Added help message for self_in_typedefs feature gate

src/librustc_mir/hair/pattern/check_match.rs

@@ -539,7 +539,7 @@ fn check_legality_of_move_bindings(cx: &MatchVisitor,
                 .emit();
         } else if has_guard && !cx.tcx.allow_bind_by_move_patterns_with_guards() {
             let mut err = struct_span_err!(cx.tcx.sess, p.span, E0008,
-                                       "cannot bind by-move into a pattern guard");
+                                           "cannot bind by-move into a pattern guard");
             err.span_label(p.span, "moves value into pattern guard");
             if cx.tcx.sess.opts.unstable_features.is_nightly_build() && cx.tcx.use_mir_borrowck() {
                 err.help("add #![feature(bind_by_move_pattern_guards)] to the \

src/librustc_resolve/lib.rs

@@ -42,8 +42,9 @@ use rustc::lint;
 use rustc::hir::def::*;
 use rustc::hir::def::Namespace::*;
 use rustc::hir::def_id::{CRATE_DEF_INDEX, LOCAL_CRATE, DefId};
-use rustc::ty;
 use rustc::hir::{Freevar, FreevarMap, TraitCandidate, TraitMap, GlobMap};
+use rustc::session::config::nightly_options;
+use rustc::ty;
 use rustc::util::nodemap::{NodeMap, NodeSet, FxHashMap, FxHashSet, DefIdMap};
 
 use rustc_metadata::creader::CrateLoader;
@@ -1381,6 +1382,9 @@ pub struct Resolver<'a, 'b: 'a> {
     /// The current self type if inside an impl (used for better errors).
     current_self_type: Option<Ty>,
 
+    /// The current self item if inside an ADT (used for better errors).
+    current_self_item: Option<NodeId>,
+
     /// The idents for the primitive types.
     primitive_type_table: PrimitiveTypeTable,
 
@@ -1710,6 +1714,7 @@ impl<'a, 'crateloader: 'a> Resolver<'a, 'crateloader> {
 
             current_trait_ref: None,
             current_self_type: None,
+            current_self_item: None,
 
             primitive_type_table: PrimitiveTypeTable::new(),
 
@@ -2186,15 +2191,17 @@ impl<'a, 'crateloader: 'a> Resolver<'a, 'crateloader> {
     }
 
     fn resolve_adt(&mut self, item: &Item, generics: &Generics) {
-        self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind), |this| {
-            let item_def_id = this.definitions.local_def_id(item.id);
-            if this.session.features_untracked().self_in_typedefs {
-                this.with_self_rib(Def::SelfTy(None, Some(item_def_id)), |this| {
+        self.with_current_self_item(item, |this| {
+            this.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind), |this| {
+                let item_def_id = this.definitions.local_def_id(item.id);
+                if this.session.features_untracked().self_in_typedefs {
+                    this.with_self_rib(Def::SelfTy(None, Some(item_def_id)), |this| {
+                        visit::walk_item(this, item);
+                    });
+                } else {
                     visit::walk_item(this, item);
-                });
-            } else {
-                visit::walk_item(this, item);
-            }
+                }
+            });
         });
     }
 
@@ -2435,6 +2442,15 @@ impl<'a, 'crateloader: 'a> Resolver<'a, 'crateloader> {
         result
     }
 
+    fn with_current_self_item<T, F>(&mut self, self_item: &Item, f: F) -> T
+        where F: FnOnce(&mut Resolver) -> T
+    {
+        let previous_value = replace(&mut self.current_self_item, Some(self_item.id));
+        let result = f(self);
+        self.current_self_item = previous_value;
+        result
+    }
+
     /// This is called to resolve a trait reference from an `impl` (i.e. `impl Trait for Foo`)
     fn with_optional_trait_ref<T, F>(&mut self, opt_trait_ref: Option<&TraitRef>, f: F) -> T
         where F: FnOnce(&mut Resolver, Option<DefId>) -> T
@@ -3004,6 +3020,10 @@ impl<'a, 'crateloader: 'a> Resolver<'a, 'crateloader> {
                     "traits and impls"
                 };
                 err.span_label(span, format!("`Self` is only available in {}", available_in));
+                if this.current_self_item.is_some() && nightly_options::is_nightly_build() {
+                    err.help("add #![feature(self_in_typedefs)] to the crate attributes \
+                              to enable");
+                }
                 return (err, Vec::new());
             }
             if is_self_value(path, ns) {

src/librustc_typeck/check/method/probe.rs

@@ -17,6 +17,9 @@ use check::FnCtxt;
 use hir::def_id::DefId;
 use hir::def::Def;
 use namespace::Namespace;
+use rustc::hir;
+use rustc::lint;
+use rustc::session::config::nightly_options;
 use rustc::ty::subst::{Subst, Substs};
 use rustc::traits::{self, ObligationCause};
 use rustc::ty::{self, Ty, ToPolyTraitRef, ToPredicate, TraitRef, TypeFoldable};
@@ -28,8 +31,6 @@ use rustc::middle::stability;
 use syntax::ast;
 use syntax::util::lev_distance::{lev_distance, find_best_match_for_name};
 use syntax_pos::{Span, symbol::Symbol};
-use rustc::hir;
-use rustc::lint;
 use std::mem;
 use std::ops::Deref;
 use std::rc::Rc;
@@ -1073,9 +1074,9 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
             self.tcx.item_path_str(stable_pick.item.def_id),
         ));
 
-        if ::rustc::session::config::nightly_options::is_nightly_build() {
+        if nightly_options::is_nightly_build() {
             for (candidate, feature) in unstable_candidates {
-                diag.note(&format!(
+                diag.help(&format!(
                     "add #![feature({})] to the crate attributes to enable `{}`",
                     feature,
                     self.tcx.item_path_str(candidate.item.def_id),

src/test/ui/feature-gates/feature-gate-self_in_typedefs.stderr

@@ -3,6 +3,8 @@ error[E0411]: cannot find type `Self` in this scope
    |
 LL |     Cons(T, &'a Self)
    |                 ^^^^ `Self` is only available in traits and impls
+   |
+   = help: add #![feature(self_in_typedefs)] to the crate attributes to enable
 
 error: aborting due to previous error
 

src/test/ui/inference/inference_unstable.stderr

@@ -8,5 +8,5 @@ LL |     assert_eq!('x'.ipu_flatten(), 1);
    = warning: once this method is added to the standard library, the ambiguity may cause an error or change in behavior!
    = note: for more information, see issue #48919 <https://github.com/rust-lang/rust/issues/48919>
    = help: call with fully qualified syntax `inference_unstable_itertools::IpuItertools::ipu_flatten(...)` to keep using the current method
-   = note: add #![feature(ipu_flatten)] to the crate attributes to enable `inference_unstable_iterator::IpuIterator::ipu_flatten`
+   = help: add #![feature(ipu_flatten)] to the crate attributes to enable `inference_unstable_iterator::IpuIterator::ipu_flatten`