Rollup merge of #47613 - estebank:rustc_on_unimplemented, r=nikomatsakis

Add filtering options to `rustc_on_unimplemented`

- Add filtering options to `rustc_on_unimplemented` for local traits, filtering on `Self` and type arguments.
- Add a way to provide custom notes.
- Tweak binops text.
- Add filter to detect wether `Self` is local or belongs to another crate.
- Add filter to `Iterator` diagnostic for `&str`.

Partly addresses #44755 with a different syntax, as a first approach. Fixes #46216, fixes #37522, CC #34297, #46806.

19 files changed, 234 insertions, 83 deletions

diff --git a/src/libcore/fmt/mod.rs b/src/libcore/fmt/mod.rs
index 6c8a1c3062b..8ad5a9861a0 100644
--- a/src/libcore/fmt/mod.rs
+++ b/src/libcore/fmt/mod.rs
@@ -530,9 +530,12 @@ impl<'a> Display for Arguments<'a> {
 /// }
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_on_unimplemented = "`{Self}` cannot be formatted using `:?`; if it is \
-                            defined in your crate, add `#[derive(Debug)]` or \
-                            manually implement it"]
+#[rustc_on_unimplemented(
+    on(crate_local, label="`{Self}` cannot be formatted using `:?`; \
+                            add `#[derive(Debug)]` or manually implement `{Debug}`"),
+    message="`{Self}` doesn't implement `{Debug}`",
+    label="`{Self}` cannot be formatted using `:?` because it doesn't implement `{Debug}`",
+)]
 #[lang = "debug_trait"]
 pub trait Debug {
     /// Formats the value using the given formatter.
@@ -593,9 +596,11 @@ pub trait Debug {
 ///
 /// println!("The origin is: {}", origin);
 /// ```
-#[rustc_on_unimplemented = "`{Self}` cannot be formatted with the default \
-                            formatter; try using `:?` instead if you are using \
-                            a format string"]
+#[rustc_on_unimplemented(
+    message="`{Self}` doesn't implement `{Display}`",
+    label="`{Self}` cannot be formatted with the default formatter; \
+           try using `:?` instead if you are using a format string",
+)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait Display {
     /// Formats the value using the given formatter.
diff --git a/src/libcore/iter/iterator.rs b/src/libcore/iter/iterator.rs
index 35cd7441c66..296fb8733ba 100644
--- a/src/libcore/iter/iterator.rs
+++ b/src/libcore/iter/iterator.rs
@@ -28,8 +28,13 @@ fn _assert_is_object_safe(_: &Iterator<Item=()>) {}
 /// [module-level documentation]: index.html
 /// [impl]: index.html#implementing-iterator
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_on_unimplemented = "`{Self}` is not an iterator; maybe try calling \
-                            `.iter()` or a similar method"]
+#[rustc_on_unimplemented(
+    on(
+        _Self="&str",
+        label="`{Self}` is not an iterator; try calling `.chars()` or `.bytes()`"
+    ),
+    label="`{Self}` is not an iterator; maybe try calling `.iter()` or a similar method"
+)]
 #[doc(spotlight)]
 pub trait Iterator {
     /// The type of the elements being iterated over.
diff --git a/src/libcore/ops/arith.rs b/src/libcore/ops/arith.rs
index 8b3d662a6db..d0d0c09869e 100644
--- a/src/libcore/ops/arith.rs
+++ b/src/libcore/ops/arith.rs
@@ -75,7 +75,18 @@
 /// ```
 #[lang = "add"]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} + {RHS}`"]
+#[rustc_on_unimplemented(
+    on(
+        all(_Self="{integer}", RHS="{float}"),
+        message="cannot add a float to an integer",
+    ),
+    on(
+        all(_Self="{float}", RHS="{integer}"),
+        message="cannot add an integer to a float",
+    ),
+    message="cannot add `{RHS}` to `{Self}`",
+    label="no implementation for `{Self} + {RHS}`",
+)]
 pub trait Add<RHS=Self> {
     /// The resulting type after applying the `+` operator.
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -170,7 +181,8 @@ add_impl! { usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 f32 f64 }
 /// ```
 #[lang = "sub"]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} - {RHS}`"]
+#[rustc_on_unimplemented(message="cannot substract `{RHS}` from `{Self}`",
+                         label="no implementation for `{Self} - {RHS}`")]
 pub trait Sub<RHS=Self> {
     /// The resulting type after applying the `-` operator.
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -287,7 +299,8 @@ sub_impl! { usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 f32 f64 }
 /// ```
 #[lang = "mul"]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} * {RHS}`"]
+#[rustc_on_unimplemented(message="cannot multiply `{RHS}` to `{Self}`",
+                         label="no implementation for `{Self} * {RHS}`")]
 pub trait Mul<RHS=Self> {
     /// The resulting type after applying the `*` operator.
