Fix #18649: Use loBound of param types when materializing a context function. #18651
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…ext function. Since the param types come from type arguments to `ContextFunctionN[...]`, nothing prevents them a priori from being wildcard type params, i.e., `TypeBounds`. However, that is not a valid type to give to a concrete term param. We can arbitrarily choose any type that conforms to the bounds, which realistically means one of the two bounds. Since type inference already chooses the lower bound when explicitly writing the context function, we align and choose the lower bound when materializing it.
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Since the param types come from type arguments to
ContextFunctionN[...], nothing prevents them a priori from being wildcard type params, i.e.,TypeBounds. However, that is not a valid type to give to a concrete term param.We can arbitrarily choose any type that conforms to the bounds, which realistically means one of the two bounds. Since type inference already chooses the lower bound when explicitly writing the context function, we align and choose the lower bound when materializing it.
Giving this one to @nicolasstucki, since you've been playing with function types recently.