move ExplicitSelf to rustc::ty::util, and use it to implement object safety checks

Author: mikeyhew

src/librustc/traits/object_safety.rs

@@ -23,6 +23,7 @@ use hir::def_id::DefId;
 use traits;
 use ty::{self, Ty, TyCtxt, TypeFoldable};
 use ty::subst::Substs;
+use ty::util::ExplicitSelf;
 use std::borrow::Cow;
 use syntax::ast;
 
@@ -57,6 +58,8 @@ impl ObjectSafetyViolation {
                          in its arguments or return type", name).into(),
             ObjectSafetyViolation::Method(name, MethodViolationCode::Generic) =>
                 format!("method `{}` has generic type parameters", name).into(),
+            ObjectSafetyViolation::Method(name, MethodViolationCode::NonStandardSelfType) =>
+                format!("method `{}` has a non-standard `self` type. Only `&self`, `&mut self`, and `Box<Self>` are currently supported for trait objects", name).into(),
             ObjectSafetyViolation::AssociatedConst(name) =>
                 format!("the trait cannot contain associated consts like `{}`", name).into(),
         }
@@ -74,6 +77,9 @@ pub enum MethodViolationCode {
 
     /// e.g., `fn foo<A>()`
     Generic,
+
+    /// arbitrary `self` type, e.g. `self: Rc<Self>`
+    NonStandardSelfType,
 }
 
 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
@@ -260,9 +266,16 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             return Some(MethodViolationCode::StaticMethod);
         }
 
+        let sig = self.fn_sig(method.def_id);
+
+        let self_ty = self.mk_self_type();
+        let self_arg_ty = sig.skip_binder().inputs()[0];
+        if let ExplicitSelf::Other = ExplicitSelf::determine(self_arg_ty, |ty| ty == self_ty) {
+            return Some(MethodViolationCode::NonStandardSelfType);
+        }
+
         // The `Self` type is erased, so it should not appear in list of
         // arguments or return type apart from the receiver.
-        let ref sig = self.fn_sig(method.def_id);
         for input_ty in &sig.skip_binder().inputs()[1..] {
             if self.contains_illegal_self_type_reference(trait_def_id, input_ty) {
                 return Some(MethodViolationCode::ReferencesSelf);

src/librustc/ty/util.rs

@@ -12,6 +12,7 @@
 
 use hir::def_id::{DefId, LOCAL_CRATE};
 use hir::map::DefPathData;
+use hir;
 use ich::NodeIdHashingMode;
 use middle::const_val::ConstVal;
 use traits::{self, Reveal};
@@ -1178,6 +1179,56 @@ fn layout_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     layout
 }
 
+pub enum ExplicitSelf<'tcx> {
+    ByValue,
+    ByReference(ty::Region<'tcx>, hir::Mutability),
+    ByBox,
+    Other
+}
+
+impl<'tcx> ExplicitSelf<'tcx> {
+    /// Categorizes an explicit self declaration like `self: SomeType`
+    /// into either `self`, `&self`, `&mut self`, `Box<self>`, or
+    /// `Other`.
+    /// This is mainly used to require the arbitrary_self_types feature
+    /// in the case of `Other`, to improve error messages in the common cases,
+    /// and to make `Other` non-object-safe.
+    ///
+    /// Examples:
+    ///
+    /// ```
+    /// impl<'a> Foo for &'a T {
+    ///     // Legal declarations:
+    ///     fn method1(self: &&'a T); // ExplicitSelf::ByReference
+    ///     fn method2(self: &'a T); // ExplicitSelf::ByValue
+    ///     fn method3(self: Box<&'a T>); // ExplicitSelf::ByBox
+    ///     fn method4(self: Rc<&'a T>); // ExplicitSelf::Other
+    ///
+    ///     // Invalid cases will be caught by `check_method_receiver`:
+    ///     fn method_err1(self: &'a mut T); // ExplicitSelf::Other
+    ///     fn method_err2(self: &'static T) // ExplicitSelf::ByValue
+    ///     fn method_err3(self: &&T) // ExplicitSelf::ByReference
+    /// }
+    /// ```
+    ///
+    pub fn determine<P>(
+        self_arg_ty: Ty<'tcx>,
+        is_self_ty: P
+    ) -> ExplicitSelf<'tcx>
+    where
+        P: Fn(Ty<'tcx>) -> bool
+    {
+        use self::ExplicitSelf::*;
+
+        match self_arg_ty.sty {
+            _ if is_self_ty(self_arg_ty) => ByValue,
+            ty::TyRef(region, ty::TypeAndMut { ty, mutbl}) if is_self_ty(ty) => ByReference(region, mutbl),
+            ty::TyAdt(def, _) if def.is_box() && is_self_ty(self_arg_ty.boxed_ty()) => ByBox,
+            _ => Other
+        }
+    }
+}
+
 pub fn provide(providers: &mut ty::maps::Providers) {
     *providers = ty::maps::Providers {
         is_copy_raw,

