macros: characterization tests for ? operator fail #7069
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cc @Veykril |
joshka
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When a `?` operator is used in a tokio entry point function (wrapped in `#[tokio::main]`), which has a Option or Result return type, but where the function does not actually return that type correctly, currently the compiler returns two errors instead of just one. The first of which is incorrect and only exists due to the macro expanding to an async block. ``` cannot use the `?` operator in an async block that returns `()` ``` This commit is a characterization test for this behavior to help show when it's fixed (or even changed for better / worse)
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Since this is a draft PR, are you looking for input? This looks like it's just new tests? I'm happy to add tests. |
I was going to attempt to solve the problem, but it seemed like there was a bunch of hidden complexity around a couple of parts of this. Happy to see it reviewed instead as just the test. |
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When a
?operator is used in a tokio entry point function (wrapped in#[tokio::main]), which has a Option or Result return type, but wherethe function does not actually return that type correctly, currently the
compiler returns two errors instead of just one. The first of which is
incorrect and only exists due to the macro expanding to an async block.
This commit is a characterization test for this behavior to help show
when it's fixed (or even changed for better / worse)
Motivation
Annoyed by incorrect error message. "cannot use the
?operator in an async block that returns()". More specifically, when editing code in ways that break the code (by changing return values, or changing the order of things, seeing error messages that aren't actually relevant to fixes can be annoying, particularly in situations where these errors are reported inline to the code. There's a small amount of time where the brain leaves the problem at hand and moves into solve the bug mode, which is unnecessary (and hence worth addressing)More details at #6930 (comment)
Solution
This PR is about just identifying and capturing the problem. It can be merged as-is, or can be left open while considering the options to fix this.