Entertaining Stack Overflow discussion (from April 1st) of .png source code input to a C++ compiler: https://stackoverflow.com/questions/5508110/why-is-this-program-erroneously-rejected-by-three-c-compilers
I'm slightly horrified that you could accept .png source code and still be a standards compliant compiler!
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Co-Authored-By: An old Stack Overflow answer, blindly accepting the compiler's suggestions, and a linter.
On the challenge of writing accurate source spans on Unicode source code: https://reedmullanix.com/posts/unicode-source-spans.html
Also (see footnotes) a fair number of LSP clients assume UTF-8 despite early versions of LSP mandating UTF-16!
Over a sufficiently long time horizon, all code you write is legacy code.