Fix #11389 Add UTF32String constructor for Vector{UInt32}

base/utf32.jl

@@ -3,15 +3,16 @@
 ## UTF-32 in the native byte order, i.e. plain old character arrays ##
 
 immutable UTF32String <: DirectIndexString
-    data::Array{Char,1} # includes 32-bit NULL termination after string chars
+    data::Vector{Char} # includes 32-bit NULL termination after string chars
 
-    function UTF32String(a::Array{Char,1})
+    function UTF32String(a::Vector{Char})
         if length(a) < 1 || a[end] != Char(0)
             throw(ArgumentError("UTF32String data must be NULL-terminated"))
         end
         new(a)
     end
 end
+UTF32String(data::Vector{UInt32}) = UTF32String(reinterpret(Char, data))
 
 next(s::UTF32String, i::Int) = (s.data[i], i+1)
 endof(s::UTF32String) = length(s.data) - 1

doc/stdlib/strings.rst

@@ -383,7 +383,7 @@
 
 .. function:: utf32(s)
 
-   Create a UTF-32 string from a byte array, array of ``UInt32``, or
+   Create a UTF-32 string from a byte array, array of ``Char`` or ``UInt32``, or
    any other string type.  (Conversions of byte arrays check for a
    byte-order marker in the first four bytes, and do not include it in
    the resulting string.)
@@ -393,7 +393,7 @@
    string (so that it is mostly invisible in Julia); this allows the
    string to be passed directly to external functions requiring
    NUL-terminated data.  This NUL is appended automatically by the
-   `utf32(s)` conversion function.  If you have a ``UInt32`` array
+   `utf32(s)` conversion function.  If you have a ``Char`` or ``UInt32`` array
    ``A`` that is already NUL-terminated UTF-32 data, then you
    can instead use `UTF32String(A)`` to construct the string without
    making a copy of the data and treating the NUL as a terminator

test/strings.jl

@@ -1603,3 +1603,16 @@ let s = "ba\0d"
     @test_throws ArgumentError Base.unsafe_convert(Cstring, s)
     @test_throws ArgumentError Base.unsafe_convert(Cwstring, wstring(s))
 end
+
+# issue # 11389: Vector{UInt32} was copied with UTF32String, unlike Vector{Char}
+a = UInt32[48,0]
+b = UTF32String(a)
+@test b=="0"
+a[1] = 65
+@test b=="A"
+c = Char['0','\0']
+d = UTF32String(c)
+@test d=="0"
+c[1] = 'A'
+@test d=="A"
+