compiler: pull in dependencies in more finely grained way (fixes #181).

artiq/compiler/__init__.py

@@ -1,2 +0,0 @@
-from .module import Module, Source
-from .embedding import Stitcher

artiq/compiler/types.py

@@ -5,7 +5,6 @@ in :mod:`asttyped`.
 
 import string
 from collections import OrderedDict
-from pythonparser import diagnostic
 from . import iodelay
 
 
@@ -426,6 +425,8 @@ class TDelay(Type):
     """
 
     def __init__(self, duration, cause):
+        # Avoid pulling in too many dependencies with `artiq.language`.
+        from pythonparser import diagnostic
         assert duration is None or isinstance(duration, iodelay.Expr)
         assert cause is None or isinstance(cause, diagnostic.Diagnostic)
         assert (not (duration and cause)) and (duration or cause)

artiq/coredevice/core.py

@@ -6,7 +6,8 @@ from artiq.language.core import *
 from artiq.language.types import *
 from artiq.language.units import *
 
-from artiq.compiler import Stitcher, Module
+from artiq.compiler.module import Module
+from artiq.compiler.embedding import Stitcher
 from artiq.compiler.targets import OR1KTarget
 
 # Import for side effects (creating the exception classes).