Change FromStr for String to use Infallible directly #67925
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src/liballoc/string.rs
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| #[stable(feature = "str_parse_error", since = "1.5.0")] | ||
| pub type ParseError = core::convert::Infallible; | ||
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| #[stable(feature = "rust1", since = "1.0.0")] | ||
| impl FromStr for String { | ||
| type Err = core::convert::Infallible; | ||
| #[inline] | ||
| fn from_str(s: &str) -> Result<String, ParseError> { | ||
| fn from_str(s: &str) -> Result<String, core::convert::Infallible> { |
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Does this make ParseError unused?
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Yes. I think the obvious thing for downstream code that needs to specify ParseError for some reason to do is replace it with Infallible. Of course, that's a backwards compatibility issue: your code won't compile with older versions of Rust.
Though I'd expect it to be a fairly rare one, as I doubt much downstream code needs to actually mention ParseError directly.
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This might as well be -> Result<String, Self::Err> to prevent any future churn.
src/liballoc/string.rs
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| /// defined, but, given that a [`String`] can always be made into a new | ||
| /// [`String`] without error, this type will never actually be returned. As | ||
| /// such, it is only here to satisfy said signature, and is useless otherwise. | ||
| /// This alias exists for backwards compatibility, and will be eventually deprecated. |
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Why will it be deprecated? Says who?
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If the never type works on all editions I don't see why people would ever use Infalliable long-term. Deprecation doesn't prevent its usage, just discourage it.
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ping from triage: |
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@JohnCSimon @shepmaster I changed it to return |
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The code change itself looks fine, but I'm not cool enough to vet the changes about deprecation. |
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I think this is fine as is. The only non-doc changes are definitely non-breaking. And mentioning |
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Ping from triage: @SimonSapin - can you please review this? |
Fixes the confusing documentation on `ParseError` by making it irrelevant.
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@bors r+ |
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📌 Commit 883e69d has been approved by |
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☀️ Test successful - checks-azure |
Fixes the confusing documentation on
ParseErrorby making it irrelevant.It might be fine to mark it as depreciated right now too - I can't imagine much code uses
ParseErrordirectly.