The usage of ば is complicated.
If volition / request / etc is involved, the sentence is invalid, unless there are special conditions fulfilled (addressed after this example):
X 卒業すれば、彼女と結婚するつもりです。(volitional structure つもりです)
Usage of such volitional structures is allowed under two circumstances:
- If the subjects (主語) of the two sentences are different:
O 彼女が希望すれば、彼女と結婚するつもりです。(subjects are 彼女 and わたし (implied))
- If the verb is not an action verb (adjective, stative verb, etc):
O わからないことがあれば、わたしにきいてください。(あれば stative verb, as it expresses the state of being)
O 質問があれば、(あなたが)聞いてください。(あれば stative verb)
These two conditions can be found in various materials, such as the top answer to the question in this link.
"The main clause must be a constant non-volitional reaction to the conditional clause unless the conditional clause shows state or if the subjects of the two clauses differ."
This much information can be found in various materials. However, I noticed that when rule 2 applies, the subjects are often automatically different (i.e. rule 1 is applied too). What if adjectives / stative verbs are used when the subjects are the same? (note: example sentence below has been edited from 声をかけてください)
? (あなたが)そこにいれば、(あなたが)何か言ってください。(eg. when on the phone)
? (あなたが)そんなに悲しければ、(あなたが)帰ってください。
? (あなたが)ひまであれば/なら、(あなたが)てつだってください。