embedding: reimplement 373578b properly.

whitequark · whitequark · commit 2678bb060a9f · 2016-07-07T16:01:22.000Z
The core of the problem that 373578b was attempting to solve is that diagnostics sometimes should be chained; one way of chaining is the loc.expanded_from feature, which handles macro-like expansion, but another is providing context. Before this commit, context was provided using an ad-hoc override of a diagnostic engine, which did not work in cases where diagnostic engine was not threaded through the call stack. This commit uses the newly added pythonparser context feature to elegantly handle the problem.
diff --git a/artiq/compiler/embedding.py b/artiq/compiler/embedding.py
@@ -425,24 +425,18 @@ def _compute_value_type(self, object_value, object_type, object_loc, attr_name,
                 attr_value_type = builtins.TList(builtins.TInt64())
 
         if attr_value_type is None:
-            # Slow path. We don't know what exactly is the attribute value,
-            # so we quote it only for the error message that may possibly result.
-            ast = self.quote(attr_value, object_loc.loc)
-
-            def proxy_diagnostic(diag):
-                note = diagnostic.Diagnostic("note",
-                    "while inferring a type for an attribute '{attr}' of a host object",
-                    {"attr": attr_name},
-                    loc)
-                diag.notes.append(note)
-
-                self.engine.process(diag)
+            note = diagnostic.Diagnostic("note",
+                "while inferring a type for an attribute '{attr}' of a host object",
+                {"attr": attr_name},
+                loc)
 
-            proxy_engine = diagnostic.Engine()
-            proxy_engine.process = proxy_diagnostic
-            Inferencer(engine=proxy_engine).visit(ast)
-            IntMonomorphizer(engine=proxy_engine).visit(ast)
-            attr_value_type = ast.type
+            with self.engine.context(note):
+                # Slow path. We don't know what exactly is the attribute value,
+                # so we quote it only for the error message that may possibly result.
+                ast = self.quote(attr_value, object_loc.expanded_from)
+                Inferencer(engine=self.engine).visit(ast)
+                IntMonomorphizer(engine=self.engine).visit(ast)
+                attr_value_type = ast.type
 
         return attributes, attr_value_type
 
@@ -716,32 +710,24 @@ def _type_of_param(self, function, loc, param, is_syscall):
                 notes=self._call_site_note(loc, is_syscall))
             self.engine.process(diag)
         elif param.default is not inspect.Parameter.empty:
-            # Try and infer the type from the default value.
-            # This is tricky, because the default value might not have
-            # a well-defined type in APython.
-            # In this case, we bail out, but mention why we do it.
-            ast = self._quote(param.default, None)
-
-            def proxy_diagnostic(diag):
-                note = diagnostic.Diagnostic("note",
-                    "expanded from here while trying to infer a type for an"
-                    " unannotated optional argument '{argument}' from its default value",
-                    {"argument": param.name},
-                    self._function_loc(function))
-                diag.notes.append(note)
-
-                note = self._call_site_note(loc, is_syscall)
-                if note:
-                    diag.notes += note
-
-                self.engine.process(diag)
-
-            proxy_engine = diagnostic.Engine()
-            proxy_engine.process = proxy_diagnostic
-            Inferencer(engine=proxy_engine).visit(ast)
-            IntMonomorphizer(engine=proxy_engine).visit(ast)
-
-            return ast.type
+            notes = []
+            notes.append(diagnostic.Diagnostic("note",
+                "expanded from here while trying to infer a type for an"
+                " unannotated optional argument '{argument}' from its default value",
+                {"argument": param.name},
+                self._function_loc(function)))
+            if loc is not None:
+                notes.append(self._call_site_note(loc, is_syscall))
+
+            with self.engine.context(*notes):
+                # Try and infer the type from the default value.
+                # This is tricky, because the default value might not have
+                # a well-defined type in APython.
+                # In this case, we bail out, but mention why we do it.
+                ast = self._quote(param.default, None)
+                Inferencer(engine=self.engine).visit(ast)
+                IntMonomorphizer(engine=self.engine).visit(ast)
+                return ast.type
         else:
             # Let the rest of the program decide.
             return types.TVar()
diff --git a/artiq/test/lit/embedding/error_host_only.py b/artiq/test/lit/embedding/error_host_only.py
@@ -0,0 +1,19 @@
+# RUN: %python -m artiq.compiler.testbench.embedding +diag %s 2>%t
+# RUN: OutputCheck %s --file-to-check=%t
+
+from artiq.language.core import *
+from artiq.language.types import *
+
+class foo:
+    # CHECK-L: ${LINE:+2}: fatal: this function cannot be called as an RPC
+    @host_only
+    def pause(self):
+        pass
+
+x = foo()
+
+@kernel
+def entrypoint():
+    # CHECK-L: ${LINE:+2}: note: in function called remotely here
+    # CHECK-L: ${LINE:+1}: note: while inferring a type for an attribute 'pause' of a host object
+    x.pause()
