Fixed type assertions for named tuples (PY-4611)

python/src/com/jetbrains/python/codeInsight/stdlib/PyNamedTupleType.java

@@ -29,7 +29,7 @@ public class PyNamedTupleType extends PyClassType implements PyCallableType {
   private final boolean myDefinition;
   private final PsiElement myDeclaration;
   private final List<String> myFields;
-  
+
   private static final ImmutableSet<String> ourClassMembers = ImmutableSet.of("_fields", "_make");
   private static final ImmutableSet<String> ourInstanceMembers = ImmutableSet.of("_asdict", "_replace");
 
@@ -83,7 +83,7 @@ public class PyNamedTupleType extends PyClassType implements PyCallableType {
 
   @Override
   public String getName() {
-    return "namedtuple '" + myName + "'";
+    return myName;
   }
 
   @Override
@@ -99,6 +99,16 @@ public class PyNamedTupleType extends PyClassType implements PyCallableType {
     return null;
   }
 
+  @Override
+  public PyClassType toInstance() {
+    return myIsDefinition ? new PyNamedTupleType(myDeclaration, myName, myFields, false) : this;
+  }
+
+  @Override
+  public String toString() {
+    return "PyNamedTupleType: " + myName;
+  }
+
   @Nullable
   public static PyType fromCall(PyCallExpression call) {
     final String name = PyUtil.strValue(call.getArgument(0, PyExpression.class));

python/testData/inspections/PyUnresolvedReferencesInspection/namedTuple.py

@@ -10,3 +10,6 @@ print p.__add__
 print p._asdict()
 print Point._fields
 print p._replace
+
+if isinstance(p, Point):
+    p.x