Reduce unstubbing while processing instance level declarations (PY-27863)

Stub->AST switch happened when passed location was inside unstubbed file.

python/src/com/jetbrains/python/psi/impl/PyClassImpl.java

@@ -1269,8 +1269,8 @@ public class PyClassImpl extends PyBaseElementImpl<PyClassStub> implements PyCla
 
   @Override
   public boolean processInstanceLevelDeclarations(@NotNull PsiScopeProcessor processor, @Nullable PsiElement location) {
-    Map<String, PyTargetExpression> declarationsInMethod = new HashMap<>();
-    PyFunction instanceMethod = PsiTreeUtil.getParentOfType(location, PyFunction.class);
+    final Map<String, PyTargetExpression> declarationsInMethod = new HashMap<>();
+    final PyFunction instanceMethod = PsiTreeUtil.getStubOrPsiParentOfType(location, PyFunction.class);
     final PyClass containingClass = instanceMethod != null ? instanceMethod.getContainingClass() : null;
     if (instanceMethod != null && containingClass != null && CompletionUtil.getOriginalElement(containingClass) == this) {
       collectInstanceAttributes(instanceMethod, declarationsInMethod);

python/testData/resolve/AttributeClassLevelAnnotation.py

@@ -0,0 +1,3 @@
+import b
+b.B().some_attr
+#       <ref>

python/testData/resolve/AttributeClassLevelAnnotation/b.py

@@ -0,0 +1,3 @@
+class B(object):
+    def __init__(self) -> None:
+        self.some_attr = unresolved

python/testSrc/com/jetbrains/python/PyResolveTest.java

@@ -1,10 +1,7 @@
 // Copyright 2000-2017 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package com.jetbrains.python;
 
-import com.intellij.psi.PsiElement;
-import com.intellij.psi.PsiPolyVariantReference;
-import com.intellij.psi.PsiReference;
-import com.intellij.psi.ResolveResult;
+import com.intellij.psi.*;
 import com.intellij.psi.util.PsiTreeUtil;
 import com.intellij.testFramework.UsefulTestCase;
 import com.jetbrains.python.codeInsight.controlflow.ScopeOwner;
@@ -14,6 +11,8 @@ import com.jetbrains.python.fixtures.PyResolveTestCase;
 import com.jetbrains.python.psi.*;
 import com.jetbrains.python.psi.impl.PyPsiUtils;
 import com.jetbrains.python.psi.resolve.ImportedResolveResult;
+import com.jetbrains.python.psi.resolve.PyResolveContext;
+import com.jetbrains.python.psi.types.PyClassTypeImpl;
 import com.jetbrains.python.psi.types.TypeEvalContext;
 
 public class PyResolveTest extends PyResolveTestCase {
@@ -1247,4 +1246,22 @@ public class PyResolveTest extends PyResolveTestCase {
     myFixture.copyDirectoryToProject("resolve/" + getTestName(false), "");
     assertResolvesTo(PyFunction.class, "append");
   }
+
+  // PY-27863
+  public void testAttributeClassLevelAnnotation() {
+    myFixture.copyDirectoryToProject("resolve/" + getTestName(false), "");
+
+    final PyTargetExpression target = assertResolvesTo(PyTargetExpression.class, "some_attr");
+
+    final PsiFile file = myFixture.getFile();
+    final TypeEvalContext context = TypeEvalContext.codeAnalysis(myFixture.getProject(), file);
+    final PyResolveContext resolveContext = PyResolveContext.noImplicits().withTypeEvalContext(context);
+
+    // It's like an attempt to find type annotation for attribute on the class level.
+    final PyClassTypeImpl classType = new PyClassTypeImpl(target.getContainingClass(), true);
+    assertEmpty(classType.resolveMember(target.getReferencedName(), target, AccessDirection.READ, resolveContext, true));
+
+    assertProjectFilesNotParsed(file);
+    assertSdkRootsNotParsed(file);
+  }
 }