add SlashEqual operator

examples/hello.v

@@ -60,6 +60,7 @@ fn main(a int) int {
 	str.len += 1
 	str.len -= 1
 	str.len *= 1
+	str.len /= 1
 }
 
 fn (v Typ) voidfunc() {}

src/parser.zig

@@ -703,6 +703,7 @@ pub const Parser = struct {
 
         if (self.compareAnyOf(&[_]TokenType{
             .ColonEqual, .Equal, .PlusEqual, .MinusEqual, .StarEqual,
+            .SlashEqual,
         })) {
             return try self.finishAssignment(expr, mutable);
         }
@@ -725,15 +726,27 @@ pub const Parser = struct {
             .PlusEqual => .Plus,
             .MinusEqual => .Minus,
             .StarEqual => .Star,
+            .SlashEqual => .Slash,
+
             else => unreachable,
         };
 
+        // we create new_lexeme so that
+        // the AST printer properly prints
+        //  x += 1
+        // as
+        //  (set x (+ x 1))
+        // and not
+        //  (set x (+= x 1))
         const new_lexeme: []const u8 = switch (op.ttype) {
             .ColonEqual => ":=",
             .Equal => "=",
+
             .PlusEqual => "+",
             .MinusEqual => "-",
             .StarEqual => "*",
+            .SlashEqual => "/",
+
             else => unreachable,
         };
 

src/scanner.zig

@@ -315,7 +315,10 @@ pub const Scanner = struct {
 
             '/' => blk: {
                 var next = self.peekNext();
+
                 switch (next) {
+                    '=' => return self.makeToken(.SlashEqual),
+
                     '/' => blk2: {
                         while (self.peek() != '\n' and !self.isAtEnd()) {
                             _ = self.advance();

src/tokens.zig

@@ -31,6 +31,7 @@ pub const TokenType = enum {
     MinusEqual,
     ColonEqual,
     StarEqual,
+    SlashEqual,
 
     // comparison ones
     EqualEqual,