[fine] A concrete syntax tree parser

Where in the world am I going with this?

fine/src/tokens.rs

@@ -17,6 +17,9 @@ pub enum TokenKind {
     Slash,
     Star,
 
+    Arrow,
+    Colon,
+
     Bang,
     BangEqual,
     Equal,
@@ -414,8 +417,15 @@ impl<'a> Tokens<'a> {
             ')' => self.token(pos, TokenKind::RightParen),
             ',' => self.token(pos, TokenKind::Comma),
             '.' => self.token(pos, TokenKind::Dot),
-            '-' => self.token(pos, TokenKind::Minus),
+            '-' => {
+                if self.matches('>') {
+                    self.token(pos, TokenKind::Arrow)
+                } else {
+                    self.token(pos, TokenKind::Minus)
+                }
+            }
             '+' => self.token(pos, TokenKind::Plus),
+            ':' => self.token(pos, TokenKind::Colon),
             ';' => self.token(pos, TokenKind::Semicolon),
             '/' => self.token(pos, TokenKind::Slash),
             '*' => self.token(pos, TokenKind::Star),
@@ -555,7 +565,7 @@ mod tests {
 
     test_tokens!(
         symbols,
-        "{ } ( ) [ ] . ! != < <= > >= = == , - + * / ;",
+        "{ } ( ) [ ] . ! != < <= > >= = == , - -> + * / ; :",
         (0, LeftBrace, "{"),
         (2, RightBrace, "}"),
         (4, LeftParen, "("),
@@ -573,9 +583,11 @@ mod tests {
         (31, EqualEqual, "=="),
         (34, Comma, ","),
         (36, Minus, "-"),
-        (38, Plus, "+"),
-        (40, Star, "*"),
-        (42, Slash, "/"),
-        (44, Semicolon, ";")
+        (38, Arrow, "->"),
+        (41, Plus, "+"),
+        (43, Star, "*"),
+        (45, Slash, "/"),
+        (47, Semicolon, ";"),
+        (49, Colon, ":")
     );
 }