diff --git a/src/astgen.zig b/src/astgen.zig
index 08166d23fbf9a17bfa23cea35cb2769c6bc2ee17..a57b1760057d28c378ad8244c131def00376ab7a 100644
--- a/src/astgen.zig
+++ b/src/astgen.zig
@@ -84,7 +84,7 @@ const Parser = struct {
     }
 
     fn tryEatSymbol(comptime self: *Parser, comptime needle: string) bool {
-        switch (self.tokens[self.index]) {
+        switch (self.tokens[self.index].data) {
             .symbol => |sym| {
                 if (std.mem.eql(u8, sym, needle)) {
                     self.index += 1;
@@ -126,7 +126,7 @@ const Parser = struct {
     }
 
     pub fn doValue(comptime self: *Parser) Value {
-        if (self.tokens[self.index] == .string) {
+        if (self.tokens[self.index].data == .string) {
             return Value{ .string = self.eat(.string) };
         }
         if (self.tryEatSymbol("{")) {
@@ -193,8 +193,13 @@ const Parser = struct {
         return ret;
     }
 
-    fn eat(comptime self: *Parser, comptime typ: std.meta.Tag(Token)) string {
+    fn eat(comptime self: *Parser, comptime typ: std.meta.Tag(Token.Data)) string {
         defer self.index += 1;
-        return @field(self.tokens[self.index], @tagName(typ));
+        const tok = self.tokens[self.index];
+        const tag = std.meta.activeTag(tok.data);
+        if (tag != typ) {
+            @compileError(std.fmt.comptimePrint("pek: file:{d}:{d}: expected {s}, found {s}", .{ tok.line, tok.pos, @tagName(tag), @tagName(typ) }));
+        }
+        return @field(tok.data, @tagName(typ));
     }
 };
diff --git a/src/tokenize.zig b/src/tokenize.zig
index 97211ad56e52ce647238707f4b708bd5ac9de96a..ce49a9ccc0590ee463efcb665674e5ec701505c8 100644
--- a/src/tokenize.zig
+++ b/src/tokenize.zig
@@ -4,12 +4,18 @@ const string = []const u8;
 //
 //
 
-pub const Token = union(enum) {
-    word: string,
-    symbol: string,
-    string: string,
+pub const Token = struct {
+    data: Data,
+    line: usize,
+    pos: usize,
 
     pub const skippedChars = &[_]u8{ ' ', '\n', '\t', '\r' };
+
+    pub const Data = union(enum) {
+        word: string,
+        symbol: string,
+        string: string,
+    };
 };
 
 //
@@ -58,7 +64,11 @@ pub fn do(comptime input: string, comptime symbols: []const u8) []const Token {
             }
             if (mode == 2) {
                 if (c == input[start]) {
-                    ret = ret ++ &[_]Token{.{ .string = input[start .. i + 1] }};
+                    ret = ret ++ &[_]Token{.{
+                        .data = .{ .string = input[start .. i + 1] },
+                        .line = line,
+                        .pos = pos,
+                    }};
                     start = i + 1;
                     end = i;
                     mode = 0;
@@ -84,7 +94,11 @@ pub fn do(comptime input: string, comptime symbols: []const u8) []const Token {
         if (shouldFlush) {
             if (mode == 0) {
                 if (end - start > 0) {
-                    ret = ret ++ &[_]Token{.{ .word = input[start..end] }};
+                    ret = ret ++ &[_]Token{.{
+                        .data = .{ .word = input[start..end] },
+                        .line = line,
+                        .pos = pos,
+                    }};
                     start = i;
                     end = i;
                 }
@@ -93,7 +107,11 @@ pub fn do(comptime input: string, comptime symbols: []const u8) []const Token {
                     end += 1;
                 }
                 if (std.mem.indexOfScalar(u8, symbols, c)) |_| {
-                    ret = ret ++ &[_]Token{.{ .symbol = s }};
+                    ret = ret ++ &[_]Token{.{
+                        .data = .{ .symbol = s },
+                        .line = line,
+                        .pos = pos,
+                    }};
                     start += 1;
                     end += 1;
                 }