfUpper), self.r.dummy_binding);
         }
 
         for param in &generics.params {
@@ -737,15 +734,17 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
         ns: Namespace,
         record_used_id: Option<NodeId>,
         path_span: Span,
-    ) -> Option<LexicalScopeBinding<'a>> {
-        self.r.resolve_ident_in_lexical_scope(
-            ident,
-            ns,
-            &self.parent_scope,
-            record_used_id,
-            path_span,
-            &self.ribs[ns],
-        )
+    ) -> Option<&'a NameBinding<'a>> {
+        self.r
+            .resolve_ident_in_lexical_scope(
+                ident,
+                ns,
+                &self.parent_scope,
+                record_used_id,
+                path_span,
+                &self.ribs[ns],
+            )
+            .ok()
     }
 
     fn resolve_path(
@@ -903,6 +902,10 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
     }
 
     fn future_proof_import(&mut self, use_tree: &UseTree) {
+        if !self.should_report_errs() {
+            return;
+        }
+
         let segments = &use_tree.prefix.segments;
         if !segments.is_empty() {
             let ident = segments[0].ident;
@@ -914,31 +917,42 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                 UseTreeKind::Simple(..) if segments.len() == 1 => &[TypeNS, ValueNS][..],
                 _ => &[TypeNS],
             };
+
+            let from_ribs = |binding: &NameBinding<'_>| {
+                matches!(
+                    binding.res(),
+                    Res::Local(..)
+                        | Res::SelfTy(..)
+                        | Res::Def(DefKind::TyParam | DefKind::ConstParam, ..)
+                )
+            };
             let report_error = |this: &Self, ns| {
                 let what = if ns == TypeNS { "type parameters" } else { "local variables" };
-                if this.should_report_errs() {
-                    this.r
-                        .session
-                        .span_err(ident.span, &format!("imports cannot refer to {}", what));
-                }
+                let msg = format!("imports cannot refer to {what}");
+                this.r.session.span_err(ident.span, &msg);
             };
 
             for &ns in nss {
-                match self.resolve_ident_in_lexical_scope(ident, ns, None, use_tree.prefix.span) {
-                    Some(LexicalScopeBinding::Res(..)) => {
+                if let Some(binding) =
+                    self.resolve_ident_in_lexical_scope(ident, ns, None, use_tree.prefix.span)
+                {
+                    if from_ribs(binding) {
                         report_error(self, ns);
-                    }
-                    Some(LexicalScopeBinding::Item(binding)) => {
+                    } else {
                         let orig_unusable_binding =
                             replace(&mut self.r.unusable_binding, Some(binding));
-                        if let Some(LexicalScopeBinding::Res(..)) = self
-                            .resolve_ident_in_lexical_scope(ident, ns, None, use_tree.prefix.span)
-                        {
-                            report_error(self, ns);
+                        if let Some(binding) = self.resolve_ident_in_lexical_scope(
+                            ident,
+                            ns,
+                            None,
+                            use_tree.prefix.span,
+                        ) {
+                            if from_ribs(binding) {
+                                report_error(self, ns);
+                            }
                         }
                         self.r.unusable_binding = orig_unusable_binding;
                     }
-                    None => {}
                 }
             }
         } else if let UseTreeKind::Nested(use_trees) = &use_tree.kind {
@@ -1135,8 +1149,12 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                 _ => unreachable!(),
             };
             let res = Res::Def(def_kind, self.r.local_def_id(param.id).to_def_id());
+            let binding =
+                (res, ty::Visibility::Invisible, param.ident.span, self.parent_scope.expansion)
+                    .to_name_binding(self.r.arenas);
+
             self.r.record_partial_res(param.id, PartialRes::new(res));
-            rib.bindings.insert(ident, res);
+            rib.bindings.insert(ident, binding);
         }
 
         self.ribs[ValueNS].push(function_value_rib);
@@ -1256,10 +1274,12 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
     }
 
     fn with_self_rib_ns(&mut self, ns: Namespace, self_res: Res, f: impl FnOnce(&mut Self)) {
+        let binding = (self_res, ty::Visibility::Invisible, DUMMY_SP, self.parent_scope.expansion)
+            .to_name_binding(self.r.arenas);
         let mut self_type_rib = Rib::new(NormalRibKind);
 
         // Plain insert (no renaming, since types are not currently hygienic)
-        self_type_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), self_res);
+        self_type_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), binding);
         self.ribs[ns].push(self_type_rib);
         f(self);
         self.ribs[ns].pop();
@@ -1470,7 +1490,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
     /// this is done hygienically. This could arise for a macro
     /// that expands into an or-pattern where one 'x' was from the
     /// user and one 'x' came from the macro.
-    fn binding_mode_map(&mut self, pat: &Pat) -> BindingMap {
+    fn binding_mode_map(&mut self, pat: &Pat) -> FxHashMap<Ident, BindingInfo> {
         let mut binding_map = FxHashMap::default();
 
         pat.walk(&mut |pat| {
@@ -1503,7 +1523,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
 
     /// Checks that all of the arms in an or-pattern have exactly the
     /// same set of bindings, with the same binding modes for each.
-    fn check_consistent_bindings(&mut self, pats: &[P<Pat>]) -> Vec<BindingMap> {
+    fn check_consistent_bindings(&mut self, pats: &[P<Pat>]) -> Vec<FxHashMap<Ident, BindingInfo>> {
         let mut missing_vars = FxHashMap::default();
         let mut inconsistent_vars = FxHashMap::default();
 
