In the book I'm reading, I came across the following sentence:
あたしは[怒]{おこ}るに[怒]{おこ}れなくなった。 (furigana added by me)
My translation is something like "I couldn't stay angry [at him]". ("My anger melted away.")
I don't actually understand the grammar, though. The phrase 「怒るに怒れない」 has what appears to be particle-に following the dictionary form of a verb. It sounds contrastive. I can't seem to find this pattern in my dictionaries, though, so I feel unsure.
I'm interpreting it as 「怒る(の)に怒れない」, with a zero-nominalizer after the verb. Is this correct?
Is this a set phrase preserving old grammar of some kind?