Ambiguous scoping of if statement body

[acutmore]

🔎 Search Terms

type, scoping, ifStatement

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about type scoping

⏯ Playground Link

https://www.typescriptlang.org/play/?ts=5.6.2#code/GYVwdgxgLglg9mABMAjACgJSIN4ChEGIzCJpQBOIAphvoYVAJ4AOViAzogLwcUxgBzANx16iCAnZwANlQB00uALQAiFYgCGndhhH1cAX1y5QkWAmQAmTDlFESZSjVtj6TVh269y-YXaP0EmBSsgpKqupaHLqGuEA

💻 Code

function f1() {
 if (true)
 type s = string;
 console.log("" as s);
}

function f2() {
 if (true) {
 type s = string;
 }
 console.log("" as s);
}

🙁 Actual behavior

From type-system perspective in the first if it appear that the console.log is part of the body of the if because the type is in scope. However the JS emit is:

function f1() {
 if (true)
 ;
 console.log("");
}

So the console.log is not part of the if body.

🙂 Expected behavior

function f1() {
 if (true)
 type s = string;
 // @ts-expect-error : "cannot find name 's'"
 console.log("" as s);
}

Also happy for this to be a parse error. An if statement with only a type declaration as a body hopefully has no use cases.

Additional information about the issue

No response

[RyanCavanaugh]

Parse error seems like the best option; we can use the same logic that disallows

if (true) let n = 3;