Lower MSRV to 1.65 (#313)

## Synopsis

The MSRV bump in #300 is
unnecessary. The 1.72 minimum is only needed for tests, but the actual
implementation depends on 1.65.

## Solution

- Lower MSRV from 1.72 to 1.65.
- Omit tests requiring higher MSRV in `msrv` CI job.
- Describe "MSRV policy" in README.

Co-authored-by: Kai Ren <tyranron@gmail.com>

.github/workflows/ci.yml

@@ -54,7 +54,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        msrv: ["1.72.0"]
+        msrv: ["1.65.0"]
         os:
           - ubuntu
           - macOS
@@ -74,6 +74,9 @@ jobs:
 
       - run: cargo test --workspace --features full,testing-helpers
                         -- --skip compile_fail
+        env:
+          RUSTFLAGS: --cfg msrv
+          RUSTDOCFLAGS: --cfg msrv
 
   no_std:
     runs-on: ubuntu-latest

CHANGELOG.md

@@ -10,7 +10,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Breaking changes
 
-- The minimum supported Rust version (MSRV) is now Rust 1.72.
+- The minimum supported Rust version (MSRV) is now Rust 1.65.
 - Add the `std` feature which should be disabled in `no_std` environments.
 - All Cargo features, except `std`, are now disabled by default. The `full`
   feature can be used to get the old behavior of supporting all possible

Cargo.toml

@@ -2,7 +2,7 @@
 name = "derive_more"
 version = "1.0.0-beta.6"
 edition = "2021"
-rust-version = "1.72.0"
+rust-version = "1.65.0"
 description = "Adds #[derive(x)] macros for more traits"
 authors = ["Jelte Fennema <github-tech@jeltef.nl>"]
 license = "MIT"

README.md

@@ -4,7 +4,7 @@
 [![Latest Version](https://img.shields.io/crates/v/derive_more.svg)](https://crates.io/crates/derive_more)
 [![Rust Documentation](https://docs.rs/derive_more/badge.svg)](https://docs.rs/derive_more)
 [![GitHub license](https://img.shields.io/badge/license-MIT-blue.svg)](https://raw.githubusercontent.com/JelteF/derive_more/master/LICENSE)
-[![Rust 1.72+](https://img.shields.io/badge/rustc-1.72+-lightgray.svg)](https://blog.rust-lang.org/2023/08/24/Rust-1.72.0.html)
+[![Rust 1.65+](https://img.shields.io/badge/rustc-1.65+-lightgray.svg)](https://blog.rust-lang.org/2022/11/03/Rust-1.65.0.html)
 [![Unsafe Forbidden](https://img.shields.io/badge/unsafe-forbidden-success.svg)](https://github.com/rust-secure-code/safety-dance)
 
 Rust has lots of builtin traits that are implemented for its basic types, such
@@ -137,13 +137,22 @@ These don't derive traits, but derive static methods instead.
 4. [`TryUnwrap`], for each variant `foo` of an enum type, derives an `try_unwrap_foo` method.
 
 
+### Re-exports
+
+This crate also re-exports all the standard library traits that it adds derives
+for. So, both the `Display` derive and the `Display` trait will be in scope when
+you add the following code:
+```rust
+use derive_more::Display;
+```
+
+
 
 
 ## Installation
 
-This library requires Rust 1.72 or higher. To avoid redundant compilation times, by
-default no derives are supported. You have to enable each type of derive as a feature
-in `Cargo.toml`:
+To avoid redundant compilation times, by default no derives are supported.
+You have to enable each type of derive as a feature in `Cargo.toml`:
 
 ```toml
 [dependencies]
@@ -176,14 +185,25 @@ extern crate derive_more;
 # fn main() {} // omit wrapping statements above into `main()` in tests
 ```
 
-## Re-exports
 
-This crate also re-exports all of the standard library traits that it adds
-derives for. So both the `Display` derive and the `Display` trait will be in
-scope when you add the following code:
-```rust
-use derive_more::Display;
-```
+## [MSRV] policy
+
+This library requires Rust 1.65 or higher.
+
+Changing [MSRV] (minimum supported Rust version) of this crate is treated as a **minor version change** in terms of [Semantic Versioning].
+- So, if [MSRV] changes are **NOT concerning** for your project, just use the default [caret requirement]:
+  ```toml
+  [dependencies]
+  derive_more = "1" # or "1.0", or "^1.0"
+  ```
+- However, if [MSRV] changes are concerning for your project, then use the [tilde requirement] to **omit breaking code**:
+  ```toml
+  [dependencies]
+  derive_more = "~1.0" # or "~1.0.0"
+  ```
+
+
+
 
 [`cargo-expand`]: https://github.com/dtolnay/cargo-expand
 [`derive-new`]: https://github.com/nrc/derive-new
@@ -216,3 +236,8 @@ use derive_more::Display;
 [`IsVariant`]: https://jeltef.github.io/derive_more/derive_more/is_variant.html
 [`Unwrap`]: https://jeltef.github.io/derive_more/derive_more/unwrap.html
 [`TryUnwrap`]: https://jeltef.github.io/derive_more/derive_more/try_unwrap.html
+
+[caret requirement]: https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#caret-requirements
+[tilde requirement]: https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#tilde-requirements
+[MSRV]: https://doc.rust-lang.org/cargo/reference/manifest.html#the-rust-version-field
+[Semantic Versioning]: http://semver.org

clippy.toml

@@ -2,7 +2,7 @@
 # See full lints list at:
 # https://rust-lang.github.io/rust-clippy/master/index.html
 
-msrv = "1.72.0"
+msrv = "1.65.0"
 
 # Ensures consistent bracing for macro calls in the codebase.
 # Extends default settings:

impl/Cargo.toml

@@ -2,7 +2,7 @@
 name = "derive_more-impl"
 version = "1.0.0-beta.6"
 edition = "2021"
-rust-version = "1.72.0"
+rust-version = "1.65.0"
 description = "Internal implementation of `derive_more` crate"
 authors = ["Jelte Fennema <github-tech@jeltef.nl>"]
 license = "MIT"

impl/doc/try_from.md

@@ -12,6 +12,8 @@ The type can be changed with a `#[repr(u/i*)]` attribute, e.g., `#[repr(u8)]` or
 Only field-less variants can be constructed from their variant, therefor the `TryFrom` implementation will return an error for a discriminant representing a variant with fields.
 
 ```rust
+# #[cfg(msrv)] fn main() {} // TODO: Remove once MSRV bumps 1.66 or higher.
+# #[cfg(not(msrv))] fn main() {
 # use derive_more::TryFrom;
 #[derive(TryFrom, Debug, PartialEq)]
 #[try_from(repr)]
@@ -29,4 +31,5 @@ assert_eq!(Enum::EmptySeven{}, Enum::try_from(7).unwrap());
 
 // Variants with fields are not supported, as the value for their fields would be undefined.
 assert!(Enum::try_from(6).is_err());
+# }
 ```

tests/try_from.rs

@@ -56,6 +56,7 @@ fn enum_with_complex_repr() {
     assert!(Enum::try_from(-1).is_err());
 }
 
+#[cfg(not(msrv))] // TODO: Remove once MSRV bumps 1.66 or higher.
 #[test]
 fn test_discriminants_on_enum_with_fields() {
     #[derive(TryFrom, Clone, Copy, Debug, Eq, PartialEq)]