Implement more AsRef<AsciiStr> and genericize Extend and IntoIterator

* Implement identity AsRef and AsMut for AsciiStr.
* Implement AsRe<AsciiStr> for AsciiChar.
* implement Extend and IntoIterator<AsciiString> for
  any iterable with Item=AsRef<AsciiChar>.

Author: tormol

src/ascii_str.rs

@@ -3,7 +3,7 @@
 use core::fmt;
 use core::ops::{Index, IndexMut};
 use core::ops::{Range, RangeTo, RangeFrom, RangeFull, RangeInclusive, RangeToInclusive};
-use core::slice::{Iter, IterMut};
+use core::slice::{self, Iter, IterMut};
 #[cfg(feature = "std")]
 use std::error::Error;
 #[cfg(feature = "std")]
@@ -355,6 +355,18 @@ impl From<Box<[AsciiChar]>> for Box<AsciiStr> {
     }
 }
 
+impl AsRef<AsciiStr> for AsciiStr {
+    #[inline]
+    fn as_ref(&self) -> &AsciiStr {
+        self
+    }
+}
+impl AsMut<AsciiStr> for AsciiStr {
+    #[inline]
+    fn as_mut(&mut self) -> &mut AsciiStr {
+        self
+    }
+}
 impl AsRef<AsciiStr> for [AsciiChar] {
     #[inline]
     fn as_ref(&self) -> &AsciiStr {
@@ -408,6 +420,13 @@ widen_box! {[AsciiChar]}
 widen_box! {[u8]}
 widen_box! {str}
 
+// allows &AsciiChar to be used by generic AsciiString Extend and FromIterator
+impl AsRef<AsciiStr> for AsciiChar {
+    fn as_ref(&self) -> &AsciiStr {
+        slice::from_ref(self).into()
+    }
+}
+
 impl fmt::Display for AsciiStr {
     #[inline]
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {

src/ascii_string.rs

@@ -566,65 +566,21 @@ impl fmt::Write for AsciiString {
     }
 }
 
-impl FromIterator<AsciiChar> for AsciiString {
-    fn from_iter<I: IntoIterator<Item = AsciiChar>>(iter: I) -> AsciiString {
+impl<A: AsRef<AsciiStr>> FromIterator<A> for AsciiString {
+    fn from_iter<I: IntoIterator<Item = A>>(iter: I) -> AsciiString {
         let mut buf = AsciiString::new();
         buf.extend(iter);
         buf
     }
 }
 
-impl<'a> FromIterator<&'a AsciiStr> for AsciiString {
-    fn from_iter<I: IntoIterator<Item = &'a AsciiStr>>(iter: I) -> AsciiString {
-        let mut buf = AsciiString::new();
-        buf.extend(iter);
-        buf
-    }
-}
-
-impl<'a> FromIterator<Cow<'a, AsciiStr>> for AsciiString {
-    fn from_iter<I: IntoIterator<Item = Cow<'a, AsciiStr>>>(iter: I) -> AsciiString {
-        let mut buf = AsciiString::new();
-        buf.extend(iter);
-        buf
-    }
-}
-
-impl Extend<AsciiChar> for AsciiString {
-    fn extend<I: IntoIterator<Item = AsciiChar>>(&mut self, iterable: I) {
-        let iterator = iterable.into_iter();
-        let (lower_bound, _) = iterator.size_hint();
-        self.reserve(lower_bound);
-        for ch in iterator {
-            self.push(ch)
-        }
-    }
-}
-
-impl<'a> Extend<&'a AsciiChar> for AsciiString {
-    fn extend<I: IntoIterator<Item = &'a AsciiChar>>(&mut self, iter: I) {
-        self.extend(iter.into_iter().cloned())
-    }
-}
-
-impl<'a> Extend<&'a AsciiStr> for AsciiString {
-    fn extend<I: IntoIterator<Item = &'a AsciiStr>>(&mut self, iterable: I) {
-        let iterator = iterable.into_iter();
-        let (lower_bound, _) = iterator.size_hint();
-        self.reserve(lower_bound);
-        for s in iterator {
-            self.push_str(s)
-        }
-    }
-}
-
-impl<'a> Extend<Cow<'a, AsciiStr>> for AsciiString {
-    fn extend<I: IntoIterator<Item = Cow<'a,AsciiStr>>>(&mut self, iterable: I) {
+impl<A: AsRef<AsciiStr>> Extend<A> for AsciiString {
+    fn extend<I: IntoIterator<Item = A>>(&mut self, iterable: I) {
         let iterator = iterable.into_iter();
         let (lower_bound, _) = iterator.size_hint();
         self.reserve(lower_bound);
-        for s in iterator {
-            self.push_str(&*s);
+        for item in iterator {
+            self.push_str(item.as_ref())
         }
     }
 }

tests.rs

@@ -137,5 +137,6 @@ fn extend_from_iterator() {
             }
         });
     s.extend(cows);
-    assert_eq!(s, "abcabconetwothreeASCIIASCIIASCII");
+    s.extend(&[AsciiChar::LineFeed]);
+    assert_eq!(s, "abcabconetwothreeASCIIASCIIASCII\n");
 }