Latest nightly (rustc 1.64.0-nightly (62b272d25 2022-07-21)) introduces a new borrowcheck error in previously compiling mdbook 0.4.20 #99591

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1. mitchmindtree

   added

   C-bugCategory: This is a bug.Category: This is a bug.

   regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

   on Jul 22, 2022
2. rustbot

   added

   I-prioritizeIssue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}Issue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}

   on Jul 22, 2022
5. ehuss commented on Jul 22, 2022

   

   ehuss

   on Jul 22, 2022

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   Confirmed that it is caused by #99413. Here is a slightly smaller repro:

   #![allow(unused)]
   use std::collections::BTreeMap;
   use std::marker::PhantomData;
   use std::rc::Rc;
   
   fn main() {
       let mut rc = RenderContext {
           local_helpers: BTreeMap::new(),
       };
       foo(&mut rc);
   }
   
   #[derive(Clone)]
   struct RenderContext<'rc> {
       local_helpers: BTreeMap<String, Rc<dyn HelperDef + 'rc>>,
   }
   
   pub trait HelperDef {}
   
   fn foo(rc: &mut RenderContext<'_>) {
       let mut local_rc = rc.clone();
       let local_ctx: BTreeMap<String, String> = BTreeMap::new();
       render(&local_ctx, &mut local_rc);
   }
   
   fn render<'rc>(ctx: &'rc BTreeMap<String, String>, rc: &mut RenderContext<'rc>) {}

   I think the error here is correct and #99413 is a valid fix. It's just a consequence of how the lifetimes in the handlebars crate are defined that cause the error.
6. danielhenrymantilla commented on Jul 22, 2022

   

   danielhenrymantilla

   on Jul 22, 2022

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   Until the fix to mdbook is officially released, btw, for those running into this, the workaround is to use the git dev, potentially as a patch:

   • for those using cargo install mdbook, instead, do

     cargo install mdbook --git 'https://github.com/rust-lang/mdBook' --rev '8f01d0234f708042ea8d0dc5cac63859b3f14cb1'

   • for those depending on mdbook as a library, on the Cargo.toml file of your workspace (where the Cargo.lock file lies / is generated), add:

     [patch.crates-io.mdbook]
     version = "0.4.20"
     git = "https://github.com/rust-lang/mdBook"
     rev = "8f01d0234f708042ea8d0dc5cac63859b3f14cb1"
7. apiraino

   removed

   I-prioritizeIssue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}Issue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}

   on Aug 9, 2022
8. Jules-Bertholet commented on Jun 10, 2023

   

   Jules-Bertholet

   on Jun 10, 2023

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   @rustbot label -regression-untriaged +regression-from-stable-to-stable
9. rustbot

   added

   regression-from-stable-to-stablePerformance or correctness regression from one stable version to another.Performance or correctness regression from one stable version to another.

   I-prioritizeIssue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}Issue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}

   and removed

   regression-untriagedUntriaged performance or correctness regression.Untriaged performance or correctness regression.

   on Jun 10, 2023
10. apiraino commented on Jun 21, 2023

    

    apiraino

    on Jun 21, 2023

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    @Jules-Bertholet changed the label to regression on stable: did you experience that it's still an issue? I've compiled mdbook (both on stable and nightly) and the reproducible at this comment now shows a better error, I believe.
11. ehuss commented on Jun 21, 2023

    

    ehuss

    on Jun 21, 2023

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    I think this should be closed since it was an intentional soundness fix.

    👍React with 👍2Reacted by apiraino and Jubilee
12. apiraino

    closed this as not plannedon Jun 21, 2023
13. apiraino

    removed

    I-prioritizeIssue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}Issue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}

    on Jun 21, 2023