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -408,7 +421,8 @@ mul_impl! { usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 f32 f64 }
 /// ```
 #[lang = "div"]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} / {RHS}`"]
+#[rustc_on_unimplemented(message="cannot divide `{Self}` by `{RHS}`",
+                         label="no implementation for `{Self} / {RHS}`")]
 pub trait Div<RHS=Self> {
     /// The resulting type after applying the `/` operator.
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -490,7 +504,8 @@ div_impl_float! { f32 f64 }
 /// ```
 #[lang = "rem"]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} % {RHS}`"]
+#[rustc_on_unimplemented(message="cannot mod `{Self}` by `{RHS}`",
+                         label="no implementation for `{Self} % {RHS}`")]
 pub trait Rem<RHS=Self> {
     /// The resulting type after applying the `%` operator.
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -647,7 +662,8 @@ neg_impl_numeric! { isize i8 i16 i32 i64 i128 f32 f64 }
 /// ```
 #[lang = "add_assign"]
 #[stable(feature = "op_assign_traits", since = "1.8.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} += {Rhs}`"]
+#[rustc_on_unimplemented(message="cannot add-assign `{Rhs}` to `{Self}`",
+                         label="no implementation for `{Self} += {Rhs}`")]
 pub trait AddAssign<Rhs=Self> {
     /// Performs the `+=` operation.
     #[stable(feature = "op_assign_traits", since = "1.8.0")]
@@ -700,7 +716,8 @@ add_assign_impl! { usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 f32 f64 }
 /// ```
 #[lang = "sub_assign"]
 #[stable(feature = "op_assign_traits", since = "1.8.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} -= {Rhs}`"]
+#[rustc_on_unimplemented(message="cannot substract-assign `{Rhs}` from `{Self}`",
+                         label="no implementation for `{Self} -= {Rhs}`")]
 pub trait SubAssign<Rhs=Self> {
     /// Performs the `-=` operation.
     #[stable(feature = "op_assign_traits", since = "1.8.0")]
@@ -744,7 +761,8 @@ sub_assign_impl! { usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 f32 f64 }
 /// ```
 #[lang = "mul_assign"]
 #[stable(feature = "op_assign_traits", since = "1.8.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} *= {Rhs}`"]
+#[rustc_on_unimplemented(message="cannot multiply-assign `{Rhs}` to `{Self}`",
+                         label="no implementation for `{Self} *= {Rhs}`")]
 pub trait MulAssign<Rhs=Self> {
     /// Performs the `*=` operation.
     #[stable(feature = "op_assign_traits", since = "1.8.0")]
@@ -788,7 +806,8 @@ mul_assign_impl! { usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 f32 f64 }
 /// ```
 #[lang = "div_assign"]
 #[stable(feature = "op_assign_traits", since = "1.8.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} /= {Rhs}`"]
+#[rustc_on_unimplemented(message="cannot divide-assign `{Self}` by `{Rhs}`",
+                         label="no implementation for `{Self} /= {Rhs}`")]
 pub trait DivAssign<Rhs=Self> {
     /// Performs the `/=` operation.
     #[stable(feature = "op_assign_traits", since = "1.8.0")]
@@ -835,7 +854,8 @@ div_assign_impl! { usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 f32 f64 }
 /// ```
 #[lang = "rem_assign"]
 #[stable(feature = "op_assign_traits", since = "1.8.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} %= {Rhs}`"]
+#[rustc_on_unimplemented(message="cannot mod-assign `{Self}` by `{Rhs}``",
+                         label="no implementation for `{Self} %= {Rhs}`")]
 pub trait RemAssign<Rhs=Self> {
     /// Performs the `%=` operation.
     #[stable(feature = "op_assign_traits", since = "1.8.0")]
diff --git a/src/libcore/ops/bit.rs b/src/libcore/ops/bit.rs
index 7ac5fc4debf..a0ecd6cf75c 100644
--- a/src/libcore/ops/bit.rs
+++ b/src/libcore/ops/bit.rs
@@ -120,7 +120,8 @@ not_impl! { bool usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 }
 /// ```
 #[lang = "bitand"]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} & {RHS}`"]
+#[rustc_on_unimplemented(message="no implementation for `{Self} & {RHS}`",
+                         label="no implementation for `{Self} & {RHS}`")]
 pub trait BitAnd<RHS=Self> {
     /// The resulting type after applying the `&` operator.
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -201,7 +202,8 @@ bitand_impl! { bool usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 }
 /// ```
 #[lang = "bitor"]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} | {RHS}`"]
+#[rustc_on_unimplemented(message="no implementation for `{Self} | {RHS}`",
+                         label="no implementation for `{Self} | {RHS}`")]
 pub trait BitOr<RHS=Self> {
     /// The resulting type after applying the `|` operator.
