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Improve E0308: suggest user meant to use byte literal, w/ tests and fix

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suggested by Nilstrieb

Co-authored-by: nils <48135649+Nilstrieb@users.noreply.github.com>
This commit is contained in:
Nick Lamb 2023-01-14 14:51:17 +00:00
parent 44a500c8c1
commit 130d02b62e
3 changed files with 76 additions and 0 deletions
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16
compiler/rustc_infer/src/infer/error_reporting/mod.rs
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@ -1923,6 +1923,22 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
(ty::Tuple(fields), _) => {
self.emit_tuple_wrap_err(&mut err, span, found, fields)
}
// If a byte was expected and the found expression is a char literal
// containing a single ASCII character, perhaps the user meant to write `b'c'` to
// specify a byte literal
(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())
{
err.span_suggestion(
span,
"if you meant to write a byte literal, prefix with `b`",
format!("b'{}'", escape_literal(code)),
Applicability::MachineApplicable,
);
}
}
// If a character was expected and the found expression is a string literal
// containing a single character, perhaps the user meant to write `'c'` to
// specify a character literal (issue #92479)