Weird stack overflow when compiling 4-line code with function, untyped variable, operator and spread operator within cycle

[Veetaha]

TypeScript Version: 3.0.1+ (including typescript@3.5.0-dev.20190407)

Search Terms:

• Maximum callstack
• Stack overflow

Code

let foo = () => {};     // if you remove or change foo definition to not a function, bug disappears
let bar;                // if you add type annotation here, bug disappears
while (1)               // if you remove while, bug disappears
    bar = ~foo(...bar); // if you remove unary or spread operator, bug disappears

//  bar =  || foo(...bar); // though this is a syntax error, it produces stack overflow also

Expected behavior:
Should compile with error report for spreading undefined and/or leaving bar as implicit any

Actual behavior:
Prints Maximum call stack size exceeded.
Or if you run this script with ts-node:

View ts-node stack trace

Playground Link:

This is weird, playground from typescriptlang.com seems to work well, but playground from typescript-play.js.org produces the stack overflow as it does locally in my terminal (Ubuntu 18.04.2 LTS). You may see the error for the second playground in your browser console.

Related Issues:
#25149 To some degree

[andrewbranch]

@Veetaha can you reproduce this without ts-node? If not, can you please share what version of ts-node and tsconfig-paths you're using?

[Veetaha]

@andrewbranch As I wrote:

Or if you run this script with ts-node:

I meant to use ts-node in order to get the compiler stack trace, because if I reproduce this bug without ts-node, i.e. with tsc I only get "Maximum call stack size exceeded." string printed to the terminal. So yes, you can reproduce this bug with tsc v3.0.1 +

And sorry for tsconfig-paths, those options were left from my production code where I detected this bug, they don't influence the bug.

[Veetaha]

Here is what you get when trying to compile the problem code with tsc:

Peek screenshot

[Veetaha]

One more important condition, this bug appears when you use the following minimum tsconfig.json:

{
    "compilerOptions": {
        "noImplicitAny": true,
    }
}

It seems noImplicitAny is the guy to blame here because if you remove that option or set it to false, the bug disappears.

[andrewbranch]

Ah yep, noImplicitAny is what I was missing in order to repro. Thanks!