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -285,7 +287,8 @@ bitor_impl! { bool usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 }
 /// ```
 #[lang = "bitxor"]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} ^ {RHS}`"]
+#[rustc_on_unimplemented(message="no implementation for `{Self} ^ {RHS}`",
+                         label="no implementation for `{Self} ^ {RHS}`")]
 pub trait BitXor<RHS=Self> {
     /// The resulting type after applying the `^` operator.
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -365,7 +368,8 @@ bitxor_impl! { bool usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 }
 /// ```
 #[lang = "shl"]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} << {RHS}`"]
+#[rustc_on_unimplemented(message="no implementation for `{Self} << {RHS}`",
+                         label="no implementation for `{Self} << {RHS}`")]
 pub trait Shl<RHS> {
     /// The resulting type after applying the `<<` operator.
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -466,7 +470,8 @@ shl_impl_all! { u8 u16 u32 u64 u128 usize i8 i16 i32 i64 isize i128 }
 /// ```
 #[lang = "shr"]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} >> {RHS}`"]
+#[rustc_on_unimplemented(message="no implementation for `{Self} >> {RHS}`",
+                         label="no implementation for `{Self} >> {RHS}`")]
 pub trait Shr<RHS> {
     /// The resulting type after applying the `>>` operator.
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -579,7 +584,8 @@ shr_impl_all! { u8 u16 u32 u64 u128 usize i8 i16 i32 i64 i128 isize }
 /// ```
 #[lang = "bitand_assign"]
 #[stable(feature = "op_assign_traits", since = "1.8.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} &= {Rhs}`"]
+#[rustc_on_unimplemented(message="no implementation for `{Self} &= {Rhs}`",
+                         label="no implementation for `{Self} &= {Rhs}`")]
 pub trait BitAndAssign<Rhs=Self> {
     /// Performs the `&=` operation.
     #[stable(feature = "op_assign_traits", since = "1.8.0")]
@@ -626,7 +632,8 @@ bitand_assign_impl! { bool usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 }
 /// ```
 #[lang = "bitor_assign"]
 #[stable(feature = "op_assign_traits", since = "1.8.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} |= {Rhs}`"]
+#[rustc_on_unimplemented(message="no implementation for `{Self} |= {Rhs}`",
+                         label="no implementation for `{Self} |= {Rhs}`")]
 pub trait BitOrAssign<Rhs=Self> {
     /// Performs the `|=` operation.
     #[stable(feature = "op_assign_traits", since = "1.8.0")]
@@ -673,7 +680,8 @@ bitor_assign_impl! { bool usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 }
 /// ```
 #[lang = "bitxor_assign"]
 #[stable(feature = "op_assign_traits", since = "1.8.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} ^= {Rhs}`"]
+#[rustc_on_unimplemented(message="no implementation for `{Self} ^= {Rhs}`",
+                         label="no implementation for `{Self} ^= {Rhs}`")]
 pub trait BitXorAssign<Rhs=Self> {
     /// Performs the `^=` operation.
     #[stable(feature = "op_assign_traits", since = "1.8.0")]
@@ -718,7 +726,8 @@ bitxor_assign_impl! { bool usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 }
 /// ```
 #[lang = "shl_assign"]
 #[stable(feature = "op_assign_traits", since = "1.8.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} <<= {Rhs}`"]
+#[rustc_on_unimplemented(message="no implementation for `{Self} <<= {Rhs}`",
+                         label="no implementation for `{Self} <<= {Rhs}`")]
 pub trait ShlAssign<Rhs> {
     /// Performs the `<<=` operation.
     #[stable(feature = "op_assign_traits", since = "1.8.0")]
@@ -784,7 +793,8 @@ shl_assign_impl_all! { u8 u16 u32 u64 u128 usize i8 i16 i32 i64 i128 isize }
 /// ```
 #[lang = "shr_assign"]
 #[stable(feature = "op_assign_traits", since = "1.8.0")]
-#[rustc_on_unimplemented = "no implementation for `{Self} >>= {Rhs}`"]
+#[rustc_on_unimplemented(message="no implementation for `{Self} >>= {Rhs}`",
+                         label="no implementation for `{Self} >>= {Rhs}`")]
 pub trait ShrAssign<Rhs=Self> {
     /// Performs the `>>=` operation.
     #[stable(feature = "op_assign_traits", since = "1.8.0")]
diff --git a/src/librustc/traits/error_reporting.rs b/src/librustc/traits/error_reporting.rs
index 7b86791026b..d4bcf00be80 100644
--- a/src/librustc/traits/error_reporting.rs
+++ b/src/librustc/traits/error_reporting.rs
@@ -348,7 +348,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         if direct {
             // this is a "direct", user-specified, rather than derived,
             // obligation.
-            flags.push(("direct", None));
+            flags.push(("direct".to_string(), None));
         }
 
