Modify primary span label for E0308

compiler/rustc_hir_analysis/src/check/check.rs

@@ -442,6 +442,7 @@ fn check_opaque_meets_bounds<'tcx>(
     match ocx.eq(&misc_cause, param_env, opaque_ty, hidden_ty) {
         Ok(()) => {}
         Err(ty_err) => {
+            let ty_err = ty_err.to_string(tcx);
             tcx.sess.delay_span_bug(
                 span,
                 &format!("could not unify `{hidden_ty}` with revealed type:\n{ty_err}"),

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -259,7 +259,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let mode = no_match_data.mode;
         let tcx = self.tcx;
         let rcvr_ty = self.resolve_vars_if_possible(rcvr_ty);
-        let ty_str = with_forced_trimmed_paths!(self.ty_to_string(rcvr_ty));
+        let (ty_str, ty_file) = tcx.short_ty_string(rcvr_ty);
+        let short_ty_str = with_forced_trimmed_paths!(rcvr_ty.to_string());
         let is_method = mode == Mode::MethodCall;
         let unsatisfied_predicates = &no_match_data.unsatisfied_predicates;
         let similar_candidate = no_match_data.similar_candidate;
@@ -276,11 +277,24 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
         };
 
-        if self.suggest_wrapping_range_with_parens(tcx, rcvr_ty, source, span, item_name, &ty_str)
-            || self.suggest_constraining_numerical_ty(
-                tcx, rcvr_ty, source, span, item_kind, item_name, &ty_str,
-            )
-        {
+        // We could pass the file for long types into these two, but it isn't strictly necessary
+        // given how targetted they are.
+        if self.suggest_wrapping_range_with_parens(
+            tcx,
+            rcvr_ty,
+            source,
+            span,
+            item_name,
+            &short_ty_str,
+        ) || self.suggest_constraining_numerical_ty(
+            tcx,
+            rcvr_ty,
+            source,
+            span,
+            item_kind,
+            item_name,
+            &short_ty_str,
+        ) {
             return None;
         }
         span = item_name.span;
@@ -319,6 +333,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             rcvr_ty.prefix_string(self.tcx),
             ty_str_reported,
         );
+        let ty_str = if short_ty_str.len() < ty_str.len() && ty_str.len() > 10 {
+            short_ty_str
+        } else {
+            ty_str
+        };
+        if let Some(file) = ty_file {
+            err.note(&format!("the full type name has been written to '{}'", file.display(),));
+        }
         if rcvr_ty.references_error() {
             err.downgrade_to_delayed_bug();
         }
@@ -826,7 +848,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 let primary_message = primary_message.unwrap_or_else(|| {
                     format!(
                         "the {item_kind} `{item_name}` exists for {actual_prefix} `{ty_str}`, \
-                    but its trait bounds were not satisfied"
+                         but its trait bounds were not satisfied"
                     )
                 });
                 err.set_primary_message(&primary_message);

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -67,6 +67,7 @@ use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::Node;
 use rustc_middle::dep_graph::DepContext;
+use rustc_middle::ty::print::with_forced_trimmed_paths;
 use rustc_middle::ty::relate::{self, RelateResult, TypeRelation};
 use rustc_middle::ty::{
     self, error::TypeError, List, Region, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable,
@@ -1612,16 +1613,31 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 {
                     format!("expected this to be `{}`", expected)
                 } else {
-                    terr.to_string()
+                    terr.to_string(self.tcx).to_string()
                 };
                 label_or_note(sp, &terr);
                 label_or_note(span, &msg);
             } else {
-                label_or_note(span, &terr.to_string());
+                label_or_note(span, &terr.to_string(self.tcx));
                 label_or_note(sp, &msg);
             }
         } else {
-            label_or_note(span, &terr.to_string());
+            if let Some(values) = values
+                && let Some((e, f)) = values.ty()
+                && let TypeError::ArgumentSorts(..) | TypeError::Sorts(_) = terr
+            {
+                let e = self.tcx.erase_regions(e);
+                let f = self.tcx.erase_regions(f);
+                let expected = with_forced_trimmed_paths!(e.sort_string(self.tcx));
+                let found = with_forced_trimmed_paths!(f.sort_string(self.tcx));
+                if expected == found {
+                    label_or_note(span, &terr.to_string(self.tcx));
+                } else {
+                    label_or_note(span, &format!("expected {expected}, found {found}"));
+                }
+            } else {
+                label_or_note(span, &terr.to_string(self.tcx));
+            }
         }
 
