Use rlua_ asserts instead of unreachable!, changelog updates for 0.14

0.14 will be released alongside `failure` 1.0 with a dependency update.

CHANGELOG.md

@@ -1,3 +1,27 @@
+## [0.14.0]
+- Lots of performance improvements, with one major one: Lua handles no longer
+  necessarily point into the registry, they now can instead point into a
+  preallocated stack area.  All together, you can expect (VERY rough estimate)
+  somewhere on the order of 30%-60% CPU time reduction in the cost of bindings,
+  depending on usage patterns, but the handle behavior change comes with API
+  breakage.
+- API incompatible change: Lua handles now must ONLY be used with the `Lua`
+  instance from which they were derived.  Before, this would work if both
+  instances were from the same base state, but are now restricted to ONLY the
+  matching `Lua` instance itself.  This was previously only possible through
+  unsafe code, `Lua::scope`, and things like the `rental` crate which allow self
+  borrowing.  For `Lua::scope` functions, you can use `Function::bind`, and for
+  everything else you can use the `RegistryKey` API.
+- Several stack size bugfixes that could have lead to unsafety in release mode.
+- Another API incompatible change: `Lua` (and associated handle values) are no
+  longer `UnwindSafe` / `RefUnwindSafe`.  They should not have been marked as
+  such before, because they are *extremely* internally mutable, so this can be
+  considered a bugfix.  All `rlua` types should actually be perfectly panic safe
+  as far as *internal* invariants are concerned, but (afaict) they should not be
+  marked as `UnwindSafe` due to internal mutability and *user* invariants.
+- Addition of some simple criterion.rs based benchmarking.
+- `rlua` now depends on `failure` 1.0 and `cc` 1.0
+
 ## [0.13.0]
 - Small API incompatible change which fixes unsafety: Scope and scope created
   handle lifetimes have been changed to disallow them from escaping the scope

src/lua.rs

@@ -721,7 +721,7 @@ impl Lua {
 
             ffi::LUA_TTHREAD => Value::Thread(Thread(self.pop_ref())),
 
-            _ => unreachable!("internal error: LUA_TNONE in pop_value"),
+            _ => rlua_panic!("LUA_TNONE in pop_value"),
         }
     }
 
@@ -1157,8 +1157,7 @@ impl Lua {
             let mut args = MultiValue::new();
             args.reserve(stack_nargs as usize);
 
-            // First, convert all of the reference types in the ref stack area into LuaRef types
-            // in-place.
+            // Convert all of the reference types in the ref stack area into LuaRef types in-place.
             for i in 0..stack_nargs {
                 let n = stack_nargs - i;
 
@@ -1215,7 +1214,7 @@ impl Lua {
                         args.push_front(Value::Thread(Thread(make_ref())));
                     }
 
-                    _ => unreachable!("internal error: LUA_TNONE in pop_value"),
+                    _ => rlua_panic!("LUA_TNONE in setup_callback_stack_slots"),
                 }
             }
 
@@ -1232,7 +1231,6 @@ impl Lua {
                     extra_args.push(self.pop_value());
                 }
                 extra_args.extend(args.into_vec_rev());
-
                 MultiValue::from_vec_rev(extra_args)
             } else {
                 args