Auto merge of #15891 - Veykril:orphan-impls, r=Veykril

feat: Diagnose some orphan trait impl cases

crates/hir-def/src/body/pretty.rs

@@ -54,7 +54,7 @@ pub(super) fn print_body_hir(db: &dyn DefDatabase, body: &Body, owner: DefWithBo
     let mut p = Printer { db, body, buf: header, indent_level: 0, needs_indent: false };
     if let DefWithBodyId::FunctionId(it) = owner {
         p.buf.push('(');
-        body.params.iter().zip(&db.function_data(it).params).for_each(|(&param, ty)| {
+        body.params.iter().zip(db.function_data(it).params.iter()).for_each(|(&param, ty)| {
             p.print_pat(param);
             p.buf.push(':');
             p.print_type_ref(ty);

crates/hir-def/src/data.rs

@@ -34,7 +34,7 @@ use crate::{
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct FunctionData {
     pub name: Name,
-    pub params: Vec<Interned<TypeRef>>,
+    pub params: Box<[Interned<TypeRef>]>,
     pub ret_type: Interned<TypeRef>,
     pub attrs: Attrs,
     pub visibility: RawVisibility,
@@ -177,7 +177,7 @@ pub struct TypeAliasData {
     pub rustc_has_incoherent_inherent_impls: bool,
     pub rustc_allow_incoherent_impl: bool,
     /// Bounds restricting the type alias itself (eg. `type Ty: Bound;` in a trait or impl).
-    pub bounds: Vec<Interned<TypeBound>>,
+    pub bounds: Box<[Interned<TypeBound>]>,
 }
 
 impl TypeAliasData {
@@ -210,7 +210,7 @@ impl TypeAliasData {
             is_extern: matches!(loc.container, ItemContainerId::ExternBlockId(_)),
             rustc_has_incoherent_inherent_impls,
             rustc_allow_incoherent_impl,
-            bounds: typ.bounds.to_vec(),
+            bounds: typ.bounds.clone(),
         })
     }
 }

crates/hir-def/src/generics.rs

@@ -227,7 +227,7 @@ impl GenericParams {
                 let mut expander = Lazy::new(|| {
                     (module.def_map(db), Expander::new(db, loc.source(db).file_id, module))
                 });
-                for param in &func_data.params {
+                for param in func_data.params.iter() {
                     generic_params.fill_implicit_impl_trait_args(db, &mut expander, param);
                 }
 

crates/hir-def/src/item_tree/lower.rs

@@ -396,14 +396,7 @@ impl<'a> Ctx<'a> {
         let bounds = self.lower_type_bounds(type_alias);
         let generic_params = self.lower_generic_params(HasImplicitSelf::No, type_alias);
         let ast_id = self.source_ast_id_map.ast_id(type_alias);
-        let res = TypeAlias {
+        let res = TypeAlias { name, visibility, bounds, generic_params, type_ref, ast_id };
-            name,
-            visibility,
-            bounds: bounds.into_boxed_slice(),
-            generic_params,
-            type_ref,
-            ast_id,
-        };
         Some(id(self.data().type_aliases.alloc(res)))
     }
 
@@ -637,13 +630,13 @@ impl<'a> Ctx<'a> {
         Interned::new(generics)
     }
 
-    fn lower_type_bounds(&mut self, node: &dyn ast::HasTypeBounds) -> Vec<Interned<TypeBound>> {
+    fn lower_type_bounds(&mut self, node: &dyn ast::HasTypeBounds) -> Box<[Interned<TypeBound>]> {
         match node.type_bound_list() {
             Some(bound_list) => bound_list
                 .bounds()
                 .map(|it| Interned::new(TypeBound::from_ast(&self.body_ctx, it)))
                 .collect(),
-            None => Vec::new(),
+            None => Box::default(),
         }
     }
 

crates/hir-ty/src/db.rs

@@ -20,8 +20,8 @@ use crate::{
     method_resolution::{InherentImpls, TraitImpls, TyFingerprint},
     mir::{BorrowckResult, MirBody, MirLowerError},
     Binders, CallableDefId, ClosureId, Const, FnDefId, GenericArg, ImplTraitId, InferenceResult,
-    Interner, PolyFnSig, QuantifiedWhereClause, ReturnTypeImplTraits, Substitution, TraitRef, Ty,
+    Interner, PolyFnSig, QuantifiedWhereClause, ReturnTypeImplTraits, Substitution,
-    TyDefId, ValueTyDefId,
+    TraitEnvironment, TraitRef, Ty, TyDefId, ValueTyDefId,
 };
 use hir_expand::name::Name;
 
@@ -47,7 +47,7 @@ pub trait HirDatabase: DefDatabase + Upcast<dyn DefDatabase> {
         &self,
         def: DefWithBodyId,
         subst: Substitution,
-        env: Arc<crate::TraitEnvironment>,
+        env: Arc<TraitEnvironment>,
     ) -> Result<Arc<MirBody>, MirLowerError>;
 
     #[salsa::invoke(crate::mir::monomorphized_mir_body_for_closure_query)]
@@ -55,7 +55,7 @@ pub trait HirDatabase: DefDatabase + Upcast<dyn DefDatabase> {
         &self,
         def: ClosureId,
         subst: Substitution,
-        env: Arc<crate::TraitEnvironment>,
+        env: Arc<TraitEnvironment>,
     ) -> Result<Arc<MirBody>, MirLowerError>;
 