         if let Some((expected, found, exp_p, found_p)) = expected_found {
@@ -1849,6 +1865,18 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         self.check_and_note_conflicting_crates(diag, terr);
 
         self.note_and_explain_type_err(diag, terr, cause, span, cause.body_id.to_def_id());
+        if let Some(exp_found) = exp_found
+            && let exp_found = TypeError::Sorts(exp_found)
+            && exp_found != terr
+        {
+            self.note_and_explain_type_err(
+                diag,
+                exp_found,
+                cause,
+                span,
+                cause.body_id.to_def_id(),
+            );
+        }
 
         if let Some(ValuePairs::PolyTraitRefs(exp_found)) = values
             && let ty::Closure(def_id, _) = exp_found.expected.skip_binder().self_ty().kind()

compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs

@@ -137,25 +137,25 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                             diag.help(
                                 "given a type parameter `T` and a method `foo`:
 ```
-trait Trait<T> { fn foo(&tcx) -> T; }
+trait Trait<T> { fn foo(&self) -> T; }
 ```
 the only ways to implement method `foo` are:
 - constrain `T` with an explicit type:
 ```
 impl Trait<String> for X {
-    fn foo(&tcx) -> String { String::new() }
+    fn foo(&self) -> String { String::new() }
 }
 ```
 - add a trait bound to `T` and call a method on that trait that returns `Self`:
 ```
 impl<T: std::default::Default> Trait<T> for X {
-    fn foo(&tcx) -> T { <T as std::default::Default>::default() }
+    fn foo(&self) -> T { <T as std::default::Default>::default() }
 }
 ```
 - change `foo` to return an argument of type `T`:
 ```
 impl<T> Trait<T> for X {
-    fn foo(&tcx, x: T) -> T { x }
+    fn foo(&self, x: T) -> T { x }
 }
 ```",
                             );
@@ -218,6 +218,13 @@ impl<T> Trait<T> for X {
                             );
                         }
                     }
+                    (ty::FnPtr(_), ty::FnDef(def, _))
+                    if let hir::def::DefKind::Fn = tcx.def_kind(def) => {
+                        diag.note(
+                            "when the arguments and return types match, functions can be coerced \
+                             to function pointers",
+                        );
+                    }
                     _ => {}
                 }
                 debug!(
@@ -389,14 +396,14 @@ impl<T> Trait<T> for X {
 ```
 trait Trait {
 type T;
-fn foo(&tcx) -> Self::T;
+fn foo(&self) -> Self::T;
 }
 ```
 the only way of implementing method `foo` is to constrain `T` with an explicit associated type:
 ```
 impl Trait for X {
 type T = String;
-fn foo(&tcx) -> Self::T { String::new() }
+fn foo(&self) -> Self::T { String::new() }
 }
 ```",
             );

compiler/rustc_infer/src/infer/error_reporting/suggest.rs

@@ -404,7 +404,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                         (msg, sug)
                     }
                 };
-                diag.span_suggestion(span, msg, sug, Applicability::MaybeIncorrect);
+                diag.span_suggestion_verbose(span, msg, sug, Applicability::MaybeIncorrect);
             }
             (ty::FnDef(did1, substs1), ty::FnDef(did2, substs2)) => {
                 let expected_sig =