Question

A developer writes a local value to fetch a specific subnet CIDR by position: local.cidrs = element(var.subnet_cidrs, 0). The variable subnet_cidrs is declared as type set(string). After running terraform plan, Terraform returns an error indicating the argument type is invalid for the element function. What is the correct explanation and fix?

Accepted Answer

The element function only accepts lists (or tuples); sets are unordered and have no index, so the value must first be converted with tolist(var.subnet_cidrs).

Answer

The element function requires a map, so var.subnet_cidrs should be redeclared as type map(string) and accessed by key.

Answer

The element function cannot take 0 as an index because indexing starts at 1; changing the index to 1 resolves the error.

Answer

The error occurs because element is deprecated; the developer should use the lookup function to retrieve a set member by index.