VSCode "Convert to template" refactor unescapes literals unexpectedly

[thw0rted]

TypeScript Version: 4.0, I think -- this is an issue with TS as bundled in VSCode
VSCode Version: 1.49.0

Search Terms: VSCode template string refactor

Code

Run the "convert to template string" refactor action in VSCode on a string concatenation with escape sequences like "\b" + foo + "\f";

Expected behavior: Escape sequences are preserved, like \b${foo}\f;

Actual behavior: Escape sequences are converted to literal ASCII non-printable equivalents, resulting in "missing character" or other placeholders depending on font.

Related Issues: None, but might have been introduced by #37743 -- the author said to file a new issue.