PY-13484 Allow to extract constant from parameter default value

python/src/com/jetbrains/python/refactoring/introduce/constant/PyIntroduceConstantHandler.java

@@ -24,6 +24,7 @@ import com.jetbrains.python.codeInsight.controlflow.ScopeOwner;
 import com.jetbrains.python.codeInsight.imports.AddImportHelper;
 import com.jetbrains.python.psi.PyExpression;
 import com.jetbrains.python.psi.PyFile;
+import com.jetbrains.python.psi.PyParameterList;
 import com.jetbrains.python.refactoring.PyReplaceExpressionUtil;
 import com.jetbrains.python.refactoring.introduce.IntroduceHandler;
 import com.jetbrains.python.refactoring.introduce.IntroduceOperation;
@@ -65,6 +66,11 @@ public class PyIntroduceConstantHandler extends IntroduceHandler {
     return names;
   }
 
+  @Override
+  protected boolean isValidIntroduceContext(PsiElement element) {
+    return super.isValidIntroduceContext(element) || PsiTreeUtil.getParentOfType(element, PyParameterList.class) != null;
+  }
+
   @Override
   protected String getHelpId() {
     return "python.reference.introduceConstant";

python/testData/refactoring/introduceConstant/fromParameterDefaultValue.after.py

@@ -0,0 +1,5 @@
+a = 1 + 2
+
+
+def func(x=a + 3):
+    pass

python/testData/refactoring/introduceConstant/fromParameterDefaultValue.py

@@ -0,0 +1,2 @@
+def func(x=<selection>1 + 2</selection> + 3):
+    pass

python/testSrc/com/jetbrains/python/refactoring/PyIntroduceConstantTest.java

@@ -51,7 +51,7 @@ public class PyIntroduceConstantTest extends PyIntroduceTestCase {
   public void testSuggestUniqueNames() {  // PY-4409
     doTestSuggestions(PyExpression.class, "S1");
   }
-  
+
   public void testSuggestUniqueNamesGlobalScope() {  // PY-4409
     doTestSuggestions(PyExpression.class, "S1");
   }
@@ -60,6 +60,11 @@ public class PyIntroduceConstantTest extends PyIntroduceTestCase {
     doTestInplace(null);
   }
 
+  // PY-13484
+  public void testFromParameterDefaultValue() {
+    doTest();
+  }
+
   @Override
   protected String getTestDataPath() {
     return super.getTestDataPath() + "/refactoring/introduceConstant";