Roll back MSRV to 1.57.0

1.60.0 is needed for dev-dependencies only, so adjust CI to only build those on not-msrv.

.circleci/config.yml

@@ -14,12 +14,13 @@ workflows:
                 # be easier on the CI hosts since presumably those fat lower layers will already be cached, and
                 # therefore faster than a minimal, customized alpine.
                 # MSRV
-                'rust:1.60.0'
+                'rust:1.57.0'
               ]
               # a hacky scheme to work around CircleCI's inability to deal with mutable docker tags, forcing us to
               # get a nightly or stable toolchain via rustup instead of a mutable docker tag
               toolchain_override: [
                 '__msrv__', # won't add any other toolchains, just uses what's in the docker image
+                '1.60.0', # minimum needed to build dev-dependencies
                 'stable',
                 'nightly'
               ]
@@ -62,9 +63,16 @@ jobs:
               rustup component add clippy
               cargo clippy --all-targets
             fi
+      - run:
+          name: Build main target
+          command: cargo build
       - run:
           name: Build all targets
-          command: cargo build --all-targets
+          command: |
+            if [[ '<< parameters.toolchain_override >>' != '__msrv__' ]]
+            then
+              cargo build --all-targets
+            fi
       - run:
           name: Build without default features
           command: cargo build --no-default-features
@@ -81,8 +89,13 @@ jobs:
           name: Build ARM with only alloc feature
           command: cargo build --target thumbv6m-none-eabi --no-default-features --features alloc
       - run:
+          # dev dependencies can't build on 1.57.0
           name: Run tests
-          command: cargo test --verbose
+          command: |
+            if [[ '<< parameters.toolchain_override >>' != '__msrv__' ]]
+            then
+              cargo test --verbose
+            fi
       - run:
           name: Build docs
           command: cargo doc --verbose

Cargo.toml

@@ -10,7 +10,8 @@ keywords = ["base64", "utf8", "encode", "decode", "no_std"]
 categories = ["encoding"]
 license = "MIT OR Apache-2.0"
 edition = "2021"
-rust-version = "1.60.0"
+# dev-dependencies require 1.60, but the main code doesn't
+rust-version = "1.57.0"
 
 [[bench]]
 name = "benchmarks"

README.md

@@ -63,7 +63,7 @@ optionally may allow other behaviors.
 
 ## Rust version compatibility
 
-The minimum supported Rust version is 1.60.0.
+The minimum supported Rust version is 1.57.0.
 
 # Contributing
 

RELEASE-NOTES.md

@@ -1,3 +1,7 @@
+# 0.21.2
+
+- Rollback MSRV to 1.57.0 -- only dev dependencies need 1.60, not the main code
+
 # 0.21.1
 
 - Remove the possibility of panicking during decoded length calculations

clippy.toml

@@ -1 +1 @@
-msrv = "1.60.0"
+msrv = "1.57.0"