fix unused imports

library/contracts/safety/src/lib.rs

@@ -3,9 +3,8 @@
 
 use proc_macro::TokenStream;
 use proc_macro_error::proc_macro_error;
-use syn::{Fields, ItemStruct, parse_macro_input};
-use syn::spanned::Spanned;
-use quote::{quote, quote_spanned};
+use syn::{ItemStruct, parse_macro_input};
+use quote::quote;
 
 #[cfg(kani_host)]
 #[path = "kani.rs"]
@@ -20,7 +19,7 @@ mod tool;
 pub fn invariant(attr: TokenStream, item: TokenStream) -> TokenStream {
     let safe_body = proc_macro2::TokenStream::from(attr);
     let item = parse_macro_input!(item as ItemStruct);
-    let mut item_name = &item.ident;
+    let item_name = &item.ident;
     let (impl_generics, ty_generics, where_clause) = item.generics.split_for_impl();
 
     let expanded = quote! {

library/core/src/alloc/layout.rs

@@ -8,11 +8,13 @@ use safety::{invariant, requires};
 use crate::error::Error;
 use crate::ptr::{Alignment, NonNull};
 use crate::{assert_unsafe_precondition, cmp, fmt, mem};
-use crate::ub_checks::Invariant;
 
 #[cfg(kani)]
 use crate::kani;
 
+#[cfg(kani)]
+use crate::ub_checks::Invariant;
+
 // While this function is used in one place and its implementation
 // could be inlined, the previous attempts to do so made rustc
 // slower:

library/core/src/ptr/alignment.rs

@@ -1,11 +1,14 @@
 use safety::{ensures, invariant, requires};
 use crate::num::NonZero;
-use crate::ub_checks::{assert_unsafe_precondition, Invariant};
+use crate::ub_checks::assert_unsafe_precondition;
 use crate::{cmp, fmt, hash, mem, num};
 
 #[cfg(kani)]
 use crate::kani;
 
+#[cfg(kani)]
+use crate::ub_checks::Invariant;
+
 /// A type storing a `usize` which is a power of two, and thus
 /// represents a possible alignment in the Rust abstract machine.
 ///