fix to issue #56 "Better error for with block misuse", commented-out …

…test for #57

pyrtl/helperfuncs.py

@@ -13,7 +13,6 @@
 
 import core
 import wire
-import memblock
 
 
 # -----------------------------------------------------------------
@@ -31,6 +30,7 @@ def as_wires(val, bitwidth=None, truncating=True, block=None):
     most operations in an attempt to coerce values into WireVectors (for example,
     operations such as "x+1" where "1" needs to be converted to a Const WireVectors.)
     """
+    import memblock  # import here to avoid cylic dependence memblock->wire->helper->memblock
     block = core.working_block(block)
 
     if isinstance(val, (int, basestring)):

pyrtl/wire.py

@@ -224,6 +224,13 @@ def __getitem__(self, item):
     def __len__(self):
         return self.bitwidth
 
+    def __enter__(self):
+        raise core.PyrtlError('error, WireVector cannot be used directly as a context.  '
+                              '(you might be missing a ConditionalUpdate in your "with" block?)')
+
+    def __exit__(self, type, value, tb):
+        pass  # needed to allow the error raised in __enter__ to propagate up to the user
+
     def sign_extended(self, bitwidth):
         """ return a sign extended wirevector derived from self """
         return self._extend_with_bit(bitwidth, self[-1])

tests/test_conditional.py

@@ -269,6 +269,28 @@ def test_condition_wire_shortcut(self):
             o |= 1
         self.check_trace('i 01230123\no 11101110\n')
 
+    def test_condition_nice_error_message_nested(self):
+        with self.assertRaises(pyrtl.PyrtlError):
+            i = pyrtl.Register(bitwidth=2, name='i')
+            o = pyrtl.WireVector(bitwidth=2, name='o')
+            i.next <<= i + 1
+            with pyrtl.ConditionalUpdate() as condition:
+                with condition(i<=2):
+                    with condition(i==0):
+                        o |= 2
+                    with i==1:
+                        o |= 1
+                with condition.default:
+                    o |= 0
+
+    def test_condition_nice_error_message_shortcut(self):
+        with self.assertRaises(pyrtl.PyrtlError):
+            i = pyrtl.Register(bitwidth=2, name='i')
+            o = pyrtl.WireVector(bitwidth=2, name='o')
+            i.next <<= i + 1
+            with i<=2:
+                o |= 1
+
 
 if __name__ == "__main__":
     unittest.main()

tests/test_memblock.py

@@ -43,7 +43,18 @@ def test_memblock_direct_assignment_error(self):
         memory = pyrtl.MemBlock(bitwidth=self.bitwidth, addrwidth=self.addrwidth, name='memory')
         memory[self.mem_write_address] <<= 5
 
+""" -- TEST for Error comparing Mem reads #57
+    def test_memblock_to_memblock_direct_operation(self):
+        memory = pyrtl.MemBlock(bitwidth=self.bitwidth, addrwidth=self.addrwidth, name='memory')
+        temp = (memory[self.mem_read_address1] == memory[self.mem_read_address2])
+        temp = (memory[self.mem_read_address1] != memory[self.mem_read_address2])
+        temp = (memory[self.mem_read_address1] & memory[self.mem_read_address2])
+        temp = (memory[self.mem_read_address1] | memory[self.mem_read_address2])
+        temp = (memory[self.mem_read_address1] + memory[self.mem_read_address2])
+        temp = (memory[self.mem_read_address1] - memory[self.mem_read_address2])
+        temp = (memory[self.mem_read_address1] * memory[self.mem_read_address2])
+        self.output1 <<= temp
+"""
+
 if __name__ == "__main__":
     unittest.main()
-
-