     #[salsa::invoke(crate::mir::borrowck_query)]
@@ -81,7 +81,7 @@ pub trait HirDatabase: DefDatabase + Upcast<dyn DefDatabase> {
         &self,
         def: GeneralConstId,
         subst: Substitution,
-        trait_env: Option<Arc<crate::TraitEnvironment>>,
+        trait_env: Option<Arc<TraitEnvironment>>,
     ) -> Result<Const, ConstEvalError>;
 
     #[salsa::invoke(crate::consteval::const_eval_static_query)]
@@ -104,16 +104,12 @@ pub trait HirDatabase: DefDatabase + Upcast<dyn DefDatabase> {
         &self,
         def: AdtId,
         subst: Substitution,
-        env: Arc<crate::TraitEnvironment>,
+        env: Arc<TraitEnvironment>,
     ) -> Result<Arc<Layout>, LayoutError>;
 
     #[salsa::invoke(crate::layout::layout_of_ty_query)]
     #[salsa::cycle(crate::layout::layout_of_ty_recover)]
-    fn layout_of_ty(
+    fn layout_of_ty(&self, ty: Ty, env: Arc<TraitEnvironment>) -> Result<Arc<Layout>, LayoutError>;
-        &self,
-        ty: Ty,
-        env: Arc<crate::TraitEnvironment>,
-    ) -> Result<Arc<Layout>, LayoutError>;
 
     #[salsa::invoke(crate::layout::target_data_layout_query)]
     fn target_data_layout(&self, krate: CrateId) -> Option<Arc<TargetDataLayout>>;
@@ -121,7 +117,7 @@ pub trait HirDatabase: DefDatabase + Upcast<dyn DefDatabase> {
     #[salsa::invoke(crate::method_resolution::lookup_impl_method_query)]
     fn lookup_impl_method(
         &self,
-        env: Arc<crate::TraitEnvironment>,
+        env: Arc<TraitEnvironment>,
         func: FunctionId,
         fn_subst: Substitution,
     ) -> (FunctionId, Substitution);
@@ -149,10 +145,10 @@ pub trait HirDatabase: DefDatabase + Upcast<dyn DefDatabase> {
 
     #[salsa::invoke(crate::lower::trait_environment_for_body_query)]
     #[salsa::transparent]
-    fn trait_environment_for_body(&self, def: DefWithBodyId) -> Arc<crate::TraitEnvironment>;
+    fn trait_environment_for_body(&self, def: DefWithBodyId) -> Arc<TraitEnvironment>;
 
     #[salsa::invoke(crate::lower::trait_environment_query)]
-    fn trait_environment(&self, def: GenericDefId) -> Arc<crate::TraitEnvironment>;
+    fn trait_environment(&self, def: GenericDefId) -> Arc<TraitEnvironment>;
 
     #[salsa::invoke(crate::lower::generic_defaults_query)]
     #[salsa::cycle(crate::lower::generic_defaults_recover)]
@@ -249,7 +245,7 @@ pub trait HirDatabase: DefDatabase + Upcast<dyn DefDatabase> {
     fn normalize_projection(
         &self,
         projection: crate::ProjectionTy,
-        env: Arc<crate::TraitEnvironment>,
+        env: Arc<TraitEnvironment>,
     ) -> Ty;
 
     #[salsa::invoke(trait_solve_wait)]

crates/hir-ty/src/diagnostics.rs

@@ -11,9 +11,3 @@ pub use crate::diagnostics::{
     },
     unsafe_check::{missing_unsafe, unsafe_expressions, UnsafeExpr},
 };
-
-#[derive(Debug, PartialEq, Eq)]
-pub struct IncoherentImpl {
-    pub file_id: hir_expand::HirFileId,
-    pub impl_: syntax::AstPtr<syntax::ast::Impl>,
-}

crates/hir-ty/src/layout.rs

@@ -1,5 +1,7 @@
 //! Compute the binary representation of a type
 
+use std::fmt;
+
 use chalk_ir::{AdtId, FloatTy, IntTy, TyKind, UintTy};
 use hir_def::{
     layout::{
@@ -26,12 +28,6 @@ pub use self::{
     target::target_data_layout_query,
 };
 
-macro_rules! user_error {
-    ($it: expr) => {
-        return Err(LayoutError::UserError(format!($it).into()))
-    };
-}
-
 mod adt;
 mod target;
 
@@ -73,13 +69,38 @@ pub type Variants = hir_def::layout::Variants<RustcFieldIdx, RustcEnumVariantIdx
 
