Auto merge of #44174 - jimmycuadra:try-from-infallible, r=sfackler

Add blanket TryFrom impl when From is implemented.

Adds `impl<T, U> TryFrom<T> for U where U: From<T>`.

Removes `impl<'a, T> TryFrom<&'a str> for T where T: FromStr` (originally added in #40281) due to overlapping impls caused by the new blanket impl. This removal is to be discussed further on the tracking issue for TryFrom.

Refs #33417.

/cc @sfackler, @scottmcm (thank you for the help!), and @aturon

1 files changed, 2 insertions, 5 deletions

diff --git a/src/libcore/str/mod.rs b/src/libcore/str/mod.rs
index 62367b051fc..0af9fcf0a3d 100644
--- a/src/libcore/str/mod.rs
+++ b/src/libcore/str/mod.rs
@@ -18,7 +18,6 @@ use self::pattern::Pattern;
 use self::pattern::{Searcher, ReverseSearcher, DoubleEndedSearcher};
 
 use char;
-use convert::TryFrom;
 use fmt;
 use iter::{Map, Cloned, FusedIterator, TrustedLen};
 use iter_private::TrustedRandomAccess;
@@ -2198,7 +2197,7 @@ pub trait StrExt {
     #[stable(feature = "core", since = "1.6.0")]
     fn is_empty(&self) -> bool;
     #[stable(feature = "core", since = "1.6.0")]
-    fn parse<'a, T: TryFrom<&'a str>>(&'a self) -> Result<T, T::Error>;
+    fn parse<T: FromStr>(&self) -> Result<T, T::Err>;
 }
 
 // truncate `&str` to length at most equal to `max`
@@ -2518,9 +2517,7 @@ impl StrExt for str {
     fn is_empty(&self) -> bool { self.len() == 0 }
 
     #[inline]
-    fn parse<'a, T>(&'a self) -> Result<T, T::Error> where T: TryFrom<&'a str> {
-        T::try_from(self)
-    }
+    fn parse<T: FromStr>(&self) -> Result<T, T::Err> { FromStr::from_str(self) }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]