X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=compiler%2Frustc_hir_typeck%2Fsrc%2Fcoercion.rs;h=43c7127b0d4c56b0e8495508eb2e9f51fa784d0d;hb=a673364c543986789cfbb844c925063519fb872a;hp=174b43313825e1b770760d191e3249529beacc89;hpb=e2301154e3c39f4bf606b6137d9cf5bf29a5f52e;p=rust.git

diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs
index 174b4331382..43c7127b0d4 100644
--- a/compiler/rustc_hir_typeck/src/coercion.rs
+++ b/compiler/rustc_hir_typeck/src/coercion.rs
@@ -630,8 +630,7 @@ fn coerce_unsized(&self, mut source: Ty<'tcx>, mut target: Ty<'tcx>) -> CoerceRe
             cause,
             coerce_unsized_did,
             0,
-            coerce_source,
-            &[coerce_target.into()]
+            [coerce_source, coerce_target]
         )];
 
         let mut has_unsized_tuple_coercion = false;
@@ -748,7 +747,7 @@ fn coerce_dyn_star(
         &self,
         a: Ty<'tcx>,
         b: Ty<'tcx>,
-        predicates: &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>,
+        predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
         b_region: ty::Region<'tcx>,
     ) -> CoerceResult<'tcx> {
         if !self.tcx.features().dyn_star {
@@ -775,7 +774,7 @@ fn coerce_dyn_star(
 
         // Check the obligations of the cast -- for example, when casting
         // `usize` to `dyn* Clone + 'static`:
-        let obligations = predicates
+        let mut obligations: Vec<_> = predicates
             .iter()
             .map(|predicate| {
                 // For each existential predicate (e.g., `?Self: Clone`) substitute
@@ -785,16 +784,32 @@ fn coerce_dyn_star(
                 let predicate = predicate.with_self_ty(self.tcx, a);
                 Obligation::new(self.tcx, self.cause.clone(), self.param_env, predicate)
             })
-            // Enforce the region bound (e.g., `usize: 'static`, in our example).
-            .chain([Obligation::new(
+            .chain([
+                // Enforce the region bound (e.g., `usize: 'static`, in our example).
+                Obligation::new(
+                    self.tcx,
+                    self.cause.clone(),
+                    self.param_env,
+                    ty::Binder::dummy(ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
+                        a, b_region,
+                    ))),
+                ),
+            ])
+            .collect();
+
+        // Enforce that the type is `usize`/pointer-sized. For now, only those
+        // can be coerced to `dyn*`, except for `dyn* -> dyn*` upcasts.
+        if !a.is_dyn_star() {
+            obligations.push(Obligation::new(
                 self.tcx,
                 self.cause.clone(),
                 self.param_env,
-                self.tcx.mk_predicate(ty::Binder::dummy(ty::PredicateKind::TypeOutlives(
-                    ty::OutlivesPredicate(a, b_region),
-                ))),
-            )])
-            .collect();
+                ty::Binder::dummy(
+                    self.tcx.at(self.cause.span).mk_trait_ref(hir::LangItem::PointerSized, [a]),
+                )
+                .to_poly_trait_predicate(),
+            ));
+        }
 
         Ok(InferOk {
             value: (vec![Adjustment { kind: Adjust::DynStar, target: b }], b),
@@ -1069,8 +1084,7 @@ pub fn deref_once_mutably_for_diagnostic(&self, expr_ty: Ty<'tcx>) -> Option<Ty<
             self.infcx
                 .type_implements_trait(
                     self.tcx.lang_items().deref_mut_trait()?,
-                    expr_ty,
-                    ty::List::empty(),
+                    [expr_ty],
                     self.param_env,
                 )
                 .may_apply()
@@ -1544,7 +1558,9 @@ pub(crate) fn coerce_inner<'a>(
                 // Mark that we've failed to coerce the types here to suppress
                 // any superfluous errors we might encounter while trying to
                 // emit or provide suggestions on how to fix the initial error.
-                fcx.set_tainted_by_errors();
+                fcx.set_tainted_by_errors(
+                    fcx.tcx.sess.delay_span_bug(cause.span, "coercion error but no error emitted"),
+                );
                 let (expected, found) = if label_expression_as_expected {
                     // In the case where this is a "forced unit", like
                     // `break`, we want to call the `()` "expected"