 #[derive(Debug, PartialEq, Eq, Clone)]
 pub enum LayoutError {
-    UserError(Box<str>),
+    HasErrorConst,
+    HasErrorType,
+    HasPlaceholder,
+    InvalidSimdType,
+    NotImplemented,
+    RecursiveTypeWithoutIndirection,
     SizeOverflow,
     TargetLayoutNotAvailable,
-    HasPlaceholder,
-    HasErrorType,
-    NotImplemented,
     Unknown,
+    UserReprTooSmall,
+}
+
+impl std::error::Error for LayoutError {}
+impl fmt::Display for LayoutError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            LayoutError::HasErrorConst => write!(f, "type contains an unevaluatable const"),
+            LayoutError::HasErrorType => write!(f, "type contains an error"),
+            LayoutError::HasPlaceholder => write!(f, "type contains placeholders"),
+            LayoutError::InvalidSimdType => write!(f, "invalid simd type definition"),
+            LayoutError::NotImplemented => write!(f, "not implemented"),
+            LayoutError::RecursiveTypeWithoutIndirection => {
+                write!(f, "recursive type without indirection")
+            }
+            LayoutError::SizeOverflow => write!(f, "size overflow"),
+            LayoutError::TargetLayoutNotAvailable => write!(f, "target layout not available"),
+            LayoutError::Unknown => write!(f, "unknown"),
+            LayoutError::UserReprTooSmall => {
+                write!(f, "the `#[repr]` hint is too small to hold the discriminants of the enum")
+            }
+        }
+    }
 }
 
 struct LayoutCx<'a> {
@@ -118,9 +139,7 @@ fn layout_of_simd_ty(
 
     let f0_ty = match fields.iter().next() {
         Some(it) => it.1.clone().substitute(Interner, subst),
-        None => {
+        None => return Err(LayoutError::InvalidSimdType),
-            user_error!("simd type with zero fields");
-        }
     };
 
     // The element type and number of elements of the SIMD vector
@@ -134,7 +153,7 @@ fn layout_of_simd_ty(
         // Extract the number of elements from the layout of the array field:
         let FieldsShape::Array { count, .. } = db.layout_of_ty(f0_ty.clone(), env.clone())?.fields
         else {
-            user_error!("Array with non array layout");
+            return Err(LayoutError::Unknown);
         };
 
         (e_ty.clone(), count, true)
@@ -146,7 +165,7 @@ fn layout_of_simd_ty(
     // Compute the ABI of the element type:
     let e_ly = db.layout_of_ty(e_ty, env.clone())?;
     let Abi::Scalar(e_abi) = e_ly.abi else {
-        user_error!("simd type with inner non scalar type");
+        return Err(LayoutError::Unknown);
     };
 
     // Compute the size and alignment of the vector:
@@ -259,9 +278,7 @@ pub fn layout_of_ty_query(
             cx.univariant(dl, &fields, &ReprOptions::default(), kind).ok_or(LayoutError::Unknown)?
         }
         TyKind::Array(element, count) => {
-            let count = try_const_usize(db, &count).ok_or(LayoutError::UserError(Box::from(
+            let count = try_const_usize(db, &count).ok_or(LayoutError::HasErrorConst)? as u64;
-                "unevaluated or mistyped const generic parameter",
-            )))? as u64;
             let element = db.layout_of_ty(element.clone(), trait_env.clone())?;
             let size = element.size.checked_mul(count, dl).ok_or(LayoutError::SizeOverflow)?;
 
@@ -352,7 +369,7 @@ pub fn layout_of_ty_query(
             let mut unit = layout_of_unit(&cx, dl)?;
             match unit.abi {
                 Abi::Aggregate { ref mut sized } => *sized = false,
-                _ => user_error!("bug"),
+                _ => return Err(LayoutError::Unknown),
             }
             unit
         }
@@ -418,7 +435,7 @@ pub fn layout_of_ty_recover(
     _: &Ty,
     _: &Arc<TraitEnvironment>,
 ) -> Result<Arc<Layout>, LayoutError> {
-    user_error!("infinite sized recursive type");
+    Err(LayoutError::RecursiveTypeWithoutIndirection)
 }
 
 fn layout_of_unit(cx: &LayoutCx<'_>, dl: &TargetDataLayout) -> Result<Layout, LayoutError> {

crates/hir-ty/src/layout/adt.rs

@@ -145,7 +145,7 @@ pub fn layout_of_adt_recover(
     _: &Substitution,
     _: &Arc<TraitEnvironment>,
 ) -> Result<Arc<Layout>, LayoutError> {
-    user_error!("infinite sized recursive type");
+    Err(LayoutError::RecursiveTypeWithoutIndirection)
 }
 
 /// Finds the appropriate Integer type and signedness for the given
@@ -169,11 +169,7 @@ fn repr_discr(
         let discr = Integer::from_attr(dl, ity);
         let fit = if ity.is_signed() { signed_fit } else { unsigned_fit };
         if discr < fit {
-            return Err(LayoutError::UserError(
+            return Err(LayoutError::UserReprTooSmall);
-                "Integer::repr_discr: `#[repr]` hint too small for \
-                      discriminant range of enum "
-                    .into(),
-            ));
         }
         return Ok((discr, ity.is_signed()));
     }

