refactor slightly and fix bug in lexer

1 files changed, 9 insertions, 9 deletions

diff --git a/src/lexer.zig b/src/lexer.zig
index 608b755..3621a1c 100644
--- a/src/lexer.zig
+++ b/src/lexer.zig
@@ -4,7 +4,7 @@ pub const Token = struct {
     loc: Location,
     type: Type,
 
-    pub const Type = union(enum) {
+    pub const Type = enum {
         left_paren,
         right_paren,
         integer_literal,
@@ -20,7 +20,7 @@ pub const Location = struct {
     end: usize,
 
     pub fn combine(a: Location, b: Location) Location {
-        if (a.end > b.start) unreachable;
+        std.debug.assert(a.end <= b.start);
         return .{ .start = @min(a.start, b.start), .end = @max(a.end, b.end) };
     }
 
@@ -36,10 +36,11 @@ pub const Location = struct {
 };
 
 source: []const u8,
-last_end: usize = 0,
+start: usize = 0,
 pos: usize = 0,
 
 pub fn next(self: *Self) ?Token {
+    self.start = self.pos;
     return s: switch (self.eat() orelse return self.create(.eof)) {
         '(' => self.create(.left_paren),
         ')' => self.create(.right_paren),
@@ -47,7 +48,7 @@ pub fn next(self: *Self) ?Token {
         '+' => self.create(.plus),
         '-' => self.create(.minus),
         ' ' => {
-            self.last_end = self.pos;
+            self.start = self.pos;
             continue :s (self.eat() orelse return self.create(.eof));
         },
         else => self.create(.invalid),
@@ -55,7 +56,7 @@ pub fn next(self: *Self) ?Token {
 }
 
 fn integerLiteral(self: *Self) Token {
-    var value: ?u64 = 0;
+    var value: ?u64 = self.source[self.start] - '0';
     while (digitValue(self.peek())) |v| {
         var nxt: ?u64 = null;
         if (value) |val|
@@ -68,14 +69,13 @@ fn integerLiteral(self: *Self) Token {
         _ = self.eat();
     }
     return if (value != null)
-        self.create(.{ .integer_literal = {} })
+        self.create(.integer_literal)
     else
-        self.create(.{ .invalid = {} });
+        self.create(.invalid);
 }
 
 fn create(self: *Self, tajp: Token.Type) Token {
-    const start = self.last_end;
-    self.last_end = self.pos;
+    const start = self.start;
     return .{ .loc = .{ .start = start, .end = self.pos }, .type = tajp };
 }