Use try_from instead of the cast crate.

Now that `try_from` is in stable Rust, we can use it here.

cranelift/wasm/src/sections_translator.rs

@@ -12,6 +12,7 @@ use crate::translation_utils::{
     type_to_type, FuncIndex, Global, GlobalIndex, GlobalInit, Memory, MemoryIndex, SignatureIndex,
     Table, TableElementType, TableIndex,
 };
+use core::convert::TryFrom;
 use cranelift_codegen::ir::{self, AbiParam, Signature};
 use cranelift_entity::EntityRef;
 use std::vec::Vec;
@@ -270,7 +271,7 @@ pub fn parse_element_section<'data>(
                 ref s => panic!("unsupported init expr in element section: {:?}", s),
             };
             let items_reader = items.get_items_reader()?;
-            let mut elems = Vec::with_capacity(cast::usize(items_reader.get_count()));
+            let mut elems = Vec::with_capacity(usize::try_from(items_reader.get_count()).unwrap());
             for item in items_reader {
                 let x = item?;
                 elems.push(FuncIndex::from_u32(x));