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

@@ -210,16 +210,13 @@ fn recursive() {
         struct BoxLike<T: ?Sized>(*mut T);
         struct Goal(BoxLike<Goal>);
     }
-    check_fail(
+    check_fail(r#"struct Goal(Goal);"#, LayoutError::RecursiveTypeWithoutIndirection);
-        r#"struct Goal(Goal);"#,
-        LayoutError::UserError("infinite sized recursive type".into()),
-    );
     check_fail(
         r#"
         struct Foo<T>(Foo<T>);
         struct Goal(Foo<i32>);
         "#,
-        LayoutError::UserError("infinite sized recursive type".into()),
+        LayoutError::RecursiveTypeWithoutIndirection,
     );
 }
 

crates/hir-ty/src/lib.rs

@@ -80,6 +80,7 @@ pub use mapping::{
     lt_from_placeholder_idx, to_assoc_type_id, to_chalk_trait_id, to_foreign_def_id,
     to_placeholder_idx,
 };
+pub use method_resolution::check_orphan_rules;
 pub use traits::TraitEnvironment;
 pub use utils::{all_super_traits, is_fn_unsafe_to_call};
 

crates/hir-ty/src/lower.rs

@@ -1383,51 +1383,50 @@ pub(crate) fn generic_predicates_for_param_query(
     let ctx = TyLoweringContext::new(db, &resolver, def.into())
         .with_type_param_mode(ParamLoweringMode::Variable);
     let generics = generics(db.upcast(), def);
+
+    // we have to filter out all other predicates *first*, before attempting to lower them
+    let predicate = |pred: &&_| match pred {
+        WherePredicate::ForLifetime { target, bound, .. }
+        | WherePredicate::TypeBound { target, bound, .. } => {
+            let invalid_target = match target {
+                WherePredicateTypeTarget::TypeRef(type_ref) => {
+                    ctx.lower_ty_only_param(type_ref) != Some(param_id)
+                }
+                &WherePredicateTypeTarget::TypeOrConstParam(local_id) => {
+                    let target_id = TypeOrConstParamId { parent: def, local_id };
+                    target_id != param_id
+                }
+            };
+            if invalid_target {
+                return false;
+            }
+
+            match &**bound {
+                TypeBound::ForLifetime(_, path) | TypeBound::Path(path, _) => {
+                    // Only lower the bound if the trait could possibly define the associated
+                    // type we're looking for.
+
+                    let Some(assoc_name) = &assoc_name else { return true };
+                    let Some(TypeNs::TraitId(tr)) =
+                        resolver.resolve_path_in_type_ns_fully(db.upcast(), path)
+                    else {
+                        return false;
+                    };
+
+                    all_super_traits(db.upcast(), tr).iter().any(|tr| {
+                        db.trait_data(*tr).items.iter().any(|(name, item)| {
+                            matches!(item, AssocItemId::TypeAliasId(_)) && name == assoc_name
+                        })
+                    })
+                }
+                TypeBound::Lifetime(_) | TypeBound::Error => false,
+            }
+        }
+        WherePredicate::Lifetime { .. } => false,
+    };
     let mut predicates: Vec<_> = resolver
         .where_predicates_in_scope()
-        // we have to filter out all other predicates *first*, before attempting to lower them
+        .filter(predicate)
-        .filter(|pred| match pred {
-            WherePredicate::ForLifetime { target, bound, .. }
-            | WherePredicate::TypeBound { target, bound, .. } => {
-                match target {
-                    WherePredicateTypeTarget::TypeRef(type_ref) => {
-                        if ctx.lower_ty_only_param(type_ref) != Some(param_id) {
-                            return false;
-                        }
-                    }
-                    &WherePredicateTypeTarget::TypeOrConstParam(local_id) => {
-                        let target_id = TypeOrConstParamId { parent: def, local_id };
-                        if target_id != param_id {
-                            return false;
-                        }
-                    }
-                };
-
-                match &**bound {
-                    TypeBound::ForLifetime(_, path) | TypeBound::Path(path, _) => {
-                        // Only lower the bound if the trait could possibly define the associated
-                        // type we're looking for.
-
-                        let assoc_name = match &assoc_name {
-                            Some(it) => it,
-                            None => return true,
-                        };
-                        let tr = match resolver.resolve_path_in_type_ns_fully(db.upcast(), path) {
-                            Some(TypeNs::TraitId(tr)) => tr,
-                            _ => return false,
-                        };
-
-                        all_super_traits(db.upcast(), tr).iter().any(|tr| {
-                            db.trait_data(*tr).items.iter().any(|(name, item)| {
-                                matches!(item, AssocItemId::TypeAliasId(_)) && name == assoc_name
-                            })
-                        })
-                    }
-                    TypeBound::Lifetime(_) | TypeBound::Error => false,
-                }
-            }
-            WherePredicate::Lifetime { .. } => false,
-        })
         .flat_map(|pred| {
             ctx.lower_where_predicate(pred, true).map(|p| make_binders(db, &generics, p))
         })
@@ -1519,7 +1518,12 @@ pub(crate) fn trait_environment_query(
 
     let env = chalk_ir::Environment::new(Interner).add_clauses(Interner, clauses);
 
-    Arc::new(TraitEnvironment { krate, block: None, traits_from_clauses: traits_in_scope, env })
+    Arc::new(TraitEnvironment {
+        krate,
+        block: None,
+        traits_from_clauses: traits_in_scope.into_boxed_slice(),
+        env,
+    })
 }
 
 /// Resolve the where clause(s) of an item with generics.

