# `Dialyxir.Warnings.MapUpdate`
[🔗](https://github.com/jeremyjh/dialyxir/blob/1.4.8/lib/dialyxir/warnings/map_update.ex#L1)

Elixir can only use the map update syntax to update a key that is in
the map.

## Example

    defmodule Example do
      @spec error() :: map
      def error() do
        map = %{exists: :exists}
        %{map | does_not_exist: :fail}
      end
    end

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*Consult [api-reference.md](api-reference.md) for complete listing*