Account sized bounds in parentheses printing inside of ptr/ref of rpit.

crates/hir_def/src/type_ref.rs

@@ -307,7 +307,9 @@ impl TypeBound {
                     Some(_) => TraitBoundModifier::Maybe,
                     None => TraitBoundModifier::None,
                 };
-                lower_path_type(path_type).map(|p| TypeBound::Path(p, m)).unwrap_or(TypeBound::Error)
+                lower_path_type(path_type)
+                    .map(|p| TypeBound::Path(p, m))
+                    .unwrap_or(TypeBound::Error)
             }
             ast::TypeBoundKind::ForType(for_type) => {
                 let lt_refs = match for_type.generic_param_list() {

crates/hir_ty/src/display.rs

@@ -377,10 +377,20 @@ impl HirDisplay for Ty {
                 }
 
                 // FIXME: all this just to decide whether to use parentheses...
-                let datas;
-                let predicates: Vec<_> = match t.kind(&Interner) {
+                let conains_impl_fn = |bounds: &[QuantifiedWhereClause]| {
+                    bounds.iter().any(|bound| {
+                        if let WhereClause::Implemented(trait_ref) = bound.skip_binders() {
+                            let trait_ = trait_ref.hir_trait_id();
+                            fn_traits(f.db.upcast(), trait_).any(|it| it == trait_)
+                        } else {
+                            false
+                        }
+                    })
+                };
+                let (preds_to_print, has_impl_fn_pred) = match t.kind(&Interner) {
                     TyKind::Dyn(dyn_ty) if dyn_ty.bounds.skip_binders().interned().len() > 1 => {
-                        dyn_ty.bounds.skip_binders().interned().iter().cloned().collect()
+                        let bounds = dyn_ty.bounds.skip_binders().interned();
+                        (bounds.len(), conains_impl_fn(bounds))
                     }
                     TyKind::Alias(AliasTy::Opaque(OpaqueTy {
                         opaque_ty_id,
@@ -390,33 +400,54 @@ impl HirDisplay for Ty {
                         let impl_trait_id =
                             f.db.lookup_intern_impl_trait_id((*opaque_ty_id).into());
                         if let ImplTraitId::ReturnTypeImplTrait(func, idx) = impl_trait_id {
-                            datas =
+                            let datas =
                                 f.db.return_type_impl_traits(func)
                                     .expect("impl trait id without data");
                             let data = (*datas)
                                 .as_ref()
                                 .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
                             let bounds = data.substitute(&Interner, parameters);
-                            bounds.into_value_and_skipped_binders().0
+                            let mut len = bounds.skip_binders().len();
+
+                            // Don't count Sized but count when it absent
+                            // (i.e. when explicit ?Sized bound is set).
+                            let default_sized = SizedByDefault::Sized {
+                                anchor: func.lookup(f.db.upcast()).module(f.db.upcast()).krate(),
+                            };
+                            let sized_bounds = bounds
+                                .skip_binders()
+                                .iter()
+                                .filter(|b| {
+                                    matches!(
+                                        b.skip_binders(),
+                                        WhereClause::Implemented(trait_ref)
+                                            if default_sized.is_sized_trait(
+                                                trait_ref.hir_trait_id(),
+                                                f.db.upcast(),
+                                            ),
+                                    )
+                                })
+                                .count();
+                            match sized_bounds {
+                                0 => len += 1,
+                                _ => {
+                                    len = len.saturating_sub(sized_bounds);
+                                }
+                            }
+
+                            (len, conains_impl_fn(bounds.skip_binders()))
                         } else {
-                            Vec::new()
+                            (0, false)
                         }
                     }
-                    _ => Vec::new(),
+                    _ => (0, false),
                 };
 
-                if let Some(WhereClause::Implemented(trait_ref)) =
-                    predicates.get(0).map(|b| b.skip_binders())
-                {
-                    let trait_ = trait_ref.hir_trait_id();
-                    if fn_traits(f.db.upcast(), trait_).any(|it| it == trait_)
-                        && predicates.len() <= 2
-                    {
-                        return t.hir_fmt(f);
-                    }
+                if has_impl_fn_pred && preds_to_print <= 2 {
+                    return t.hir_fmt(f);
                 }
 
