From cb2f18ee37b05868a814ef0b25f752097993a7bc Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Wed, 16 Jan 2019 15:55:28 +0000
Subject: [PATCH] hdl.ast: fix naming of Signal.like() signals when tracer
 fails.

---
 nmigen/hdl/ast.py           | 10 +++++++---
 nmigen/test/test_hdl_ast.py |  2 ++
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/nmigen/hdl/ast.py b/nmigen/hdl/ast.py
index 5a03ef7..be1440b 100644
--- a/nmigen/hdl/ast.py
+++ b/nmigen/hdl/ast.py
@@ -611,7 +611,7 @@ class Signal(Value, DUID):
         self.decoder = decoder
 
     @classmethod
-    def like(cls, other, src_loc_at=0, **kwargs):
+    def like(cls, other, name=None, src_loc_at=0, **kwargs):
         """Create Signal based on another.
 
         Parameters
@@ -619,8 +619,12 @@ class Signal(Value, DUID):
         other : Value
             Object to base this Signal on.
         """
-        kw = dict(shape=cls.wrap(other).shape(),
-                  name=tracer.get_var_name(depth=2 + src_loc_at))
+        if name is None:
+            try:
+                name = tracer.get_var_name(depth=2 + src_loc_at)
+            except tracer.NameNotFound:
+                name = "$like"
+        kw = dict(shape=cls.wrap(other).shape(), name=name)
         if isinstance(other, cls):
             kw.update(reset=other.reset, reset_less=other.reset_less,
                       attrs=other.attrs, decoder=other.decoder)
diff --git a/nmigen/test/test_hdl_ast.py b/nmigen/test/test_hdl_ast.py
index bf6b0fd..603a6cc 100644
--- a/nmigen/test/test_hdl_ast.py
+++ b/nmigen/test/test_hdl_ast.py
@@ -458,6 +458,8 @@ class SignalTestCase(FHDLTestCase):
         self.assertEqual(s5.decoder, str)
         s6 = Signal.like(10)
         self.assertEqual(s6.shape(), (4, False))
+        s7 = [Signal.like(Signal(4))][0]
+        self.assertEqual(s7.name, "$like")
 
 
 class ClockSignalTestCase(FHDLTestCase):
-- 
2.30.2