regression: reduce on iterator conflicts

[Mark-Simulacrum]

#79805 stabilized Iterator::reduce, which conflicts with a similar method in the reduce crate.

This caused a number of regressions, as detected by the beta crater run:

• https://crater-reports.s3.amazonaws.com/beta-1.51-1/beta-2021-02-14/gh/7e11.FullTextSearch/log.txt
• https://crater-reports.s3.amazonaws.com/beta-1.51-1/beta-2021-02-14/gh/ChrisMacNaughton.euler-rs/log.txt
• https://crater-reports.s3.amazonaws.com/beta-1.51-1/beta-2021-02-14/gh/Tismas.aoc2020/log.txt
• https://crater-reports.s3.amazonaws.com/beta-1.51-1/beta-2021-02-14/gh/akuraj.gomoku/log.txt
• https://crater-reports.s3.amazonaws.com/beta-1.51-1/beta-2021-02-14/gh/davidszotten.advent-of-code-2020/log.txt
• https://crater-reports.s3.amazonaws.com/beta-1.51-1/beta-2021-02-14/gh/guilgaly.advent-of-code-2020/log.txt
• https://crater-reports.s3.amazonaws.com/beta-1.51-1/beta-2021-02-14/gh/guillermomuntaner.AdventOfCode2020-Rust/log.txt
• https://crater-reports.s3.amazonaws.com/beta-1.51-1/beta-2021-02-14/gh/ptrkalm.AoC2020/log.txt
• https://crater-reports.s3.amazonaws.com/beta-1.51-1/beta-2021-02-14/gh/reline.AdventOfCode2020/log.txt
• https://crater-reports.s3.amazonaws.com/beta-1.51-1/beta-2021-02-14/gh/rklaehn.tag-index/log.txt
• https://crater-reports.s3.amazonaws.com/beta-1.51-1/beta-2021-02-14/gh/tqdv.switchable/log.txt
• https://crater-reports.s3.amazonaws.com/beta-1.51-1/beta-2021-02-14/reg/csvsc-1.4.0/log.txt
• https://crater-reports.s3.amazonaws.com/beta-1.51-1/beta-2021-02-14/reg/fp_rust-0.1.39/log.txt
• https://crater-reports.s3.amazonaws.com/beta-1.51-1/beta-2021-02-14/reg/reduce-0.1.4/log.txt
• https://crater-reports.s3.amazonaws.com/beta-1.51-1/beta-2021-02-14/reg/switchable-0.1.0/log.txt

I suspect that we'll be inclined to accept this breakage, but wanted to file an issue to get a 👍 from T-libs, hopefully; we should also likely ping the authors of these crates. Many of them appear to be Advent of Code repositories where breakage is actually somewhat unlikely to even get noticed.

[apiraino]

@Mark-Simulacrum excluding the advent of code crates (I wonder if they should stay in the crater run), I've tried compiling the other failing ones from their respective master branch:

• gomoku compiles on stable with just a lint warning, fails on beta+nightly => will regress
• tag-index: same as above
• switchable: same as above
• reduce: compiles on nightly,beta, stable => no regression
• csvsc: same as above

hope this helps!

[Mark-Simulacrum]

The master branch not compiling or continuing to compile matters more for git repositories, but for published crates it's encouraging sign if things have been fixed; we ultimately need a point release if we want to streamline upgrade paths.

[m-ou-se]

to get a 👍 from T-libs

We briefly discussed this in the libs meeting just now. Here it is: 👍

[Mark-Simulacrum]

Ok, closing in that case.

[apiraino]

@rustbot label -I-prioritize -I-nominated