crates/hir-ty/src/method_resolution.rs

@@ -862,6 +862,62 @@ fn is_inherent_impl_coherent(
     }
 }
 
+/// Checks whether the impl satisfies the orphan rules.
+///
+/// Given `impl<P1..=Pn> Trait<T1..=Tn> for T0`, an `impl`` is valid only if at least one of the following is true:
+/// - Trait is a local trait
+/// - All of
+///   - At least one of the types `T0..=Tn`` must be a local type. Let `Ti`` be the first such type.
+///   - No uncovered type parameters `P1..=Pn` may appear in `T0..Ti`` (excluding `Ti`)
+pub fn check_orphan_rules(db: &dyn HirDatabase, impl_: ImplId) -> bool {
+    let substs = TyBuilder::placeholder_subst(db, impl_);
+    let Some(impl_trait) = db.impl_trait(impl_) else {
+        // not a trait impl
+        return true;
+    };
+
+    let local_crate = impl_.lookup(db.upcast()).container.krate();
+    let is_local = |tgt_crate| tgt_crate == local_crate;
+
+    let trait_ref = impl_trait.substitute(Interner, &substs);
+    let trait_id = from_chalk_trait_id(trait_ref.trait_id);
+    if is_local(trait_id.module(db.upcast()).krate()) {
+        // trait to be implemented is local
+        return true;
+    }
+
+    let unwrap_fundamental = |ty: Ty| match ty.kind(Interner) {
+        TyKind::Ref(_, _, referenced) => referenced.clone(),
+        &TyKind::Adt(AdtId(hir_def::AdtId::StructId(s)), ref subs) => {
+            let struct_data = db.struct_data(s);
+            if struct_data.flags.contains(StructFlags::IS_FUNDAMENTAL) {
+                let next = subs.type_parameters(Interner).next();
+                match next {
+                    Some(ty) => ty,
+                    None => ty,
+                }
+            } else {
+                ty
+            }
+        }
+        _ => ty,
+    };
+    //   - At least one of the types `T0..=Tn`` must be a local type. Let `Ti`` be the first such type.
+    let is_not_orphan = trait_ref.substitution.type_parameters(Interner).any(|ty| {
+        match unwrap_fundamental(ty).kind(Interner) {
+            &TyKind::Adt(AdtId(id), _) => is_local(id.module(db.upcast()).krate()),
+            TyKind::Error => true,
+            TyKind::Dyn(it) => it.principal().map_or(false, |trait_ref| {
+                is_local(from_chalk_trait_id(trait_ref.trait_id).module(db.upcast()).krate())
+            }),
+            _ => false,
+        }
+    });
+    // FIXME: param coverage
+    //   - No uncovered type parameters `P1..=Pn` may appear in `T0..Ti`` (excluding `Ti`)
+    is_not_orphan
+}
+
 pub fn iterate_path_candidates(
     ty: &Canonical<Ty>,
     db: &dyn HirDatabase,

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

@@ -4439,42 +4439,42 @@ fn test(v: S<i32>) {
 fn associated_type_in_argument() {
     check(
         r#"
-    trait A {
+trait A {
-        fn m(&self) -> i32;
+    fn m(&self) -> i32;
-    }
+}
 
-    fn x<T: B>(k: &<T as B>::Ty) {
+fn x<T: B>(k: &<T as B>::Ty) {
-        k.m();
+    k.m();
-    }
+}
 
-    struct X;
+struct X;
-    struct Y;
+struct Y;
 
-    impl A for X {
+impl A for X {
-        fn m(&self) -> i32 {
+    fn m(&self) -> i32 {
-            8
+        8
-        }
     }
+}
 
-    impl A for Y {
+impl A for Y {
-        fn m(&self) -> i32 {
+    fn m(&self) -> i32 {
-            32
+        32
-        }
     }
+}
 
-    trait B {
+trait B {
-        type Ty: A;
+    type Ty: A;
-    }
+}
 
-    impl B for u16 {
+impl B for u16 {
-        type Ty = X;
+    type Ty = X;
-    }
+}
 
-    fn ttt() {
+fn ttt() {
-        let inp = Y;
+    let inp = Y;
-        x::<u16>(&inp);
+    x::<u16>(&inp);
-               //^^^^ expected &X, got &Y
+           //^^^^ expected &X, got &Y
-    }
+}
-    "#,
+"#,
     );
 }

crates/hir-ty/src/traits.rs

@@ -48,7 +48,7 @@ pub struct TraitEnvironment {
     pub krate: CrateId,
     pub block: Option<BlockId>,
     // FIXME make this a BTreeMap
-    pub(crate) traits_from_clauses: Vec<(Ty, TraitId)>,
+    pub(crate) traits_from_clauses: Box<[(Ty, TraitId)]>,
     pub env: chalk_ir::Environment<Interner>,
 }
 
@@ -57,7 +57,7 @@ impl TraitEnvironment {
         TraitEnvironment {
             krate,
             block: None,
-            traits_from_clauses: Vec::new(),
+            traits_from_clauses: Box::default(),
             env: chalk_ir::Environment::new(Interner),
         }
     }

crates/hir/src/diagnostics.rs

@@ -3,7 +3,7 @@
 //!
 //! This probably isn't the best way to do this -- ideally, diagnostics should
 //! be expressed in terms of hir types themselves.
-pub use hir_ty::diagnostics::{CaseType, IncoherentImpl, IncorrectCase};
+pub use hir_ty::diagnostics::{CaseType, IncorrectCase};
 
