Don't emit missing_docs lint with dummy spans

Author: Urgau

compiler/rustc_lint/src/builtin.rs

@@ -438,11 +438,10 @@ impl MissingDoc {
         let attrs = cx.tcx.hir().attrs(cx.tcx.local_def_id_to_hir_id(def_id));
         let has_doc = attrs.iter().any(has_doc);
         if !has_doc {
-            cx.emit_span_lint(
-                MISSING_DOCS,
-                cx.tcx.def_span(def_id),
-                BuiltinMissingDoc { article, desc },
-            );
+            let sp = cx.tcx.def_span(def_id);
+            if !sp.is_dummy() {
+                cx.emit_span_lint(MISSING_DOCS, sp, BuiltinMissingDoc { article, desc });
+            }
         }
     }
 }