Fix clippy warnings

build/find_normal.rs

@@ -22,12 +22,12 @@ pub fn probe_lua() -> PathBuf {
 
     let need_lua_lib = cfg!(any(not(feature = "module"), target_os = "windows"));
 
-    if include_dir != "" {
+    if !include_dir.is_empty() {
         if need_lua_lib {
-            if lib_dir == "" {
+            if lib_dir.is_empty() {
                 panic!("LUA_LIB is not set");
             }
-            if lua_lib == "" {
+            if lua_lib.is_empty() {
                 panic!("LUA_LIB_NAME is not set");
             }
 

src/conversion.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::wrong_self_convention)]
+
 use std::borrow::Cow;
 use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet};
 use std::ffi::{CStr, CString};

src/error.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::wrong_self_convention)]
+
 use std::error::Error as StdError;
 use std::fmt;
 use std::io::Error as IoError;

src/ffi/compat53.rs

@@ -538,6 +538,7 @@ pub unsafe fn lua_stringtonumber(L: *mut lua_State, s: *const c_char) -> usize {
     0
 }
 
+#[allow(clippy::branches_sharing_code)]
 pub unsafe fn lua_getextraspace(L: *mut lua_State) -> *mut c_void {
     use super::glue::LUA_EXTRASPACE;
 

src/multi.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::wrong_self_convention)]
+
 use std::iter::FromIterator;
 use std::ops::{Deref, DerefMut};
 use std::result::Result as StdResult;