Bump MSRV 1.88, syn 3.0 and darling 0.24

.cargo/config.toml

@@ -0,0 +1,5 @@
+# We don't want to hold back upgrades for dev dependencies and there is no override
+# for them unfortunately, so we ignore incompatible rust versions for our lock file,
+# but the script `scripts/test-msrv.sh` overrides this.
+[resolver]
+incompatible-rust-versions = "allow"

.github/workflows/ci.yml

@@ -133,14 +133,6 @@ jobs:
           cd bon && cargo test ${{ matrix.locked }} --no-default-features \
             --features=experimental-overwritable,alloc
 
-      - run: |
-          cd bon && cargo test ${{ matrix.locked }} --no-default-features \
-            --features=experimental-overwritable,implied-bounds
-
-      - run: |
-          cd bon && cargo test ${{ matrix.locked }} --no-default-features \
-            --features=experimental-overwritable,alloc,implied-bounds
-
       - run: |
           cd bon && cargo test ${{ matrix.locked }} \
             --features=experimental-generics-setters
@@ -153,14 +145,6 @@ jobs:
           cd bon && cargo test ${{ matrix.locked }} --no-default-features \
             --features=experimental-generics-setters,alloc
 
-      - run: |
-          cd bon && cargo test ${{ matrix.locked }} --no-default-features \
-            --features=experimental-generics-setters,implied-bounds
-
-      - run: |
-          cd bon && cargo test ${{ matrix.locked }} --no-default-features \
-            --features=experimental-generics-setters,alloc,implied-bounds
-
   test-msrv:
     runs-on: ${{ matrix.os }}-latest
 
@@ -169,10 +153,7 @@ jobs:
       matrix:
         os: [ubuntu, windows, macos]
         toolchain:
-          # Default MSRV
-          - 1.59.0
-          # Slightly higher MSRV for `#[builder(const)]`
-          - 1.61.0
+          - 1.88.0
 
     steps:
       - uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3

Cargo.toml

@@ -8,7 +8,7 @@ members = [
   "bon-sandbox",
   "website/doctests",
 ]
-resolver = "2"
+resolver = "3"
 
 # This config is used for the benchmarks
 [profile.release]
@@ -28,6 +28,19 @@ manual_let_else = "allow"
 # by `unwrap_or` or `unwrap_or_else`
 map_unwrap_or = "allow"
 
+# This lint computes the layout of futures, which makes `clippy` on nightly
+# ICE with "unexpected rigid alias in layout_of after normalization" on the
+# opaque types generated by `#[builder(into_future)]` in
+# `bon/tests/integration/builder/attr_into_future.rs`. A regression from the
+# next-generation trait solver being enabled on nightly. The code itself
+# compiles fine (`cargo check` passes); only `clippy` crashes.
+#
+# https://github.com/rust-lang/rust/issues/161495
+#
+# The fix landed in rust-lang/rust#161416 (merged 2026-08-24), so this can be
+# removed once CI's nightly is newer than that.
+large_futures = "allow"
+
 # Turn on lints that are allow by default in `clippy`.
 #
 # We set them to a `warn` level instead of `deny` to prevent clippy from
@@ -152,12 +165,6 @@ unescaped_backticks      = "warn"
 [workspace.lints.rust]
 unexpected_cfgs = { level = "warn", check-cfg = ['cfg(nightly)'] }
 
-# This lint is used only to warn about the changes in drop order during the
-# transition from Rust 2021 to Rust 2024. There are too many instances of this
-# lint in our code base and some of them may be false positives. So we just allow
-# this lint globally.
-tail_expr_drop_order = { level = "allow", priority = 2 }
-
 unsafe_code       = "warn"
 unstable_features = "warn"
 
@@ -188,11 +195,8 @@ unused_macro_rules             = "warn"
 unused_qualifications          = "warn"
 variant_size_differences       = "warn"
 
-rust_2024_compatibility = { level = "warn", priority = 1 }
-
 # Unstable but desirable lints.
 # [workspace.lints.rust]
 # must_not_suspend           = "warn"
-# rust_2024_incompatible_pat = "warn"
 # lossy_provenance_casts     = "warn"
 # fuzzy_provenance_casts     = "warn"

README.md

@@ -23,7 +23,7 @@
     /></a>
         <a href="https://docs.rs/bon/latest/bon/"><img
         alt="docs.rs"
-        src="https://img.shields.io/badge/MSRV-1.59.0-b83fbf?style=for-the-badge&labelColor=555555&logo=docs.rs"
+        src="https://img.shields.io/badge/MSRV-1.88.0-b83fbf?style=for-the-badge&labelColor=555555&logo=docs.rs"
         height="25"
     /></a>
 </div>

benchmarks/compilation/Cargo.toml

@@ -8,7 +8,7 @@ description = """
   proc-macros in the `bon` crate and other alternatives.
 """
 
-edition = "2021"
+edition = "2024"
 version = "0.1.0"
 
 [dependencies]

benchmarks/compilation/codegen/Cargo.toml

@@ -7,7 +7,7 @@ description = """
   Generates code for the compilation benchmarks.
 """
 
-edition = "2021"
+edition = "2024"
 version = "0.1.0"
 
 [dependencies]