typeck: Save the index of private fields

src/librustc_typeck/check/mod.rs

@@ -3081,12 +3081,14 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                     if let Some(index) = fields.iter().position(|f| f.name.to_ident() == ident) {
                         let field = &fields[index];
                         let field_ty = self.field_ty(expr.span, field, substs);
+                        // Save the index of all fields regardless of their visibility in case
+                        // of error recovery.
+                        self.write_field_index(expr.id, index);
                         if field.vis.is_accessible_from(def_scope, self.tcx) {
                             let adjustments = autoderef.adjust_steps(needs);
                             self.apply_adjustments(base, adjustments);
                             autoderef.finalize();
 
-                            self.write_field_index(expr.id, index);
                             self.tcx.check_stability(field.did, Some(expr.id), expr.span);
                             return field_ty;
                         }

src/test/compile-fail-fulldeps/proc-macro/auxiliary/issue_50493.rs

@@ -0,0 +1,32 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// force-host
+// no-prefer-dynamic
+
+#![feature(proc_macro, proc_macro_lib)]
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+use proc_macro::TokenStream;
+
+#[proc_macro_derive(Derive)]
+pub fn derive(_: TokenStream) -> TokenStream {
+    let code = "
+        fn one(r: Restricted) {
+            r.field;
+        }
+        fn two(r: Restricted) {
+            r.field;
+        }
+    ";
+
+    code.parse().unwrap()
+}

src/test/compile-fail-fulldeps/proc-macro/issue-50493.rs

@@ -0,0 +1,27 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// aux-build:issue_50493.rs
+// ignore-stage1
+
+#![feature(proc_macro)]
+
+#[macro_use]
+extern crate issue_50493;
+
+#[derive(Derive)] //~ ERROR field `field` of struct `Restricted` is private
+struct Restricted {
+    pub(in restricted) field: usize, //~ visibilities can only be restricted to ancestor modules
+}
+
+mod restricted {}
+
+fn main() {}
+