chore: bump MSRV to 1.56 (#2546)

As part of upgrading syn to 2.0 (e.g.,
#2516), we need to bump the MSRV
to 1.56. As part of this PR, I've:
- Updated the text descriptions of what would be an in-policy MSRV bump
  to use more recent versions of rustc. The _niceness_ of said version
  numbers are purely coincidental.
- I've removed some of the exceptions made in CI.yml in order to support
  some crates with a higher MSRV.

.github/workflows/CI.yml

@@ -121,7 +121,7 @@ jobs:
       shell: bash
 
   check-msrv:
-    # Run `cargo check` on our minimum supported Rust version (1.49.0). This
+    # Run `cargo check` on our minimum supported Rust version (1.56.0). This
     # checks with minimal versions; maximal versions are checked above.
     name: "cargo check (+MSRV -Zminimal-versions)"
     needs: check
@@ -143,20 +143,8 @@ jobs:
         - tracing-tower
         - tracing
         toolchain:
-        - 1.49.0
+        - 1.56.0
         - stable
-        # TODO(eliza): remove this when appender is on the same MSRV.
-        #              same for tracing subscriber
-        exclude:
-        - subcrate: tracing-appender
-          toolchain: 1.49.0
-        - subcrate: tracing-subscriber
-          toolchain: 1.49.0
-        include:
-        - subcrate: tracing-appender
-          toolchain: 1.53.0
-        - subcrate: tracing-subscriber
-          toolchain: 1.50.0
     steps:
     - uses: actions/checkout@v3
     - name: install Rust nightly

README.md

@@ -254,14 +254,14 @@ attachment that `Future::instrument` does.
 ## Supported Rust Versions
 
 Tracing is built against the latest stable release. The minimum supported
-version is 1.49. The current Tracing version is not guaranteed to build on Rust
+version is 1.56. The current Tracing version is not guaranteed to build on Rust
 versions earlier than the minimum supported version.
 
 Tracing follows the same compiler support policies as the rest of the Tokio
 project. The current stable Rust compiler and the three most recent minor
 versions before it will always be supported. For example, if the current stable
-compiler version is 1.45, the minimum supported version will not be increased
-past 1.42, three minor versions prior. Increasing the minimum supported compiler
+compiler version is 1.69, the minimum supported version will not be increased
+past 1.66, three minor versions prior. Increasing the minimum supported compiler
 version is not considered a semver breaking change as long as doing so complies
 with this policy.
 

examples/Cargo.toml

@@ -3,7 +3,7 @@ name = "tracing-examples"
 version = "0.0.0"
 publish = false
 edition = "2018"
-rust-version = "1.49.0"
+rust-version = "1.56.0"
 
 [features]
 default = []

tracing-appender/README.md

@@ -152,8 +152,8 @@ Rust versions earlier than the minimum supported version.
 Tracing follows the same compiler support policies as the rest of the Tokio
 project. The current stable Rust compiler and the three most recent minor
 versions before it will always be supported. For example, if the current
-stable compiler version is 1.45, the minimum supported version will not be
-increased past 1.42, three minor versions prior. Increasing the minimum
+stable compiler version is 1.69, the minimum supported version will not be
+increased past 1.66, three minor versions prior. Increasing the minimum
 supported compiler version is not considered a semver breaking change as
 long as doing so complies with this policy.
 

tracing-appender/src/lib.rs

@@ -116,8 +116,8 @@
 //! Tracing follows the same compiler support policies as the rest of the Tokio
 //! project. The current stable Rust compiler and the three most recent minor
 //! versions before it will always be supported. For example, if the current
-//! stable compiler version is 1.45, the minimum supported version will not be
-//! increased past 1.42, three minor versions prior. Increasing the minimum
+//! stable compiler version is 1.69, the minimum supported version will not be
+//! increased past 1.66, three minor versions prior. Increasing the minimum
 //! supported compiler version is not considered a semver breaking change as
 //! long as doing so complies with this policy.
 //!

tracing-attributes/Cargo.toml

@@ -28,7 +28,7 @@ keywords = ["logging", "tracing", "macro", "instrument", "log"]
 license = "MIT"
 readme = "README.md"
 edition = "2018"
-rust-version = "1.49.0"
+rust-version = "1.56.0"
 
 [lib]
 proc-macro = true

tracing-attributes/README.md

@@ -37,7 +37,7 @@ structured, event-based diagnostic information. This crate provides the
 
 Note that this macro is also re-exported by the main `tracing` crate.
 
