resolve: Do not build expensive suggestions if they are not actually used

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -9,7 +9,7 @@ use crate::def_collector::collect_definitions;
 use crate::imports::{Import, ImportKind};
 use crate::macros::{MacroRulesBinding, MacroRulesScope, MacroRulesScopeRef};
 use crate::Namespace::{self, MacroNS, TypeNS, ValueNS};
-use crate::{CrateLint, Determinacy, ExternPreludeEntry, Module, ModuleKind, ModuleOrUniformRoot};
+use crate::{Determinacy, ExternPreludeEntry, Finalize, Module, ModuleKind, ModuleOrUniformRoot};
 use crate::{NameBinding, NameBindingKind, ParentScope, PathResult, PerNS, ResolutionError};
 use crate::{Resolver, ResolverArenas, Segment, ToNameBinding, VisResolutionError};
 
@@ -235,16 +235,16 @@ impl<'a> AsMut<Resolver<'a>> for BuildReducedGraphVisitor<'a, '_> {
 
 impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
     fn resolve_visibility(&mut self, vis: &ast::Visibility) -> ty::Visibility {
-        self.resolve_visibility_speculative(vis, false).unwrap_or_else(|err| {
+        self.try_resolve_visibility(vis, true).unwrap_or_else(|err| {
             self.r.report_vis_error(err);
             ty::Visibility::Public
         })
     }
 
-    fn resolve_visibility_speculative<'ast>(
+    fn try_resolve_visibility<'ast>(
         &mut self,
         vis: &'ast ast::Visibility,
-        speculative: bool,
+        finalize: bool,
     ) -> Result<ty::Visibility, VisResolutionError<'ast>> {
         let parent_scope = &self.parent_scope;
         match vis.kind {
@@ -296,13 +296,11 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                     &segments,
                     Some(TypeNS),
                     parent_scope,
-                    !speculative,
-                    path.span,
-                    CrateLint::SimplePath(id),
+                    if finalize { Finalize::SimplePath(id, path.span) } else { Finalize::No },
                 ) {
                     PathResult::Module(ModuleOrUniformRoot::Module(module)) => {
                         let res = module.res().expect("visibility resolved to unnamed block");
-                        if !speculative {
+                        if finalize {
                             self.r.record_partial_res(id, PartialRes::new(res));
                         }
                         if module.is_normal() {
@@ -772,7 +770,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                         // correct visibilities for unnamed field placeholders specifically, so the
                         // constructor visibility should still be determined correctly.
                         let field_vis = self
-                            .resolve_visibility_speculative(&field.vis, true)
+                            .try_resolve_visibility(&field.vis, false)
                             .unwrap_or(ty::Visibility::Public);
                         if ctor_vis.is_at_least(field_vis, &*self.r) {
                             ctor_vis = field_vis;
@@ -1131,8 +1129,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                     ident,
                     MacroNS,
                     &self.parent_scope,
-                    false,
-                    ident.span,
+                    None,
                 );
                 if let Ok(binding) = result {
                     let import = macro_use_import(self, ident.span);
@@ -1272,9 +1269,9 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
             let vis = match item.kind {
                 // Visibilities must not be resolved non-speculatively twice
                 // and we already resolved this one as a `fn` item visibility.
-                ItemKind::Fn(..) => self
-                    .resolve_visibility_speculative(&item.vis, true)
-                    .unwrap_or(ty::Visibility::Public),
+                ItemKind::Fn(..) => {
+                    self.try_resolve_visibility(&item.vis, false).unwrap_or(ty::Visibility::Public)
+                }
                 _ => self.resolve_visibility(&item.vis),
             };
             if vis != ty::Visibility::Public {

compiler/rustc_resolve/src/diagnostics.rs

@@ -24,10 +24,8 @@ use tracing::debug;
 use crate::imports::{Import, ImportKind, ImportResolver};
 use crate::path_names_to_string;
 use crate::{AmbiguityError, AmbiguityErrorMisc, AmbiguityKind};
-use crate::{
-    BindingError, CrateLint, HasGenericParams, MacroRulesScope, Module, ModuleOrUniformRoot,
-};
-use crate::{NameBinding, NameBindingKind, PrivacyError, VisResolutionError};
+use crate::{BindingError, HasGenericParams, MacroRulesScope, Module, ModuleOrUniformRoot};
+use crate::{Finalize, NameBinding, NameBindingKind, PrivacyError, VisResolutionError};
 use crate::{ParentScope, PathResult, ResolutionError, Resolver, Scope, ScopeSet, Segment};
 
 type Res = def::Res<ast::NodeId>;
@@ -1076,9 +1074,8 @@ impl<'a> Resolver<'a> {
                 ident,
                 ScopeSet::All(ns, false),
                 &parent_scope,
+                None,
                 false,
-                false,
-                ident.span,
             ) {
                 let desc = match binding.res() {
                     Res::Def(DefKind::Macro(MacroKind::Bang), _) => {
@@ -1405,10 +1402,10 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
             _ => return None,
         }
 
