`tapioca gem`: a method with an anonymous block + RBS-comment: compiled to invalid syntax

If we add a test compiling the following code (to spec/tapioca/gem/pipeline_spec.rb):

class Foo
  #: { -> void } -> void
  def foo(&); end
end

the test will fail with

Tapioca::Gem::PipelineSpec::Tapioca::Gem::Pipeline
  it compiles RBS signature for a method with ananymous block     FAIL (0.36s)
        Tapioca::Gem::Pipeline#compile should not have any unhandled errors reported.
        Please either fix your changes to ensure no errors are reported, or explicity pass
        in a custom `error_handler: ->(err) { ... }` to the `compile()` method to handle
        expected errors.
        .
        Expected ["Unable to compile signature for method: Foo#foo\n  Exception raised when loading signature: #<RuntimeError: The declaration for `foo` is missing parameter(s): &>\n"] to be empty.
        spec/tapioca/gem/pipeline_spec.rb:61:in 'Tapioca::Gem::PipelineSpec#compile'
        spec/tapioca/gem/pipeline_spec.rb:4907:in 'block (2 levels) in <class:PipelineSpec>'


Finished in 0.39466s
1 tests, 2 assertions, 1 failures, 0 errors, 0 skips

Buf if we try to generate an RBI-file for a gem with such method, we get a definition with invalid syntax, like

    sig { params(_arg0: ).returns(T.untyped) }
    def foo(&_arg0); end

Expected result signatures:

sig { params("&": T.proc.void).void }
def foo(&); end

or

sig { params(block: T.proc.void).void }
def foo(&block); end

Start with the reproduction in spec/tapioca/gem/pipeline_spec.rb, especially the test for compiling an RBS signature on a method with an anonymous block. Trace how the signature is compiled and how the RBI method parameters are generated. Done means the compile test reports no unhandled errors and generated RBI contains valid syntax with a proc block parameter, such as &block.