add nicer error handling, whitespace skipping

src/main.zig

@@ -16,7 +16,15 @@ fn run(allocator: *Allocator, data: []u8) !void {
     var scanner = scanners.Scanner.init(allocator, data);
 
     while (true) {
-        var tok = try scanner.nextToken();
+        var tok = scanner.nextToken() catch |err| {
+            try stdout.print(
+                "error at '{}': {}\n",
+                scanner.currentLexeme(),
+                err,
+            );
+
+            return Result.CompileError;
+        };
         if (tok.ttype == .EOF) break;
         try stdout.print("{x}\n", tok);
     }

src/scanner.zig

@@ -104,7 +104,7 @@ pub const Scanner = struct {
         return self.source[self.current - 1];
     }
 
-    fn currentLexeme(self: *Scanner) []const u8 {
+    pub fn currentLexeme(self: *Scanner) []const u8 {
         return self.source[self.start..self.current];
     }
 
@@ -156,7 +156,25 @@ pub const Scanner = struct {
         return self.source[self.current + 1];
     }
 
+    fn skipWhitespace(self: *Scanner) void {
+        while (true) {
+            var c = self.peek();
+
+            switch (c) {
+                ' ', '\r', '\t' => blk: {
+                    _ = self.advance();
+                },
+                '\n' => blk: {
+                    self.line += 1;
+                    _ = self.advance();
+                },
+                else => return,
+            }
+        }
+    }
+
     pub fn nextToken(self: *Scanner) !Token {
+        self.skipWhitespace();
         self.start = self.current;
 
         if (self.isAtEnd()) return self.makeToken(TokenType.EOF);