Use Option<Symbol> in DuplicateLangItem.

For the the symbols that might not be present, instead of `kw::Empty`.

Author: nnethercote

Diff for: compiler/rustc_passes/src/errors.rs

@@ -1348,12 +1348,12 @@ pub(crate) struct DuplicateLangItem {
     pub local_span: Option<Span>,
     pub lang_item_name: Symbol,
     pub crate_name: Symbol,
-    pub dependency_of: Symbol,
+    pub dependency_of: Option<Symbol>,
     pub is_local: bool,
     pub path: String,
     pub first_defined_span: Option<Span>,
-    pub orig_crate_name: Symbol,
-    pub orig_dependency_of: Symbol,
+    pub orig_crate_name: Option<Symbol>,
+    pub orig_dependency_of: Option<Symbol>,
     pub orig_is_local: bool,
     pub orig_path: String,
     pub(crate) duplicate: Duplicate,
@@ -1374,18 +1374,24 @@ impl<G: EmissionGuarantee> Diagnostic<'_, G> for DuplicateLangItem {
         diag.code(E0152);
         diag.arg("lang_item_name", self.lang_item_name);
         diag.arg("crate_name", self.crate_name);
-        diag.arg("dependency_of", self.dependency_of);
+        if let Some(dependency_of) = self.dependency_of {
+            diag.arg("dependency_of", dependency_of);
+        }
         diag.arg("path", self.path);
-        diag.arg("orig_crate_name", self.orig_crate_name);
-        diag.arg("orig_dependency_of", self.orig_dependency_of);
+        if let Some(orig_crate_name) = self.orig_crate_name {
+            diag.arg("orig_crate_name", orig_crate_name);
+        }
+        if let Some(orig_dependency_of) = self.orig_dependency_of {
+            diag.arg("orig_dependency_of", orig_dependency_of);
+        }
         diag.arg("orig_path", self.orig_path);
         if let Some(span) = self.local_span {
             diag.span(span);
         }
         if let Some(span) = self.first_defined_span {
             diag.span_note(span, fluent::passes_first_defined_span);
         } else {
-            if self.orig_dependency_of.is_empty() {
+            if self.orig_dependency_of.is_none() {
                 diag.note(fluent::passes_first_defined_crate);
             } else {
                 diag.note(fluent::passes_first_defined_crate_depends);

Diff for: compiler/rustc_passes/src/lang_items.rs

@@ -16,7 +16,7 @@ use rustc_hir::{LangItem, LanguageItems, MethodKind, Target};
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{ResolverAstLowering, TyCtxt};
 use rustc_session::cstore::ExternCrate;
-use rustc_span::{Span, kw};
+use rustc_span::Span;
 
 use crate::errors::{
     DuplicateLangItem, IncorrectTarget, LangItemOnIncorrectTarget, UnknownLangItem,
@@ -98,7 +98,7 @@ impl<'ast, 'tcx> LanguageItemCollector<'ast, 'tcx> {
         {
             let lang_item_name = lang_item.name();
             let crate_name = self.tcx.crate_name(item_def_id.krate);
-            let mut dependency_of = kw::Empty;
+            let mut dependency_of = None;
             let is_local = item_def_id.is_local();
             let path = if is_local {
                 String::new()
@@ -112,8 +112,8 @@ impl<'ast, 'tcx> LanguageItemCollector<'ast, 'tcx> {
             };
 
             let first_defined_span = self.item_spans.get(&original_def_id).copied();
-            let mut orig_crate_name = kw::Empty;
-            let mut orig_dependency_of = kw::Empty;
+            let mut orig_crate_name = None;
+            let mut orig_dependency_of = None;
             let orig_is_local = original_def_id.is_local();
             let orig_path = if orig_is_local {
                 String::new()
@@ -127,11 +127,11 @@ impl<'ast, 'tcx> LanguageItemCollector<'ast, 'tcx> {
             };
 
             if first_defined_span.is_none() {
-                orig_crate_name = self.tcx.crate_name(original_def_id.krate);
+                orig_crate_name = Some(self.tcx.crate_name(original_def_id.krate));
                 if let Some(ExternCrate { dependency_of: inner_dependency_of, .. }) =
                     self.tcx.extern_crate(original_def_id.krate)
                 {
-                    orig_dependency_of = self.tcx.crate_name(*inner_dependency_of);
+                    orig_dependency_of = Some(self.tcx.crate_name(*inner_dependency_of));
                 }
             }
 
@@ -140,7 +140,7 @@ impl<'ast, 'tcx> LanguageItemCollector<'ast, 'tcx> {
             } else {
                 match self.tcx.extern_crate(item_def_id.krate) {
                     Some(ExternCrate { dependency_of: inner_dependency_of, .. }) => {
-                        dependency_of = self.tcx.crate_name(*inner_dependency_of);
+                        dependency_of = Some(self.tcx.crate_name(*inner_dependency_of));
                         Duplicate::CrateDepends
                     }
                     _ => Duplicate::Crate,