fix other cases of registering obligations in a snapshot

No test cases for these ones, but they would all ICE if they ever run
with a non-empty set of obligations.

src/librustc_typeck/check/coercion.rs

@@ -883,8 +883,7 @@ fn try_find_coercion_lub<E>(&self,
                 return self.commit_if_ok(|_| {
                     self.at(cause, self.param_env)
                         .lub(prev_ty, new_ty)
-                        .map(|ok| self.register_infer_ok_obligations(ok))
-                });
+                }).map(|ok| self.register_infer_ok_obligations(ok));
             }
         }
 
@@ -897,8 +896,7 @@ fn try_find_coercion_lub<E>(&self,
                     self.commit_if_ok(|_| {
                         self.at(cause, self.param_env)
                             .lub(prev_ty, new_ty)
-                            .map(|ok| self.register_infer_ok_obligations(ok))
-                    })
+                    }).map(|ok| self.register_infer_ok_obligations(ok))
                 }
             }
             Ok(ok) => {

src/librustc_typeck/check/regionck.rs

@@ -1815,12 +1815,12 @@ fn declared_projection_bounds_from_trait(&self,
                     // check whether this predicate applies to our current projection
                     let cause = self.fcx.misc(span);
                     match self.at(&cause, self.fcx.param_env).eq(outlives.0, ty) {
-                        Ok(ok) => {
-                            self.register_infer_ok_obligations(ok);
-                            Ok(outlives.1)
-                        }
-                        Err(_) => { Err(()) }
+                        Ok(ok) => Ok((ok, outlives.1)),
+                        Err(_) => Err(())
                     }
+                }).map(|(ok, result)| {
+                    self.register_infer_ok_obligations(ok);
+                    result
                 });
 
                 debug!("projection_bounds: region_result={:?}",