 use base_db::CrateId;
 use cfg::{CfgExpr, CfgOptions};
@@ -38,6 +38,7 @@ diagnostics![
     IncorrectCase,
     InvalidDeriveTarget,
     IncoherentImpl,
+    TraitImplOrphan,
     MacroDefError,
     MacroError,
     MacroExpansionParseError,
@@ -280,3 +281,15 @@ pub struct MovedOutOfRef {
     pub ty: Type,
     pub span: InFile<SyntaxNodePtr>,
 }
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct IncoherentImpl {
+    pub file_id: HirFileId,
+    pub impl_: AstPtr<ast::Impl>,
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct TraitImplOrphan {
+    pub file_id: HirFileId,
+    pub impl_: AstPtr<ast::Impl>,
+}

crates/hir/src/display.rs

@@ -616,7 +616,7 @@ impl HirDisplay for TypeAlias {
         write_where_clause(def_id, f)?;
         if !data.bounds.is_empty() {
             f.write_str(": ")?;
-            f.write_joined(&data.bounds, " + ")?;
+            f.write_joined(data.bounds.iter(), " + ")?;
         }
         if let Some(ty) = &data.type_ref {
             f.write_str(" = ")?;

crates/hir/src/lib.rs

@@ -60,7 +60,7 @@ use hir_def::{
 };
 use hir_expand::{name::name, MacroCallKind};
 use hir_ty::{
-    all_super_traits, autoderef,
+    all_super_traits, autoderef, check_orphan_rules,
     consteval::{try_const_usize, unknown_const_as_generic, ConstEvalError, ConstExt},
     diagnostics::BodyValidationDiagnostic,
     known_const_to_ast,
@@ -95,7 +95,7 @@ pub use crate::{
         MacroExpansionParseError, MalformedDerive, MismatchedArgCount,
         MismatchedTupleStructPatArgCount, MissingFields, MissingMatchArms, MissingUnsafe,
         MovedOutOfRef, NeedMut, NoSuchField, PrivateAssocItem, PrivateField,
-        ReplaceFilterMapNextWithFindMap, TypeMismatch, TypedHole, UndeclaredLabel,
+        ReplaceFilterMapNextWithFindMap, TraitImplOrphan, TypeMismatch, TypedHole, UndeclaredLabel,
         UnimplementedBuiltinMacro, UnreachableLabel, UnresolvedExternCrate, UnresolvedField,
         UnresolvedImport, UnresolvedMacroCall, UnresolvedMethodCall, UnresolvedModule,
         UnresolvedProcMacro, UnusedMut, UnusedVariable,
@@ -624,6 +624,11 @@ impl Module {
                 acc.push(IncoherentImpl { impl_: ast_id_map.get(node.ast_id()), file_id }.into())
             }
 
+            if !impl_def.check_orphan_rules(db) {
+                let ast_id_map = db.ast_id_map(file_id);
+                acc.push(TraitImplOrphan { impl_: ast_id_map.get(node.ast_id()), file_id }.into())
+            }
+
             for item in impl_def.items(db) {
                 let def: DefWithBody = match item {
                     AssocItem::Function(it) => it.into(),
@@ -3398,6 +3403,10 @@ impl Impl {
         db.impl_data(self.id).is_negative
     }
 
+    pub fn is_unsafe(self, db: &dyn HirDatabase) -> bool {
+        db.impl_data(self.id).is_unique()
+    }
+
     pub fn module(self, db: &dyn HirDatabase) -> Module {
         self.id.lookup(db.upcast()).container.into()
     }
@@ -3406,6 +3415,10 @@ impl Impl {
         let src = self.source(db)?;
         src.file_id.as_builtin_derive_attr_node(db.upcast())
     }
+
+    pub fn check_orphan_rules(self, db: &dyn HirDatabase) -> bool {
+        check_orphan_rules(db, self.id)
+    }
 }
 
 #[derive(Clone, PartialEq, Eq, Debug, Hash)]

