YJIT: Tiny refactors (ruby#14505)

Addressed some suggestions from clippy that made sense to me.

Author: st0012

yjit/src/asm/mod.rs

@@ -441,12 +441,12 @@ impl CodeBlock {
 
         // Ignore empty code ranges
         if start_addr == end_addr {
-            return (0..0).into_iter();
+            return 0..0;
         }
 
         let start_page = (start_addr.raw_addr(self) - mem_start) / self.page_size;
         let end_page = (end_addr.raw_addr(self) - mem_start - 1) / self.page_size;
-        (start_page..end_page + 1).into_iter()
+        start_page..end_page + 1
     }
 
     /// Get a (possibly dangling) direct pointer to the current write position

yjit/src/backend/ir.rs

@@ -1602,7 +1602,7 @@ impl Assembler
                 if c_args.len() > 0 {
                     // Resolve C argument dependencies
                     let c_args_len = c_args.len() as isize;
-                    let moves = Self::reorder_reg_moves(&c_args.drain(..).into_iter().collect());
+                    let moves = Self::reorder_reg_moves(&c_args.drain(..).collect());
                     shift_live_ranges(&mut shifted_live_ranges, asm.insns.len(), moves.len() as isize - c_args_len);
 
                     // Push batched C arguments

yjit/src/core.rs

@@ -1099,7 +1099,7 @@ impl Context {
                 MapToLocal(local_idx) => {
                     bits.push_op(CtxOp::MapTempLocal);
                     bits.push_u3(stack_idx as u8);
-                    bits.push_u3(local_idx as u8);
+                    bits.push_u3(local_idx);
                 }
 
                 MapToSelf => {

yjit/src/utils.rs

@@ -92,10 +92,7 @@ pub fn ruby_str_to_rust(v: VALUE) -> String {
     let str_ptr = unsafe { rb_RSTRING_PTR(v) } as *mut u8;
     let str_len: usize = unsafe { rb_RSTRING_LEN(v) }.try_into().unwrap();
     let str_slice: &[u8] = unsafe { slice::from_raw_parts(str_ptr, str_len) };
-    match String::from_utf8(str_slice.to_vec()) {
-        Ok(utf8) => utf8,
-        Err(_) => String::new(),
-    }
+    String::from_utf8(str_slice.to_vec()).unwrap_or_default()
 }
 
 // Location is the file defining the method, colon, method name.