[rust] use nightly rust

.bazelrc

@@ -165,6 +165,9 @@ build --cxxopt="-fbracket-depth=512" --host_cxxopt="-fbracket-depth=512"
 build --@rules_rust//:extra_rustc_flag=-Cdebug-assertions=n
 build --@rules_rust//:extra_exec_rustc_flags=-Cdebug-assertions=n
 build --@rules_rust//:rustfmt.toml=//src/rust:rustfmt.toml
+# We use nightly because of https://github.com/bazelbuild/rules_rust/issues/3459
+build --@rules_rust//rust/toolchain/channel=nightly
+build --@rules_rust//rust/settings:experimental_use_allocator_libraries_with_mangled_symbols
 
 # We default to not enabling debug assertions and unwinding for Rust. For debug builds this is not
 # the right setting, but unfortunately we can't set that directly.

build/rust_lint.bazelrc

@@ -23,7 +23,7 @@ build:rust-enable-clippy-checks --output_groups=+clippy_checks
 # - clippy::non_std_lazy_statics – triggers on lazy_static, non-trivial to replace
 # - clippy::format_push_string – avoids single memory allocation, but makes code less readable
 # - clippy::cast_possible_truncation - usize/u64 conversion warning is unbelievably noisy
-build:rust-enable-clippy-checks --@rules_rust//:clippy_flags=-Wclippy::pedantic,-Wclippy::redundant_clone,-Wclippy::str_to_string,-Wclippy::string_to_string,-Wclippy::to_string_in_format_args,-Wclippy::unnecessary_to_owned,-Wclippy::implicit_clone,-Wclippy::suspicious_to_owned,-Wclippy::unnecessary_to_owned,-Wclippy::nursery,-Wclippy::dbg_macro,-Wclippy::unwrap_used,-Wclippy::allow_attributes,-Aclippy::missing_const_for_fn,-Aclippy::cognitive_complexity,-Aclippy::trait_duplication_in_bounds,-Aclippy::non_send_fields_in_send_ty,-Aclippy::option_if_let_else,-Aclippy::missing_errors_doc,-Aclippy::must_use_candidate,-Aclippy::future_not_send,-Aclippy::trivial_regex,-Aclippy::literal_string_with_formatting_args,-Aclippy::non_std_lazy_statics,-Aclippy::format_push_string,-Aclippy::cast_possible_truncation,-Dwarnings
+build:rust-enable-clippy-checks --@rules_rust//:clippy_flags=-Wclippy::pedantic,-Wclippy::redundant_clone,-Wclippy::str_to_string,-Wclippy::to_string_in_format_args,-Wclippy::unnecessary_to_owned,-Wclippy::implicit_clone,-Wclippy::suspicious_to_owned,-Wclippy::unnecessary_to_owned,-Wclippy::nursery,-Wclippy::dbg_macro,-Wclippy::unwrap_used,-Wclippy::allow_attributes,-Aclippy::missing_const_for_fn,-Aclippy::cognitive_complexity,-Aclippy::trait_duplication_in_bounds,-Aclippy::non_send_fields_in_send_ty,-Aclippy::option_if_let_else,-Aclippy::missing_errors_doc,-Aclippy::must_use_candidate,-Aclippy::future_not_send,-Aclippy::trivial_regex,-Aclippy::literal_string_with_formatting_args,-Aclippy::non_std_lazy_statics,-Aclippy::format_push_string,-Aclippy::cast_possible_truncation,-Dwarnings
 build --@rules_rust//rust/settings:clippy.toml=//src/rust:clippy.toml
 
 # enable rustfmt checks

build/rust_toolchains.bzl

@@ -3,9 +3,18 @@ load("@rules_rust//rust:repositories.bzl", "rules_rust_dependencies", "rust_regi
 load("@rules_rust//tools/rust_analyzer:deps.bzl", "rust_analyzer_dependencies")
 load("//deps/rust/crates:crates.bzl", "crate_repositories")
 
-RUST_STABLE_VERSION = "1.86.0"  # LLVM 19
+# We use nightly because of https://github.com/bazelbuild/rules_rust/issues/3459
+RUST_VERSION = "nightly/2025-09-18"
 
-RUST_NIGHTLY_VERSION = "nightly/2025-02-20"
+# List of allowed unstable features
+ALLOWED_FEATURES = []
+
+# rustc flags applied to all workerd source code
+RUSTC_FLAGS = [
+    # We can't enable this in .bazelrc because 3rd-party crates don't like this.
+    # used manually everywhere instead.
+    "-Zallow-features=" + ",".join(ALLOWED_FEATURES),
+]
 
