rollup merge of rust-lang#18346 : aochagavia/closure-fields

Author: alexcrichton

src/librustc/middle/typeck/check/method.rs

@@ -223,17 +223,37 @@ pub fn report_error(fcx: &FnCtxt,
 {
  match error {
  NoMatch(static_sources) => {
+ let cx = fcx.tcx();
+ let method_ustring = method_name.user_string(cx);
+
+ // True if the type is a struct and contains a field with
+ // the same name as the not-found method
+ let is_field = match ty::get(rcvr_ty).sty {
+ ty_struct(did, _) =>
+ ty::lookup_struct_fields(cx, did)
+ .iter()
+ .any(|f| f.name.user_string(cx) == method_ustring),
+ _ => false
+ };
+
  fcx.type_error_message(
  span,
  |actual| {
  format!("type `{}` does not implement any \
  method in scope named `{}`",
  actual,
- method_name.user_string(fcx.tcx()))
+ method_ustring)
  },
  rcvr_ty,
  None);
 
+ // If the method has the name of a field, give a help note
+ if is_field {
+ cx.sess.span_note(span,
+ format!("use `(s.{0})(...)` if you meant to call the \
+ function stored in the `{0}` field", method_ustring).as_slice());
+ }
+
  if static_sources.len() > 0 {
  fcx.tcx().sess.fileline_note(
  span,

src/test/compile-fail/issue-18343.rs

@@ -0,0 +1,19 @@
+// Copyright 2014 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.
+
+struct Obj<'a> {
+ closure: ||: 'a -> u32
+}
+
+fn main() {
+ let o = Obj { closure: || 42 };
+ o.closure(); //~ ERROR type `Obj<'_>` does not implement any method in scope named `closure`
+ //~^ NOTE use `(s.closure)(...)` if you meant to call the function stored in the `closure` field
+}