Bump MSRV to rustc 1.75.0

We generally align our MSRV with Debian's stable channel. Debian 13
'Trixie' was just released, shipping rustc 1.85. However, as 1.85.0 is
only about ~7months old at this point, we opt to bump to the more
conservative 1.75.0, which approaches two years of age.

Author: tnull

.github/workflows/build.yml

@@ -31,10 +31,10 @@ jobs:
       fail-fast: false
       matrix:
         platform: [ self-hosted, windows-latest, macos-latest ]
-        toolchain: [ stable, beta, 1.63.0 ] # 1.63.0 is the MSRV for all crates but `lightning-transaction-sync`.
+        toolchain: [ stable, beta, 1.75.0 ] # 1.75.0 is the MSRV for all crates
         exclude:
           - platform: windows-latest
-            toolchain: 1.63.0
+            toolchain: 1.75.0
           - platform: windows-latest
             toolchain: beta
           - platform: macos-latest
@@ -60,7 +60,7 @@ jobs:
           shellcheck ci/*.sh -aP ci
           shellcheck contrib/*.sh -aP contrib
       - name: Set RUSTFLAGS to deny warnings
-        if: "matrix.toolchain == '1.63.0'"
+        if: "matrix.toolchain == '1.75.0'"
         run: echo "RUSTFLAGS=-D warnings" >> "$GITHUB_ENV"
       - name: Run CI script
         shell: bash # Default on Winblows is powershell
@@ -71,7 +71,7 @@ jobs:
       fail-fast: false
       matrix:
         platform: [ ubuntu-latest, macos-latest ]
-        toolchain: [ stable, beta, 1.75.0 ] # 1.75.0 is the MSRV for `lightning-transaction-sync`.
+        toolchain: [ stable, beta, 1.75.0 ]
     runs-on: ${{ matrix.platform }}
     steps:
       - name: Checkout source code
@@ -236,17 +236,13 @@ jobs:
   fuzz:
     runs-on: self-hosted
     env:
-      TOOLCHAIN: 1.63
+      TOOLCHAIN: 1.75
     steps:
       - name: Checkout source code
         uses: actions/checkout@v4
       - name: Install Rust ${{ env.TOOLCHAIN }} toolchain
         run: |
           curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --profile=minimal --default-toolchain ${{ env.TOOLCHAIN }}
-      - name: Pin the regex dependency
-        run: |
-          cd fuzz && cargo update -p regex --precise "1.9.6" --verbose
-          cd write-seeds && cargo update -p regex --precise "1.9.6" --verbose
       - name: Sanity check fuzz targets on Rust ${{ env.TOOLCHAIN }}
         run: |
           cd fuzz
@@ -275,7 +271,7 @@ jobs:
   rustfmt:
     runs-on: ubuntu-latest
     env:
-      TOOLCHAIN: 1.63.0
+      TOOLCHAIN: 1.75.0
     steps:
       - name: Checkout source code
         uses: actions/checkout@v4

CONTRIBUTING.md

@@ -88,7 +88,7 @@ be covered by functional tests.
 When refactoring, structure your PR to make it easy to review and don't
 hesitate to split it into multiple small, focused PRs.
 
-The Minimum Supported Rust Version (MSRV) currently is 1.63.0 (enforced by
+The Minimum Supported Rust Version (MSRV) currently is 1.75.0 (enforced by
 our GitHub Actions). We support reading serialized LDK objects written by any
 version of LDK 0.0.99 and above. We support LDK versions 0.0.113 and above
 reading serialized LDK objects written by modern LDK. Any expected issues with
@@ -124,7 +124,7 @@ display fine at any tab-length display setting. We use `rustfmt` to establish
 uniform coding standards throughout the codebase. Please run
 
 ```bash
-cargo +1.63.0 fmt
+cargo +1.75.0 fmt
 ```
 
 before committing and pushing any changes, as compliance will also be checked

ci/check-lint.sh

@@ -47,7 +47,6 @@ CLIPPY() {
 		-A clippy::len_without_is_empty \
 		-A clippy::len_zero \
 		-A clippy::let_and_return \
-		-A clippy::manual_div_ceil `# to be removed once we hit MSRV 1.73.0` \
 		-A clippy::manual_filter \
 		-A clippy::manual_map \
 		-A clippy::manual_memcpy \
@@ -106,9 +105,7 @@ CLIPPY() {
 		-A clippy::unnecessary_unwrap \
 		-A clippy::unused_unit \
 		-A clippy::useless_conversion \
-		-A clippy::unnecessary_map_or `# to be removed once we hit MSRV 1.70` \
 		-A clippy::manual_repeat_n `# to be removed once we hit MSRV 1.86` \
-		-A clippy::io_other_error `# to be removed once we hit MSRV 1.74` \
 		-A clippy::uninlined-format-args
 }
 

ci/ci-tests.sh

@@ -1,41 +1,18 @@
 #!/bin/bash
 set -eox pipefail
 
-RUSTC_MINOR_VERSION=$(rustc --version | awk '{ split($2,a,"."); print a[2] }')
+# Currently unused as we don't have to pin anything for MSRV:
+#RUSTC_MINOR_VERSION=$(rustc --version | awk '{ split($2,a,"."); print a[2] }')
 