-        self.make_missing_self_suggestion(span, path.clone(), parent_scope)
-            .or_else(|| self.make_missing_crate_suggestion(span, path.clone(), parent_scope))
-            .or_else(|| self.make_missing_super_suggestion(span, path.clone(), parent_scope))
-            .or_else(|| self.make_external_crate_suggestion(span, path, parent_scope))
+        self.make_missing_self_suggestion(path.clone(), parent_scope)
+            .or_else(|| self.make_missing_crate_suggestion(path.clone(), parent_scope))
+            .or_else(|| self.make_missing_super_suggestion(path.clone(), parent_scope))
+            .or_else(|| self.make_external_crate_suggestion(path, parent_scope))
     }
 
     /// Suggest a missing `self::` if that resolves to an correct module.
@@ -1420,13 +1417,12 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
     /// ```
     fn make_missing_self_suggestion(
         &mut self,
-        span: Span,
         mut path: Vec<Segment>,
         parent_scope: &ParentScope<'b>,
     ) -> Option<(Vec<Segment>, Vec<String>)> {
         // Replace first ident with `self` and check if that is valid.
         path[0].ident.name = kw::SelfLower;
-        let result = self.r.resolve_path(&path, None, parent_scope, false, span, CrateLint::No);
+        let result = self.r.resolve_path(&path, None, parent_scope, Finalize::No);
         debug!("make_missing_self_suggestion: path={:?} result={:?}", path, result);
         if let PathResult::Module(..) = result { Some((path, Vec::new())) } else { None }
     }
@@ -1440,13 +1436,12 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
     /// ```
     fn make_missing_crate_suggestion(
         &mut self,
-        span: Span,
         mut path: Vec<Segment>,
         parent_scope: &ParentScope<'b>,
     ) -> Option<(Vec<Segment>, Vec<String>)> {
         // Replace first ident with `crate` and check if that is valid.
         path[0].ident.name = kw::Crate;
-        let result = self.r.resolve_path(&path, None, parent_scope, false, span, CrateLint::No);
+        let result = self.r.resolve_path(&path, None, parent_scope, Finalize::No);
         debug!("make_missing_crate_suggestion:  path={:?} result={:?}", path, result);
         if let PathResult::Module(..) = result {
             Some((
@@ -1472,13 +1467,12 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
     /// ```
     fn make_missing_super_suggestion(
         &mut self,
-        span: Span,
         mut path: Vec<Segment>,
         parent_scope: &ParentScope<'b>,
     ) -> Option<(Vec<Segment>, Vec<String>)> {
         // Replace first ident with `crate` and check if that is valid.
         path[0].ident.name = kw::Super;
-        let result = self.r.resolve_path(&path, None, parent_scope, false, span, CrateLint::No);
+        let result = self.r.resolve_path(&path, None, parent_scope, Finalize::No);
         debug!("make_missing_super_suggestion:  path={:?} result={:?}", path, result);
         if let PathResult::Module(..) = result { Some((path, Vec::new())) } else { None }
     }
@@ -1495,7 +1489,6 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
     /// name as the first part of path.
     fn make_external_crate_suggestion(
         &mut self,
-        span: Span,
         mut path: Vec<Segment>,
         parent_scope: &ParentScope<'b>,
     ) -> Option<(Vec<Segment>, Vec<String>)> {
@@ -1513,7 +1506,7 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
         for name in extern_crate_names.into_iter() {
             // Replace first ident with a crate name and check if that is valid.
             path[0].ident.name = name;
-            let result = self.r.resolve_path(&path, None, parent_scope, false, span, CrateLint::No);
+            let result = self.r.resolve_path(&path, None, parent_scope, Finalize::No);
             debug!(
                 "make_external_crate_suggestion: name={:?} path={:?} result={:?}",
                 name, path, result