Fix symbol conflict diagnostic mistakenly being shown instead of missing crate diagnostic

compiler/rustc_metadata/src/creader.rs

@@ -148,11 +148,15 @@ impl CStore {
         assert_eq!(self.metas.len(), self.stable_crate_ids.len());
         let num = CrateNum::new(self.stable_crate_ids.len());
         if let Some(&existing) = self.stable_crate_ids.get(&root.stable_crate_id()) {
-            let crate_name0 = root.name();
-            if let Some(crate_name1) = self.metas[existing].as_ref().map(|data| data.name()) {
+            // Check for (potential) conflicts with the local crate
+            if existing == LOCAL_CRATE {
+                Err(CrateError::SymbolConflictsCurrent(root.name()))
+            } else if let Some(crate_name1) = self.metas[existing].as_ref().map(|data| data.name())
+            {
+                let crate_name0 = root.name();
                 Err(CrateError::StableCrateIdCollision(crate_name0, crate_name1))
             } else {
-                Err(CrateError::SymbolConflictsCurrent(crate_name0))
+                Err(CrateError::NotFound(root.name()))
             }
         } else {
             self.metas.push(None);

compiler/rustc_metadata/src/locator.rs

@@ -961,6 +961,7 @@ pub(crate) enum CrateError {
     DlSym(String),
     LocatorCombined(Box<CombinedLocatorError>),
     NonDylibPlugin(Symbol),
+    NotFound(Symbol),
 }
 
 enum MetadataError<'a> {
@@ -1131,6 +1132,18 @@ impl CrateError {
             CrateError::NonDylibPlugin(crate_name) => {
                 sess.emit_err(errors::NoDylibPlugin { span, crate_name });
             }
+            CrateError::NotFound(crate_name) => {
+                sess.emit_err(errors::CannotFindCrate {
+                    span,
+                    crate_name,
+                    add_info: String::new(),
+                    missing_core,
+                    current_crate: sess.opts.crate_name.clone().unwrap_or("<unknown>".to_string()),
+                    is_nightly_build: sess.is_nightly_build(),
+                    profiler_runtime: Symbol::intern(&sess.opts.unstable_opts.profiler_runtime),
+                    locator_triple: sess.opts.target_triple.clone(),
+                });
+            }
         }
     }
 }

tests/run-make/issue-83045/Makefile

@@ -29,5 +29,5 @@ all:
 				  --crate-type=rlib \
 				  --edition=2018 \
 				  c.rs 2>&1 | tee $(TMPDIR)/output.txt || exit 0
-	$(CGREP) E0519 < $(TMPDIR)/output.txt
+	$(CGREP) E0463 < $(TMPDIR)/output.txt
 	$(CGREP) -v "internal compiler error" < $(TMPDIR)/output.txt