 # List of additional triples to be configured on top of the local platform triple
 RUST_TARGET_TRIPLES = [
@@ -29,17 +38,14 @@ def rust_toolchains():
             "aarch64-unknown-linux-gnu": ["-Ctarget-feature=+crc"],
             # No options needed for aarch64-apple-darwin: CRC feature is enabled by default.
         },
-        versions = [
-            RUST_STABLE_VERSION,
-            RUST_NIGHTLY_VERSION,
-        ],
+        versions = [RUST_VERSION],
     )
 
     for t in RUST_TARGET_TRIPLES:
         rustfmt_toolchain_repository(
             name = "rustfmt_toolchain_" + t,
             exec_triple = t,
-            version = RUST_NIGHTLY_VERSION,
+            version = RUST_VERSION,
         )
 
     crate_universe_dependencies()

build/wd_rust_binary.bzl

@@ -1,4 +1,5 @@
 load("@rules_rust//rust:defs.bzl", "rust_binary", "rust_test")
+load("@workerd//:build/rust_toolchains.bzl", "RUSTC_FLAGS")
 load("@workerd//:build/wd_rust_crate.bzl", "rust_cxx_bridge")
 
 def wd_rust_binary(
@@ -62,6 +63,7 @@ def wd_rust_binary(
             "@//build/config:no_build": ["@platforms//:incompatible"],
             "//conditions:default": [],
         }),
+        rustc_flags = RUSTC_FLAGS,
     )
 
     rust_test(
@@ -83,4 +85,5 @@ def wd_rust_binary(
             "//conditions:default": [],
         }),
         size = test_size,
+        rustc_flags = RUSTC_FLAGS,
     )

build/wd_rust_capnp_library.bzl

@@ -1,11 +1,13 @@
 """wd_rust_capnp_library definition"""
 
 load("@capnp-cpp//src/capnp:rust_capnp_library.bzl", "rust_capnp_library")
+load("@workerd//:build/rust_toolchains.bzl", "RUSTC_FLAGS")
 
 def wd_rust_capnp_library(**kwargs):
     """Wrapper for rust_capnp_library that sets common attributes
     """
     rust_capnp_library(
         src_prefix = "src",
+        rustc_flags = RUSTC_FLAGS,
         **kwargs
     )

build/wd_rust_crate.bzl

@@ -1,4 +1,5 @@
 load("@rules_rust//rust:defs.bzl", "rust_library", "rust_test", "rust_unpretty")
+load("@workerd//:build/rust_toolchains.bzl", "RUSTC_FLAGS")
 
 def rust_cxx_bridge(
         name,
@@ -120,6 +121,7 @@ def wd_rust_crate(
             "@//build/config:no_build": ["@platforms//:incompatible"],
             "//conditions:default": [],
         }),
+        rustc_flags = RUSTC_FLAGS,
     )
 
     rust_test(
@@ -140,6 +142,7 @@ def wd_rust_crate(
             "@platforms//os:windows": 0,
             "//conditions:default": 1,
         }),
+        rustc_flags = RUSTC_FLAGS,
     )
 
     if len(proc_macro_deps) + len(cxx_bridge_srcs) > 0:

src/rust/cxx-integration-test/lib.rs

@@ -1,7 +1,6 @@
 //! Non-production crate to help test various aspects of rust/c++ integration.
 
 use std::io::Error;
-use std::io::ErrorKind;
 use std::pin::Pin;
 use std::time::Duration;
 
@@ -100,7 +99,7 @@ fn result_ok() -> Result<i32> {
 }
 
 fn result_error() -> Result<i32> {
-    Err(Error::new(ErrorKind::Other, "test error"))
+    Err(Error::other("test error"))
 }
 
 fn log_every_level() {

src/rust/kj/http.rs

@@ -14,7 +14,7 @@ use crate::io::AsyncIoStream;
 #[cxx::bridge(namespace = "kj::rust")]
 #[expect(clippy::missing_panics_doc)]
 #[expect(clippy::missing_safety_doc)]
-#[expect(clippy::needless_lifetimes)]
+#[expect(clippy::elidable_lifetime_names)]
 pub mod ffi {
     unsafe extern "C++" {
         include!("workerd/rust/kj/ffi.h");