ast.rb: Fix bug for source of multibyte characters

first_column and last_column return byte positions, but existing implementations
did not consider multibyte.

1 files changed, 2 insertions, 2 deletions

diff --git a/ast.rb b/ast.rb
index fa9b69507c..51ee5b3d59 100644
--- a/ast.rb
+++ b/ast.rb
@@ -265,8 +265,8 @@ module RubyVM::AbstractSyntaxTree
       lines = script_lines
       if lines
         lines = lines[first_lineno - 1 .. last_lineno - 1]
-        lines[-1] = lines[-1][0...last_column]
-        lines[0] = lines[0][first_column..-1]
+        lines[-1] = lines[-1].byteslice(0...last_column)
+        lines[0] = lines[0].byteslice(first_column..-1)
         lines.join
       else
         nil