crates/ide-diagnostics/src/handlers/trait_impl_orphan.rs

@@ -0,0 +1,106 @@
+use hir::InFile;
+
+use crate::{Diagnostic, DiagnosticCode, DiagnosticsContext};
+
+// Diagnostic: trait-impl-orphan
+//
+// Only traits defined in the current crate can be implemented for arbitrary types
+pub(crate) fn trait_impl_orphan(
+    ctx: &DiagnosticsContext<'_>,
+    d: &hir::TraitImplOrphan,
+) -> Diagnostic {
+    Diagnostic::new_with_syntax_node_ptr(
+        ctx,
+        DiagnosticCode::RustcHardError("E0117"),
+        format!("only traits defined in the current crate can be implemented for arbitrary types"),
+        InFile::new(d.file_id, d.impl_.clone().into()),
+    )
+    // Not yet checked for false positives
+    .experimental()
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::check_diagnostics;
+
+    #[test]
+    fn simple() {
+        check_diagnostics(
+            r#"
+//- /foo.rs crate:foo
+pub trait Foo {}
+//- /bar.rs crate:bar
+pub struct Bar;
+//- /main.rs crate:main deps:foo,bar
+struct LocalType;
+trait LocalTrait {}
+  impl foo::Foo for bar::Bar {}
+//^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: only traits defined in the current crate can be implemented for arbitrary types
+impl foo::Foo for LocalType {}
+impl LocalTrait for bar::Bar {}
+"#,
+        );
+    }
+
+    #[test]
+    fn generics() {
+        check_diagnostics(
+            r#"
+//- /foo.rs crate:foo
+pub trait Foo<T> {}
+//- /bar.rs crate:bar
+pub struct Bar<T>(T);
+//- /main.rs crate:main deps:foo,bar
+struct LocalType<T>;
+trait LocalTrait<T> {}
+  impl<T> foo::Foo<T> for bar::Bar<T> {}
+//^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: only traits defined in the current crate can be implemented for arbitrary types
+
+  impl<T> foo::Foo<T> for bar::Bar<LocalType<T>> {}
+//^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: only traits defined in the current crate can be implemented for arbitrary types
+
+  impl<T> foo::Foo<LocalType<T>> for bar::Bar<T> {}
+
+  impl<T> foo::Foo<bar::Bar<LocalType<T>>> for bar::Bar<LocalType<T>> {}
+//^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: only traits defined in the current crate can be implemented for arbitrary types
+"#,
+        );
+    }
+
+    #[test]
+    fn fundamental() {
+        check_diagnostics(
+            r#"
+//- /foo.rs crate:foo
+pub trait Foo<T> {}
+//- /bar.rs crate:bar
+pub struct Bar<T>(T);
+#[lang = "owned_box"]
+#[fundamental]
+pub struct Box<T>(T);
+//- /main.rs crate:main deps:foo,bar
+struct LocalType;
+  impl<T> foo::Foo<T> for bar::Box<T> {}
+//^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: only traits defined in the current crate can be implemented for arbitrary types
+  impl<T> foo::Foo<T> for &LocalType {}
+  impl<T> foo::Foo<T> for bar::Box<LocalType> {}
+"#,
+        );
+    }
+
+    #[test]
+    fn dyn_object() {
+        check_diagnostics(
+            r#"
+//- /foo.rs crate:foo
+pub trait Foo<T> {}
+//- /bar.rs crate:bar
+pub struct Bar;
+//- /main.rs crate:main deps:foo,bar
+trait LocalTrait {}
+impl<T> foo::Foo<T> for dyn LocalTrait {}
+impl<T> foo::Foo<dyn LocalTrait> for Bar {}
+"#,
+        );
+    }
+}

crates/ide-diagnostics/src/lib.rs

@@ -44,6 +44,7 @@ mod handlers {
     pub(crate) mod private_assoc_item;
     pub(crate) mod private_field;
     pub(crate) mod replace_filter_map_next_with_find_map;
+    pub(crate) mod trait_impl_orphan;
     pub(crate) mod typed_hole;
     pub(crate) mod type_mismatch;
     pub(crate) mod unimplemented_builtin_macro;
@@ -358,6 +359,7 @@ pub fn diagnostics(
             AnyDiagnostic::PrivateAssocItem(d) => handlers::private_assoc_item::private_assoc_item(&ctx, &d),
             AnyDiagnostic::PrivateField(d) => handlers::private_field::private_field(&ctx, &d),
             AnyDiagnostic::ReplaceFilterMapNextWithFindMap(d) => handlers::replace_filter_map_next_with_find_map::replace_filter_map_next_with_find_map(&ctx, &d),
+            AnyDiagnostic::TraitImplOrphan(d) => handlers::trait_impl_orphan::trait_impl_orphan(&ctx, &d),
             AnyDiagnostic::TypedHole(d) => handlers::typed_hole::typed_hole(&ctx, &d),
             AnyDiagnostic::TypeMismatch(d) => handlers::type_mismatch::type_mismatch(&ctx, &d),
             AnyDiagnostic::UndeclaredLabel(d) => handlers::undeclared_label::undeclared_label(&ctx, &d),

crates/ide-diagnostics/src/tests.rs

@@ -5,7 +5,7 @@ use expect_test::Expect;
 use ide_db::{
     assists::AssistResolveStrategy,
     base_db::{fixture::WithFixture, SourceDatabaseExt},
-    RootDatabase,
+    LineIndexDatabase, RootDatabase,
 };
 use stdx::trim_indent;
 use test_utils::{assert_eq_text, extract_annotations, MiniCore};
@@ -103,6 +103,7 @@ pub(crate) fn check_diagnostics(ra_fixture: &str) {
 pub(crate) fn check_diagnostics_with_config(config: DiagnosticsConfig, ra_fixture: &str) {
     let (db, files) = RootDatabase::with_many_files(ra_fixture);
     for file_id in files {
+        let line_index = db.line_index(file_id);
         let diagnostics = super::diagnostics(&db, &config, &AssistResolveStrategy::All, file_id);
 
         let expected = extract_annotations(&db.file_text(file_id));
@@ -136,8 +137,16 @@ pub(crate) fn check_diagnostics_with_config(config: DiagnosticsConfig, ra_fixtur
             }
         }
         if expected != actual {
-            let fneg = expected.iter().filter(|x| !actual.contains(x)).collect::<Vec<_>>();
+            let fneg = expected
-            let fpos = actual.iter().filter(|x| !expected.contains(x)).collect::<Vec<_>>();
+                .iter()
+                .filter(|x| !actual.contains(x))
+                .map(|(range, s)| (line_index.line_col(range.start()), range, s))
+                .collect::<Vec<_>>();
+            let fpos = actual
+                .iter()
+                .filter(|x| !expected.contains(x))
+                .map(|(range, s)| (line_index.line_col(range.start()), range, s))
+                .collect::<Vec<_>>();
 
             panic!("Diagnostic test failed.\nFalse negatives: {fneg:?}\nFalse positives: {fpos:?}");
         }

crates/ide/src/inlay_hints.rs

@@ -563,6 +563,7 @@ mod tests {
     use hir::ClosureStyle;
     use itertools::Itertools;
     use test_utils::extract_annotations;
+    use text_edit::{TextRange, TextSize};
 
     use crate::inlay_hints::{AdjustmentHints, AdjustmentHintsMode};
     use crate::DiscriminantHints;
@@ -629,6 +630,22 @@ mod tests {
         expect.assert_debug_eq(&inlay_hints)
     }
 
