PY-27186 Use generic type information from .pyi stub in the respective .py file

by implementing missing getGenericType() and getGenericSubstitutions()
in PyiTypeProvider.

python/src/com/jetbrains/python/pyi/PyiTypeProvider.java

@@ -17,16 +17,16 @@ package com.jetbrains.python.pyi;
 
 import com.intellij.openapi.util.Ref;
 import com.intellij.psi.PsiElement;
+import com.jetbrains.python.codeInsight.typing.PyTypingTypeProvider;
 import com.jetbrains.python.psi.*;
 import com.jetbrains.python.psi.impl.PyCallExpressionHelper;
 import com.jetbrains.python.psi.types.*;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
+
+import static com.jetbrains.python.psi.PyUtil.as;
 
 /**
  * @author vlan
@@ -139,4 +139,24 @@ public class PyiTypeProvider extends PyTypeProviderBase {
     }
     return null;
   }
+
+  @Nullable
+  @Override
+  public PyType getGenericType(@NotNull PyClass cls, @NotNull TypeEvalContext context) {
+    final PyClass classStub = as(PyiUtil.getPythonStub(cls), PyClass.class);
+    if (classStub != null) {
+      return new PyTypingTypeProvider().getGenericType(classStub, context);
+    }
+    return null;
+  }
+
+  @NotNull
+  @Override
+  public Map<PyType, PyType> getGenericSubstitutions(@NotNull PyClass cls, @NotNull TypeEvalContext context) {
+    final PyClass classStub = as(PyiUtil.getPythonStub(cls), PyClass.class);
+    if (classStub != null) {
+      return new PyTypingTypeProvider().getGenericSubstitutions(classStub, context);
+    }
+    return Collections.emptyMap();
+  }
 }

python/testData/pyi/type/genericClassDefinitionInOtherFile/GenericClassDefinitionInOtherFile.py

@@ -0,0 +1,3 @@
+from other import Holder
+
+ex<caret>pr = Holder(42).get()

python/testData/pyi/type/genericClassDefinitionInOtherFile/other.py

@@ -0,0 +1,6 @@
+class Holder:
+    def __init__(self, x):
+        self.x = x
+
+    def get(self):
+        return self.x

python/testData/pyi/type/genericClassDefinitionInOtherFile/other.pyi

@@ -0,0 +1,11 @@
+from typing import Generic, TypeVar
+
+T = TypeVar('T')
+
+
+class Holder(Generic[T]):
+    def __init__(self, x: T):
+        pass
+
+    def get(self) -> T:
+        pass

python/testData/pyi/type/genericClassDefinitionInSameFile/GenericClassDefinitionInSameFile.py

@@ -0,0 +1,9 @@
+class Holder:
+    def __init__(self, x):
+        self.x = x
+
+    def get(self):
+        return self.x
+
+
+ex<caret>pr = Holder(42).get()

python/testData/pyi/type/genericClassDefinitionInSameFile/GenericClassDefinitionInSameFile.pyi

@@ -0,0 +1,11 @@
+from typing import Generic, TypeVar
+
+T = TypeVar('T')
+
+
+class Holder(Generic[T]):
+    def __init__(self, x: T):
+        pass
+
+    def get(self) -> T:
+        pass

python/testSrc/com/jetbrains/python/pyi/PyiTypeTest.java

@@ -133,4 +133,13 @@ public class PyiTypeTest extends PyTestCase {
   public void testOverloadedNotMatchedGenericType() {
     doTest("Union[Dict[str, Any], list]");
   }
+
+  public void testGenericClassDefinitionInOtherFile() {
+    doTest("int");
+  }
+
+  // PY-27186
+  public void testGenericClassDefinitionInSameFile() {
+    doTest("int");
+  }
 }