build: Bump minimum Rust version to 1.56

.azure-pipelines/main.yml

@@ -70,7 +70,7 @@ pool:
 steps:
 - template: steps/setup-rust.yml
   parameters:
-    version: '1.45.0'
+    version: '1.56.0'
 - template: steps/-build.yml
 - template: steps/setup-emacs.yml
 - template: steps/-test.yml

CHANGELOG.md

@@ -5,6 +5,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## [Unreleased]
 - Upgraded to Rust 2021 edition.
+    - This also raised the minimum supported Rust version to 1.56.
 - Added support for Rust's non-zero integer types.
 
 ## [0.18.0] - 2021-09-26

build.rs

@@ -5,8 +5,8 @@ use rustc_version::{version, Version};
 
 fn main() {
     let version = version().unwrap();
-    if version < Version::parse("1.45.0").unwrap() {
-        eprintln!("emacs-module-rs requires rustc 1.45.0 or newer, got {}", version);
+    if version < Version::parse("1.56.0").unwrap() {
+        eprintln!("emacs-module-rs requires rustc 1.56.0 or newer, got {}", version);
         exit(1);
     }
 }