Set MSRV to 1.51.0

Yay const generics!

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: stable
+          toolchain: 1.51.0
           override: true
       - name: Run tests
         uses: actions-rs/cargo@v1
@@ -30,7 +30,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: stable
+          toolchain: 1.51.0
           override: true
       # Build benchmarks to prevent bitrot
       - name: Build benchmarks
@@ -44,6 +44,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
+      - uses: actions-rs/toolchain@v1
+        with:
+          toolchain: 1.51.0
+          override: true
       - name: Setup mdBook
         uses: peaceiris/actions-mdbook@v1
         with:
@@ -52,20 +56,20 @@ jobs:
         run: mdbook test book/
 
   clippy:
-    name: Clippy (stable)
+    name: Clippy (1.51.0)
     timeout-minutes: 30
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: stable
+          toolchain: 1.51.0
           components: clippy
           override: true
       - name: Run clippy
         uses: actions-rs/clippy-check@v1
         with:
-          name: Clippy (stable)
+          name: Clippy (1.51.0)
           token: ${{ secrets.GITHUB_TOKEN }}
           args: --all-features --all-targets -- -D warnings
 
@@ -123,7 +127,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: nightly
+          toolchain: 1.51.0
           override: true
       - name: cargo fetch
         uses: actions-rs/cargo@v1
@@ -136,7 +140,7 @@ jobs:
         uses: actions-rs/cargo@v1
         with:
           command: doc
-          args: --all --document-private-items
+          args: --document-private-items
 
   fmt:
     name: Rustfmt
@@ -146,7 +150,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: stable
+          toolchain: 1.51.0
           override: true
       - run: rustup component add rustfmt
       - uses: actions-rs/cargo@v1

README.md

@@ -2,6 +2,8 @@
 
 **IMPORTANT**: This library is being actively developed and should not be used in production software.
 
+Requires Rust 1.51+.
+
 ## Documentation
 
 - [The Orchard Book](https://zcash.github.io/orchard/)

rust-toolchain

@@ -0,0 +1 @@
+1.51.0