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.

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.

codecov · 2025-10-25T21:05:54Z

Codecov Report

❌ Patch coverage is 73.74517% with 68 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.79%. Comparing base (be24841) to head (724caa8).
⚠️ Report is 2 commits behind head on main.

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   88.81%   88.79%   -0.02%     
==========================================
  Files         180      180              
  Lines      137105   137120      +15     
  Branches   137105   137120      +15     
==========================================
- Hits       121765   121761       -4     
- Misses      12529    12539      +10     
- Partials     2811     2820       +9

Flag	Coverage Δ
fuzzing	`21.60% <1.98%> (+<0.01%)`	⬆️
tests	`88.64% <73.74%> (-0.02%)`	⬇️

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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.

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.

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

TheBlueMatt force-pushed the 2025-10-msrv-less-box branch 13 times, most recently from 4edab1f to e8fa417 Compare October 25, 2025 20:54

TheBlueMatt added 3 commits October 25, 2025 20:55

Move lightning-transaction-sync back into the main workspace

b2b4b67

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

164240e

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.

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

TheBlueMatt added 3 commits October 25, 2025 21:08

Drop required Boxing of lightning-block-sync Futures

c5e675d

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.

Drop Boxing of iterators during BOLT 11 invoice serialization

004c76a

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 force-pushed the 2025-10-msrv-less-box branch from d54050d to 004c76a Compare October 25, 2025 21:08

Fix new warning-errors in 1.75 CI builds

724caa8

TheBlueMatt force-pushed the 2025-10-msrv-less-box branch 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

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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

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

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