Rollup of 4 pull requests

src/bootstrap/test.rs

@@ -528,7 +528,7 @@ impl Step for Clippy {
                 host,
                 "test",
                 "src/tools/clippy",
-                SourceType::Submodule,
+                SourceType::InTree,
                 &[],
             );
 

src/bootstrap/toolstate.rs

@@ -78,7 +78,6 @@ static STABLE_TOOLS: &[(&str, &str)] = &[
     ("edition-guide", "src/doc/edition-guide"),
     ("rls", "src/tools/rls"),
     ("rustfmt", "src/tools/rustfmt"),
-    ("clippy-driver", "src/tools/clippy"),
 ];
 
 // These tools are permitted to not build on the beta/stable channels.

src/libcore/cell.rs

@@ -1023,6 +1023,31 @@ impl<T: ?Sized> RefCell<T> {
     }
 }
 
+impl<T: Default> RefCell<T> {
+    /// Takes the wrapped value, leaving `Default::default()` in its place.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the value is currently borrowed.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(refcell_take)]
+    /// use std::cell::RefCell;
+    ///
+    /// let c = RefCell::new(5);
+    /// let five = c.take();
+    ///
+    /// assert_eq!(five, 5);
+    /// assert_eq!(c.into_inner(), 0);
+    /// ```
+    #[unstable(feature = "refcell_take", issue = "71395")]
+    pub fn take(&self) -> T {
+        self.replace(Default::default())
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 unsafe impl<T: ?Sized> Send for RefCell<T> where T: Send {}
 

src/librustc_mir/borrow_check/type_check/mod.rs

@@ -2290,36 +2290,54 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 right,
             ) => {
                 let ty_left = left.ty(body, tcx);
-                if let ty::RawPtr(_) | ty::FnPtr(_) = ty_left.kind {
-                    let ty_right = right.ty(body, tcx);
-                    let common_ty = self.infcx.next_ty_var(TypeVariableOrigin {
-                        kind: TypeVariableOriginKind::MiscVariable,
-                        span: body.source_info(location).span,
-                    });
-                    self.sub_types(
-                        common_ty,
-                        ty_left,
-                        location.to_locations(),
-                        ConstraintCategory::Boring,
-                    )
-                    .unwrap_or_else(|err| {
-                        bug!("Could not equate type variable with {:?}: {:?}", ty_left, err)
-                    });
-                    if let Err(terr) = self.sub_types(
-                        common_ty,
-                        ty_right,
-                        location.to_locations(),
-                        ConstraintCategory::Boring,
-                    ) {
-                        span_mirbug!(
-                            self,
-                            rvalue,
-                            "unexpected comparison types {:?} and {:?} yields {:?}",
+                match ty_left.kind {
+                    // Types with regions are comparable if they have a common super-type.
+                    ty::RawPtr(_) | ty::FnPtr(_) => {
+                        let ty_right = right.ty(body, tcx);
+                        let common_ty = self.infcx.next_ty_var(TypeVariableOrigin {
+                            kind: TypeVariableOriginKind::MiscVariable,
+                            span: body.source_info(location).span,
+                        });
+                        self.relate_types(
+                            common_ty,
+                            ty::Variance::Contravariant,
                             ty_left,
-                            ty_right,
-                            terr
+                            location.to_locations(),
+                            ConstraintCategory::Boring,
                         )
+                        .unwrap_or_else(|err| {
+                            bug!("Could not equate type variable with {:?}: {:?}", ty_left, err)
+                        });
+                        if let Err(terr) = self.relate_types(
+                            common_ty,
+                            ty::Variance::Contravariant,
+                            ty_right,
+                            location.to_locations(),
+                            ConstraintCategory::Boring,
+                        ) {
+                            span_mirbug!(
+                                self,
+                                rvalue,
+                                "unexpected comparison types {:?} and {:?} yields {:?}",
+                                ty_left,
+                                ty_right,
+                                terr
+                            )
+                        }
                     }
+                    // For types with no regions we can just check that the
+                    // both operands have the same type.
+                    ty::Int(_) | ty::Uint(_) | ty::Bool | ty::Char | ty::Float(_)
+                        if ty_left == right.ty(body, tcx) => {}
+                    // Other types are compared by trait methods, not by
+                    // `Rvalue::BinaryOp`.
+                    _ => span_mirbug!(
+                        self,
+                        rvalue,
+                        "unexpected comparison types {:?} and {:?}",
+                        ty_left,
+                        right.ty(body, tcx)
+                    ),
                 }
             }
 

src/librustc_typeck/check/coercion.rs

@@ -74,7 +74,7 @@ use rustc_trait_selection::traits::{self, ObligationCause, ObligationCauseCode};
 use smallvec::{smallvec, SmallVec};
 use std::ops::Deref;
 
-pub struct Coerce<'a, 'tcx> {
+struct Coerce<'a, 'tcx> {
     fcx: &'a FnCtxt<'a, 'tcx>,
     cause: ObligationCause<'tcx>,
     use_lub: bool,
@@ -126,15 +126,15 @@ fn success<'tcx>(
 }
 
 impl<'f, 'tcx> Coerce<'f, 'tcx> {
-    pub fn new(
+    fn new(
         fcx: &'f FnCtxt<'f, 'tcx>,
         cause: ObligationCause<'tcx>,
         allow_two_phase: AllowTwoPhase,
     ) -> Self {
         Coerce { fcx, cause, allow_two_phase, use_lub: false }
     }
 
-    pub fn unify(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> InferResult<'tcx, Ty<'tcx>> {
+    fn unify(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> InferResult<'tcx, Ty<'tcx>> {
         debug!("unify(a: {:?}, b: {:?}, use_lub: {})", a, b, self.use_lub);
         self.commit_if_ok(|_| {
             if self.use_lub {
@@ -841,6 +841,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         self.probe(|_| coerce.coerce(source, target)).is_ok()
     }
 
+    /// Given a type and a target type, this function will calculate and return
+    /// how many dereference steps needed to achieve `expr_ty <: target`. If
+    /// it's not possible, return `None`.
+    pub fn deref_steps(&self, expr_ty: Ty<'tcx>, target: Ty<'tcx>) -> Option<usize> {
+        let cause = self.cause(rustc_span::DUMMY_SP, ObligationCauseCode::ExprAssignable);
+        // We don't ever need two-phase here since we throw out the result of the coercion
+        let coerce = Coerce::new(self, cause, AllowTwoPhase::No);
+        coerce
+            .autoderef(rustc_span::DUMMY_SP, expr_ty)
+            .find_map(|(ty, steps)| coerce.unify(ty, target).ok().map(|_| steps))
+    }
+
     /// Given some expressions, their known unified type and another expression,
     /// tries to unify the types, potentially inserting coercions on any of the
     /// provided expressions and returns their LUB (aka "common supertype").