Rename Iterator::len to count

This commit carries out the request from issue #14678:

> The method `Iterator::len()` is surprising, as all the other uses of
> `len()` do not consume the value. `len()` would make more sense to be
> called `count()`, but that would collide with the current
> `Iterator::count(|T| -> bool) -> unit` method. That method, however, is
> a bit redundant, and can be easily replaced with
> `iter.filter(|x| x < 5).count()`.
> After this change, we could then define the `len()` method
> on `iter::ExactSize`.

Closes #14678.

[breaking-change]

1 files changed, 1 insertions, 1 deletions

diff --git a/src/libstd/rt/backtrace.rs b/src/libstd/rt/backtrace.rs
index ac421bf78be..fe6d84d4d2e 100644
--- a/src/libstd/rt/backtrace.rs
+++ b/src/libstd/rt/backtrace.rs
@@ -84,7 +84,7 @@ fn demangle(writer: &mut Writer, s: &str) -> IoResult<()> {
             if i == 0 {
                 valid = chars.next().is_none();
                 break
-            } else if chars.by_ref().take(i - 1).len() != i - 1 {
+            } else if chars.by_ref().take(i - 1).count() != i - 1 {
                 valid = false;
             }
         }