Consider the following simple example:

defmodule Test.Foo do
  defmacro foo(regex) do
    IO.inspect(regex)
  end
end

defmodule Test do
  require Test.Foo

  Test.Foo.foo(~r/test/)
end

{:sigil_r, [delimiter: "/", line: 10], [{:<<>>, [line: 10], ["test"]}, []]}
iex>

Here, the sigil passed to Test.Foo.foo becomes a quoted expression. When using the macro for code generation, one would simple call unquote/1 on arg and get the sigil representation again.

However, if I do this in the above example (IO.inspect(unquote(regex))), I get the following error:

warning: variable “regex” does not exist and is being expanded to “regex()”, please use parentheses to remove the ambiguity or change the variable name
macro_why.exs:3: Test.Foo
** (CompileError) macro_why.exs:3: undefined function regex/0 (there is no such import)

Note that I don’t have a quote block in my macro. The actual code I’m working on parses the AST directly into an internal representation, so there is no need to quote anything. This is whats kinda throwing me for a loop here.