-                if predicates.len() > 1 {
+                if preds_to_print > 1 {
                     write!(f, "(")?;
                     t.hir_fmt(f)?;
                     write!(f, ")")?;
@@ -1085,7 +1116,6 @@ impl HirDisplay for TypeBound {
     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
         match self {
             TypeBound::Path(path, modifier) => {
-                // todo don't print implicit Sized; implicit ?Sized on Self of a trait
                 match modifier {
                     TraitBoundModifier::None => (),
                     TraitBoundModifier::Maybe => write!(f, "?")?,

crates/hir_ty/src/lower.rs

@@ -828,7 +828,9 @@ impl<'a> TyLoweringContext<'a> {
         trait_ref: TraitRef,
     ) -> impl Iterator<Item = QuantifiedWhereClause> + 'a {
         let last_segment = match bound {
-            TypeBound::Path(path, TraitBoundModifier::None) | TypeBound::ForLifetime(_, path) => path.segments().last(),
+            TypeBound::Path(path, TraitBoundModifier::None) | TypeBound::ForLifetime(_, path) => {
+                path.segments().last()
+            }
             TypeBound::Path(_, TraitBoundModifier::Maybe)
             | TypeBound::Error
             | TypeBound::Lifetime(_) => None,

crates/hir_ty/src/tests/display_source_code.rs

@@ -42,16 +42,15 @@ fn main() {
 
 #[test]
 fn render_raw_ptr_impl_ty() {
-    // FIXME: remove parens, they apper because there is an implicit Sized bound
     check_types_source_code(
         r#"
 //- minicore: sized
 trait Unpin {}
-fn foo() -> *const impl Unpin { loop {} }
+fn foo() -> *const (impl Unpin + Sized) { loop {} }
 fn main() {
     let foo = foo();
     foo;
-} //^^^ *const (impl Unpin)
+} //^^^ *const impl Unpin
 "#,
     );
 }
@@ -94,9 +93,9 @@ fn test(
     d;
   //^ S<impl Foo>
     ref_any;
-  //^ &impl ?Sized
+  //^^^^^^^ &impl ?Sized
     empty;
-} //^ impl Sized
+} //^^^^^ impl Sized
 "#,
     );
 }
@@ -107,11 +106,50 @@ fn sized_bounds_rpit() {
         r#"
 //- minicore: sized
 trait Foo {}
-fn foo() -> impl Foo { loop {} }
-fn test<T: Foo>() {
-    let foo = foo();
+fn foo1() -> impl Foo { loop {} }
+fn foo2() -> impl Foo + Sized { loop {} }
+fn foo3() -> impl Foo + ?Sized { loop {} }
+fn test() {
+    let foo = foo1();
     foo;
-}   //^ impl Foo
+  //^^^ impl Foo
+    let foo = foo2();
+    foo;
+  //^^^ impl Foo
+    let foo = foo3();
+    foo;
+} //^^^ impl Foo + ?Sized
+"#,
+    );
+}
+
+#[test]
+fn parenthesize_ptr_rpit_sized_bounds() {
+    check_types_source_code(
+        r#"
+//- minicore: sized
+trait Foo {}
+fn foo1() -> *const impl Foo { loop {} }
+fn foo2() -> *const (impl Foo + Sized) { loop {} }
+fn foo3() -> *const (impl Sized + Foo) { loop {} }
+fn foo4() -> *const (impl Foo + ?Sized) { loop {} }
+fn foo5() -> *const (impl ?Sized + Foo) { loop {} }
+fn test() {
+    let foo = foo1();
+    foo;
+  //^^^ *const impl Foo
+    let foo = foo2();
+    foo;
+  //^^^ *const impl Foo
+    let foo = foo3();
+    foo;
+  //^^^ *const impl Foo
+    let foo = foo4();
+    foo;
+  //^^^ *const (impl Foo + ?Sized)
+    let foo = foo5();
+    foo;
+} //^^^ *const (impl Foo + ?Sized)
 "#,
     );
 }

