Fix associated bound suggestion span issue

Author: chenyukang

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

@@ -105,7 +105,13 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                         if !sp.contains(p_span) {
                             diag.span_label(p_span, format!("{expected}this type parameter"));
                         }
-                        let parent = p_def_id.as_local().and_then(|id| {
+                        let param_def_id = match *proj.self_ty().kind() {
+                            ty::Param(param) => {
+                                tcx.generics_of(body_owner_def_id).type_param(param, tcx).def_id
+                            }
+                            _ => p_def_id,
+                        };
+                        let parent = param_def_id.as_local().and_then(|id| {
                             let local_id = tcx.local_def_id_to_hir_id(id);
                             let generics = tcx.parent_hir_node(local_id).generics()?;
                             Some((id, generics))

tests/ui/trait-bounds/associated-error-bound-issue-145586.fixed

@@ -0,0 +1,38 @@
+//@ run-rustfix
+
+#![allow(dead_code)]
+
+use std::marker::PhantomData;
+
+trait Visitor<'de> {
+    type Value;
+}
+
+trait Deserializer<'de> {
+    type Error;
+
+    fn deserialize_ignored_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>;
+}
+
+struct Wrapper<'de, T, E>(Result<T, E>, PhantomData<&'de ()>);
+
+impl<'de, T, E> Deserializer<'de> for Wrapper<'de, T, E>
+where
+    T: Deserializer<'de, Error = E>,
+{
+    type Error = E;
+
+    fn deserialize_ignored_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>,
+    {
+        match self.0 {
+            Ok(deserializer) => deserializer.deserialize_ignored_any(visitor), //~ ERROR mismatched types
+            Err(error) => Err(error),
+        }
+    }
+}
+
+fn main() {}

tests/ui/trait-bounds/associated-error-bound-issue-145586.rs

@@ -0,0 +1,38 @@
+//@ run-rustfix
+
+#![allow(dead_code)]
+
+use std::marker::PhantomData;
+
+trait Visitor<'de> {
+    type Value;
+}
+
+trait Deserializer<'de> {
+    type Error;
+
+    fn deserialize_ignored_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>;
+}
+
+struct Wrapper<'de, T, E>(Result<T, E>, PhantomData<&'de ()>);
+
+impl<'de, T, E> Deserializer<'de> for Wrapper<'de, T, E>
+where
+    T: Deserializer<'de>,
+{
+    type Error = E;
+
+    fn deserialize_ignored_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>,
+    {
+        match self.0 {
+            Ok(deserializer) => deserializer.deserialize_ignored_any(visitor), //~ ERROR mismatched types
+            Err(error) => Err(error),
+        }
+    }
+}
+
+fn main() {}

tests/ui/trait-bounds/associated-error-bound-issue-145586.stderr

@@ -0,0 +1,22 @@
+error[E0308]: mismatched types
+  --> $DIR/associated-error-bound-issue-145586.rs:32:33
+   |
+LL | impl<'de, T, E> Deserializer<'de> for Wrapper<'de, T, E>
+   |              - expected this type parameter
+...
+LL |     fn deserialize_ignored_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+   |                                                        ----------------------------- expected `Result<<V as Visitor<'de>>::Value, E>` because of return type
+...
+LL |             Ok(deserializer) => deserializer.deserialize_ignored_any(visitor),
+   |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `Result<<V as Visitor<'_>>::Value, E>`, found `Result<<V as Visitor<'_>>::Value, ...>`
+   |
+   = note: expected enum `Result<_, E>`
+              found enum `Result<_, <T as Deserializer<'de>>::Error>`
+help: consider further restricting this bound
+   |
+LL |     T: Deserializer<'de, Error = E>,
+   |                        +++++++++++
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.