Various minor/cosmetic improvements to code

src/librustc_codegen_llvm/debuginfo/mod.rs

@@ -488,7 +488,7 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                     );
 
                     // Only "class" methods are generally understood by LLVM,
-                    // so avoid methods on other types (e.g. `<*mut T>::null`).
+                    // so avoid methods on other types (e.g., `<*mut T>::null`).
                     match impl_self_ty.sty {
                         ty::Adt(def, ..) if !def.is_box() => {
                             Some(type_metadata(cx, impl_self_ty, syntax_pos::DUMMY_SP))