Code shared from the Rust Playground

playground.rs

	fn derive_switch_int(&mut self, generator: NodeId, discr: Operand<'tcx>, switch_ty: Ty, values: Cow<'tcx,[u128]>, targets: Vec<BasicBlock>, sir: &mut Sir) -> Vec<Frame<'tcx>> {
		let new_memory = self.current_memory.clone();
		let compare_to = self.process_operand(discr, generator, sir);
		let otherwise_target = targets.pop().unwrap();
		let all_other = targets.iter(); 
		let (expressions, frames): (Vec<Expr>, Vec<Option<Frame>>) = values.iter().zip(all_other).map(|(desired_val, target)| {
			let comp = Expr::Value(SymTy::from_scalar(*desired_val, switch_ty));
			let prec = Expr::BinOp(Rator::Eq, Box::new(comp), Box::new(compare_to));
			(prec, self.block_to_frame(generator, *target, Some(prec)))
		}).unzip();


		let init_val = expressions.pop().unwrap();

		let otherwise_expr = expressions.into_iter().fold(init_val, |x,y| Expr::UnOp(Rator::Not, Box::new(Expr::BinOp(Rator::And, Box::new(x), Box::new(y)))));

		frames.push(self.block_to_frame(generator, otherwise_target, Some(otherwise_expr)));

		frames.into_iter().filter_map(|x| if let Some(val) = x {
			Some(val)
		} else {
			None
		}).collect()
	}