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switch exhaustiveness check not working within deconstruction pattern

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#1,260 1 comment 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
java, vscode
Domain
devtools

Research direction

Reproduce the nested deconstruction-pattern switch from the issue in the listed VS Code and Java environment, and compare the extension diagnostic with pure javac. Trace where the “A switch expression should have a default case” diagnostic is produced. Done means the exhaustive example builds without that diagnostic while genuinely non-exhaustive switches still report it.

Written by the indexing model from the issue text.

Description

ai-triaged bug compile

Build fails on missing default case, even though switch is exhaustive.

Environment
  • Operating System: Windows 10
  • JDK version: 19
  • Visual Studio Code version: 1.73.1
  • Java extension version: 1.12.0
  • Java Debugger extension version: 0.46.0
Steps To Reproduce

make (exhaustive) switch expression with nested deconstruction pattern
build fails -> "Add default case"

Example:

package dev.redio;

import static dev.redio.Main.Activity.*;

public class Main {

    public static void main(String[] args) {
        record Pair(boolean weekend, Activity activity) {}
        var pair = new Pair(true, new Sleeping(8));
        var msg = switch (pair) {   // <- A switch expression should have a default caseJava(1073743531)
            case Pair(boolean b, Sleeping s) -> "3";
            case Pair(boolean b, Skiing s) -> "4";
            case Pair(boolean b, Coding c) -> "5";
        };
        
        System.out.println(msg);
    }

    sealed interface Activity {
        record Sleeping(int hours) implements Activity {}
        record Skiing(String resort) implements Activity {}
        record Coding() implements Activity {}
    }
    
}
Current Result

Build Error (A switch expression should have a default caseJava(1073743531))

Expected Result

Build Success(Switch is exhaustive since all nested deconstruction possibilities are covered)

Additional Informations

Compiles with pure javac without errors
Intended and correct syntax confirmed by member of development team of the feature.

Dominant language
TypeScript
Stars
591
Forks
429
Avg merge
1d 9h
Merged PRs (30d)
19

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