duplicates:

• SR-7193 Segfaults after using KeyPath on array in REPL

Issue Description:

Here are three lines of code (rather fun and educational ones, but besides the point):

let a = 9007199254740991.0
(a * a - a * a).squareRoot()
(a * a).addingProduct(-a, a).squareRoot()

If I enter these line-by-line into a REPL, it'll just hang after line 3.

But it's not the content of line 3 that's the problem. I can enter line 1, line 3, then line 2, and it'll hang after I press enter the third time (line 2).

I've notice this lately experimenting with various other expressions; the REPL will just hang, and I'll start over in a new Terminal tab and the same expression will be fine. But it's annoying.