Not a issue, just for learn, why lucky can check the const missing in the method definition. (Error: undefined constant SignIns::Delete)

[zw963]

Following code no any issue, just for learn and curious.

Following output come from the generated project use lucky init with auth enabled, but the file src/actions/sign_ins/delete.cr was deleted. when i run shards build. i get following error. (that was expected)

 ╰─ $ 1  shards build
Dependencies are satisfied
Building: app
Error target app failed to compile:
Showing last frame. Use --error-trace for full trace.

In src/pages/main_layout.cr:37:26

 37 | link "Sign out", to: SignIns::Delete, flow_id: "sign-out-button"
                           ^--------------
Error: undefined constant SignIns::Delete

I just curious, why the const SignIns::Delete missing error in the following method can be checked at compile time when build (i believe the file src/pages/main_layout.cr is not loaded when i first visit the index page, it not logged in, right?)

  private def render_signed_in_user
   puts "1"*100
    text current_user.email
    text " - "
    link "Sign out", to: SignIns::Delete, flow_id: "sign-out-button"
  end

As a comparative example, following code can't check the missing const Foo unless the #foo is invoked.

class Foo
  def foo
    puts "1"*100
    Bar
  end
end

foo = Foo.new
# foo.foo  # => will raise const missing only if uncomment this line.

Thanks very much.

[jwoertink]

I think this is because one of the methods in the HTML builder ends up getting called during compilation. It's a bit complex, so I forget exactly the structure, but when link() gets called, it'll typecheck the arguments. This is part of why we say Lucky has a focus on compile-time safety 😄