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.

2 files changed, 53 insertions, 18 deletions

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)),
         }
     }
 }