Don't warn about using values with generic types as normal Python values (PY-7244)

Generics are not a part of Python, they are used in PyCharm as a convenient tool for more powerful code completion and weak type checking. Python programmers are not expected to annotate their classes with generics instantiation annotations.

python/src/com/jetbrains/python/psi/types/PyTypeChecker.java

@@ -50,9 +50,6 @@ public class PyTypeChecker {
     if (actual instanceof PyTypeReference) {
       return match(expected, ((PyTypeReference)actual).resolve(null, context), context, substitutions, false);
     }
-    if (isUnknown(actual)) {
-      return true;
-    }
     if (expected instanceof PyGenericType && substitutions != null) {
       final PyGenericType generic = (PyGenericType)expected;
       final PyType subst = substitutions.get(generic);
@@ -72,6 +69,9 @@ public class PyTypeChecker {
         return true;
       }
     }
+    if (isUnknown(actual)) {
+      return true;
+    }
     if (actual instanceof PyUnionType) {
       for (PyType m : ((PyUnionType)actual).getMembers()) {
         if (!match(expected, m, context, substitutions, recursive)) {
@@ -149,7 +149,7 @@ public class PyTypeChecker {
   }
 
   public static boolean isUnknown(@Nullable PyType type) {
-    if (type == null || type instanceof PyTypeReference) {
+    if (type == null || type instanceof PyTypeReference || type instanceof PyGenericType) {
       return true;
     }
     if (type instanceof PyUnionType) {

python/testData/inspections/PyTypeCheckerInspection/GenericArguments.py

@@ -0,0 +1,18 @@
+class B(object):
+    def __init__(self, x):
+        """
+        :type x: T
+        :rtype: B of T
+        """
+        self._x = x
+
+    def foo(self):
+        """
+        :rtype: T
+        """
+        return self._x
+
+class C(B):
+    def bar(self):
+        expr = self.foo()
+        return 'foo' + expr #pass

python/testData/inspections/PyUnresolvedReferencesInspection/attributesOfGenerics.py

@@ -0,0 +1,18 @@
+class B(object):
+    def __init__(self, x):
+        """
+        :type x: T
+        :rtype: B of T
+        """
+        self._x = x
+
+    def foo(self):
+        """
+        :rtype: T
+        """
+        return self._x
+
+class C(B):
+    def bar(self):
+        expr = self.foo()
+        return expr.upper() #pass

python/testSrc/com/jetbrains/python/inspections/PyTypeCheckerInspectionTest.java

@@ -140,4 +140,9 @@ public class PyTypeCheckerInspectionTest extends PyTestCase {
   public void testAssignedOperator() {
     doTest();
   }
+
+  // PY-7244
+  public void testGenericArguments() {
+    doTest();
+  }
 }

python/testSrc/com/jetbrains/python/inspections/PyUnresolvedReferencesInspectionTest.java

@@ -175,6 +175,11 @@ public class PyUnresolvedReferencesInspectionTest extends PyTestCase {
     doTest();
   }
 
+  // PY-7244
+  public void testAttributesOfGenerics() {
+    doTest();
+  }
+
   private void doTest() {
     myFixture.configureByFile(TEST_DIRECTORY + getTestName(true) + ".py");
     myFixture.enableInspections(PyUnresolvedReferencesInspection.class);