remove the bad rhs value error and panic instead. the typechecker prevent this

src/error.rs

@@ -5,7 +5,6 @@
 use memory::Pointer;
 use rustc_const_math::ConstMathErr;
 use syntax::codemap::Span;
-use primval::PrimVal;
 
 #[derive(Clone, Debug)]
 pub enum EvalError<'tcx> {
@@ -29,7 +28,6 @@ pub enum EvalError<'tcx> {
     ExecuteMemory,
     ArrayIndexOutOfBounds(Span, u64, u64),
     Math(Span, ConstMathErr),
-    InvalidBitShiftRhs(PrimVal),
 }
 
 pub type EvalResult<'tcx, T> = Result<T, EvalError<'tcx>>;
@@ -68,8 +66,6 @@ fn description(&self) -> &str {
                 "array index out of bounds",
             EvalError::Math(..) =>
                 "mathematical operation failed",
-            EvalError::InvalidBitShiftRhs(..) =>
-                "bit shift rhs not an int",
         }
     }
 

src/primval.rs

@@ -91,7 +91,7 @@ fn unrelated_ptr_ops<'tcx>(bin_op: mir::BinOp) -> EvalResult<'tcx, PrimVal> {
                 U16(i) => (i & ((1 << mask_bits) - 1)) as u32,
                 U32(i) => (i & ((1 << mask_bits) - 1)) as u32,
                 U64(i) => (i & ((1 << mask_bits) - 1)) as u32,
-                _ => return Err(EvalError::InvalidBitShiftRhs(right)),
+                _ => panic!("bad MIR: bitshift rhs is not integral"),
             };
             macro_rules! shift {
                 ($v:ident, $l:ident, $r:ident) => ({