No "Block-scoped variable '...' used before its declaration." error for earlier function call

[donaldpipowitch]

TypeScript Version: Playground (2.3.4?)

Code

class Bar {
    constructor() {
        console.log(foo); // BUG: no error
    }
}
const bar = new Bar();

function Bar2() {
    console.log(foo); // BUG: no error
}
const bar2 = new Bar2();

function bar3() {
    console.log(foo); // BUG: no error
}
bar3();

console.log(foo); // error is thrown

const foo = 2;

Expected behavior:

"Block-scoped variable 'foo' used before its declaration." error for the three cases mentioned in the code example.

I don't know if this is out of scope for TypeScript, but maybe flow analysis could catch very simple cases like this:

function bar() {
    console.log(foo);
}
bar();

const foo = 2;

Actual behavior:

No "Block-scoped variable 'foo' used before its declaration." error for the three cases mentioned in the code example.

[RyanCavanaugh]

Duplicate of #13320

[donaldpipowitch]

I see, thanks. Well #13320 was closed because

Correctly detecting this in all cases would require all function calls to trace out their call graphs, which would be pretty expensive relative to the number of bugs we'd actually detect.

I don't know how expensive it would be to detect some cases for some function calls? I actually stumbled over this when I re-ordered functions inside one file with no complex code.

Feel free to close this, if you think its too expensive anyway :)

[mhegazy]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.