Is my analysis correct?
I think in type 1 conditionals, "can" and "will be able to" are both acceptable in some scenarios while in others not. "Can" means opportunity or possibility while "will be able to " means the gaining of future ability. Here's my rule of thumb to distinguish between occasions where both "can" and "will be able to" are possible and those where only "will be able to" is likely to be used.
PS: I don't know how to type strikethroughs here so I use grey square behind the word "can" to mean that it's not a less likely choice than "will be able to" in the example scenarios.
- Achievement or opportunity: both "can" and "will be able to" can be used because both “possibility” and “future ability” are suitable interpretations. E.g. If we work harder, we can/will be able to defeat them.
- Gaining of future ability: “will be able to” is far better. “Can” is likely to be seen as the wrong tense choice. It’s hard to fit the meaning of possibility of “can” into a sentence that obviously refers to the gaining of future ability. E.g. If he finds the key, he
can
will be able to open the gate. - Ability that exists now and will extend into the future: Both "can" and "will be able to" are possible. E.g. If he aims for its head, he can/will be able to kill the beast.
- Permission, suggestions, offering, things someone decides now but will happen in the future (scheduling): "Can" is more likely to be used in these scenarios, but "will be able to" can also be used although it will purely mean the gaining of ability with the intended meaning gone.
E.g.
a. If you finish your homework, you can/will be able to go home early (Permission).
b. If he gives me the address, I can/will be able to send the book to his place tonight (offering to do something).
c. If it stops raining, we can/will be able to hold the party in the park on Friday. (Things someone decides now but will happen in the future)
d. If he comes to the party tonight, you can/will be able to ask him for more information about the stock market. (suggestion)
- Negation: "won't be able to" is more likely to be accepted, except for the denial of permission and the suggestion that someone should not do something.
E.g.
a. If it rains, we can't/won't be able to hold the party in the park. (can't means we should not while won't be able to means we will lose the ability to hold the party in the park)
b. If it rains, he can't
won't be able to play basketball in the park. (can't can only be interpreted as "not allowed to," which is not a suitable interpretation. won't be able to is more appropriate.)
Am I right about this analysis?