Merge #10817

10817: ide: hover omits unnamed where preds r=Veykril a=jhgg

fixes #10800

Co-authored-by: Jake Heinz <jh@discordapp.com>

crates/hir/src/display.rs

@@ -325,7 +325,21 @@ fn write_generic_params(def: GenericDefId, f: &mut HirFormatter) -> Result<(), H
 
 fn write_where_clause(def: GenericDefId, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
     let params = f.db.generic_params(def);
-    if params.where_predicates.is_empty() {
+
+    // unnamed type targets are displayed inline with the argument itself, e.g. `f: impl Y`.
+    let is_unnamed_type_target = |target: &WherePredicateTypeTarget| match target {
+        WherePredicateTypeTarget::TypeRef(_) => false,
+        WherePredicateTypeTarget::TypeParam(id) => params.types[*id].name.is_none(),
+    };
+
+    let has_displayable_predicate = params
+        .where_predicates
+        .iter()
+        .any(|pred| {
+            !matches!(pred, WherePredicate::TypeBound { target, .. } if is_unnamed_type_target(target))
+        });
+
+    if !has_displayable_predicate {
         return Ok(());
     }
 
@@ -348,6 +362,7 @@ fn write_where_clause(def: GenericDefId, f: &mut HirFormatter) -> Result<(), Hir
         };
 
         match pred {
+            WherePredicate::TypeBound { target, .. } if is_unnamed_type_target(target) => {}
             WherePredicate::TypeBound { target, bound } => {
                 if matches!(prev_pred, Some(WherePredicate::TypeBound { target: target_, .. }) if target_ == target)
                 {

crates/ide/src/hover/tests.rs

@@ -340,6 +340,48 @@ fn main() { m::f$0oo(); }
     );
 }
 
+#[test]
+fn hover_omits_unnamed_where_preds() {
+    check(
+        r#"
+pub fn foo(bar: impl T) { }
+
+fn main() { fo$0o(); }
+        "#,
+        expect![[r#"
+            *foo*
+
+            ```rust
+            test
+            ```
+
+            ```rust
+            pub fn foo(bar: impl T)
+            ```
+        "#]],
+    );
+    check(
+        r#"
+pub fn foo<V: AsRef<str>>(bar: impl T, baz: V) { }
+
+fn main() { fo$0o(); }
+        "#,
+        expect![[r#"
+            *foo*
+
+            ```rust
+            test
+            ```
+
+            ```rust
+            pub fn foo<V>(bar: impl T, baz: V)
+            where
+                V: AsRef<str>,
+            ```
+        "#]],
+    );
+}
+
 #[test]
 fn hover_shows_fn_signature_with_type_params() {
     check(