Refactoring extraction methods leads to syntax errors.

[provide a description of the issue]

Environment
-Operating System: Windows11
-JDK version: 17
-Visual Studio Code version: 1.88
-Java extension version: 1.29

Steps to Reproduce:

1. select " this.value = value;"
2. click “Refacator-Extract to method”

class ExtractMethodTest {
private final int value;
public ExtractMethodTest(int value) {
// extract method
this.value = value;
}
}

refactoring result：

Reason: The final field ExtractMethodTest.value cannot be assigned

Expected behavior: Check before and after refactoring, and issue a warning if there are syntax errors

Start by reproducing the extraction-method refactoring on the Java snippet with JDK 17, VS Code 1.88, and Java extension 1.29. Trace the extraction refactoring entry point and its validation flow, then verify that invalid output is detected and a warning is issued rather than silently producing syntax errors.