[assert-instr] simplify

library/stdarch/assert-instr/src/lib.rs

@@ -246,13 +246,11 @@ pub fn assert(fnptr: usize, expected: &str) {
         if let Some(part) = instr.parts.get(0) {
             // Truncates the instruction with the length of the expected
             // instruction: tzcntl => tzcnt and compares that.
-            if let Some(part) = part.get(0..expected.len()) {
-                if part == expected {
+            if part.starts_with(expected) {
                 return
             }
         }
     }
-    }
 
     // Help debug by printing out the found disassembly, and then panic as we
     // didn't find the instruction.