"none" keyword for optionals + more memory fixes

compiler/fn.v

@@ -33,7 +33,34 @@ mut:
 	//gen_types []string
 }
 
-fn (f &Fn) find_var(name string) Var {
+fn (f &Fn) find_var(name string) ?Var {
+	for i in 0 .. f.var_idx {
+		if f.local_vars[i].name == name {
+			return f.local_vars[i]
+		}
+	}
+	return none
+}
+
+fn (p &Parser) find_var_check_new_var(name string) ?Var {
+	for i in 0 .. p.cur_fn.var_idx {
+		if p.cur_fn.local_vars[i].name == name {
+			return p.cur_fn.local_vars[i]
+		}
+	}
+	// A hack to allow `newvar := Foo{ field: newvar }`
+	// Declare the variable so that it can be used in the initialization
+	if name == 'main__' + p.var_decl_name {
+		return Var{
+			name : p.var_decl_name
+			typ : 'voidptr'
+			is_mut : true
+		}
+	}
+	return none
+}
+
+fn (f &Fn) find_var2(name string) Var {
 	for i in 0 .. f.var_idx {
 		if f.local_vars[i].name == name {
 			return f.local_vars[i]
@@ -73,8 +100,10 @@ fn (p mut Parser) mark_var_changed(v Var) {
 }
 
 fn (f mut Fn) known_var(name string) bool {
-	v := f.find_var(name)
-	return v.name.len > 0
+	_ := f.find_var(name) or {
+		return false
+	}	
+	return true
 }
 
 fn (f mut Fn) register_var(v Var) {
@@ -819,9 +848,9 @@ fn (p mut Parser) fn_call_args(f mut Fn) &Fn {
 			}
 			p.check(.key_mut)
 			var_name := p.lit
-			v := p.cur_fn.find_var(var_name)
-			if v.name == '' {
+			v := p.cur_fn.find_var(var_name) or {
 				p.error('`$arg.name` is a mutable argument, you need to provide a variable to modify: `$f.name(... mut a...)`')
+				exit(1)
 			}
 			if !v.is_changed {
 				p.mark_var_changed(v)