Doug Gregor be6393b7ca Use any Error for caught error type of an exhaustive, non-throwing do..catch ...

Prior to the introduction of typed throws, a `do..catch` always had a caught
error type of `any Error`, even if there were no throwing sites within
the `do` body. With typed throws, such a `do..catch` would have a
caught error type of `Never`, because it never throws. Unfortunately,
this causes code like the following to produce an error, because
`Never` cannot be pattern-matched to `HomeworkError.forgot`:

    func test() {
      do {
        try nonthrowing()
      } catch HomeworkError.forgot {
      } catch {
      }
    }

For source-compatibility reasons, adjust the caught error type to
`any Error` in this case, so we continue to accept the code above.
Don't do this adjustment under `FullTypedThrows`, because it's only
there for compatibility.

Fixes rdar://121526201.

2024-01-24 14:42:56 -08:00

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