Avoid the path trimming ICE lint in error reporting

Author: saethlin

compiler/rustc_const_eval/src/interpret/cast.rs

@@ -147,8 +147,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 if src.layout.size != dest.layout.size {
                     let src_bytes = src.layout.size.bytes();
                     let dest_bytes = dest.layout.size.bytes();
-                    let src_ty = format!("{}", src.layout.ty);
-                    let dest_ty = format!("{}", dest.layout.ty);
+                    let src_ty = src.layout.ty;
+                    let dest_ty = dest.layout.ty;
                     throw_ub_custom!(
                         fluent::const_eval_invalid_transmute,
                         src_bytes = src_bytes,