resolve: Make bindings for derive helper attributes unique

instead of creating them every time such attribute is used

compiler/rustc_resolve/src/diagnostics.rs

@@ -1032,7 +1032,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                                 .get(&expn_id)
                                 .into_iter()
                                 .flatten()
-                                .map(|ident| TypoSuggestion::typo_from_ident(*ident, res)),
+                                .map(|(ident, _)| TypoSuggestion::typo_from_ident(*ident, res)),
                         );
                     }
                 }

compiler/rustc_resolve/src/ident.rs

@@ -421,26 +421,11 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             orig_ident.span.ctxt(),
             |this, scope, use_prelude, ctxt| {
                 let ident = Ident::new(orig_ident.name, orig_ident.span.with_ctxt(ctxt));
-                let ok = |res, span, arenas| {
-                    Ok((
-                        (res, Visibility::Public, span, LocalExpnId::ROOT).to_name_binding(arenas),
-                        Flags::empty(),
-                    ))
-                };
                 let result = match scope {
                     Scope::DeriveHelpers(expn_id) => {
-                        if let Some(attr) = this
+                        if let Some(binding) = this.helper_attrs.get(&expn_id).and_then(|attrs| {
-                            .helper_attrs
+                            attrs.iter().rfind(|(i, _)| ident == *i).map(|(_, binding)| *binding)
-                            .get(&expn_id)
+                        }) {
-                            .and_then(|attrs| attrs.iter().rfind(|i| ident == **i))
-                        {
-                            let binding = (
-                                Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper),
-                                Visibility::Public,
-                                attr.span,
-                                expn_id,
-                            )
-                                .to_name_binding(this.arenas);
                             Ok((binding, Flags::empty()))
                         } else {
                             Err(Determinacy::Determined)
@@ -459,11 +444,14 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                             ) {
                                 Ok((Some(ext), _)) => {
                                     if ext.helper_attrs.contains(&ident.name) {
-                                        result = ok(
+                                        let binding = (
                                             Res::NonMacroAttr(NonMacroAttrKind::DeriveHelperCompat),
+                                            Visibility::Public,
                                             derive.span,
-                                            this.arenas,
+                                            LocalExpnId::ROOT,
-                                        );
+                                        )
+                                            .to_name_binding(this.arenas);
+                                        result = Ok((binding, Flags::empty()));
                                         break;
                                     }
                                 }

compiler/rustc_resolve/src/lib.rs

@@ -1047,7 +1047,7 @@ pub struct Resolver<'a, 'tcx> {
     /// `macro_rules` scopes produced by `macro_rules` item definitions.
     macro_rules_scopes: FxHashMap<LocalDefId, MacroRulesScopeRef<'a>>,
     /// Helper attributes that are in scope for the given expansion.
-    helper_attrs: FxHashMap<LocalExpnId, Vec<Ident>>,
+    helper_attrs: FxHashMap<LocalExpnId, Vec<(Ident, NameBinding<'a>)>>,
     /// Ready or in-progress results of resolving paths inside the `#[derive(...)]` attribute
     /// with the given `ExpnId`.
     derive_data: FxHashMap<LocalExpnId, DeriveData>,

compiler/rustc_resolve/src/macros.rs

@@ -7,7 +7,7 @@ use crate::errors::{
 use crate::Namespace::*;
 use crate::{BuiltinMacroState, Determinacy};
 use crate::{DeriveData, Finalize, ParentScope, ResolutionError, Resolver, ScopeSet};
-use crate::{ModuleKind, ModuleOrUniformRoot, NameBinding, PathResult, Segment};
+use crate::{ModuleKind, ModuleOrUniformRoot, NameBinding, PathResult, Segment, ToNameBinding};
 use rustc_ast::expand::StrippedCfgItem;
 use rustc_ast::{self as ast, attr, Crate, Inline, ItemKind, ModKind, NodeId};
 use rustc_ast_pretty::pprust;
@@ -20,10 +20,10 @@ use rustc_expand::base::{SyntaxExtension, SyntaxExtensionKind};
 use rustc_expand::compile_declarative_macro;
 use rustc_expand::expand::{AstFragment, Invocation, InvocationKind, SupportsMacroExpansion};
 use rustc_hir::def::{self, DefKind, NonMacroAttrKind};
-use rustc_hir::def_id::{CrateNum, LocalDefId};
+use rustc_hir::def_id::{CrateNum, DefId, LocalDefId};
 use rustc_middle::middle::stability;
 use rustc_middle::ty::RegisteredTools;
-use rustc_middle::ty::TyCtxt;
+use rustc_middle::ty::{TyCtxt, Visibility};
 use rustc_session::lint::builtin::{
     LEGACY_DERIVE_HELPERS, SOFT_UNSTABLE, UNKNOWN_DIAGNOSTIC_ATTRIBUTES,
 };
@@ -401,8 +401,17 @@ impl<'a, 'tcx> ResolverExpand for Resolver<'a, 'tcx> {
         }
         // Sort helpers in a stable way independent from the derive resolution order.
         entry.helper_attrs.sort_by_key(|(i, _)| *i);
-        self.helper_attrs
+        let helper_attrs = entry
-            .insert(expn_id, entry.helper_attrs.iter().map(|(_, ident)| *ident).collect());
+            .helper_attrs
+            .iter()
+            .map(|(_, ident)| {
+                let res = Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
+                let binding = (res, Visibility::<DefId>::Public, ident.span, expn_id)
+                    .to_name_binding(self.arenas);
+                (*ident, binding)
+            })
+            .collect();
+        self.helper_attrs.insert(expn_id, helper_attrs);
         // Mark this derive as having `Copy` either if it has `Copy` itself or if its parent derive
         // has `Copy`, to support cases like `#[derive(Clone, Copy)] #[derive(Debug)]`.
         if entry.has_derive_copy || self.has_derive_copy(parent_scope.expansion) {