feat: Implement object safety and its hovering hint

crates/hir-ty/src/chalk_db.rs

@@ -381,9 +381,9 @@ impl chalk_solve::RustIrDatabase<Interner> for ChalkContext<'_> {
         TyKind::Error.intern(Interner)
     }
 
-    fn is_object_safe(&self, _trait_id: chalk_ir::TraitId<Interner>) -> bool {
-        // FIXME: implement actual object safety
-        true
+    fn is_object_safe(&self, trait_id: chalk_ir::TraitId<Interner>) -> bool {
+        let trait_ = from_chalk_trait_id(trait_id);
+        crate::object_safety::object_safety(self.db, trait_).is_none()
     }
 
     fn closure_kind(

crates/hir-ty/src/consteval/tests.rs

@@ -2007,7 +2007,7 @@ fn function_traits() {
     );
     check_number(
         r#"
-    //- minicore: coerce_unsized, fn
+    //- minicore: coerce_unsized, fn, dispatch_from_dyn
     fn add2(x: u8) -> u8 {
         x + 2
     }
@@ -2062,7 +2062,7 @@ fn function_traits() {
 fn dyn_trait() {
     check_number(
         r#"
-    //- minicore: coerce_unsized, index, slice
+    //- minicore: coerce_unsized, index, slice, dispatch_from_dyn
     trait Foo {
         fn foo(&self) -> u8 { 10 }
     }
@@ -2085,7 +2085,7 @@ fn dyn_trait() {
     );
     check_number(
         r#"
-    //- minicore: coerce_unsized, index, slice
+    //- minicore: coerce_unsized, index, slice, dispatch_from_dyn
     trait Foo {
         fn foo(&self) -> i32 { 10 }
     }
@@ -2109,7 +2109,7 @@ fn dyn_trait() {
     );
     check_number(
         r#"
-    //- minicore: coerce_unsized, index, slice
+    //- minicore: coerce_unsized, index, slice, dispatch_from_dyn
     trait A {
         fn x(&self) -> i32;
     }

crates/hir-ty/src/consteval/tests/intrinsics.rs

@@ -89,7 +89,7 @@ fn size_of_val() {
     );
     check_number(
         r#"
-        //- minicore: coerce_unsized, fmt, builtin_impls
+        //- minicore: coerce_unsized, fmt, builtin_impls, dispatch_from_dyn
         extern "rust-intrinsic" {
             pub fn size_of_val<T: ?Sized>(_: *const T) -> usize;
         }

crates/hir-ty/src/db.rs

@@ -11,7 +11,7 @@ use base_db::{
 use hir_def::{
     db::DefDatabase, hir::ExprId, layout::TargetDataLayout, AdtId, BlockId, CallableDefId,
     ConstParamId, DefWithBodyId, EnumVariantId, FunctionId, GeneralConstId, GenericDefId, ImplId,
-    LifetimeParamId, LocalFieldId, StaticId, TypeAliasId, TypeOrConstParamId, VariantId,
+    LifetimeParamId, LocalFieldId, StaticId, TraitId, TypeAliasId, TypeOrConstParamId, VariantId,
 };
 use la_arena::ArenaMap;
 use smallvec::SmallVec;
@@ -24,6 +24,7 @@ use crate::{
     lower::{GenericDefaults, GenericPredicates},
     method_resolution::{InherentImpls, TraitImpls, TyFingerprint},
     mir::{BorrowckResult, MirBody, MirLowerError},
+    object_safety::ObjectSafetyViolation,
     Binders, ClosureId, Const, FnDefId, ImplTraitId, ImplTraits, InferenceResult, Interner,
     PolyFnSig, Substitution, TraitEnvironment, TraitRef, Ty, TyDefId, ValueTyDefId,
 };
@@ -107,6 +108,9 @@ pub trait HirDatabase: DefDatabase + Upcast<dyn DefDatabase> {
     #[salsa::invoke(crate::layout::target_data_layout_query)]
     fn target_data_layout(&self, krate: CrateId) -> Result<Arc<TargetDataLayout>, Arc<str>>;
 
