Set MSRV to 1.54 without std, 1.63 with.

.github/workflows/clippy.yml

@@ -8,15 +8,22 @@ on:
 jobs:
   clippy:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        include:
+          - rust: 1.54
+            features: ''
+          - rust: 1.63
+            features: ''
+          - rust: 1.63
+            features: 'std'
     steps:
       - uses: actions/checkout@v2
       - name: Install Rust
         uses: actions-rs/toolchain@v1
         with:
-            toolchain: 1.63
+            toolchain: ${{matrix.rust}}
             components: clippy
             override: true
-      - name: Build
-        run: cargo clippy
-      - name: Build for std
-        run: cargo clippy --features std
+      - name: Clippy check
+        run: cargo clippy --features "${{matrix.features}}"

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "critical-section"
 version = "1.0.0"
-edition = "2021"
+edition = "2018"
 description = "Cross-platform critical section"
 repository = "https://github.com/rust-embedded/critical-section"
 readme = "README.md"

README.md

@@ -191,7 +191,12 @@ which would be unsound.
 
 ## Minimum Supported Rust Version (MSRV)
 
-This crate is guaranteed to compile on stable Rust 1.63 and up. It might compile with older versions but that may change in any new patch release.
+This crate is guaranteed to compile on the following Rust versions:
+
+- If the `std` feature is not enabled: stable Rust 1.54 and up. 
+- If the `std` feature is enabled: stable Rust 1.63 and up. 
+
+It might compile with older versions but that may change in any new patch release.
 
 ## License