Element type of string ranges

This article attempts to summarize the arguments in the thread Major performance problem with std.array.front().

Comparison

One of the proposals in the thread is to switch the iteration type of string ranges from dchar to the string's character type.

Argument	Old	New
Searching for a particular dchar in a string.	s.canFind('é')	Will result in a pragma warning in some places, will fail silently in others (when specified via predicate).
Searching for a particular dchar in a non-normalized string.	Above fails for combining marks, as that requires normalization.
Case conversion, insensitive comparison in ranges for certain languages	s.count!((a, b) => std.uni.toLower(a) == std.uni.toLower(b))("é")	Fails silently.
Case conversion, insensitive comparison in ranges for other languages	Correct case conversion for all languages is dependent on locale information. (E.g. Turkish I / ı and İ / i).
Correctness	Only works for certain languages and alphabets	Only works for ASCII
Performance	Implicit decoding everywhere, unless each algorithm is specialized not to	As fast as ubyte[]
Implementation difficulty	phobos/std $ grep ElementEncodingType *.d | wc -l 80	Strings are treated as any other arrays
Consistency	Range algorithms return values different from array algorithms	String ranges work like ranges of any other arrays