-*Compiler support: [requires `rustc` 1.49+][msrv]*
+*Compiler support: [requires `rustc` 1.56+][msrv]*
 
 [msrv]: #supported-rust-versions
 
@@ -69,14 +69,14 @@ pub fn my_function(my_arg: usize) {
 ## Supported Rust Versions
 
 Tracing is built against the latest stable release. The minimum supported
-version is 1.49. The current Tracing version is not guaranteed to build on Rust
+version is 1.56. The current Tracing version is not guaranteed to build on Rust
 versions earlier than the minimum supported version.
 
 Tracing follows the same compiler support policies as the rest of the Tokio
 project. The current stable Rust compiler and the three most recent minor
 versions before it will always be supported. For example, if the current stable
-compiler version is 1.45, the minimum supported version will not be increased
-past 1.42, three minor versions prior. Increasing the minimum supported compiler
+compiler version is 1.69, the minimum supported version will not be increased
+past 1.66, three minor versions prior. Increasing the minimum supported compiler
 version is not considered a semver breaking change as long as doing so complies
 with this policy.
 

tracing-attributes/src/lib.rs

@@ -6,7 +6,7 @@
 //!
 //! Note that this macro is also re-exported by the main `tracing` crate.
 //!
-//! *Compiler support: [requires `rustc` 1.49+][msrv]*
+//! *Compiler support: [requires `rustc` 1.56+][msrv]*
 //!
 //! [msrv]: #supported-rust-versions
 //!
@@ -41,14 +41,14 @@
 //! ## Supported Rust Versions
 //!
 //! Tracing is built against the latest stable release. The minimum supported
-//! version is 1.49. The current Tracing version is not guaranteed to build on
+//! version is 1.56. The current Tracing version is not guaranteed to build on
 //! Rust versions earlier than the minimum supported version.
 //!
 //! Tracing follows the same compiler support policies as the rest of the Tokio
 //! project. The current stable Rust compiler and the three most recent minor
 //! versions before it will always be supported. For example, if the current
-//! stable compiler version is 1.45, the minimum supported version will not be
-//! increased past 1.42, three minor versions prior. Increasing the minimum
+//! stable compiler version is 1.69, the minimum supported version will not be
+//! increased past 1.66, three minor versions prior. Increasing the minimum
 //! supported compiler version is not considered a semver breaking change as
 //! long as doing so complies with this policy.
 //!

tracing-core/Cargo.toml

@@ -24,7 +24,7 @@ categories = [
 ]
 keywords = ["logging", "tracing", "profiling"]
 edition = "2018"
-rust-version = "1.49.0"
+rust-version = "1.56.0"
 
 [features]
 default = ["std"]

tracing-core/README.md

@@ -53,7 +53,7 @@ The crate provides:
 In addition, it defines the global callsite registry and per-thread current
 dispatcher which other components of the tracing system rely on.
 
-*Compiler support: [requires `rustc` 1.49+][msrv]*
+*Compiler support: [requires `rustc` 1.56+][msrv]*
 
 [msrv]: #supported-rust-versions
 
@@ -99,14 +99,14 @@ The following crate feature flags are available:
 ## Supported Rust Versions
 
 Tracing is built against the latest stable release. The minimum supported
-version is 1.49. The current Tracing version is not guaranteed to build on Rust
+version is 1.56. The current Tracing version is not guaranteed to build on Rust
 versions earlier than the minimum supported version.
 
 Tracing follows the same compiler support policies as the rest of the Tokio
 project. The current stable Rust compiler and the three most recent minor
 versions before it will always be supported. For example, if the current stable
-compiler version is 1.45, the minimum supported version will not be increased
-past 1.42, three minor versions prior. Increasing the minimum supported compiler
+compiler version is 1.69, the minimum supported version will not be increased
+past 1.69, three minor versions prior. Increasing the minimum supported compiler
 version is not considered a semver breaking change as long as doing so complies
 with this policy.
 

tracing-core/src/lib.rs

@@ -23,7 +23,7 @@
 //! In addition, it defines the global callsite registry and per-thread current
 //! dispatcher which other components of the tracing system rely on.
 //!
-//! *Compiler support: [requires `rustc` 1.49+][msrv]*
+//! *Compiler support: [requires `rustc` 1.56+][msrv]*
 //!
 //! [msrv]: #supported-rust-versions
 //!
@@ -109,14 +109,14 @@
 //! ## Supported Rust Versions
 //!
 //! Tracing is built against the latest stable release. The minimum supported
-//! version is 1.49. The current Tracing version is not guaranteed to build on
+//! version is 1.56. The current Tracing version is not guaranteed to build on
 //! Rust versions earlier than the minimum supported version.
 //!
 //! Tracing follows the same compiler support policies as the rest of the Tokio
 //! project. The current stable Rust compiler and the three most recent minor
 //! versions before it will always be supported. For example, if the current
-//! stable compiler version is 1.45, the minimum supported version will not be
-//! increased past 1.42, three minor versions prior. Increasing the minimum
+//! stable compiler version is 1.69, the minimum supported version will not be
+//! increased past 1.66, three minor versions prior. Increasing the minimum
 //! supported compiler version is not considered a semver breaking change as
 //! long as doing so complies with this policy.
 //!

