Make Iterator a lang item

compiler/rustc_interface/src/passes.rs

@@ -856,6 +856,11 @@ fn analysis(tcx: TyCtxt<'_>, (): ()) -> Result<()> {
         // This check has to be run after all lints are done processing. We don't
         // define a lint filter, as all lint checks should have finished at this point.
         sess.time("check_lint_expectations", || tcx.ensure().check_expectations(None));
+
+        // This query is only invoked normally if a diagnostic is emitted that needs any
+        // diagnostic item. If the crate compiles without checking any diagnostic items,
+        // we will fail to emit overlap diagnostics. Thus we invoke it here unconditionally.
+        let _ = tcx.all_diagnostic_items(());
     });
 
     if sess.opts.unstable_opts.print_vtable_sizes {