Cleanup/fixup of nested-reference handling

Signed-off-by: Matthew Ballance <matt.ballance@gmail.com>

src/vsc/model/expr_indexed_field_ref_model.py

@@ -27,18 +27,24 @@ def get_target(self, root=None):
             ret = root
         elif isinstance(self.root, ExprArraySubscriptModel):
             ret = self.root.subscript()
+        elif isinstance(self.root, ExprIndexedFieldRefModel):
+            from vsc.visitors.expr2field_visitor import Expr2FieldVisitor
+            fm = Expr2FieldVisitor().field(self.root)
+            ret = fm
         else:
             ret = self.root.fm
 
         for i in self.idx_t:
             ret = ret.get_field(i)
-            
+
         return ret
 
 
     def build(self, btor, ctx_width=-1):
         t = self.get_target()
         ret = t.build(btor)
+        if ret is None:
+            raise Exception("Expression %s produced null node" % str(t))
         return ret
 
     def is_signed(self):

src/vsc/types.py

@@ -180,6 +180,10 @@ def __getattr__(self, name):
         em = object.__getattribute__(self, "em")
         fm_t = Expr2FieldTypeVisitor().fieldtype(em)
 
+        # This pops 'this expr' off the stack, so we can
+        # replace it with an extended expression
+        pop_expr()
+
         if fm_t is not None:
             if name in fm_t.field_id_m.keys():
                 idx = fm_t.field_id_m[name]

src/vsc/visitors/expr2fieldtype_visitor.py

@@ -12,7 +12,7 @@
 class Expr2FieldTypeVisitor(ModelVisitor):
     """Traverses an array-reference expression, returning element-type information"""
 
-    DEBUG_EN = True
+    DEBUG_EN = False
 
     def __init__(self):
         super().__init__()

ve/unit/test_compound_obj.py

@@ -571,3 +571,4 @@ def eq_c(self):
 
 
         item = Parent()
+        item.randomize(debug=False)