         if let ObligationCauseCode::ItemObligation(item) = obligation.cause.code {
@@ -359,21 +359,37 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
             // Currently I'm leaving it for what I need for `try`.
             if self.tcx.trait_of_item(item) == Some(trait_ref.def_id) {
                 method = self.tcx.item_name(item);
-                flags.push(("from_method", None));
-                flags.push(("from_method", Some(&*method)));
+                flags.push(("from_method".to_string(), None));
+                flags.push(("from_method".to_string(), Some(method.to_string())));
             }
         }
 
         if let Some(k) = obligation.cause.span.compiler_desugaring_kind() {
             desugaring = k.as_symbol().as_str();
-            flags.push(("from_desugaring", None));
-            flags.push(("from_desugaring", Some(&*desugaring)));
+            flags.push(("from_desugaring".to_string(), None));
+            flags.push(("from_desugaring".to_string(), Some(desugaring.to_string())));
+        }
+        let generics = self.tcx.generics_of(def_id);
+        let self_ty = trait_ref.self_ty();
+        let self_ty_str = self_ty.to_string();
+        flags.push(("_Self".to_string(), Some(self_ty_str.clone())));
+
+        for param in generics.types.iter() {
+            let name = param.name.as_str().to_string();
+            let ty = trait_ref.substs.type_for_def(param);
+            let ty_str = ty.to_string();
+            flags.push((name.clone(),
+                        Some(ty_str.clone())));
+        }
+
+        if let Some(true) = self_ty.ty_to_def_id().map(|def_id| def_id.is_local()) {
+            flags.push(("crate_local".to_string(), None));
         }
 
         if let Ok(Some(command)) = OnUnimplementedDirective::of_item(
             self.tcx, trait_ref.def_id, def_id
         ) {
-            command.evaluate(self.tcx, trait_ref, &flags)
+            command.evaluate(self.tcx, trait_ref, &flags[..])
         } else {
             OnUnimplementedNote::empty()
         }
@@ -549,7 +565,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                 .map(|t| (format!(" in `{}`", t), format!("within `{}`, ", t)))
                             .unwrap_or((String::new(), String::new()));
 
-                        let OnUnimplementedNote { message, label }
+                        let OnUnimplementedNote { message, label, note }
                             = self.on_unimplemented_note(trait_ref, obligation);
                         let have_alt_message = message.is_some() || label.is_some();
 
@@ -578,6 +594,10 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                      trait_ref,
                                                      trait_ref.self_ty()));
                         }
+                        if let Some(ref s) = note {
+                            // If it has a custom "#[rustc_on_unimplemented]" note, let's display it
+                            err.note(s.as_str());
+                        }
 
                         self.suggest_borrow_on_unsized_slice(&obligation.cause.code, &mut err);
 
diff --git a/src/librustc/traits/on_unimplemented.rs b/src/librustc/traits/on_unimplemented.rs
index 757b078086d..8c2c1cfa454 100644
--- a/src/librustc/traits/on_unimplemented.rs
+++ b/src/librustc/traits/on_unimplemented.rs
@@ -29,16 +29,18 @@ pub struct OnUnimplementedDirective {
     pub subcommands: Vec<OnUnimplementedDirective>,
     pub message: Option<OnUnimplementedFormatString>,
     pub label: Option<OnUnimplementedFormatString>,
+    pub note: Option<OnUnimplementedFormatString>,
 }
 
 pub struct OnUnimplementedNote {
     pub message: Option<String>,
     pub label: Option<String>,
+    pub note: Option<String>,
 }
 
 impl OnUnimplementedNote {
     pub fn empty() -> Self {
-        OnUnimplementedNote { message: None, label: None }
+        OnUnimplementedNote { message: None, label: None, note: None }
     }
 }
 
