Handle context function arguments in overloading resolution #16511
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Fixes scala#16506 We now handle the cases where an argument of an overloaded method is a context closure. The closure must be given implicitly. It cannot be inferred since at the time where the argument is typed, there is no expected expected type to expand it to a context closure.
prolativ
reviewed
Dec 14, 2022
| def bar2 = foo((ctx: Ctx) => 123) | ||
| def bar3 = foo(ctx ?=> 123) | ||
| def bar4 = foo((ctx: Ctx) ?=> 123) | ||
| // def bar5 = foo(123) does not work |
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What about
def f1: Ctx => Int = ???
def f2: Ctx ?=> Int = ???
def bar6 = foo(f1)
def bar7 = foo(f2)?
Unfortunately bar7 doesn't compile:
19 |def bar7 = foo(f2)
| ^^
| Found: (Ctx) ?=> Int
| Required: Ctx => <?>Isn't this a separate case from bar5 as f2 is already known to be a context function?
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Unfortunately, no. If we expanded bar7 it would look like this:
foo(ctx ?=> f2(using ctx)So when we see f2 we immediately apply it to a Context argument which is missing, so compilation fails. That's baked in, and I think it will be impossible to change. We exploit this uniformity in our compilation scheme for context functions to make them more efficient.
prolativ
approved these changes
Dec 15, 2022
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Fixes #16506
We now handle the cases where an argument of an overloaded method is a context closure. The closure must be given implicitly. It cannot be inferred since at the time where the argument is typed, there is no expected expected type to expand it to a context closure.