[Feature Request]Tell the compiler the type

[kgtkr]

Background

Currently, it is not possible to tell the compiler the type of the variable.
Although it can be solved by creating new variables, extra overhead occurs.

Proposal

x is Type;

Example

Current

try{
  ...
}catch(ex){
  const e:TypeError=ex;
}

Better

try{
  ...
}catch(e){
  e is TypeError;
}

[billba]

try{
  ...
}catch(e: TypeError){
  ...
}

[kgtkr]

@billba

Catch clause variable cannot have a type annotation.

And, try-catch is an example

[yortus]

@kgtkr for your example it's probably better to use a type guard, since e might be anything:

try {
    // ...
}
catch (e) {
    if (e instanceof TypeError) {
        // e is TypeError here
    }
    else {
        throw e;
    }
}

If you are suggesting a more general proposal, is there something here not already covered by #10421 (type assertion statements at block scope), or just plain type assertions?

[kgtkr]

It was a duplicate of #10421
I did not notice duplication. sorry
Close this issue