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Rollup merge of #107709 - tialaramex:master, r=compiler-errors

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Fix problem noticed in PR106859 with char -> u8 suggestion

HN reader `@ayosec` noticed that my #106859 a few weeks back, malfunctions if you have a Unicode escape, the code suggested b'\u{0}' if you tried to use '\u{0}' where a byte should be, when of course b'\u{0}' is not a byte literal, regardless of the codepoint you can't write Unicode escapes in a byte literal at all.

My proposed fix here just checks that the "character" you wrote is fewer than 5 bytes, thus allowing \x7F and similar escapes but conveniently forbidding even the smallest Unicode escape \u{0} before offering the suggestion as before.

I have provided an updated test which includes examples which do and don't work because of this additional rule.
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Matthias Krüger 2023-02-07 17:57:17 +01:00 • committed by GitHub
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compiler/rustc_infer/src/infer/error_reporting/mod.rs
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@ -1922,7 +1922,8 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
(ty::Uint(ty::UintTy::U8), ty::Char) => {
if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
&& let Some(code) = code.strip_prefix('\'').and_then(|s| s.strip_suffix('\''))
&& code.chars().next().map_or(false, |c| c.is_ascii())
&& !code.starts_with("\\u") // forbid all Unicode escapes
&& code.chars().next().map_or(false, |c| c.is_ascii()) // forbids literal Unicode characters beyond ASCII
{
err.span_suggestion(
span,