tracing-error/Cargo.toml

@@ -32,7 +32,7 @@ keywords = [
     "backtrace"
 ]
 edition = "2018"
-rust-version = "1.49.0"
+rust-version = "1.56.0"
 
 [features]
 default = ["traced-error"]

tracing-error/README.md

@@ -48,7 +48,7 @@ The crate provides the following:
 
 **Note**: This crate is currently experimental.
 
-*Compiler support: [requires `rustc` 1.49+][msrv]*
+*Compiler support: [requires `rustc` 1.56+][msrv]*
 
 [msrv]: #supported-rust-versions
 
@@ -186,14 +186,14 @@ fn main() {
 ## Supported Rust Versions
 
 Tracing is built against the latest stable release. The minimum supported
-version is 1.49. The current Tracing version is not guaranteed to build on Rust
+version is 1.56. The current Tracing version is not guaranteed to build on Rust
 versions earlier than the minimum supported version.
 
 Tracing follows the same compiler support policies as the rest of the Tokio
 project. The current stable Rust compiler and the three most recent minor
 versions before it will always be supported. For example, if the current stable
-compiler version is 1.45, the minimum supported version will not be increased
-past 1.42, three minor versions prior. Increasing the minimum supported compiler
+compiler version is 1.69, the minimum supported version will not be increased
+past 1.66, three minor versions prior. Increasing the minimum supported compiler
 version is not considered a semver breaking change as long as doing so complies
 with this policy.
 

tracing-error/src/lib.rs

@@ -18,7 +18,7 @@
 //!
 //! **Note**: This crate is currently experimental.
 //!
-//! *Compiler support: [requires `rustc` 1.49+][msrv]*
+//! *Compiler support: [requires `rustc` 1.56+][msrv]*
 //!
 //! [msrv]: #supported-rust-versions
 //!
@@ -166,14 +166,14 @@
 //! ## Supported Rust Versions
 //!
 //! Tracing is built against the latest stable release. The minimum supported
-//! version is 1.49. The current Tracing version is not guaranteed to build on
+//! version is 1.56. The current Tracing version is not guaranteed to build on
 //! Rust versions earlier than the minimum supported version.
 //!
 //! Tracing follows the same compiler support policies as the rest of the Tokio
 //! project. The current stable Rust compiler and the three most recent minor
 //! versions before it will always be supported. For example, if the current
-//! stable compiler version is 1.45, the minimum supported version will not be
-//! increased past 1.42, three minor versions prior. Increasing the minimum
+//! stable compiler version is 1.69, the minimum supported version will not be
+//! increased past 1.66, three minor versions prior. Increasing the minimum
 //! supported compiler version is not considered a semver breaking change as
 //! long as doing so complies with this policy.
 //!

tracing-flame/Cargo.toml

@@ -19,7 +19,7 @@ categories = [
     "asynchronous",
 ]
 keywords = ["tracing", "subscriber", "flamegraph", "profiling"]
-rust-version = "1.49.0"
+rust-version = "1.56.0"
 
 [features]
 default = ["smallvec"]

tracing-flame/README.md

@@ -26,7 +26,7 @@ flamegraph/flamechart. Flamegraphs/flamecharts are useful for identifying perfor
 bottlenecks in an application. For more details, see Brendan Gregg's [post]
 on flamegraphs.
 
-*Compiler support: [requires `rustc` 1.49+][msrv]*
+*Compiler support: [requires `rustc` 1.56+][msrv]*
 
 [msrv]: #supported-rust-versions
 [post]: http://www.brendangregg.com/flamegraphs.html
@@ -106,14 +106,14 @@ _flamechart_, which _does not_ sort or collapse identical stack frames.
 ## Supported Rust Versions
 
 Tracing is built against the latest stable release. The minimum supported
-version is 1.49. The current Tracing version is not guaranteed to build on Rust
+version is 1.56. The current Tracing version is not guaranteed to build on Rust
 versions earlier than the minimum supported version.
 
