Found this quote in Chuunibyou demo Koi ga Shitai!:

> 余計なこと教えるんじゃなかった

How my brain tried to process it:

> I did not teach unnecessary things

English readability aside, it doesn't make any sense anyways, to which I found
the subtitles to be

> I shouldn't have taught her all that

which in turn completely baffled me. How does the grammar work out here?

Many thanks.
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2017-12-26T09:40:07.410
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2017-12-26T09:52:10.067
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question
grammar
How to make sense of '余計なこと教えるんじゃなかった'