Add Exception when invalid data is passed to prog builder

Author: fundamental

mrblib/parse-types.rb

@@ -2,7 +2,7 @@ class TParseType
     attr_reader :line, :file
 end
 
-class TImport
+class TImport < TParseType
     def initialize(file, line)
     end
     def inspect

mrblib/prog-ir.rb

@@ -8,6 +8,7 @@ class ProgIR
     #Initialize IR instance from parsed QML TInst 
     #representation
     def initialize(instance)
+        raise "Invalid node #{instance.inspect}, please provide a TExtend node" if instance.class == TImport
         @IR = []
         @cur_id = -1
         emit IrNode.new(SC, instance.file, 0, [])