chore(example): use u64 for fibonacci

examples/fibonacci.rs

@@ -7,7 +7,7 @@ extern crate zink;
 
 /// Calculates the nth fibonacci number.
 #[zink::external]
-pub fn fib(n: usize) -> usize {
+pub fn fib(n: u64) -> u64 {
     if n < 2 {
         n
     } else {
@@ -25,27 +25,27 @@ fn test() -> anyhow::Result<()> {
     let selector = "fib(uint64)".as_bytes();
 
     // x = 0
-    let info = contract.execute([selector, &0usize.to_bytes32()])?;
+    let info = contract.execute([selector, &0u64.to_bytes32()])?;
     assert_eq!(0.to_bytes32().to_vec(), info.ret);
 
     // x = 1
-    let info = contract.execute([selector, &1usize.to_bytes32()])?;
+    let info = contract.execute([selector, &1u64.to_bytes32()])?;
     assert_eq!(1.to_bytes32().to_vec(), info.ret);
 
     // x = 2
-    let info = contract.execute([selector, &2usize.to_bytes32()])?;
+    let info = contract.execute([selector, &2u64.to_bytes32()])?;
     assert_eq!(1.to_bytes32().to_vec(), info.ret);
 
     // x = 3
-    let info = contract.execute([selector, &3usize.to_bytes32()])?;
+    let info = contract.execute([selector, &3u64.to_bytes32()])?;
     assert_eq!(2.to_bytes32().to_vec(), info.ret);
 
     // x = 4
-    let info = contract.execute([selector, &4usize.to_bytes32()])?;
+    let info = contract.execute([selector, &4u64.to_bytes32()])?;
     assert_eq!(3.to_bytes32().to_vec(), info.ret);
 
     // x = 5
-    let info = contract.execute([selector, &5usize.to_bytes32()])?;
+    let info = contract.execute([selector, &5u64.to_bytes32()])?;
     assert_eq!(5.to_bytes32().to_vec(), info.ret);
 
     Ok(())