'fun CharSequence.iterator()' is an extension function, so one can
overload it with custom implementation.
Other "predefined" containers such as arrays and ranges have member
'fun iterator()', so these containers are not affected.
Check that 'iterator' call corresponds to an extension function
'iterator' defined in package 'kotlin.text' with a receiver of type
'kotlin.CharSequence'.
#KT-24156 Fixed
Otherwise if Char value is a result of some erased generic call,
coercing it to I (primitive int) causes CCE at run-time.
#KT-23104 Fixed Target versions 1.2.40
If the loop end value is a compile-time constant (best we can do now),
and it is safe to iterate over a given range using "naive" for loop
(using '<=' or '>=' in loop condition),
generate such loops for Longs and Chars as well Ints (Bytes, Shorts).
In Kotlin 1.3+, assignment to the for-in-array loop range variable in
the loop body doesn't affect loop execution (as if it was a loop on an
array iterator, or some other container).
#KT-21354 In Progress
#KT-21321 In Progress
For-in-string loop can be generated using specialized 'length' and
'charAt' method calls, and with cached string length.
Note that update of the string variable in loop body doesn't affect
loop execution semantics.
#KT-21322 Fixed Target versions 1.2.20
If the range expression is not a local variable (which can be updated in
the loop body affecting loop behavior, see KT-21354), we can cache the
array length, thus turning a for-in-array loop into a simple optimizable
counter loop.
#KT-21321 In Progress
When we have some custom implementation of Comparable, it's important
that we compare values exactly as 'lowBound <= a && a <= highBound'.
Make sure that evaluation order and compareTo calls match for
optimized and non-optimized case.
As of Kotlin 1.0 and 1.1, expression 'a in x .. y' is considered
equivalent to 'x.rangeTo(y).a', and should be evaluated in the following
order:
1. x
2. y
3. a
4. compare x with a
5. compare y with a (if needed)
Ilya Gorbunov