Reduce `Box`ing using `impl Trait` in trait methods post-MSRV-bump #4175

TheBlueMatt · 2025-10-25T18:28:13Z

A handful of cleanups now that we bumped the MSRV and can use impl Trait in trait methods.

ldk-reviews-bot · 2025-10-25T18:28:15Z

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TheBlueMatt · 2025-10-25T18:29:16Z

There's still a few Box::pins in lightning-background-processor that we really should be able to get rid of, but its not entirely trivial so I didn't do it here.

codecov · 2025-10-25T21:05:54Z

Codecov Report

❌ Patch coverage is 73.94636% with 68 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.84%. Comparing base (28ef147) to head (a467664).

Files with missing lines	Patch %	Lines
lightning-background-processor/src/lib.rs	0.00%	20 Missing ⚠️
lightning-block-sync/src/rest.rs	27.77%	13 Missing ⚠️
lightning-block-sync/src/rpc.rs	27.77%	13 Missing ⚠️
lightning-block-sync/src/gossip.rs	0.00%	9 Missing ⚠️
lightning/src/util/test_utils.rs	25.00%	6 Missing ⚠️
lightning-persister/src/fs_store.rs	90.90%	4 Missing ⚠️
lightning-net-tokio/src/lib.rs	60.00%	2 Missing ⚠️
lightning-liquidity/src/lsps2/service.rs	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4175      +/-   ##
==========================================
- Coverage   88.85%   88.84%   -0.02%     
==========================================
  Files         180      180              
  Lines      137863   137884      +21     
  Branches   137863   137884      +21     
==========================================
+ Hits       122496   122498       +2     
- Misses      12561    12579      +18     
- Partials     2806     2807       +1

Flag	Coverage Δ
fuzzing	`21.44% <1.96%> (+<0.01%)`	⬆️
tests	`88.68% <73.94%> (-0.02%)`	⬇️

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tnull

Given how much this cleans up the new async traits, I do wonder if we want to ship this for 0.2 afterall?

tnull · 2025-10-27T06:57:59Z

Cargo.toml

    "lightning-macros",
    "lightning-dns-resolver",
    "lightning-liquidity",
+    "lightning-transaction-sync",


As BDK is about to bump their MSRV to 1.85, let's not bother with this if we need to move it out again shortly.

I thought they agreed to keep the utility crates to 1.75?

Actually, I thought they were gonna walk it back to 1.75...

ldk-reviews-bot · 2025-10-27T07:06:20Z

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TheBlueMatt · 2025-10-27T12:26:33Z

Given how much this cleans up the new async traits, I do wonder if we want to ship this for 0.2 afterall?

Meh, I don't think they clean them up that much, they just remove a Box::pin, and actually they become a bit more annoying to work with (see the few places we have to keep the Box::pin cause of rustc mess). It becomes a bit easier to work with in edition 2024, which luckily a downstream crate could choose to use if they want.

Now that it has the same MSRV as everything else in the workspace, it doesn't need to live on its own.

Now that our MSRV is above 1.68 we can use the `pin!` macro to avoid having to `Box` various futures, avoiding some allocations, especially in `lightning-net-tokio`, which happens in a tight loop.

Now that our MSRV is 1.75, we can return `impl Trait` from trait methods. Here we use this to clean up `KVStore` methods, dropping the `Pin<Box<dyn ...>>` we had to use to have trait methods return a concrete type. Sadly, there's two places where we can't drop a `Box::pin` until we switch to edition 2024.

Now that our MSRV is 1.75, we can return `impl Trait` from trait methods. Here we use this to clean up `lightning-block-sync` trait methods, dropping the `Pin<Box<dyn ...>>` we had to use to have trait methods return a concrete type.

Now that our MSRV is 1.75, we can return `impl Trait` from trait methods. Here we use this to clean up `lightning` crate trait methods, dropping the `Pin<Box<dyn ...>>`/`AsyncResult` we had to use to have trait methods return a concrete type.

Now that we have an MSRV that supports returning `impl Trait` in trait methods, we can use it to avoid the `Box<dyn ...>` we had spewed all over our BOLT 11 invoice serialization.

TheBlueMatt · 2025-10-30T14:42:10Z

Rebased to pick up #4180, this should now pass CI (modulo fuzzing, which still confuses me).

TheBlueMatt · 2025-10-30T15:27:29Z

The CI failure is bitcoindevkit/rust-electrum-client#181 which is unrelated to this PR and its just that we're now testing it.

ldk-reviews-bot requested a review from wpaulino October 25, 2025 18:38

TheBlueMatt force-pushed the 2025-10-msrv-less-box branch 14 times, most recently from e8fa417 to d54050d Compare October 25, 2025 20:55

TheBlueMatt force-pushed the 2025-10-msrv-less-box branch 2 times, most recently from 9d5a3e2 to 724caa8 Compare October 26, 2025 11:50

tnull requested review from tnull and removed request for wpaulino October 27, 2025 06:56

tnull reviewed Oct 27, 2025

View reviewed changes

TheBlueMatt mentioned this pull request Oct 28, 2025

Bump electrsd to 0.36.1, fix CI #4180

Merged

TheBlueMatt added 4 commits October 30, 2025 13:48

Move lightning-transaction-sync back into the main workspace

82cff22

Now that it has the same MSRV as everything else in the workspace, it doesn't need to live on its own.

Trivially replace Box::pin with pin! in a few places

b55d2aa

Now that our MSRV is above 1.68 we can use the `pin!` macro to avoid having to `Box` various futures, avoiding some allocations, especially in `lightning-net-tokio`, which happens in a tight loop.

Drop required Boxing of lightning-block-sync Futures

27b8335

Now that our MSRV is 1.75, we can return `impl Trait` from trait methods. Here we use this to clean up `lightning-block-sync` trait methods, dropping the `Pin<Box<dyn ...>>` we had to use to have trait methods return a concrete type.

TheBlueMatt added 3 commits October 30, 2025 14:36

Drop Boxing of iterators during BOLT 11 invoice serialization

f089001

Now that we have an MSRV that supports returning `impl Trait` in trait methods, we can use it to avoid the `Box<dyn ...>` we had spewed all over our BOLT 11 invoice serialization.

Fix new warning-errors in 1.75 CI builds

a467664

TheBlueMatt force-pushed the 2025-10-msrv-less-box branch from 724caa8 to a467664 Compare October 30, 2025 14:36

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Reduce `Box`ing using `impl Trait` in trait methods post-MSRV-bump #4175

Reduce `Box`ing using `impl Trait` in trait methods post-MSRV-bump #4175

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Reduce `Box`ing using `impl Trait` in trait methods post-MSRV-bump #4175

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