Fixed unresolved reference to parameter inside lambda in decorator (PY-6083)

python/src/com/jetbrains/python/codeInsight/dataflow/scope/ScopeUtil.java

@@ -57,10 +57,12 @@ public class ScopeUtil {
 
   @Nullable
   public static ScopeOwner getResolveScopeOwner(PsiElement element) {
-    // References in default values of parameters are defined somewhere in outer scopes, as well as references in decorators and
-    // superclasses
-    if (PsiTreeUtil.getParentOfType(element, PyParameter.class, PyDecorator.class) != null) {
-      element = getScopeOwner(element);
+    // References in default values of parameters are defined somewhere in outer scopes, as well as references in decorators (if they are
+    // not inside a lambda, see PY-6083) and superclasses
+    final ScopeOwner initialScopeOwner = getScopeOwner(element);
+    if (!(initialScopeOwner instanceof PyLambdaExpression && PsiTreeUtil.getParentOfType(element, PyDecorator.class) != null) &&
+        PsiTreeUtil.getParentOfType(element, PyParameter.class, PyDecorator.class) != null) {
+      element = initialScopeOwner;
     }
     final PyClass containingClass = PsiTreeUtil.getParentOfType(element, PyClass.class);
     if (containingClass != null && element != null &&

python/testData/resolve/LambdaParameterInDecorator.py

@@ -0,0 +1,6 @@
+def f(y):
+    return y
+
+@f(lambda xx: xx<ref>)
+def g():
+    pass

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

@@ -457,4 +457,9 @@ public class PyResolveTest extends PyResolveTestCase {
     final PyFunction function = assertResolvesTo(PyFunction.class, "getStore");
     assertEquals("PluginMetaclass", function.getContainingClass().getName());
   }
+
+  // PY-6083
+  public void testLambdaParameterInDecorator() {
+    assertResolvesTo(PyNamedParameter.class, "xx");
+  }
 }