RBS Rewriting doesn't preserve line numbers

[gmalette]

Describe the bug

When using Spoom::Sorbet::Translate.rbs_comments_to_sorbet_sig, the line numbers aren't preserved. If the rewritten code is used in lieu of the original source, errors and stacktraces don't line up with the original source.

To Reproduce

print Spoom::Sorbet::Translate.rbs_comments_to_sorbet_sigs(<<~RB, file: "test.rb")
  # typed: true
 
  #: (
  #| Integer
  #| ) -> void
  def foo(i); end
RB

# typed: true

sig { params(i: Integer).void }
def foo(i); end

foo is defined at line 4 instead of line 6.

Expected behavior

Ideally

# typed: true

sig { params(
  i: Integer
  ).void }
def foo(i); end

But this is fine too

# typed: true

sig { params(i: Integer).void }


def foo(i); end

[amomchilov]

It's not just method signatures, either. E.g. type-level generics expand out to multiple lines:

-#: [E]
 class Box
+  extend T::Generic
+
+  E = type_member
+
-  #: -> void
+  sig { void }
   def initialize(value)
     @value = value
   end
 end
 
-puts "The last line is: #{__LINE__}" # => The last line is: 12
+puts "The last line is: #{__LINE__}" # => The last line is: 15

demo.rb

#!/usr/bin/ruby

require "spoom"

source = <<~RUBY
  require "sorbet-runtime"
  Object.extend(T::Sig)
  
  #: [E]
  class Box
    #: -> void
    def initialize(value)
      @value = value
    end
  end
  
  puts "The last line is: \#{__LINE__}" # => The last line is: 15
RUBY
  
rewriter = Spoom::Sorbet::Translate::RBSCommentsToSorbetSigs.new(source, file: "/dummy")
puts rewriter.rewrite

Depending on the use case, the feature from #924 will be able to help, but it still won't be enough. There are other cases that would still need improving, e.g. @abstract, @interface, multi-line type alias, and more.

[paracycle]

Can't we emit extend T::Generic; E = type_member all in one line (and pad with spaces if necessary)?

[paracycle]

Ah I guess we would need to do:

-#: [E]
+
-class Box
+class Box; extend T::Generic; E = type_member
-  #: -> void
+  sig { void }
   def initialize(value)
     @value = value
   end
 end
 
-puts "The last line is: #{__LINE__}" # => The last line is: 12
+puts "The last line is: #{__LINE__}" # => The last line is: 12

[amomchilov]

@paracycle Yep, exactly! I have a WIP to tackle this case, among others (e.g. multi-line type aliases always end up single-line)