Make sure we use the right context in case of goto with decorators, fixes #1427

jedi/inference/base_value.py

@@ -252,7 +252,7 @@ class Value(HelperValueMixin, BaseValue):
         return self.parent_context.is_stub()
 
     def _as_context(self):
-        raise NotImplementedError('Not all values need to be converted to contexts')
+        raise NotImplementedError('Not all values need to be converted to contexts: %s', self)
 
 
 def iterate_values(values, contextualized_node=None, is_async=False):

jedi/inference/names.py

@@ -165,7 +165,7 @@ class AbstractTreeName(AbstractNameDefinition):
                 new_dotted.children[index - 1:] = []
                 values = context.infer_node(new_dotted)
                 return unite(
-                    value.goto(name, name_context=value.as_context())
+                    value.goto(name, name_context=context)
                     for value in values
                 )
 

test/completion/decorators.py

@@ -330,3 +330,16 @@ import abc
 
 #? ['abstractmethod']
 @abc.abstractmethod
+
+# -----------------
+# Goto
+# -----------------
+x = 1
+
+#! 5 []
+@x.foo()
+def f(): pass
+
+#! 1 ['x = 1']
+@x.foo()
+def f(): pass