Fix lexer span panic with carriage return (#799)

Switch to treating bare carriage return as an OS9-style
newline, like v8.

boa/src/syntax/lexer/cursor.rs

@@ -33,13 +33,6 @@ impl<R> Cursor<R> {
         self.pos = Position::new(next_line, 1);
     }
 
-    /// Performs a carriage return to modify the position in the source.
-    #[inline]
-    fn carriage_return(&mut self) {
-        let current_line = self.pos.line_number();
-        self.pos = Position::new(current_line, 1);
-    }
-
     #[inline]
     pub(super) fn strict_mode(&self) -> bool {
         self.strict_mode
@@ -177,7 +170,14 @@ where
         };
 
         match chr {
-            Some('\r') => self.carriage_return(),
+            Some('\r') => {
+                // Try to take a newline if it's next, for windows "\r\n" newlines
+                // Otherwise, treat as a Mac OS9 bare '\r' newline
+                if self.peek()? == Some('\n') {
+                    self.peeked.take();
+                }
+                self.next_line();
+            }
             Some('\n') | Some('\u{2028}') | Some('\u{2029}') => self.next_line(),
             Some(_) => self.next_column(),
             None => {}

boa/src/syntax/lexer/tests.rs

@@ -657,3 +657,48 @@ fn non_english_str() {
 
     expect_tokens(&mut lexer, &expected);
 }
+
+mod carriage_return {
+    use super::*;
+
+    fn expect_tokens_with_lines(lines: usize, src: &str) {
+        let mut lexer = Lexer::new(src.as_bytes());
+
+        let mut expected = Vec::with_capacity(lines + 2);
+        expected.push(TokenKind::Punctuator(Punctuator::Sub));
+        for _ in 0..lines {
+            expected.push(TokenKind::LineTerminator);
+        }
+        expected.push(TokenKind::NumericLiteral(Numeric::Integer(3)));
+
+        expect_tokens(&mut lexer, &expected);
+    }
+
+    #[test]
+    fn regular_line() {
+        expect_tokens_with_lines(1, "-\n3");
+        expect_tokens_with_lines(2, "-\n\n3");
+        expect_tokens_with_lines(3, "-\n\n\n3");
+    }
+
+    #[test]
+    fn carriage_return() {
+        expect_tokens_with_lines(1, "-\r3");
+        expect_tokens_with_lines(2, "-\r\r3");
+        expect_tokens_with_lines(3, "-\r\r\r3");
+    }
+
+    #[test]
+    fn windows_line() {
+        expect_tokens_with_lines(1, "-\r\n3");
+        expect_tokens_with_lines(2, "-\r\n\r\n3");
+        expect_tokens_with_lines(3, "-\r\n\r\n\r\n3");
+    }
+
+    #[test]
+    fn mixed_line() {
+        expect_tokens_with_lines(2, "-\r\n\n3");
+        expect_tokens_with_lines(2, "-\n\r3");
+        expect_tokens_with_lines(3, "-\r\n\n\r3");
+    }
+}