fixes from feedback

base/char.jl

@@ -18,7 +18,8 @@ representable in a given `AbstractChar` type.
 Internally, an `AbstractChar` type may use a variety of encodings.  Conversion
 to `UInt32` will not reveal this encoding because it always returns the
 Unicode value of the character.  (Typically, the raw encoding can be obtained
-via [`reinterpret`](@ref).)
+via [`reinterpret`](@ref).)   Character I/O uses UTF-8 by default for all
+character types, regardless of their internal encoding.
 """
 AbstractChar
 
@@ -148,8 +149,7 @@ hash(x::Char, h::UInt) =
 # fallbacks:
 isless(x::AbstractChar, y::AbstractChar) = isless(Char(x), Char(y))
 ==(x::AbstractChar, y::AbstractChar) = Char(x) == Char(y)
-hash(x::AbstractChar, h::UInt) =
-    hash_uint64(((UInt32(x) + UInt64(0xd060fad0)) << 32) ⊻ UInt64(h))
+hash(x::AbstractChar, h::UInt) = hash(Char(x), h)
 widen(::Type{T}) where {T<:AbstractChar} = T
 
 -(x::AbstractChar, y::AbstractChar) = Int(x) - Int(y)

base/strings/basic.jl

@@ -14,8 +14,8 @@ about strings:
 * String indexing is done in terms of these code units:
   * Characters are extracted by `s[i]` with a valid string index `i`
   * Each `AbstractChar` in a string is encoded by one or more code units
-  * Only the index of the first code unit of a `AbstractChar` is a valid index
-  * The encoding of a `AbstractChar` is independent of what precedes or follows it
+  * Only the index of the first code unit of an `AbstractChar` is a valid index
+  * The encoding of an `AbstractChar` is independent of what precedes or follows it
   * String encodings are [self-synchronizing] – i.e. `isvalid(s, i)` is O(1)
 
 [self-synchronizing]: https://en.wikipedia.org/wiki/Self-synchronizing_code

base/strings/util.jl

@@ -410,7 +410,7 @@ If `count` is provided, replace at most `count` occurrences.
 or a regular expression.
 If `r` is a function, each occurrence is replaced with `r(s)`
 where `s` is the matched substring (when `pat`is a `Regex` or `AbstractString`) or
-character (when `pat` is a `AbstractChar` or a collection of `AbstractChar`).
+character (when `pat` is an `AbstractChar` or a collection of `AbstractChar`).
 If `pat` is a regular expression and `r` is a `SubstitutionString`, then capture group
 references in `r` are replaced with the corresponding matched text.
 To remove instances of `pat` from `string`, set `r` to the empty `String` (`""`).

doc/src/manual/strings.md

@@ -28,8 +28,9 @@ There are a few noteworthy high-level features about Julia's strings:
     additional `AbstractString` subtypes (e.g. for other encodings).  If you define a function expecting
     a string argument, you should declare the type as `AbstractString` in order to accept any string
     type.
-  * Like C and Java, but unlike most dynamic languages, Julia has a first-class type representing
-    a single character, called `AbstractChar`. This is just a special kind of 32-bit primitive type whose numeric value represents a Unicode code point.
+  * Like C and Java, but unlike most dynamic languages, Julia has a first-class type for representing
+    a single character, called `AbstractChar`. The built-in `Char` subtype of `AbstractChar`
+    is a 32-bit primitive type that can represent any Unicode character.
   * As in Java, strings are immutable: the value of an `AbstractString` object cannot be changed.
     To construct a different string value, you construct a new string from parts of other strings.
   * Conceptually, a string is a *partial function* from indices to characters: for some index values,