dead := make(map[ast.Node]bool)
	nodeFilter := []ast.Node{
		(*ast.IfStmt)(nil),
		(*ast.SwitchStmt)(nil),
	}
	inspect.Preorder(nodeFilter, func(n ast.Node) {
		// TODO(adonovan): move updateDead into this file.
		updateDead(pass.TypesInfo, dead, n)
	})

	nodeFilter = []ast.Node{
		(*ast.AssignStmt)(nil),
		(*ast.BinaryExpr)(nil),
	}
	inspect.Preorder(nodeFilter, func(node ast.Node) {
		if dead[node] {