I just checked the Wikipedia page on XeTeX (not knowing what the heck that is at all). It's in fact actually something very recent in terms of the TeX timeline; it was released in 2004. It has Unicode support, which seems to be the big thing.
That is more recent than, I think, the last time I used TeX; which worked absolutely fine.
Someone rewriting TeX in Rust should work with Knuth's original Pascal sources, in my opinion, not some knock-off (and look at XeTeX behaviors and documentation in order to do the Unicode stuff in a compatible way).
That's certainly not correct; while it is much closer to bug-free than most software, there have been numerous fixes since the original release (as well as a few enhancements).
I found one years ago that I didn't report. When I issued Ctrl-D on the interactive TeX prompt to bail out, it failed to issue a newline, leaving the operating system prompt juxtaposed to the right of the TeX prompt.
According to ISO C, "[w]hether the last line [of a text stream] requires a terminating new-line character is implementation-defined", so terminating the program without the last character written to stdout (a text stream) being a newline is not maximally portable.
That's a peculiar and possibly unique situation in the standard: whether or not a requirement exists is implementation-defined. Logically, that is as good as it being required, since any implementation can make it required. Those not making it required are just supplying a documented extension in place of undefined behavior.
I just checked the Wikipedia page on XeTeX (not knowing what the heck that is at all). It's in fact actually something very recent in terms of the TeX timeline; it was released in 2004. It has Unicode support, which seems to be the big thing.
That is more recent than, I think, the last time I used TeX; which worked absolutely fine.
Someone rewriting TeX in Rust should work with Knuth's original Pascal sources, in my opinion, not some knock-off (and look at XeTeX behaviors and documentation in order to do the Unicode stuff in a compatible way).