review comments

[rust.git] / src / librustc_typeck / check / cast.rs

diff --git a/src/librustc_typeck/check/cast.rs b/src/librustc_typeck/check/cast.rs
index dfeb5fb958cd8568e8d66d81000016a8e684af47..ded655c1ae32af5918b47c3367e704280996661b 100644 (file)
--- a/src/librustc_typeck/check/cast.rs
+++ b/src/librustc_typeck/check/cast.rs
@@ -341,10 +341,7 @@ fn report_cast_to_unsized_type(&self, fcx: &FnCtxt<'a, 'tcx>) {
                                          tstr);
         match self.expr_ty.kind {
             ty::Ref(_, _, mt) => {
-                let mtstr = match mt {
-                    hir::MutMutable => "mut ",
-                    hir::MutImmutable => "",
-                };
+                let mtstr = mt.prefix_str();
                 if self.cast_ty.is_trait() {
                     match fcx.tcx.sess.source_map().span_to_snippet(self.cast_span) {
                         Ok(s) => {
@@ -428,21 +425,36 @@ pub fn check(mut self, fcx: &FnCtxt<'a, 'tcx>) {
             self.report_cast_to_unsized_type(fcx);
         } else if self.expr_ty.references_error() || self.cast_ty.references_error() {
             // No sense in giving duplicate error messages
-        } else if self.try_coercion_cast(fcx) {
-            self.trivial_cast_lint(fcx);
-            debug!(" -> CoercionCast");
-            fcx.tables.borrow_mut().set_coercion_cast(self.expr.hir_id.local_id);
-
         } else {
-            match self.do_check(fcx) {
-                Ok(k) => {
-                    debug!(" -> {:?}", k);
+            match self.try_coercion_cast(fcx) {
+                Ok(()) => {
+                    self.trivial_cast_lint(fcx);
+                    debug!(" -> CoercionCast");
+                    fcx.tables.borrow_mut()
+                        .set_coercion_cast(self.expr.hir_id.local_id);
+                }
+                Err(ty::error::TypeError::ObjectUnsafeCoercion(did)) => {
+                    self.report_object_unsafe_cast(&fcx, did);
+                }
+                Err(_) => {
+                    match self.do_check(fcx) {
+                        Ok(k) => {
+                            debug!(" -> {:?}", k);
+                        }
+                        Err(e) => self.report_cast_error(fcx, e),
+                    };
                 }
-                Err(e) => self.report_cast_error(fcx, e),
             };
         }
     }
 
+    fn report_object_unsafe_cast(&self, fcx: &FnCtxt<'a, 'tcx>, did: DefId) {
+        let violations = fcx.tcx.object_safety_violations(did);
+        let mut err = fcx.tcx.report_object_safety_error(self.cast_span, did, violations);
+        err.note(&format!("required by cast to type '{}'", fcx.ty_to_string(self.cast_ty)));
+        err.emit();
+    }
+
     /// Checks a cast, and report an error if one exists. In some cases, this
     /// can return Ok and create type errors in the fcx rather than returning
     /// directly. coercion-cast is handled in check instead of here.
@@ -646,8 +658,14 @@ fn check_addr_ptr_cast(
         }
     }
 
-    fn try_coercion_cast(&self, fcx: &FnCtxt<'a, 'tcx>) -> bool {
-        fcx.try_coerce(self.expr, self.expr_ty, self.cast_ty, AllowTwoPhase::No).is_ok()
+    fn try_coercion_cast(
+        &self,
+        fcx: &FnCtxt<'a, 'tcx>,
+    ) -> Result<(), ty::error::TypeError<'_>> {
+        match fcx.try_coerce(self.expr, self.expr_ty, self.cast_ty, AllowTwoPhase::No) {
+            Ok(_) => Ok(()),
+            Err(err) => Err(err),
+        }
     }
 }