@@ -89,6 +91,7 @@ impl<'a, 'gcx, 'tcx> OnUnimplementedDirective {
 
         let mut message = None;
         let mut label = None;
+        let mut note = None;
         let mut subcommands = vec![];
         for item in item_iter {
             if item.check_name("message") && message.is_none() {
@@ -103,8 +106,14 @@ impl<'a, 'gcx, 'tcx> OnUnimplementedDirective {
                         tcx, trait_def_id, label_.as_str(), span)?);
                     continue;
                 }
+            } else if item.check_name("note") && note.is_none() {
+                if let Some(note_) = item.value_str() {
+                    note = Some(OnUnimplementedFormatString::try_parse(
+                        tcx, trait_def_id, note_.as_str(), span)?);
+                    continue;
+                }
             } else if item.check_name("on") && is_root &&
-                message.is_none() && label.is_none()
+                message.is_none() && label.is_none() && note.is_none()
             {
                 if let Some(items) = item.meta_item_list() {
                     if let Ok(subcommand) =
@@ -128,7 +137,7 @@ impl<'a, 'gcx, 'tcx> OnUnimplementedDirective {
         if errored {
             Err(ErrorReported)
         } else {
-            Ok(OnUnimplementedDirective { condition, message, label, subcommands })
+            Ok(OnUnimplementedDirective { condition, message, label, subcommands, note })
         }
     }
 
@@ -154,7 +163,8 @@ impl<'a, 'gcx, 'tcx> OnUnimplementedDirective {
                 message: None,
                 subcommands: vec![],
                 label: Some(OnUnimplementedFormatString::try_parse(
-                    tcx, trait_def_id, value.as_str(), attr.span)?)
+                    tcx, trait_def_id, value.as_str(), attr.span)?),
+                note: None,
             }))
         } else {
             return Err(parse_error(tcx, attr.span,
@@ -169,20 +179,20 @@ impl<'a, 'gcx, 'tcx> OnUnimplementedDirective {
     pub fn evaluate(&self,
                     tcx: TyCtxt<'a, 'gcx, 'tcx>,
                     trait_ref: ty::TraitRef<'tcx>,
-                    options: &[(&str, Option<&str>)])
+                    options: &[(String, Option<String>)])
                     -> OnUnimplementedNote
     {
         let mut message = None;
         let mut label = None;
-        info!("evaluate({:?}, trait_ref={:?}, options={:?})",
-              self, trait_ref, options);
+        let mut note = None;
+        info!("evaluate({:?}, trait_ref={:?}, options={:?})", self, trait_ref, options);
 
         for command in self.subcommands.iter().chain(Some(self)).rev() {
             if let Some(ref condition) = command.condition {
                 if !attr::eval_condition(condition, &tcx.sess.parse_sess, &mut |c| {
-                    options.contains(&(&c.name().as_str(),
-                                      match c.value_str().map(|s| s.as_str()) {
-                                          Some(ref s) => Some(s),
+                    options.contains(&(c.name().as_str().to_string(),
+                                      match c.value_str().map(|s| s.as_str().to_string()) {
+                                          Some(s) => Some(s),
                                           None => None
                                       }))
                 }) {
@@ -198,11 +208,16 @@ impl<'a, 'gcx, 'tcx> OnUnimplementedDirective {
             if let Some(ref label_) = command.label {
                 label = Some(label_.clone());
             }
+
+            if let Some(ref note_) = command.note {
+                note = Some(note_.clone());
+            }
         }
 
         OnUnimplementedNote {
             label: label.map(|l| l.format(tcx, trait_ref)),
-            message: message.map(|m| m.format(tcx, trait_ref))
+            message: message.map(|m| m.format(tcx, trait_ref)),
+            note: note.map(|n| n.format(tcx, trait_ref)),
         }
     }
 }
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 764b3d0a848..dc3745fc4a3 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -761,6 +761,18 @@ impl<'a> Parser<'a> {
         })
     }
 
