That sentence is not grammatical.

那个句子不合语法。

《牛津词典》

The construction is not grammatical.

这种结构不符合语法。

youdao

It is not grammatical to say 'They is.

制定是否合乎语法的语言规则。

youdao

B In fact, it's even a question whether A is A, but it's certainly not B, right? This much we know. In the grammatical sense there is no sort of mystification about the metaphor.

实际上，人们甚至对A是不是A都有疑问，但肯定不是，是吧，我们都知道这点，而从语法的角度来看,并没有像暗喻一样的神秘化。

耶鲁公开课 - 文学理论导论课程节选

This is a run-on sentence in more ways than one, and not quite grammatical, but it provides the sort of thrill every beach reader craves.

FORBES: Don't Go Near The Volcano

Not succumbing to malapropisms and grammatical mistakes does not make you a good public speaker.

FORBES: Magazine Article

And yes, the grammatical errors are theirs, not mine.

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