Relax MSRV to 1.63.0

No code changes are required, and this allows the current compiler
shipped by Debian stable (bookworm) to work. The only consideration is
that recent versions of `allocator-api2` do require 1.64, but the
minimum dependency 0.2.9 is fine, and this is optional anyway.

.github/workflows/rust.yml

@@ -50,7 +50,7 @@ jobs:
           thumbv6m-none-eabi,
           x86_64-pc-windows-gnu,
         ]
-        channel: [1.64.0, nightly]
+        channel: [1.63.0, nightly]
         include:
         - os: macos-latest
           target: x86_64-apple-darwin
@@ -60,13 +60,13 @@ jobs:
           channel: nightly
         - os: macos-latest
           target: x86_64-apple-darwin
-          channel: 1.64.0
+          channel: 1.63.0
         - os: windows-latest
           target: x86_64-pc-windows-msvc
-          channel: 1.64.0
+          channel: 1.63.0
         - os: ubuntu-latest
           target: x86_64-unknown-linux-gnu
-          channel: 1.64.0
+          channel: 1.63.0
         - os: ubuntu-latest
           target: x86_64-unknown-linux-gnu
           channel: beta

Cargo.toml

@@ -10,7 +10,7 @@ keywords = ["hash", "no_std", "hashmap", "swisstable"]
 categories = ["data-structures", "no-std"]
 exclude = [".github", "/ci/*"]
 edition = "2021"
-rust-version = "1.64.0"
+rust-version = "1.63.0"
 
 [dependencies]
 # For the default hasher

README.md

@@ -4,7 +4,7 @@ hashbrown
 [![Build Status](https://github.com/rust-lang/hashbrown/actions/workflows/rust.yml/badge.svg)](https://github.com/rust-lang/hashbrown/actions)
 [![Crates.io](https://img.shields.io/crates/v/hashbrown.svg)](https://crates.io/crates/hashbrown)
 [![Documentation](https://docs.rs/hashbrown/badge.svg)](https://docs.rs/hashbrown)
-[![Rust](https://img.shields.io/badge/rust-1.64.0%2B-blue.svg?maxAge=3600)](https://github.com/rust-lang/hashbrown)
+[![Rust](https://img.shields.io/badge/rust-1.63.0%2B-blue.svg?maxAge=3600)](https://github.com/rust-lang/hashbrown)
 
 This crate is a Rust port of Google's high-performance [SwissTable] hash
 map, adapted to make it a drop-in replacement for Rust's standard `HashMap`

ci/run.sh

@@ -16,6 +16,9 @@ if [ "${CHANNEL}" = "nightly" ]; then
     FEATURES="${FEATURES},nightly"
     export RUSTFLAGS="$RUSTFLAGS -D warnings"
 fi
+if [ "${CHANNEL}" = "1.63.0" ]; then
+    cargo update --package allocator-api2 --precise 0.2.9
+fi
 
 CARGO=cargo
 if [ "${CROSS}" = "1" ]; then