Pesachim 26A

ורבא אמר לך: עד כאן לא קאמר רבי יהודה שאין מתכוין כמתכוין ⁠— אלא לחומרא, אבל מתכוין כשאין מתכוין לקולא ⁠— לא.

And Rava could have said to you: R' Yehuda stated that one who lacks intent has the same legal status as one who has intent only with regard to a stringency. In other words, a lack of intent does not negate the fact that the prohibited act has been performed and one is liable. However, to say that one who has intent has the same legal status as one who lacks intent such that it leads to a leniency, no. There is no evidence that R' Yehuda would agree that it would ever be permitted for one who has intent to derive benefit from an otherwise prohibited object, even if he could not avoid the situation.

אמר אביי: מנא אמינא לה ⁠— דתניא: אמרו עליו על רבן יוחנן בן זכאי שהיה יושב בצילו של היכל, ודורש כל היום כולו. והא הכא דלא אפשר ומיכוין, ושרי.

Abaye said: From where do I say my opinion? As it was taught in a baraita: They said about Rabban Yoḥanan ben Zakkai that he would sit in the street adjacent to the Temple Mount in the shade of the Sanctuary and expound to a large number of people all day long. And here, isn’t it a case where it was not possible to act differently, as there was no other place where so many people could congregate, and he certainly intended to derive benefit from the shade of the Sanctuary, and yet it was permitted? Apparently, when it is not possible to avoid the situation and one intends to derive benefit, it is permitted to do so.

ורבא אמר: שאני היכל דלתוכו עשוי.

And Rava said in response: The Sanctuary is different, as it was constructed for its interior. It is prohibited to derive benefit only from the interior of the Sanctuary walls, because it was constructed for the use of its internal space; there is no prohibition at all to benefit from its shade when on the outside.