build(Cargo.toml): set minimum supported Rust version

Sets the MSRV for the crate. The `rust-toolchain.toml` file is dropped since
this is too retrictive when choosing choosing a toolchain for developing the
crate – uses exact semantics.

It is necessary to change the `flake.nix` to read this version from the
`Cargo.toml` so that it can select the rust toolchain to use via `rust-overlay`.

Signed-off-by: Lars Wirzenius <liw@liw.fi>
Co-authored-by: Fintan Halpenny <fintan.halpenny@gmail.com>

Cargo.toml

@@ -5,6 +5,9 @@ license = "MIT OR Apache-2.0"
 version = "0.1.0"
 authors = ["Fintan Halpenny <fintan.halpenny@gmail.com>"]
 edition = "2021"
+# N.B. always use the full semver so that rust-overlay in `flake.nix` can select
+# the correct version
+rust-version = "1.82.0"
 
 [dependencies]
 indexmap = { version = "2.7.1", features = ["serde"] }

flake.lock

@@ -2,11 +2,11 @@
   "nodes": {
     "crane": {
       "locked": {
-        "lastModified": 1742394900,
+        "lastModified": 1747260204,
-        "narHash": "sha256-vVOAp9ahvnU+fQoKd4SEXB2JG2wbENkpqcwlkIXgUC0=",
+        "narHash": "sha256-KUb6MFWc2DYeTCmcEkrBrrqhxAgO6NHZh5qQKwsjG6I=",
         "owner": "ipetkov",
         "repo": "crane",
-        "rev": "70947c1908108c0c551ddfd73d4f750ff2ea67cd",
+        "rev": "7f85510df37247c86a0c44032f49aa18292ee11f",
         "type": "github"
       },
       "original": {
@@ -35,11 +35,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1742998488,
+        "lastModified": 1747308931,
-        "narHash": "sha256-r7dqSLNkzg1rOPsq4Tuc6p+UtAGqNRMma4riupsuZv4=",
+        "narHash": "sha256-aFP8PqwBbokBQ6IKpD71RbhSWV4qjyg6M0y62rodRts=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "8e0b1e9c8c4dfaef0ff85e09c91294ba4afa4168",
+        "rev": "ed8ec80540abb9a7e69da65916cf3d0b26174555",
         "type": "github"
       },
       "original": {
@@ -64,11 +64,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1742956365,
+        "lastModified": 1747190175,
-        "narHash": "sha256-Slrqmt6kJ/M7Z/ce4ebQWsz2aeEodrX56CsupOEPoz0=",
+        "narHash": "sha256-s33mQ2s5L/2nyllhRTywgECNZyCqyF4MJeM3vG/GaRo=",
         "owner": "oxalica",
         "repo": "rust-overlay",
-        "rev": "a0e3395c63cdbc9c1ec17915f8328c077c79c4a1",
+        "rev": "58160be7abad81f6f8cb53120d5b88c16e01c06d",
         "type": "github"
       },
       "original": {

flake.nix

@@ -29,7 +29,10 @@
         overlays = [(import rust-overlay)];
       };
 
-      rustToolChain = pkgs.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
+      # Get the `rust-version` from the Cargo manifest
+      manifest = builtins.fromTOML (builtins.readFile ./Cargo.toml);
+      rust-version = manifest.package.rust-version;
+      rustToolChain = pkgs.rust-bin.stable.${rust-version}.default;
       craneLib = (crane.mkLib pkgs).overrideToolchain rustToolChain;
 
       src = lib.cleanSourceWith {
@@ -99,6 +102,7 @@
         # Extra inputs can be added here; cargo and rustc are provided by default
         # from the toolchain that was specified earlier.
         packages = with pkgs; [
+          cargo-nextest
           cargo-watch
           ripgrep
           rust-analyzer

rust-toolchain.toml

@@ -1,4 +0,0 @@
-[toolchain]
-channel = "1.84"
-profile = "default"
-components = [ "rust-src" ]