Why can't まちがいなく失敗 mean 'a zero-mistakes失敗'?


失敗するのを **気にしたら** 、 **まちがいなく** 失敗してしまう。 =If we think of failure, we will
certainly fail.

When I read the example the first time, thinking it's a proverb, I interpreted
it like:

_If you **mind** failure, you will fall in/encounter/make the **no-mistakes**
failure._

What prevents 'grammatically' such interpretation?

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Edit:

> **Comment on @shingo.nakanishi answer:** Can I say [ **雨ない** 年だった.] for 'It
> was a **no-rain** /rainless year.'?  
> If YES, then why can't we think of まちがいない as a 'whole word' that modifies 失敗
> in [失敗するのを気にしたら、 **まちがいない** 失敗してしまう。] also?

> **Comment on @naruto answer:** Is [雨な **く** 年だった.] for 'It was a rainless
> **ly** year' correct in Japanese?  
> If YES, then why can't we consider まちがいなく as an adverbial that modifies 失敗
> in [失敗するのを **気にしたら** 、 **まちがいなく** 失敗してしまう。] also?




You translated it as "no mistake", which is a **noun** , but you should notice
なく is the **ku-form** (≒adverbial form). The very literal translation of 間違いなく
is "error-less- **ly** " or "in an error-free manner", which is why it is
usually translated as "certainly", "undoubtedly" or "without doubt" in
English.

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**EDIT:** The basic rule you have to keep in mind is actually very simple. The
連体形 (i-form) modifies a noun (thus called "adjectival"), and the 連用形 (ku-form)
modifies a verb (thus called "adverbial"). For example 速 **い** 車 is "a fast
car" and this 速い/fast is adjectival because it modifies a noun. 速 **く** 走る is
"to run fast", and this 速く/fast is called adverbial because it modifies a verb
(although 速く is a form of an adjective).

If you said 間違いない失敗をする, it would mean something funny and paradoxical like "to
make an un-mistaken mistake" or "to make an error-less error". That's not
something you want to say. Here 間違いなく must modify 失敗する **adverbially**.

