Fix Clippy warnings

src/lib.rs

@@ -61,6 +61,7 @@ pub enum Lang {
 
 /// A kind of item to which the C volatile qualifier could apply.
 #[derive(Debug)]
+#[allow(clippy::manual_non_exhaustive)] // FIXME: Use `#[non_exhaustive]` in the future.
 pub enum VolatileItemKind {
     /// A struct field (struct_name, field_name)
     StructField(String, String),
@@ -1691,7 +1692,7 @@ impl<'a> Generator<'a> {
                 ty = rust_ty
             ));
         } else if rust_ty.starts_with('[') && rust_ty.ends_with(']') {
-            let c_ptr_ty = c_ty.split(' ').nth(0).unwrap();
+            let c_ptr_ty = c_ty.split(' ').next().unwrap();
             let mut lens = Vec::new();
             for i in c_ty.split(' ').skip(1) {
                 lens.push(i);

testcrate/build.rs

@@ -4,7 +4,7 @@ fn main() {
         .ok()
         .and_then(|s| s.parse().ok())
         .unwrap_or(0);
-    let profile = env::var("PROFILE").unwrap_or(String::new());
+    let profile = env::var("PROFILE").unwrap_or_default();
     if profile == "release" || opt_level >= 2 {
         println!("cargo:rustc-cfg=optimized");
     }

testcrate/src/t1.rs

@@ -3,7 +3,7 @@
 use libc::*;
 
 pub type T1Foo = i32;
-pub const T1S: &'static str = "foo";
+pub const T1S: &str = "foo";
 
 pub const T1N: i32 = 5;
 
@@ -69,6 +69,7 @@ extern "C" {
     pub fn T1e(a: c_uint, b: *const T1Bar);
 
     #[link_name = "T1f"]
+    #[allow(clippy::unused_unit)]
     pub fn f() -> ();
 
     pub fn T1g(a: *mut [i32; 4]);

testcrate/src/t2.rs

@@ -28,7 +28,7 @@ pub union T2Union {
 pub const T2C: i32 = 5;
 
 i! {
-    pub const T2S: &'static str = "b";
+    pub const T2S: &str = "b";
 }
 
 extern "C" {