From 031a9e26160748bc426e6d2a0b687603e1345bff Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Tue, 1 Jan 2019 03:35:34 +0000
Subject: [PATCH] hdl.rec: use a helpful error on unknown field reference.

---
 nmigen/hdl/rec.py           | 8 ++++++--
 nmigen/test/test_hdl_rec.py | 9 +++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/nmigen/hdl/rec.py b/nmigen/hdl/rec.py
index 32028af..f291087 100644
--- a/nmigen/hdl/rec.py
+++ b/nmigen/hdl/rec.py
@@ -87,10 +87,14 @@ class Record(Value):
                 self.fields[field_name] = Signal(field_shape, name=concat(name, field_name))
 
     def __getattr__(self, name):
-        return self.fields[name]
+        return self[name]
 
     def __getitem__(self, name):
-        return self.fields[name]
+        try:
+            return self.fields[name]
+        except KeyError:
+            raise NameError("Record does not have a field '{}'. Did you mean one of: {}?"
+                            .format(name, ", ".join(self.fields))) from None
 
     def shape(self):
         return sum(len(f) for f in self.fields.values()), False
diff --git a/nmigen/test/test_hdl_rec.py b/nmigen/test/test_hdl_rec.py
index 501fda9..dd5cb7b 100644
--- a/nmigen/test/test_hdl_rec.py
+++ b/nmigen/test/test_hdl_rec.py
@@ -78,3 +78,12 @@ class RecordTestCase(FHDLTestCase):
 
         self.assertEqual(repr(r), "(rec <unnamed> stb)")
         self.assertEqual(r.stb.name, "stb")
+
+    def test_wrong_field(self):
+        r = Record([
+            ("stb", 1),
+            ("ack", 1),
+        ])
+        with self.assertRaises(NameError,
+                msg="Record does not have a field 'en'. Did you mean one of: stb, ack?"):
+            r.en
-- 
2.30.2