@@ -1645,7 +1665,6 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                         .try_resolve_as_non_binding(pat_src, pat, bmode, ident, has_sub)
                         .unwrap_or_else(|| self.fresh_binding(ident, pat.id, pat_src, bindings));
                     self.r.record_partial_res(pat.id, PartialRes::new(res));
-                    self.r.record_pat_span(pat.id, pat.span);
                 }
                 PatKind::TupleStruct(ref qself, ref path, ref sub_patterns) => {
                     self.smart_resolve_path(
@@ -1735,18 +1754,24 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
         if already_bound_or {
             // `Variant1(a) | Variant2(a)`, ok
             // Reuse definition from the first `a`.
-            self.innermost_rib_bindings(ValueNS)[&ident]
+            self.innermost_rib_bindings(ValueNS)[&ident].res()
         } else {
             let res = Res::Local(pat_id);
             if ident_valid {
                 // A completely fresh binding add to the set if it's valid.
-                self.innermost_rib_bindings(ValueNS).insert(ident, res);
+                let binding =
+                    (res, ty::Visibility::Invisible, ident.span, self.parent_scope.expansion)
+                        .to_name_binding(self.r.arenas);
+                self.innermost_rib_bindings(ValueNS).insert(ident, binding);
             }
             res
         }
     }
 
-    fn innermost_rib_bindings(&mut self, ns: Namespace) -> &mut IdentMap<Res> {
+    fn innermost_rib_bindings(
+        &mut self,
+        ns: Namespace,
+    ) -> &mut FxHashMap<Ident, &'a NameBinding<'a>> {
         &mut self.ribs[ns].last_mut().unwrap().bindings
     }
 
@@ -1763,32 +1788,25 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
         // also be interpreted as a path to e.g. a constant, variant, etc.
         let is_syntactic_ambiguity = !has_sub && bm == BindingMode::ByValue(Mutability::Not);
 
-        let ls_binding = self.resolve_ident_in_lexical_scope(ident, ValueNS, None, pat.span)?;
-        let (res, binding) = match ls_binding {
-            LexicalScopeBinding::Item(binding)
-                if is_syntactic_ambiguity && binding.is_ambiguity() =>
-            {
-                // For ambiguous bindings we don't know all their definitions and cannot check
-                // whether they can be shadowed by fresh bindings or not, so force an error.
-                // issues/33118#issuecomment-233962221 (see below) still applies here,
-                // but we have to ignore it for backward compatibility.
-                self.r.record_use(ident, binding, false);
-                return None;
-            }
-            LexicalScopeBinding::Item(binding) => (binding.res(), Some(binding)),
-            LexicalScopeBinding::Res(res) => (res, None),
-        };
+        let binding = self.resolve_ident_in_lexical_scope(ident, ValueNS, None, pat.span)?;
+        if is_syntactic_ambiguity && binding.is_ambiguity() {
+            // For ambiguous bindings we don't know all their definitions and cannot check
+            // whether they can be shadowed by fresh bindings or not, so force an error.
+            // issues/33118#issuecomment-233962221 (see below) still applies here,
+            // but we have to ignore it for backward compatibility.
+            self.r.record_use(ident, binding, false);
+            return None;
+        }
 
+        let res = binding.res();
         match res {
             Res::SelfCtor(_) // See #70549.
             | Res::Def(
                 DefKind::Ctor(_, CtorKind::Const) | DefKind::Const | DefKind::ConstParam,
                 _,
             ) if is_syntactic_ambiguity => {
                 // Disambiguate in favor of a unit struct/variant or constant pattern.
-                if let Some(binding) = binding {
-                    self.r.record_use(ident, binding, false);
-                }
+                self.r.record_use(ident, binding, false);
                 Some(res)
             }
             Res::Def(DefKind::Ctor(..) | DefKind::Const | DefKind::Static, _) => {
@@ -1797,7 +1815,6 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                 // to something unusable as a pattern (e.g., constructor function),
                 // but we still conservatively report an error, see
                 // issues/33118#issuecomment-233962221 for one reason why.
-                let binding = binding.expect("no binding for a ctor or static");
                 self.report_error(
                     ident.span,
                     ResolutionError::BindingShadowsSomethingUnacceptable {
@@ -2037,19 +2054,15 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
     }
 
     fn self_type_is_available(&mut self, span: Span) -> bool {
-        let binding = self.resolve_ident_in_lexical_scope(
-            Ident::with_dummy_span(kw::SelfUpper),
-            TypeNS,
-            None,
-            span,
-        );
-        if let Some(LexicalScopeBinding::Res(res)) = binding { res != Res::Err } else { false }
+        let ident = Ident::with_dummy_span(kw::SelfUpper);
+        self.resolve_ident_in_lexical_scope(ident, TypeNS, None, span)
+            .map_or(false, |binding| binding.res() != Res::Err)
     }
 
     fn self_value_is_available(&mut self, self_span: Span, path_span: Span) -> bool {
         let ident = Ident::new(kw::SelfLower, self_span);
-        let binding = self.resolve_ident_in_lexical_scope(ident, ValueNS, None, path_span);
-        if let Some(LexicalScopeBinding::Res(res)) = binding { res != Res::Err } else { false }
+        self.resolve_ident_in_lexical_scope(ident, ValueNS, None, path_span)
+            .map_or(false, |binding| binding.res() != Res::Err)
     }
 
     /// A wrapper around [`Resolver::report_error`].
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -1294,7 +1294,8 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
             // Walk backwards up the ribs in scope and collect candidates.
             for rib in self.ribs[ns].iter().rev() {
                 // Locals and type parameters
-                for (ident, &res) in &rib.bindings {
+                for (ident, binding) in &rib.bindings {
+                    let res = binding.res();
                     if filter_fn(res) {
                         names.push(TypoSuggestion::typo_from_res(ident.name, res));
                     }
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
