compiler.embedding: default RPC return annotation is -> TNone.

artiq/compiler/embedding.py

@@ -595,12 +595,7 @@ class Stitcher:
             ret_type = self._extract_annot(function, signature.return_annotation,
                                            "return type", loc, is_syscall=syscall is not None)
         elif syscall is None:
-            diag = diagnostic.Diagnostic("error",
-                "function must have a return type annotation to be called remotely", {},
-                self._function_loc(function),
-                notes=self._call_site_note(loc, is_syscall=False))
-            self.engine.process(diag)
-            ret_type = types.TVar()
+            ret_type = builtins.TNone()
         else: # syscall is not None
             diag = diagnostic.Diagnostic("error",
                 "system call must have a return type annotation", {},

artiq/test/coredevice/embedding.py

@@ -12,7 +12,7 @@ class Roundtrip(EnvExperiment):
 class RoundtripTest(ExperimentCase):
     def assertRoundtrip(self, obj):
         exp = self.create(Roundtrip)
-        def callback(objcopy) -> TNone:
+        def callback(objcopy):
             self.assertEqual(obj, objcopy)
         exp.roundtrip(obj, callback)
 

lit-test/test/embedding/error_rpc_return.py

@@ -1,14 +0,0 @@
-# RUN: %python -m artiq.compiler.testbench.embedding %s >%t
-# RUN: OutputCheck %s --file-to-check=%t
-
-from artiq.language.core import *
-from artiq.language.types import *
-
-# CHECK-L: ${LINE:+1}: error: function must have a return type annotation to be called remotely
-def foo():
-    pass
-
-@kernel
-def entrypoint():
-    # CHECK-L: ${LINE:+1}: note: in function called remotely here
-    foo()