Problem
You would like to upgrade to the latest version of Phoenix 0.4.0 from the previous version of 0.3.1. When you try to update the dependencies and try to start phoenix again (mix phoenix.start) you get the following error:
** (Mix) You're trying to run :your_app_name on Elixir v1.0.0-rc1
but it has declared in its mix.exs file it supports
only Elixir ~> 0.15.0
Solution
After upgrading your Elixir version to the latest (1.0.0-rc1), and updating the path to your elixir installation so that it uses the new one, clear the dependencies from your project:
mix deps.clear --all
Change the dependency in your mix.exs file to be as the following:
def project do
[ app: :your_app_name,
version: "0.0.1",
elixir: "~> 1.0.0-rc1",
elixirc_paths: ["lib", "web"],
deps: deps ]
end
and then get the dependencies again with:
mix deps.get
after that you should be able to start your phoenix project with tne new version.