Fix parser translator tokens for backslashes in single-quoted strings and word arrays

These are not line continuations. They either should be taken literally,
or allow the word array to contain the following whitespace (newlines in this case)

Before:
```
  0...1: tSTRING_BEG     => "'"
 1...12: tSTRING_CONTENT => "foobar\\\n"
12...16: tSTRING_CONTENT => "baz\n"
16...17: tSTRING_END     => "'"
17...18: tNL             => nil
```

After:
```
  0...1: tSTRING_BEG     => "'"
  1...6: tSTRING_CONTENT => "foo\\\n"
 6...12: tSTRING_CONTENT => "bar\\\n"
12...16: tSTRING_CONTENT => "baz\n"
16...17: tSTRING_END     => "'"
17...18: tNL             => nil
```

Author: Earlopain

lib/prism/translation/parser/lexer.rb

@@ -377,12 +377,20 @@ def to_a
 
                 lines.each.with_index do |line, index|
                   chomped_line = line.chomp
-
-                  # When the line ends with an odd number of backslashes, it must be a line continuation.
-                  if chomped_line[/\\{1,}\z/]&.length&.odd?
-                    chomped_line.delete_suffix!("\\")
-                    current_line << chomped_line
-                    adjustment += 2
+                  backslash_count = chomped_line[/\\{1,}\z/]&.length || 0
+                  is_interpolation = interpolation?(quote_stack.last)
+                  is_percent_array = percent_array?(quote_stack.last)
+
+                  if backslash_count.odd? && (is_interpolation || is_percent_array)
+                    if is_percent_array
+                      # Remove the last backslash, keep potential newlines
+                      current_line << line.sub(/(\\)(\r?\n)\z/, '\2')
+                      adjustment += 1
+                    else
+                      chomped_line.delete_suffix!("\\")
+                      current_line << chomped_line
+                      adjustment += 2
+                    end
                     # If the string ends with a line continuation emit the remainder
                     emit = index == lines.count - 1
                   else
@@ -577,7 +585,13 @@ def unescape_string(string, quote)
           # TODO: Implement regexp escaping
           return string if quote == "/" || quote.start_with?("%r")
 
-          if quote == "'" || quote.start_with?("%q") || quote.start_with?("%w") || quote.start_with?("%i")
+          if interpolation?(quote)
+            # In interpolation, escape sequences can be written literally. For example, "\\n" becomes "\n",
+            # and "\\\\n" becomes "\\n". Unknown escapes sequences, like "\\o" simply become "o".
+            string.gsub(/\\./) do |match|
+              ESCAPES[match[1]] || match[1]
+            end
+          else
             if quote == "'"
               delimiter = "'"
             else
@@ -586,14 +600,18 @@ def unescape_string(string, quote)
 
             delimiters = Regexp.escape("#{delimiter}#{DELIMITER_SYMETRY[delimiter]}")
             string.gsub(/\\([\\#{delimiters}])/, '\1')
-          else
-            # When double-quoted, escape sequences can be written literally. For example, "\\n" becomes "\n",
-            # and "\\\\n" becomes "\\n". Unknown escapes sequences, like "\\o" simply become "o".
-            string.gsub(/\\./) do |match|
-              ESCAPES[match[1]] || match[1]
-            end
           end
         end
+
+        # Determine if characters preceeded by a backslash should be escaped or not
+        def interpolation?(quote)
+          quote != "'" && !quote.start_with?("%q", "%w", "%i")
+        end
+
+        # Determine if the string is part of a %-style array.
+        def percent_array?(quote)
+          quote.start_with?("%w", "%W", "%i", "%I")
+        end
       end
     end
   end

test/prism/fixtures/strings.txt

@@ -83,6 +83,11 @@ b\nar
 
 '\\ foo \\ bar'
 
+'foo\
+bar\\
+baz
+'
+
 "#$foo"
 
 "#@foo"

test/prism/ruby/parser_test.rb

@@ -83,7 +83,6 @@ class ParserTest < TestCase
     skip_tokens = [
       "comments.txt",
       "dash_heredocs.txt",
-      "dos_endings.txt",
       "embdoc_no_newline_at_end.txt",
       "heredoc_with_comment.txt",
       "heredocs_with_ignored_newlines.txt",