Allow defining and redefining local variables with "def"

src/compiler.cpp

@@ -633,14 +633,33 @@ Result<Expression> Compiler::compile_def(Context& context, Symbol& op,
   auto comp = TRY(compile_expr(context, var_expr));
   ex.add_code(comp.code);
 
+  if (context.toplevel) {
     TRY(ex.add_opcode(Oc::GlobalStore, {1, (int64_t)gname},
                       {0, (int64_t)comp.reg}));
-
     ex.reg = comp.reg;
+    return std::move(ex);
+  } else {
+    auto maybe_binding = context.get_var(varname_unwrapped);
+
+    if (maybe_binding.has_value()) {
+      auto reg = maybe_binding.value();
+      TRY(ex.add_opcode(Oc::Mov, {0, (int64_t)reg}, {0, (int64_t)comp.reg}));
+      ex.reg = comp.reg;
+
       context.maxreg = maxreg + 1;
+      return std::move(ex);
+    } else {
+      context.maxreg = maxreg + 1;
+      auto reg = TRY(context.add_var(varname_unwrapped));
+
+      TRY(ex.add_opcode(Oc::Mov, {0, (int64_t)reg}, {0, (int64_t)comp.reg}));
+      ex.reg = reg;
+      context.maxreg = reg + 1;
 
       return std::move(ex);
     }
+  }
+}
 
 Result<Expression> Compiler::compile_quote(Context& context, Symbol& op,
                                            const Value& expr) {
@@ -905,7 +924,7 @@ Result<Expression> Compiler::compile_body(Context& context, const Value& expr) {
     if (cur.is<Nil>()) {
       ex_res.reg = expr.reg;
     } else {
-      context.maxreg = maxreg;
+      // context.maxreg = maxreg;
     }
   }
 

test/function.vli

@@ -55,3 +55,13 @@
 ;; "do" form returns the value of last expression
 
 (assert (= (do 1 2 3) 3))
+
+;; allow definition and redefinition of variables with "def"
+
+(fn def-redef ()
+    (def x 1)
+    (def x (+ x 1))
+    (def y 4)
+    (+ x y))
+
+(assert (= (def-redef) 6))