Remove some unnecessary checks for None (#1464)

* Less paranoia in generating constraints for TypeVarType

self.actual is declared as having type Type, and (as of commit
b602ecc) cannot be None.

* Less paranoia in TypeInfo.is_generic

self.variables is declared as having type List[TypeVarDef], and can
never be None.

Author: rwbarton

mypy/constraints.py

@@ -163,10 +163,7 @@ def visit_partial_type(self, template: PartialType) -> List[Constraint]:
     # Non-trivial leaf type
 
     def visit_type_var(self, template: TypeVarType) -> List[Constraint]:
-        if self.actual:
-            return [Constraint(template.id, self.direction, self.actual)]
-        else:
-            return []
+        return [Constraint(template.id, self.direction, self.actual)]
 
     # Non-leaf types
 

mypy/nodes.py

@@ -1776,7 +1776,7 @@ def fullname(self) -> str:
 
     def is_generic(self) -> bool:
         """Is the type generic (i.e. does it have type variables)?"""
-        return self.type_vars is not None and len(self.type_vars) > 0
+        return len(self.type_vars) > 0
 
     def get(self, name: str) -> 'SymbolTableNode':
         for cls in self.mro: