compiler.embedding: always do one final inference pass.

Fixes #477.

artiq/compiler/embedding.py

@@ -560,6 +560,11 @@ class Stitcher:
                 break
             old_typedtree_hash = typedtree_hash
 
+        # When we have an excess of type information, sometimes we can infer every type
+        # in the AST without discovering every referenced attribute of host objects, so
+        # do one last pass unconditionally.
+        inferencer.visit(self.typedtree)
+
         # For every host class we embed, fill in the function slots
         # with their corresponding closures.
         for instance_type, constructor_type in list(self.type_map.values()):
@@ -579,7 +584,6 @@ class Stitcher:
                                                        getattr(constructor, attr))
                     synthesizer.finalize()
                     self._inject(ast)
-
         # After we have found all functions, synthesize a module to hold them.
         source_buffer = source.Buffer("", "<synthesized>")
         self.typedtree = asttyped.ModuleT(

artiq/test/lit/embedding/bug_477.py

@@ -0,0 +1,20 @@
+# RUN: %python -m artiq.compiler.testbench.embedding %s
+
+from artiq.experiment import *
+
+class MyClass:
+    def __init__(self, **kwargs):
+        for k, v in kwargs.items():
+            setattr(self, k, v)
+
+
+sl = [MyClass(x=1), MyClass(x=2)]
+
+@kernel
+def bug(l):
+    for c in l:
+        print(c.x)
+
+@kernel
+def entrypoint():
+    bug(sl)