Merge pull request #13 from tnull/2023-07-pin-proc-macro2

Pin additional crates to fix MSRV builds in CI

Author: tnull

.github/workflows/build.yml

@@ -25,17 +25,20 @@ jobs:
           toolchain: ${{ matrix.toolchain }}
           override: true
           profile: minimal
-      - name: Pin tokio for MSRV
-        if: matrix.msrv
-        run: cargo update -p tokio --precise "1.14.1" --verbose
-      - name: Pin serde for MSRV
+      - name: Pin crates for MSRV
         if: matrix.msrv
         run: |
+          # Tokio MSRV on versions 1.17 through 1.26 is rustc 1.49. Above 1.26 MSRV is 1.56.
+          cargo update -p tokio --precise "1.14.1" --verbose
+          # The serde_json crate switched to Rust edition 2021 starting with v1.0.101, i.e., has MSRV of 1.56
           cargo update -p serde_json --precise "1.0.99" --verbose
           cargo update -p serde --precise "1.0.156" --verbose
-      - name: Pin log for MSRV
-        if: matrix.msrv
-        run: cargo update -p log --precise "0.4.18" --verbose
+          # The quote crate switched to Rust edition 2021 starting with v1.0.31, i.e., has MSRV of 1.56
+          cargo update -p quote --precise "1.0.30" --verbose
+          # The proc-macro2 crate switched to Rust edition 2021 starting with v1.0.66, i.e., has MSRV of 1.56
+          cargo update -p proc-macro2 --precise "1.0.65" --verbose
+          # Sadly the log crate is always a dependency of tokio until 1.20, and has no reasonable MSRV guarantees
+          cargo update -p log --precise "0.4.18" --verbose
       - name: Cargo check
         run: cargo check --release
       - name: Check documentation