+ lexer.rl: reject \u after control/meta escape chars. (#807)

This commit tracks upstream commit ruby/ruby@110f242.

lib/parser/lexer.rl

@@ -705,6 +705,11 @@ class Parser::Lexer
 
   action unescape_char {
     codepoint = @source_pts[p - 1]
+
+    if @version >= 30 && (codepoint == 117 || codepoint == 85) # 'u' or 'U'
+      diagnostic :fatal, :invalid_escape
+    end
+
     if (@escape = ESCAPES[codepoint]).nil?
       @escape = encode_escape(@source_buffer.slice(p - 1))
     end

test/test_lexer.rb

@@ -3614,4 +3614,44 @@ def refute_scanned_numbered_parameter(input, message = nil)
     end
   end
 
+  def test_meta_escape_slash_u__before_30
+    setup_lexer(27)
+    assert_scanned('"\c\u0000"',
+                    :tSTRING, "\u00150000", [0, 10])
+    assert_scanned('"\c\U0000"',
+                    :tSTRING, "\u00150000", [0, 10])
+
+    assert_scanned('"\C-\u0000"',
+                    :tSTRING, "\u00150000", [0, 11])
+    assert_scanned('"\C-\U0000"',
+                    :tSTRING, "\u00150000", [0, 11])
+
+    assert_scanned('"\M-\u0000"',
+                    :tSTRING, "\xF50000", [0, 11])
+    assert_scanned('"\M-\U0000"',
+                    :tSTRING, "\xD50000", [0, 11])
+  end
+
+  def refute_scanned_meta_escape_slash_u(input)
+    setup_lexer(30)
+    source_buffer = Parser::Source::Buffer.new('(refute_scanned_meta_escape_slash_u)', source: input)
+    @lex.source_buffer = source_buffer
+
+    err = assert_raises Parser::SyntaxError do
+      @lex.advance
+    end
+
+    assert_equal :invalid_escape, err.diagnostic.reason
+  end
+
+  def test_meta_escape_slash_u__after_30
+    refute_scanned_meta_escape_slash_u('"\c\u0000"')
+    refute_scanned_meta_escape_slash_u('"\c\U0000"')
+
+    refute_scanned_meta_escape_slash_u('"\C-\u0000"')
+    refute_scanned_meta_escape_slash_u('"\C-\U0000"')
+
+    refute_scanned_meta_escape_slash_u('"\M-\u0000"')
+    refute_scanned_meta_escape_slash_u('"\M-\U0000"')
+  end
 end