Microsoft/TypeScript
Using declarations like a statement leads to strange bugs.
Aberta
#62.896 aberto em 14 de dez. de 2025
BugDomain: check: Control FlowHelp Wanted
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Description
🔎 Search Terms
function declaration statement
🕗 Version & Regression Information
v 5.9.3
⏯ Playground Link
💻 Code
if (true) var x = 0;
console.log(x); //ok
for (let i = 0; i < 3; i++) var j = i;
console.log(j) //error in compile: j is used before being assign, no error in runtime
if (true) function f() {}
f()//no error in compile time, but error in runtime: In strict mode code, functions can only be declared at top level or inside a block
🙁 Actual behavior
🙂 Expected behavior
Additional information about the issue
The questions above was raised only in academic purpose. I understand that there are no real use cases to apply code above.