src/librustc_typeck/astconv.rs

@@ -1403,53 +1403,3 @@ impl<'a, 'gcx, 'tcx> Bounds<'tcx> {
         vec
     }
 }
-
-pub enum ExplicitSelf<'tcx> {
-    ByValue,
-    ByReference(ty::Region<'tcx>, hir::Mutability),
-    ByBox,
-    Other
-}
-
-impl<'tcx> ExplicitSelf<'tcx> {
-    /// Categorizes an explicit self declaration like `self: SomeType`
-    /// into either `self`, `&self`, `&mut self`, `Box<self>`, or
-    /// `Other`.
-    /// This is mainly used to require the arbitrary_self_types feature
-    /// in the case of `Other`, to improve error messages in the common cases,
-    /// and to make `Other` non-object-safe.
-    ///
-    /// Examples:
-    ///
-    /// ```
-    /// impl<'a> Foo for &'a T {
-    ///     // Legal declarations:
-    ///     fn method1(self: &&'a T); // ExplicitSelf::ByReference
-    ///     fn method2(self: &'a T); // ExplicitSelf::ByValue
-    ///     fn method3(self: Box<&'a T>); // ExplicitSelf::ByBox
-    ///     fn method4(self: Rc<&'a T>); // ExplicitSelf::Other
-    ///
-    ///     // Invalid cases will be caught by `check_method_receiver`:
-    ///     fn method_err1(self: &'a mut T); // ExplicitSelf::Other
-    ///     fn method_err2(self: &'static T) // ExplicitSelf::ByValue
-    ///     fn method_err3(self: &&T) // ExplicitSelf::ByReference
-    /// }
-    /// ```
-    ///
-    pub fn determine<'a, 'gcx, P>(
-        self_arg_ty: Ty<'tcx>,
-        is_self_ty: P
-    ) -> ExplicitSelf<'tcx>
-    where
-        P: Fn(Ty<'tcx>) -> bool
-    {
-        use self::ExplicitSelf::*;
-
-        match self_arg_ty.sty {
-            _ if is_self_ty(self_arg_ty) => ByValue,
-            ty::TyRef(region, ty::TypeAndMut { ty, mutbl}) if is_self_ty(ty) => ByReference(region, mutbl),
-            ty::TyAdt(def, _) if def.is_box() && is_self_ty(self_arg_ty.boxed_ty()) => ByBox,
-            _ => Other
-        }
-    }
-}

src/librustc_typeck/check/compare_method.rs

@@ -13,6 +13,7 @@ use rustc::infer::{self, InferOk};
 use rustc::middle::free_region::FreeRegionMap;
 use rustc::middle::region;
 use rustc::ty::{self, TyCtxt};
+use rustc::ty::util::ExplicitSelf;
 use rustc::traits::{self, ObligationCause, ObligationCauseCode, Reveal};
 use rustc::ty::error::{ExpectedFound, TypeError};
 use rustc::ty::subst::{Subst, Substs};
@@ -21,7 +22,6 @@ use rustc::util::common::ErrorReported;
 use syntax_pos::Span;
 
 use super::{Inherited, FnCtxt};
-use astconv::ExplicitSelf;
 
 /// Checks that a method from an impl conforms to the signature of
 /// the same method as declared in the trait.

src/librustc_typeck/check/wfcheck.rs

@@ -8,14 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use astconv::ExplicitSelf;
 use check::{Inherited, FnCtxt};
 use constrained_type_params::{identify_constrained_type_params, Parameter};
 
 use hir::def_id::DefId;
 use rustc::infer::InferOk;
 use rustc::traits::{self, ObligationCauseCode};
 use rustc::ty::{self, Ty, TyCtxt};
+use rustc::ty::util::ExplicitSelf;
 use rustc::util::nodemap::{FxHashSet, FxHashMap};
 use rustc::middle::lang_items;
 

src/test/compile-fail/arbitrary-self-types-not-object-safe.rs

@@ -30,7 +30,10 @@ impl Bar for usize {
 fn make_foo() {
     let x = Box::new(5usize) as Box<Foo>;
     //~^ ERROR E0038
-    //~| NOTE the method `foo` has an arbitrary self type
+    //~| NOTE method `foo` has a non-standard `self` type
+    //~| NOTE the trait `Foo` cannot be made into an object
+    //~| ERROR E0038
+    //~| NOTE method `foo` has a non-standard `self` type
     //~| NOTE the trait `Foo` cannot be made into an object
 }