From 83ebb999c8488d88d8fdb7e0d8f3f4e976e695ff Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Fri, 28 Aug 2015 03:23:15 -0500
Subject: [PATCH] transforms.Inferencer: improve attribute unification
 diagnostic.

---
 artiq/compiler/embedding.py             |  1 +
 artiq/compiler/transforms/inferencer.py | 15 ++++++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/artiq/compiler/embedding.py b/artiq/compiler/embedding.py
index 0b903dbe0..ed9ec1ad4 100644
--- a/artiq/compiler/embedding.py
+++ b/artiq/compiler/embedding.py
@@ -10,6 +10,7 @@ from collections import OrderedDict, defaultdict
 
 from pythonparser import ast, algorithm, source, diagnostic, parse_buffer
 
+from ..language import core as language_core
 from . import types, builtins, asttyped, prelude
 from .transforms import ASTTypedRewriter, Inferencer, IntMonomorphizer
 
diff --git a/artiq/compiler/transforms/inferencer.py b/artiq/compiler/transforms/inferencer.py
index aa726e98f..852617c5e 100644
--- a/artiq/compiler/transforms/inferencer.py
+++ b/artiq/compiler/transforms/inferencer.py
@@ -91,9 +91,22 @@ class Inferencer(algorithm.Visitor):
         object_type = node.value.type.find()
         if not types.is_var(object_type):
             if node.attr in object_type.attributes:
+                def makenotes(printer, typea, typeb, loca, locb):
+                    return [
+                        diagnostic.Diagnostic("note",
+                            "expression of type {typea}",
+                            {"typea": printer.name(typea)},
+                            loca),
+                        diagnostic.Diagnostic("note",
+                            "expression of type {typeb}",
+                            {"typeb": printer.name(object_type)},
+                            node.value.loc)
+                    ]
+
                 # Assumes no free type variables in .attributes.
                 self._unify(node.type, object_type.attributes[node.attr],
-                            node.loc, None)
+                            node.loc, None,
+                            makenotes=makenotes, when=" for attribute '{}'".format(node.attr))
             elif types.is_instance(object_type) and \
                     node.attr in object_type.constructor.attributes:
                 # Assumes no free type variables in .attributes.