 # Some crates require pinning to meet our MSRV even for our downstream users,
 # which we do here.
 # Further crates which appear only as dev-dependencies are pinned further down.
 function PIN_RELEASE_DEPS {
-	# Starting with version 1.39.0, the `tokio` crate has an MSRV of rustc 1.70.0
-	[ "$RUSTC_MINOR_VERSION" -lt 70 ] && cargo update -p tokio --precise "1.38.1" --verbose
-
 	return 0 # Don't fail the script if our rustc is higher than the last check
 }
 
 PIN_RELEASE_DEPS # pin the release dependencies in our main workspace
 
-# Starting with version 1.10.0, the `regex` crate has an MSRV of rustc 1.65.0.
-[ "$RUSTC_MINOR_VERSION" -lt 65 ] && cargo update -p regex --precise "1.9.6" --verbose
-
-# The addr2line v0.21 crate (a dependency of `backtrace` starting with 0.3.69) relies on rustc 1.65
-[ "$RUSTC_MINOR_VERSION" -lt 65 ] && cargo update -p backtrace --precise "0.3.68" --verbose
-
-# The once_cell v1.21.0 crate (a dependency of `proptest`) relies on rustc 1.70
-[ "$RUSTC_MINOR_VERSION" -lt 70 ] && cargo update -p once_cell --precise "1.20.3" --verbose
-
-# proptest 1.3.0 requires rustc 1.64.0
-[ "$RUSTC_MINOR_VERSION" -lt 64 ] && cargo update -p proptest --precise "1.2.0" --verbose
-
-# parking_lot 0.12.4 requires rustc 1.64.0
-[ "$RUSTC_MINOR_VERSION" -lt 64 ] && cargo update -p parking_lot --precise "0.12.3" --verbose
-
-# parking_lot_core 0.9.11 requires rustc 1.64.0
-[ "$RUSTC_MINOR_VERSION" -lt 64 ] && cargo update -p parking_lot_core --precise "0.9.10" --verbose
-
-# lock_api 0.4.13 requires rustc 1.64.0
-[ "$RUSTC_MINOR_VERSION" -lt 64 ] && cargo update -p lock_api --precise "0.4.12" --verbose
-
 export RUST_BACKTRACE=1
 
 echo -e "\n\nChecking the workspace, except lightning-transaction-sync."
@@ -64,7 +41,6 @@ cargo test --verbose --color always
 
 echo -e "\n\nTesting upgrade from prior versions of LDK"
 pushd lightning-tests
-[ "$RUSTC_MINOR_VERSION" -lt 65 ] && cargo update -p regex --precise "1.9.6" --verbose
 cargo test
 popd
 

lightning-invoice/src/de.rs

@@ -102,7 +102,7 @@ impl FromBase32 for Bolt11InvoiceFeatures {
 		// Carry bits, 0, 1, 2, 3, or 4 bits
 		let mut carry_bits = 0;
 		let mut carry = 0u8;
-		let expected_raw_length = (field_data.len() * 5 + 7) / 8;
+		let expected_raw_length = (field_data.len() * 5).div_ceil(8);
 		let mut output = Vec::<u8>::with_capacity(expected_raw_length);
 
 		// Iterate over input in reverse

lightning-invoice/src/ser.rs

@@ -237,7 +237,7 @@ fn encode_int_be_base32(int: u64) -> impl ExactSizeIterator<Item = Fe32> {
 /// The length of the output of `encode_int_be_base32`.
 fn encoded_int_be_base32_size(int: u64) -> usize {
 	let bit_len = 64 - int.leading_zeros() as usize; // cast ok as value is in 0..=64.
-	(bit_len + 4) / 5
+	bit_len.div_ceil(5)
 }
 
 impl Base32Iterable for RawDataPart {

lightning-types/src/features.rs

@@ -688,7 +688,7 @@ mod sealed {
 	);
 	// By default, allocate enough bytes to cover up to Splice. Update this as new features are
 	// added which we expect to appear commonly across contexts.
-	pub(super) const MIN_FEATURES_ALLOCATION_BYTES: usize = (63 + 7) / 8;
+	pub(super) const MIN_FEATURES_ALLOCATION_BYTES: usize = 63_usize.div_ceil(8);
 	define_feature!(
 		259,
 		DnsResolver,

rustfmt.toml

@@ -1,5 +1,5 @@
 use_small_heuristics = "Max"
-fn_args_layout = "Compressed"
+fn_params_layout = "Compressed"
 hard_tabs = true
 use_field_init_shorthand = true
 max_width = 100