crates/hir_ty/src/tests/regression.rs

@@ -944,7 +944,7 @@ fn lifetime_from_chalk_during_deref() {
         r#"
 //- minicore: deref
 struct Box<T: ?Sized> {}
-impl<T> core::ops::Deref for Box<T> {
+impl<T: ?Sized> core::ops::Deref for Box<T> {
     type Target = T;
 
     fn deref(&self) -> &Self::Target {
@@ -1063,6 +1063,7 @@ fn cfg_tail() {
 fn impl_trait_in_option_9530() {
     check_types(
         r#"
+//- minicore: sized
 struct Option<T>;
 impl<T> Option<T> {
     fn unwrap(self) -> T { loop {} }

crates/hir_ty/src/tests/traits.rs

@@ -3534,9 +3534,7 @@ fn test() {
 fn associated_type_sized_bounds() {
     check_infer(
         r#"
-#[lang = "sized"]
-pub trait Sized {}
-
+//- minicore: sized
 struct Yes;
 trait IsSized { const IS_SIZED: Yes; }
 impl<T: Sized> IsSized for T { const IS_SIZED: Yes = Yes; }
@@ -3553,11 +3551,11 @@ fn f<F: Foo>() {
 }
 "#,
         expect![[r#"
-            142..145 'Yes': Yes
-            250..333 '{     ...ZED; }': ()
-            256..277 'F::Exp..._SIZED': Yes
-            283..304 'F::Imp..._SIZED': Yes
-            310..330 'F::Rel..._SIZED': {unknown}
+            104..107 'Yes': Yes
+            212..295 '{     ...ZED; }': ()
+            218..239 'F::Exp..._SIZED': Yes
+            245..266 'F::Imp..._SIZED': Yes
+            272..292 'F::Rel..._SIZED': {unknown}
         "#]],
     );
 }

crates/ide/src/inlay_hints.rs

@@ -932,6 +932,50 @@ fn main() {
         )
     }
 
+    #[test]
+    fn fn_hints_ptr_rpit_fn_parentheses() {
+        check_types(
+            r#"
+//- minicore: fn, sized
+trait Trait {}
+
+fn foo1() -> *const impl Fn() { loop {} }
+fn foo2() -> *const (impl Fn() + Sized) { loop {} }
+fn foo3() -> *const (impl Fn() + ?Sized) { loop {} }
+fn foo4() -> *const (impl Sized + Fn()) { loop {} }
+fn foo5() -> *const (impl ?Sized + Fn()) { loop {} }
+fn foo6() -> *const (impl Fn() + Trait) { loop {} }
+fn foo7() -> *const (impl Fn() + Sized + Trait) { loop {} }
+fn foo8() -> *const (impl Fn() + ?Sized + Trait) { loop {} }
+fn foo9() -> *const (impl Fn() -> u8 + ?Sized) { loop {} }
+fn foo10() -> *const (impl Fn() + Sized + ?Sized) { loop {} }
+
+fn main() {
+    let foo = foo1();
+    //  ^^^ *const impl Fn()
+    let foo = foo2();
+    //  ^^^ *const impl Fn()
+    let foo = foo3();
+    //  ^^^ *const (impl Fn() + ?Sized)
+    let foo = foo4();
+    //  ^^^ *const impl Fn()
+    let foo = foo5();
+    //  ^^^ *const (impl Fn() + ?Sized)
+    let foo = foo6();
+    //  ^^^ *const (impl Fn() + Trait)
+    let foo = foo7();
+    //  ^^^ *const (impl Fn() + Trait)
+    let foo = foo8();
+    //  ^^^ *const (impl Fn() + Trait + ?Sized)
+    let foo = foo9();
+    //  ^^^ *const (impl Fn() -> u8 + ?Sized)
+    let foo = foo10();
+    //  ^^^ *const impl Fn()
+}
+"#,
+        )
+    }
+
     #[test]
     fn unit_structs_have_no_type_hints() {
         check_types(