Auto merge of #52319 - tinco:issue_12590, r=pnkfelix

Track whether module declarations are inline (fixes #12590)

To track whether module declarations are inline I added a field `inline: bool` to `ast::Mod`. The main use case is for pretty to know whether it should render the items associated with the module, but perhaps there are use cases for this information to not be forgotten in the AST.

src/libsyntax/ext/expand.rs

@@ -303,6 +303,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                 krate.module = ast::Mod {
                     inner: orig_mod_span,
                     items: vec![],
+                    inline: true,
                 };
             },
             _ => unreachable!(),