Should reject using / await using in a switch case / default clause

[sapphi-red]

🔎 Search Terms

explicit resource management, using, await using, switch, case clause, default clause

🕗 Version & Regression Information

• This changed between versions ______ and _______
• This changed in commit or PR _______
• This is the behavior in every version I tried, and I reviewed the FAQ for entries about _________
• I was unable to test this on prior versions because _______

⏯ Playground Link

https://www.typescriptlang.org/play/?target=99&ts=6.0.0-dev.20251030#code/M4dwlgLgxgFgBACgLIEMIwHQCcUDsAmA9gLYICUZcA3gFBxxQrACmcADAFx31wCuwYXAHM4+AExs4AXmpwA2gGUAnsQBGhADYZ8YYAAdCLALrlqAXzhmA3N3qqszFAGsb3RizgBGLjzgoQKJB8AsKiYp7Ssooq6lo6+obMJpRUFta2cPaOLjRmNDTMAB4GWBDmNEA

💻 Code

switch (Math.random()) {
  case 0:
    using d20 = { [Symbol.dispose]() {} };
    break;

  case 1:
    await using d21 = { [Symbol.dispose]() {} };
    break;
}

export {}

🙁 Actual behavior

No error happens.

🙂 Expected behavior

The error is reported that using / await using cannot be used here.

Additional information about the issue

The spec was updated to disallow this (rbuckton/ecma262#14).
Related PRs in other projects:

• Disallow using in bare case statement babel/babel#17323
• fix: raises syntax errors on invalid using declarations acornjs/acorn#1374

Some tests needs to be updated. For example:

TypeScript/tests/cases/conformance/statements/VariableStatements/usingDeclarations/usingDeclarations.1.ts

Lines 98 to 113 in 1654ebf

	switch (Math.random()) {
	case 0:
	using d20 = { [Symbol.dispose]() {} };
	break;
	case 1:
	using d21 = { [Symbol.dispose]() {} };
	break;
	}
	if (true)
	switch (0) {
	case 0:
	using d22 = { [Symbol.dispose]() {} };
	break;
	}

[RyanCavanaugh]

🤖 This is an automated response. I looked for things that might help (duplicates, FAQ entries, etc) but didn't find anything. A human will take a look!