minor cleanup of __Cat__ and Cat to more compact code

diff --git a/nmigen/hdl/ast.py b/nmigen/hdl/ast.py
index 2f0625fa62d7d21937db46ff6d7cf4fc9febd9e0..e47c83329dbbe06aea49bbd889bd338b08277aea 100644 (file)
--- a/nmigen/hdl/ast.py
+++ b/nmigen/hdl/ast.py
@@ -155,8 +155,7 @@ class Value(metaclass=ABCMeta):
         return _InternalRepl(self, count, src_loc_at=src_loc_at)
 
     def __Cat__(self, *args, src_loc_at=0):
-        args = [self] + list(args)
-        return _InternalCat(*args, src_loc_at=src_loc_at)
+        return _InternalCat(self, *args, src_loc_at=src_loc_at)
 
     def __Mux__(self, val1, val0):
         return _InternalMux(self, val1, val0)
@@ -849,12 +848,11 @@ def Cat(*args, src_loc_at=0):
     if len(args) == 0:
         return _InternalCat(*args, src_loc_at=src_loc_at)
     # determine if the first is a UserValue.
-    if isinstance(args[0], UserValue):
-        first = args[0] # take UserValue directly, do not downcast
-    else:
-        first = Value.cast(args[0]) # ok to downcast to Value
+    first, rest = args[0], args[1:]
+    if not isinstance(args[0], UserValue):
+        first = Value.cast(first) # ok to downcast to Value
     # all other arguments are safe to downcast to Value
-    rest = [Value.cast(v) for v in flatten(args[1:])]
+    rest = map(Value.cast, rest)
     # assume first item defines the "handling" for all others
     return first.__Cat__(*rest, src_loc_at=src_loc_at)