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Expand wrap_pyfunction!() to a closure to improve deduction. #1597

Merged
merged 2 commits into from
May 6, 2021
Merged

Expand wrap_pyfunction!() to a closure to improve deduction. #1597

merged 2 commits into from
May 6, 2021

Commits on May 6, 2021

  1. Expand wrap_pyfunction!() to a closure. 

    The change to wrap_pyfunction!() in PyO3#1143 makes it impossible to
implement `context.add_wrapped(wrap_pyfunction!(something))` in
`inline-python`.
`context` does not carry the GIL lifetime, which causes type deduction
trouble now that `wrap_pyfunction` results in a generic function.

```
error[E0308]: mismatched types
  --> examples/rust-fn.rs:12:4
   |
12 |     c.add_wrapped(wrap_pyfunction!(rust_print));
   |       ^^^^^^^^^^^ one type is more general than the other
   |
   = note: expected enum `Result<&pyo3::types::PyCFunction, _>`
              found enum `Result<&pyo3::types::PyCFunction, _>`
```

By re-wrapping the function as a closure, we trigger 'closure signature
deduction' when passing `wrap_pyfunction!()` as an argument to a
function: Rustc will deduce the signature of the closure from the
function that closure is passed to. This way, the generic arguments can
be deduced in more contexts, fixing the problem.
    @m-ou-se
    m-ou-se committed May 6, 2021
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  2. Add test for wrap_pyfunction!() deduction.

    @m-ou-se
    m-ou-se committed May 6, 2021
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