This solves a format specifier warning for char32_t being converted to
an unsigned integer type, and multiple format specifier warnings for
size_t being converted to long.
Implements [[ https://wg21.link/p2071r1 | P2071 Named Universal Character Escapes ]] - as an extension in all language mode, the patch not warn in c++23 mode will be done later once this paper is plenary approved (in July).
We add
* A code generator that transforms `UnicodeData.txt` and `NameAliases.txt` to a space efficient data structure that can be queried in `O(NameLength)`
* A set of functions in `Unicode.h` to query that data, including
* A function to find an exact match of a given Unicode character name
* A function to perform a loose (ignoring case, space, underscore, medial hyphen) matching
* A function returning the best matching codepoint for a given string per edit distance
* Support of `\N{}` escape sequences in String and character Literals, with loose and typos diagnostics/fixits
* Support of `\N{}` as UCN with loose matching diagnostics/fixits.
Loose matching is considered an error to match closely the semantics of P2071.
The generated data contributes to 280kB of data to the binaries.
`UnicodeData.txt` and `NameAliases.txt` are not committed to the repository in this patch, and regenerating the data is a manual process.
Reviewed By: tahonermann
Differential Revision: https://reviews.llvm.org/D123064
Aaron Ballman