Added simple variable lifetimes

src/build/Assignment.go

@@ -14,5 +14,6 @@ func (f *Function) CompileAssignment(expr *expression.Expression) error {
 		return errors.New(&errors.UnknownIdentifier{Name: name}, f.File, expr.Children[0].Token.Position)
 	}
 
+	defer f.useVariable(variable)
 	return f.Execute(expr.Token, variable.Register, expr.Children[1])
 }