+    fn expected_ident_found(&self) -> DiagnosticBuilder<'a> {
+        let mut err = self.struct_span_err(self.span,
+                                           &format!("expected identifier, found {}",
+                                                    self.this_token_descr()));
+        if let Some(token_descr) = self.token_descr() {
+            err.span_label(self.span, format!("expected identifier, found {}", token_descr));
+        } else {
+            err.span_label(self.span, "expected identifier");
+        }
+        err
+    }
+
     pub fn parse_ident(&mut self) -> PResult<'a, ast::Ident> {
         self.parse_ident_common(true)
     }
@@ -769,15 +781,7 @@ impl<'a> Parser<'a> {
         match self.token {
             token::Ident(i) => {
                 if self.token.is_reserved_ident() {
-                    let mut err = self.struct_span_err(self.span,
-                                                       &format!("expected identifier, found {}",
-                                                                self.this_token_descr()));
-                    if let Some(token_descr) = self.token_descr() {
-                        err.span_label(self.span, format!("expected identifier, found {}",
-                                                          token_descr));
-                    } else {
-                        err.span_label(self.span, "expected identifier");
-                    }
+                    let mut err = self.expected_ident_found();
                     if recover {
                         err.emit();
                     } else {
@@ -791,14 +795,7 @@ impl<'a> Parser<'a> {
                 Err(if self.prev_token_kind == PrevTokenKind::DocComment {
                         self.span_fatal_err(self.prev_span, Error::UselessDocComment)
                     } else {
-                        let mut err = self.fatal(&format!("expected identifier, found `{}`",
-                                                          self.this_token_to_string()));
-                        if let Some(token_descr) = self.token_descr() {
-                            err.span_label(self.span, format!("expected identifier, found {}",
-                                                              token_descr));
-                        } else {
-                            err.span_label(self.span, "expected identifier");
-                        }
+                        let mut err = self.expected_ident_found();
                         if self.token == token::Underscore {
                             err.note("`_` is a wildcard pattern, not an identifier");
                         }
diff --git a/src/test/compile-fail/const-eval-overflow-4b.rs b/src/test/compile-fail/const-eval-overflow-4b.rs
index 02072e9a1a1..6028df18839 100644
--- a/src/test/compile-fail/const-eval-overflow-4b.rs
+++ b/src/test/compile-fail/const-eval-overflow-4b.rs
@@ -22,7 +22,7 @@ const A_I8_T
     : [u32; (i8::MAX as i8 + 1u8) as usize]
     //~^ ERROR mismatched types
     //~| expected i8, found u8
-    //~| ERROR the trait bound `i8: std::ops::Add<u8>` is not satisfied
+    //~| ERROR cannot add `u8` to `i8`
     = [0; (i8::MAX as usize) + 1];
 
 
diff --git a/src/test/compile-fail/ufcs-qpath-self-mismatch.rs b/src/test/compile-fail/ufcs-qpath-self-mismatch.rs
index 94a98b1582a..caf510071bd 100644
--- a/src/test/compile-fail/ufcs-qpath-self-mismatch.rs
+++ b/src/test/compile-fail/ufcs-qpath-self-mismatch.rs
@@ -12,7 +12,7 @@ use std::ops::Add;
 
 fn main() {
     <i32 as Add<u32>>::add(1, 2);
-    //~^ ERROR `i32: std::ops::Add<u32>` is not satisfied
+    //~^ ERROR cannot add `u32` to `i32`
     <i32 as Add<i32>>::add(1u32, 2);
     //~^ ERROR mismatched types
     <i32 as Add<i32>>::add(1, 2u32);
diff --git a/src/test/ui/impl-trait/equality.rs b/src/test/ui/impl-trait/equality.rs
index 36df4f0eb4d..9d9d4cef311 100644
--- a/src/test/ui/impl-trait/equality.rs
+++ b/src/test/ui/impl-trait/equality.rs
@@ -32,7 +32,7 @@ fn sum_to(n: u32) -> impl Foo {
         0
     } else {
         n + sum_to(n - 1)
-        //~^ ERROR the trait bound `u32: std::ops::Add<impl Foo>` is not satisfied
+        //~^ ERROR cannot add `impl Foo` to `u32`
     }
 }
 
diff --git a/src/test/ui/impl-trait/equality.stderr b/src/test/ui/impl-trait/equality.stderr
index 3fc08a0900f..8ec81903803 100644
--- a/src/test/ui/impl-trait/equality.stderr
+++ b/src/test/ui/impl-trait/equality.stderr
@@ -7,7 +7,7 @@ error[E0308]: mismatched types
    = note: expected type `i32`
               found type `u32`
 
-error[E0277]: the trait bound `u32: std::ops::Add<impl Foo>` is not satisfied
+error[E0277]: cannot add `impl Foo` to `u32`
   --> $DIR/equality.rs:34:11
    |
 34 |         n + sum_to(n - 1)
diff --git a/src/test/ui/mismatched_types/binops.rs b/src/test/ui/mismatched_types/binops.rs
index e45616cd67a..5144b59955c 100644
--- a/src/test/ui/mismatched_types/binops.rs
+++ b/src/test/ui/mismatched_types/binops.rs
@@ -9,10 +9,10 @@
 // except according to those terms.
 
