[ruby/prism] Rename line_to_byte_offset -> byte_offset

Also, include the column in here. Hopefully we can do some additional
optimizations later.

https://github.com/ruby/prism/commit/7759acdd26

2 files changed, 12 insertions, 10 deletions

diff --git a/lib/prism/lex_compat.rb b/lib/prism/lex_compat.rb
index 523ad39586..4960230bcf 100644
--- a/lib/prism/lex_compat.rb
+++ b/lib/prism/lex_compat.rb
@@ -816,7 +816,7 @@ module Prism
       # Manually implemented instead of `sort_by!(&:location)` for performance.
       tokens.sort_by! do |token|
         line, column = token.location
-        source.line_to_byte_offset(line) + column
+        source.byte_offset(line, column)
       end
 
       # Add :on_sp tokens
@@ -833,8 +833,10 @@ module Prism
 
       tokens.each do |token|
         line, column = token.location
-        start_offset = source.line_to_byte_offset(line) + column
-        # Ripper reports columns on line 1 without counting the BOM, so we adjust to get the real offset
+        start_offset = source.byte_offset(line, column)
+
+        # Ripper reports columns on line 1 without counting the BOM, so we
+        # adjust to get the real offset
         start_offset += 3 if line == 1 && bom
 
         if start_offset > prev_token_end
diff --git a/lib/prism/parse_result.rb b/lib/prism/parse_result.rb
index 12d19da562..be1c13f97c 100644
--- a/lib/prism/parse_result.rb
+++ b/lib/prism/parse_result.rb
@@ -76,13 +76,13 @@ module Prism
       source.byteslice(byte_offset, length) or raise
     end
 
-    # Converts the line number to a byte offset corresponding to the start of that line
-    def line_to_byte_offset(line)
-      l = line - @start_line
-      if l < 0 || l >= offsets.size
-        raise ArgumentError, "line #{line} is out of range"
-      end
-      offsets[l]
+    # Converts the line number and column in bytes to a byte offset.
+    def byte_offset(line, column)
+      normal = line - @start_line
+      raise IndexError if normal < 0
+      offsets.fetch(normal) + column
+    rescue IndexError
+      raise ArgumentError, "line #{line} is out of range"
     end
 
     # Binary search through the offsets to find the line number for the given