Add a ContextSet.

This is not bug free yet, but it's going to be a good abstraction for a lot of small things.

jedi/evaluate/compiled/__init__.py

@@ -15,6 +15,7 @@ from jedi.evaluate.filters import AbstractFilter, AbstractNameDefinition, \
     ContextNameMixin
 from jedi.evaluate.context import Context, LazyKnownContext
 from jedi.evaluate.compiled.getattr_static import getattr_static
+from jedi.common import ContextSet
 from . import fake
 
 
@@ -83,9 +84,9 @@ class CompiledObject(Context):
     def py__call__(self, params):
         if inspect.isclass(self.obj):
             from jedi.evaluate.instance import CompiledInstance
-            return set([CompiledInstance(self.evaluator, self.parent_context, self, params)])
+            return ContextSet(CompiledInstance(self.evaluator, self.parent_context, self, params))
         else:
-            return set(self._execute_function(params))
+            return ContextSet.from_iterable(self._execute_function(params))
 
     @CheckAttribute
     def py__class__(self):
@@ -221,9 +222,9 @@ class CompiledObject(Context):
     def py__getitem__(self, index):
         if type(self.obj) not in (str, list, tuple, unicode, bytes, bytearray, dict):
             # Get rid of side effects, we won't call custom `__getitem__`s.
-            return set()
+            return ContextSet()
 
-        return set([create(self.evaluator, self.obj[index])])
+        return ContextSet(create(self.evaluator, self.obj[index]))
 
     @CheckAttribute
     def py__iter__(self):
@@ -278,7 +279,7 @@ class CompiledObject(Context):
         return []  # Builtins don't have imports
 
     def dict_values(self):
-        return set(create(self.evaluator, v) for v in self.obj.values())
+        return ContextSet(create(self.evaluator, v) for v in self.obj.values())
 
 
 class CompiledName(AbstractNameDefinition):
@@ -301,7 +302,9 @@ class CompiledName(AbstractNameDefinition):
     @underscore_memoization
     def infer(self):
         module = self.parent_context.get_root_context()
-        return [_create_from_name(self._evaluator, module, self.parent_context, self.string_name)]
+        return ContextSet(_create_from_name(
+            self._evaluator, module, self.parent_context, self.string_name
+        ))
 
 
 class SignatureParamName(AbstractNameDefinition):
@@ -318,13 +321,13 @@ class SignatureParamName(AbstractNameDefinition):
     def infer(self):
         p = self._signature_param
         evaluator = self.parent_context.evaluator
-        types = set()
+        contexts = ContextSet()
         if p.default is not p.empty:
-            types.add(create(evaluator, p.default))
+            contexts = ContextSet(create(evaluator, p.default))
         if p.annotation is not p.empty:
             annotation = create(evaluator, p.annotation)
-            types |= annotation.execute_evaluated()
-        return types
+            contexts |= annotation.execute_evaluated()
+        return contexts
 
 
 class UnresolvableParamName(AbstractNameDefinition):
@@ -335,7 +338,7 @@ class UnresolvableParamName(AbstractNameDefinition):
         self.string_name = name
 
     def infer(self):
-        return set()
+        return ContextSet()
 
 
 class CompiledContextName(ContextNameMixin, AbstractNameDefinition):
@@ -356,7 +359,7 @@ class EmptyCompiledName(AbstractNameDefinition):
         self.string_name = name
 
     def infer(self):
-        return []
+        return ContextSet()
 
 
 class CompiledObjectFilter(AbstractFilter):