 fn main() {
-    1 + Some(1); //~ ERROR is not satisfied
-    2 as usize - Some(1); //~ ERROR is not satisfied
-    3 * (); //~ ERROR is not satisfied
-    4 / ""; //~ ERROR is not satisfied
+    1 + Some(1); //~ ERROR cannot add `std::option::Option<{integer}>` to `{integer}`
+    2 as usize - Some(1); //~ ERROR cannot substract `std::option::Option<{integer}>` from `usize`
+    3 * (); //~ ERROR cannot multiply `()` to `{integer}`
+    4 / ""; //~ ERROR cannot divide `{integer}` by `&str`
     5 < String::new(); //~ ERROR is not satisfied
     6 == Ok(1); //~ ERROR is not satisfied
 }
diff --git a/src/test/ui/mismatched_types/binops.stderr b/src/test/ui/mismatched_types/binops.stderr
index 8541ad52e01..1b7fba05063 100644
--- a/src/test/ui/mismatched_types/binops.stderr
+++ b/src/test/ui/mismatched_types/binops.stderr
@@ -1,31 +1,31 @@
-error[E0277]: the trait bound `{integer}: std::ops::Add<std::option::Option<{integer}>>` is not satisfied
+error[E0277]: cannot add `std::option::Option<{integer}>` to `{integer}`
   --> $DIR/binops.rs:12:7
    |
-12 |     1 + Some(1); //~ ERROR is not satisfied
+12 |     1 + Some(1); //~ ERROR cannot add `std::option::Option<{integer}>` to `{integer}`
    |       ^ no implementation for `{integer} + std::option::Option<{integer}>`
    |
    = help: the trait `std::ops::Add<std::option::Option<{integer}>>` is not implemented for `{integer}`
 
-error[E0277]: the trait bound `usize: std::ops::Sub<std::option::Option<{integer}>>` is not satisfied
+error[E0277]: cannot substract `std::option::Option<{integer}>` from `usize`
   --> $DIR/binops.rs:13:16
    |
-13 |     2 as usize - Some(1); //~ ERROR is not satisfied
+13 |     2 as usize - Some(1); //~ ERROR cannot substract `std::option::Option<{integer}>` from `usize`
    |                ^ no implementation for `usize - std::option::Option<{integer}>`
    |
    = help: the trait `std::ops::Sub<std::option::Option<{integer}>>` is not implemented for `usize`
 
-error[E0277]: the trait bound `{integer}: std::ops::Mul<()>` is not satisfied
+error[E0277]: cannot multiply `()` to `{integer}`
   --> $DIR/binops.rs:14:7
    |
-14 |     3 * (); //~ ERROR is not satisfied
+14 |     3 * (); //~ ERROR cannot multiply `()` to `{integer}`
    |       ^ no implementation for `{integer} * ()`
    |
    = help: the trait `std::ops::Mul<()>` is not implemented for `{integer}`
 
