Add E0019 error explanation #26396
Add E0019 error explanation #26396
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r? @pnkfelix (rust_highfive has picked a reviewer for you, use r? to override) |
| @@ -279,6 +279,41 @@ println!("{}", Y); | |||
| ``` | |||
| "##, | |||
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| E0019: r##" | |||
| A function call isn't allowed in the const's initialization expression | |||
| because the expression's value must be known at compile-time. Bad example: | |||
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The phrase "Bad example" is often used when one is saying that the example itself is bad -- i.e. when the example does not actually serve as a demonstration of the topic at hand.
I would instead write: "Example of erroneous code:" or "Example of non-compiling code:"
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I actually had the same comment on the other PRs I opened yesterday. I forgot to update this one, I do it.
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Updated! |
| } | ||
| ``` | ||
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| Remember: you can't use a function call inside a const's initialization |
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You should add an additional paragraph about the const fn feature, which is currently feature-gated and thus only available in Nightly (but there are other error explanations like E0152 that reference feature-gated things). The sole purpose of const fn is to be a function call that breaks the rule you wrote here. :)
Here is a demonstration of const fn:
https://play.rust-lang.org/?gist=449fb78958b96eca7528&version=nightly
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(I've been discussing the question of whether to include discussion of feature-gated things. For now I think it would be best if @GuillaumeGomez removes the final commit above from this PR, and then we land it. We can then put that final commit up as a separate PR that will only be landed after we resolve the question of how to discuss feature-gated things in error explanations.) |
Part of #24407.
cc @michaelsproul