PARIS — France’s constitutional high court on Friday rejected legal challenges to legislation that grants same-sex couples the right to marry and adopt children, clearing the legal text for passage into law by President François Hollande, who said he would do so on Saturday. The leftist majorities in both houses of Parliament passed the legislation last month amid mass demonstrations by opponents of same-sex marriage and an acrimonious political debate. Legislators from the right challenged the constitutionality of the law before the high court, the Constitutional Council, but it was widely expected that the legislation would be approved. In its ruling, the Constitutional Council found that the law would not create a “right to a child” for same-sex couples, a contention made by some opponents of the legislation. Those opponents say they fear the new law will open the way to medically assisted procreation for lesbian couples and the use of surrogate mothers, neither of which are legal practices in France.