+    #[track_caller]
+    pub(super) fn check_expect_clear_loc(
+        config: InlayHintsConfig,
+        ra_fixture: &str,
+        expect: Expect,
+    ) {
+        let (analysis, file_id) = fixture::file(ra_fixture);
+        let mut inlay_hints = analysis.inlay_hints(&config, file_id, None).unwrap();
+        inlay_hints.iter_mut().flat_map(|hint| &mut hint.label.parts).for_each(|hint| {
+            if let Some(loc) = &mut hint.linked_location {
+                loc.range = TextRange::empty(TextSize::from(0));
+            }
+        });
+        expect.assert_debug_eq(&inlay_hints)
+    }
+
     /// Computes inlay hints for the fixture, applies all the provided text edits and then runs
     /// expect test.
     #[track_caller]

crates/ide/src/inlay_hints/chaining.rs

@@ -78,7 +78,9 @@ mod tests {
     use expect_test::expect;
 
     use crate::{
-        inlay_hints::tests::{check_expect, check_with_config, DISABLED_CONFIG, TEST_CONFIG},
+        inlay_hints::tests::{
+            check_expect, check_expect_clear_loc, check_with_config, DISABLED_CONFIG, TEST_CONFIG,
+        },
         InlayHintsConfig,
     };
 
@@ -444,7 +446,7 @@ fn main() {
 
     #[test]
     fn shorten_iterator_chaining_hints() {
-        check_expect(
+        check_expect_clear_loc(
             InlayHintsConfig { chaining_hints: true, ..DISABLED_CONFIG },
             r#"
 //- minicore: iterators
@@ -484,7 +486,7 @@ fn main() {
                                         file_id: FileId(
                                             1,
                                         ),
-                                        range: 10752..10760,
+                                        range: 0..0,
                                     },
                                 ),
                                 tooltip: "",
@@ -497,7 +499,7 @@ fn main() {
                                         file_id: FileId(
                                             1,
                                         ),
-                                        range: 10784..10788,
+                                        range: 0..0,
                                     },
                                 ),
                                 tooltip: "",
@@ -522,7 +524,7 @@ fn main() {
                                         file_id: FileId(
                                             1,
                                         ),
-                                        range: 10752..10760,
+                                        range: 0..0,
                                     },
                                 ),
                                 tooltip: "",
@@ -535,7 +537,7 @@ fn main() {
                                         file_id: FileId(
                                             1,
                                         ),
-                                        range: 10784..10788,
+                                        range: 0..0,
                                     },
                                 ),
                                 tooltip: "",
@@ -560,7 +562,7 @@ fn main() {
                                         file_id: FileId(
                                             1,
                                         ),
-                                        range: 10752..10760,
+                                        range: 0..0,
                                     },
                                 ),
                                 tooltip: "",
@@ -573,7 +575,7 @@ fn main() {
                                         file_id: FileId(
                                             1,
                                         ),
-                                        range: 10784..10788,
+                                        range: 0..0,
                                     },
                                 ),
                                 tooltip: "",
@@ -598,7 +600,7 @@ fn main() {
                                         file_id: FileId(
                                             0,
                                         ),
-                                        range: 24..30,
+                                        range: 0..0,
                                     },
                                 ),
                                 tooltip: "",

crates/test-utils/src/minicore.rs

@@ -44,7 +44,7 @@
 //!     panic: fmt
 //!     phantom_data:
 //!     pin:
-//!     pointee:
+//!     pointee: copy, send, sync, ord, hash, unpin
 //!     range:
 //!     result:
 //!     send: sized
@@ -54,6 +54,7 @@
 //!     sync: sized
 //!     transmute:
 //!     try: infallible
+//!     unpin: sized
 //!     unsize: sized
 
 #![rustc_coherence_is_core]
@@ -89,6 +90,11 @@ pub mod marker {
     pub trait Unsize<T: ?Sized> {}
     // endregion:unsize
 
+    // region:unpin
+    #[lang = "unpin"]
+    pub auto trait Unpin {}
+    // endregion:unpin
+
     // region:copy
     #[lang = "copy"]
     pub trait Copy: Clone {}
@@ -387,9 +393,10 @@ pub mod ptr {
 
     // region:pointee
     #[lang = "pointee_trait"]
+    #[rustc_deny_explicit_impl(implement_via_object = false)]
     pub trait Pointee {
         #[lang = "metadata_type"]
-        type Metadata;
+        type Metadata: Copy + Send + Sync + Ord + Hash + Unpin;
     }
     // endregion:pointee
     // region:non_null