+    #[salsa::invoke(crate::object_safety::object_safety_of_trait_query)]
+    fn object_safety_of_trait(&self, trait_: TraitId) -> Option<ObjectSafetyViolation>;
+
     #[salsa::invoke(crate::lower::ty_query)]
     #[salsa::cycle(crate::lower::ty_recover)]
     fn ty(&self, def: TyDefId) -> Binders<Ty>;

crates/hir-ty/src/generics.rs

@@ -225,6 +225,23 @@ impl Generics {
     }
 }
 
+pub(crate) fn trait_self_param_idx(db: &dyn DefDatabase, def: GenericDefId) -> Option<usize> {
+    match def {
+        GenericDefId::TraitId(_) | GenericDefId::TraitAliasId(_) => {
+            let params = db.generic_params(def);
+            params.trait_self_param().map(|idx| idx.into_raw().into_u32() as usize)
+        }
+        GenericDefId::ImplId(_) => None,
+        _ => {
+            let parent_def = parent_generic_def(db, def)?;
+            let parent_params = db.generic_params(parent_def);
+            let parent_self_idx = parent_params.trait_self_param()?.into_raw().into_u32() as usize;
+            let self_params = db.generic_params(def);
+            Some(self_params.len() + parent_self_idx)
+        }
+    }
+}
+
 fn parent_generic_def(db: &dyn DefDatabase, def: GenericDefId) -> Option<GenericDefId> {
     let container = match def {
         GenericDefId::FunctionId(it) => it.lookup(db).container,

crates/hir-ty/src/lib.rs

@@ -40,6 +40,7 @@ pub mod lang_items;
 pub mod layout;
 pub mod method_resolution;
 pub mod mir;
+pub mod object_safety;
 pub mod primitive;
 pub mod traits;
 

crates/hir-ty/src/lower.rs

@@ -58,7 +58,7 @@ use crate::{
     },
     db::HirDatabase,
     error_lifetime,
-    generics::{generics, Generics},
+    generics::{generics, trait_self_param_idx, Generics},
     make_binders,
     mapping::{from_chalk_trait_id, lt_to_placeholder_idx, ToChalk},
     static_lifetime, to_assoc_type_id, to_chalk_trait_id, to_placeholder_idx,
@@ -1747,21 +1747,7 @@ fn implicitly_sized_clauses<'a, 'subst: 'a>(
         .lang_item(resolver.krate(), LangItem::Sized)
         .and_then(|lang_item| lang_item.as_trait().map(to_chalk_trait_id))?;
 
-    let get_trait_self_idx = |container: ItemContainerId| {
-        if matches!(container, ItemContainerId::TraitId(_)) {
-            let generics = generics(db.upcast(), def);
-            Some(generics.len_self())
-        } else {
-            None
-        }
-    };
-    let trait_self_idx = match def {
-        GenericDefId::TraitId(_) => Some(0),
-        GenericDefId::FunctionId(it) => get_trait_self_idx(it.lookup(db.upcast()).container),
-        GenericDefId::ConstId(it) => get_trait_self_idx(it.lookup(db.upcast()).container),
-        GenericDefId::TypeAliasId(it) => get_trait_self_idx(it.lookup(db.upcast()).container),
-        _ => None,
-    };
+    let trait_self_idx = trait_self_param_idx(db.upcast(), def);
 
     Some(
         substitution

crates/hir-ty/src/mir/eval/tests.rs

@@ -849,7 +849,7 @@ fn main() {
 fn regression_14966() {
     check_pass(
         r#"
-//- minicore: fn, copy, coerce_unsized
+//- minicore: fn, copy, coerce_unsized, dispatch_from_dyn
 trait A<T> {
     fn a(&self) {}
 }