Prevent character literals spanning lines

The single-quote character literal regex was using `[^']*` which would
match any character including newlines. This caused character literals
to incorrectly span multiple lines when there were unmatched quotes in the input.

Author: tancnle

lib/rouge/lexers/crystal.rb

@@ -80,7 +80,7 @@ def self.detect?(text)
         rule %r/\b[\p{Ll}_]\p{Word}*?[?!]?:\s+/, Str::Symbol, :expr_start
         rule %r/"/, Str::Double, :simple_string
         rule %r/(?<!\.)`/, Str::Backtick, :simple_backtick
-        rule %r/(')(\\u[a-fA-F0-9]{4}|\\u\{[a-fA-F0-9]{1,6}\}|\\[abefnrtv])?(\\\\|\\'|[^'])*(')/ do
+        rule %r/(')(\\u[a-fA-F0-9]{4}|\\u\{[a-fA-F0-9]{1,6}\}|\\[abefnrtv])?(\\\\|\\'|[^'\n])*(')/ do
           groups Str::Single, Str::Escape, Str::Single, Str::Single
         end
       end

spec/lexers/crystal_spec.rb

@@ -20,4 +20,17 @@
       assert_guess :source => '#!/usr/local/bin/crystal'
     end
   end
+
+  describe 'lexing' do
+    include Support::Lexing
+
+    it 'rejects string literal than spans multiple lines' do
+      assert_tokens_equal "'a\nb'",
+                          ['Error', "'"],
+                          ["Name", "a"],
+                          ["Text", "\n"],
+                          ["Name", "b"],
+                          ["Error", "'"]
+    end
+  end
 end