[fine] Parse is expression, partially

fine/src/tokens.rs

@@ -48,6 +48,7 @@ pub enum TokenKind {
     If,
     Import,
     In,
+    Is,
     Let,
     New,
     Or,
@@ -297,6 +298,9 @@ impl<'a> Tokens<'a> {
                 if ident == "in" {
                     return TokenKind::In;
                 }
+                if ident == "is" {
+                    return TokenKind::Is;
+                }
             }
             'l' => {
                 if ident == "let" {
@@ -593,6 +597,8 @@ mod tests {
         (58, New, "new")
     );
 
+    test_tokens!(more_more_keywords, "in is", (0, In, "in"), (3, Is, "is"));
+
     test_tokens!(
         strings,
         r#"'this is a string that\'s great!\r\n' "foo's" 'bar"s' "#,