 Tracing follows the same compiler support policies as the rest of the Tokio
 project. The current stable Rust compiler and the three most recent minor
 versions before it will always be supported. For example, if the current stable
-compiler version is 1.45, the minimum supported version will not be increased
-past 1.42, three minor versions prior. Increasing the minimum supported compiler
+compiler version is 1.69, the minimum supported version will not be increased
+past 1.66, three minor versions prior. Increasing the minimum supported compiler
 version is not considered a semver breaking change as long as doing so complies
 with this policy.
 

tracing-flame/src/lib.rs

@@ -10,7 +10,7 @@
 //! issues bottlenecks in an application. For more details, see Brendan Gregg's [post]
 //! on flamegraphs.
 //!
-//! *Compiler support: [requires `rustc` 1.49+][msrv]*
+//! *Compiler support: [requires `rustc` 1.56+][msrv]*
 //!
 //! [msrv]: #supported-rust-versions
 //! [post]: http://www.brendangregg.com/flamegraphs.html
@@ -95,14 +95,14 @@
 //! ## Supported Rust Versions
 //!
 //! Tracing is built against the latest stable release. The minimum supported
-//! version is 1.49. The current Tracing version is not guaranteed to build on
+//! version is 1.56. The current Tracing version is not guaranteed to build on
 //! Rust versions earlier than the minimum supported version.
 //!
 //! Tracing follows the same compiler support policies as the rest of the Tokio
 //! project. The current stable Rust compiler and the three most recent minor
 //! versions before it will always be supported. For example, if the current
-//! stable compiler version is 1.45, the minimum supported version will not be
-//! increased past 1.42, three minor versions prior. Increasing the minimum
+//! stable compiler version is 1.69, the minimum supported version will not be
+//! increased past 1.66, three minor versions prior. Increasing the minimum
 //! supported compiler version is not considered a semver breaking change as
 //! long as doing so complies with this policy.
 //!

tracing-futures/Cargo.toml

@@ -16,7 +16,7 @@ categories = [
 ]
 keywords = ["logging", "profiling", "tracing", "futures", "async"]
 license = "MIT"
-rust-version = "1.49.0"
+rust-version = "1.56.0"
 
 [features]
 default = ["std-future", "std"]

tracing-futures/README.md

@@ -51,21 +51,21 @@ The crate provides the following traits:
 [`Subscriber`]: https://docs.rs/tracing/latest/tracing/subscriber/index.html
 [`tracing`]: https://crates.io/crates/tracing
 
-*Compiler support: [requires `rustc` 1.49+][msrv]*
+*Compiler support: [requires `rustc` 1.56+][msrv]*
 
 [msrv]: #supported-rust-versions
 
 ## Supported Rust Versions
 
 Tracing is built against the latest stable release. The minimum supported
-version is 1.49. The current Tracing version is not guaranteed to build on Rust
+version is 1.56. The current Tracing version is not guaranteed to build on Rust
 versions earlier than the minimum supported version.
 
 Tracing follows the same compiler support policies as the rest of the Tokio
 project. The current stable Rust compiler and the three most recent minor
 versions before it will always be supported. For example, if the current stable
-compiler version is 1.45, the minimum supported version will not be increased
-past 1.42, three minor versions prior. Increasing the minimum supported compiler
+compiler version is 1.69, the minimum supported version will not be increased
+past 1.66, three minor versions prior. Increasing the minimum supported compiler
 version is not considered a semver breaking change as long as doing so complies
 with this policy.
 

tracing-futures/src/lib.rs

@@ -15,7 +15,7 @@
 //! * [`WithCollector`] allows a `tracing` [collector] to be attached to a
 //!   future, sink, stream, or executor.
 //!
-//! *Compiler support: [requires `rustc` 1.49+][msrv]*
+//! *Compiler support: [requires `rustc` 1.56+][msrv]*
 //!
 //! [msrv]: #supported-rust-versions
 //!
@@ -60,14 +60,14 @@
 //! ## Supported Rust Versions
 //!
 //! Tracing is built against the latest stable release. The minimum supported
-//! version is 1.49. The current Tracing version is not guaranteed to build on
+//! version is 1.56. The current Tracing version is not guaranteed to build on
 //! Rust versions earlier than the minimum supported version.
 //!
 //! Tracing follows the same compiler support policies as the rest of the Tokio
 //! project. The current stable Rust compiler and the three most recent minor
 //! versions before it will always be supported. For example, if the current
-//! stable compiler version is 1.45, the minimum supported version will not be
-//! increased past 1.42, three minor versions prior. Increasing the minimum
+//! stable compiler version is 1.69, the minimum supported version will not be
+//! increased past 1.66, three minor versions prior. Increasing the minimum
 //! supported compiler version is not considered a semver breaking change as
 //! long as doing so complies with this policy.
 //!