-error[E0277]: the trait bound `{integer}: std::ops::Div<&str>` is not satisfied
+error[E0277]: cannot divide `{integer}` by `&str`
   --> $DIR/binops.rs:15:7
    |
-15 |     4 / ""; //~ ERROR is not satisfied
+15 |     4 / ""; //~ ERROR cannot divide `{integer}` by `&str`
    |       ^ no implementation for `{integer} / &str`
    |
    = help: the trait `std::ops::Div<&str>` is not implemented for `{integer}`
diff --git a/src/test/ui/on-unimplemented/auxiliary/no_debug.rs b/src/test/ui/on-unimplemented/auxiliary/no_debug.rs
new file mode 100644
index 00000000000..0f833c62637
--- /dev/null
+++ b/src/test/ui/on-unimplemented/auxiliary/no_debug.rs
@@ -0,0 +1,14 @@
+// Copyright 2018 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.
+// ignore-tidy-linelength
+
+#![crate_type = "lib"]
+
+pub struct Bar;
diff --git a/src/test/ui/on-unimplemented/no-debug.rs b/src/test/ui/on-unimplemented/no-debug.rs
new file mode 100644
index 00000000000..fff6122c6b3
--- /dev/null
+++ b/src/test/ui/on-unimplemented/no-debug.rs
@@ -0,0 +1,27 @@
+// Copyright 2018 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:no_debug.rs
+
+extern crate no_debug;
+
+use no_debug::Bar;
+
+struct Foo;
+
+fn main() {
+    println!("{:?} {:?}", Foo, Bar);
+    println!("{} {}", Foo, Bar);
+}
+//~^^^ ERROR `Foo` doesn't implement `std::fmt::Debug`
+//~| ERROR `no_debug::Bar` doesn't implement `std::fmt::Debug`
+//~^^^^ ERROR `Foo` doesn't implement `std::fmt::Display`
+//~| ERROR `no_debug::Bar` doesn't implement `std::fmt::Display`
+
diff --git a/src/test/ui/on-unimplemented/no-debug.stderr b/src/test/ui/on-unimplemented/no-debug.stderr
new file mode 100644
index 00000000000..af5b1e91211
--- /dev/null
+++ b/src/test/ui/on-unimplemented/no-debug.stderr
@@ -0,0 +1,38 @@
+error[E0277]: `Foo` doesn't implement `std::fmt::Debug`
+  --> $DIR/no-debug.rs:20:27
+   |
+20 |     println!("{:?} {:?}", Foo, Bar);
+   |                           ^^^ `Foo` cannot be formatted using `:?`; add `#[derive(Debug)]` or manually implement `std::fmt::Debug`
+   |
+   = help: the trait `std::fmt::Debug` is not implemented for `Foo`
+   = note: required by `std::fmt::Debug::fmt`
+
+error[E0277]: `no_debug::Bar` doesn't implement `std::fmt::Debug`
+  --> $DIR/no-debug.rs:20:32
+   |
+20 |     println!("{:?} {:?}", Foo, Bar);
+   |                                ^^^ `no_debug::Bar` cannot be formatted using `:?` because it doesn't implement `std::fmt::Debug`
+   |
+   = help: the trait `std::fmt::Debug` is not implemented for `no_debug::Bar`
+   = note: required by `std::fmt::Debug::fmt`
+
+error[E0277]: `Foo` doesn't implement `std::fmt::Display`
+  --> $DIR/no-debug.rs:21:23
+   |
+21 |     println!("{} {}", Foo, Bar);
+   |                       ^^^ `Foo` cannot be formatted with the default formatter; try using `:?` instead if you are using a format string
+   |
+   = help: the trait `std::fmt::Display` is not implemented for `Foo`
+   = note: required by `std::fmt::Display::fmt`
+
+error[E0277]: `no_debug::Bar` doesn't implement `std::fmt::Display`
+  --> $DIR/no-debug.rs:21:28
+   |
+21 |     println!("{} {}", Foo, Bar);
+   |                            ^^^ `no_debug::Bar` cannot be formatted with the default formatter; try using `:?` instead if you are using a format string
+   |
+   = help: the trait `std::fmt::Display` is not implemented for `no_debug::Bar`
+   = note: required by `std::fmt::Display::fmt`
+
+error: aborting due to 4 previous errors
+
diff --git a/src/test/ui/span/multiline-span-simple.rs b/src/test/ui/span/multiline-span-simple.rs
index f8e4cbcbf19..dd09534480e 100644
--- a/src/test/ui/span/multiline-span-simple.rs
+++ b/src/test/ui/span/multiline-span-simple.rs
@@ -20,7 +20,7 @@ fn main() {
     let x = 1;
     let y = 2;
     let z = 3;
-    foo(1 as u32 + //~ ERROR not satisfied
+    foo(1 as u32 + //~ ERROR cannot add `()` to `u32`
 
         bar(x,
 
diff --git a/src/test/ui/span/multiline-span-simple.stderr b/src/test/ui/span/multiline-span-simple.stderr
index b068798630e..a18dfeb31d9 100644
--- a/src/test/ui/span/multiline-span-simple.stderr
+++ b/src/test/ui/span/multiline-span-simple.stderr
@@ -1,7 +1,7 @@
-error[E0277]: the trait bound `u32: std::ops::Add<()>` is not satisfied
+error[E0277]: cannot add `()` to `u32`
   --> $DIR/multiline-span-simple.rs:23:18
    |
-23 |     foo(1 as u32 + //~ ERROR not satisfied
+23 |     foo(1 as u32 + //~ ERROR cannot add `()` to `u32`
    |                  ^ no implementation for `u32 + ()`
    |
    = help: the trait `std::ops::Add<()>` is not implemented for `u32`
diff --git a/src/test/ui/suggestions/for-c-in-str.stderr b/src/test/ui/suggestions/for-c-in-str.stderr
index 7a6dc9a5040..88a7b1b49d6 100644
--- a/src/test/ui/suggestions/for-c-in-str.stderr
+++ b/src/test/ui/suggestions/for-c-in-str.stderr
@@ -2,7 +2,7 @@ error[E0277]: the trait bound `&str: std::iter::Iterator` is not satisfied
   --> $DIR/for-c-in-str.rs:14:14
    |
 14 |     for c in "asdf" {
-   |              ^^^^^^ `&str` is not an iterator; maybe try calling `.iter()` or a similar method
+   |              ^^^^^^ `&str` is not an iterator; try calling `.chars()` or `.bytes()`
    |
    = help: the trait `std::iter::Iterator` is not implemented for `&str`
    = note: required by `std::iter::IntoIterator::into_iter`