Upgrade MSRV to 1.78.0 (#3800)

## Motivation and Context
Upgrades MSRV to 1.78.0 since the [latest
Rust](https://www.rust-lang.org/) at the time of writing is 1.80.1 (we
try keeping [two releases
behind](https://github.com/awslabs/aws-sdk-rust?tab=readme-ov-file#supported-rust-versions-msrv)).

## Description
In Rust 1.78.0, `clippy` enforces stricter checks in two areas:
- `dead_code`
It seems to be able to uncover more unused code patterns, especially
when different combinations of cargo features are enabled
- `empty_docs`
Prior to 1.78.0, the codegen used to render the following empty docs
`///`, regardless whether the codegen is for the server or for the
client. This is now flagged as `empty_docs` by `clippy`:
```
///
pub(crate) mod XXX {
    ...
}
```

Other than bumping MSRV to 1.78.0, the remaining code changes address
issues related to the fixes mentioned above.

**EDIT:**
`cargo-semver-checks` required an upgrade due to incompatibility issues
following the MSRV upgrade ([example
error](https://github.com/smithy-lang/smithy-rs/actions/runs/10534205294/job/29261105195#step:4:2068)).
Specifically, after updating the MSRV to 1.78.0, the rustdoc version was
upgraded to v28. However, the version of `cargo-semver-checks` we were
using (0.24.1) only supported rustdoc [up to
v27](https://github.com/obi1kenobi/cargo-semver-checks/blob/4bce03d4a6a32cf651b9eccddb40e3418dc2c154/Cargo.toml#L18).

To resolve this, we have updated `cargo-semver-checks` to the first
version that supports rustdoc
[v28](https://github.com/obi1kenobi/cargo-semver-checks/blob/94a491f0854f0bdbccbb301099db119201bff181/Cargo.toml#L18).

## Testing
Existing tests in CI

## Checklist
<!--- If a checkbox below is not applicable, then please DELETE it
rather than leaving it unchecked -->
- [x] For changes to the smithy-rs codegen or runtime crates, I have
created a changelog entry Markdown file in the `.changelog` directory,
specifying "client," "server," or both in the `applies_to` key.
- [x] For changes to the AWS SDK, generated SDK code, or SDK runtime
crates, I have created a changelog entry Markdown file in the
`.changelog` directory, specifying "aws-sdk-rust" in the `applies_to`
key.

----

_By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice._

.changelog/1724459075.md

@@ -0,0 +1,14 @@
+---
+applies_to:
+- client
+- server
+- aws-sdk-rust
+authors:
+- ysaito1001
+references:
+- smithy-rs#3800
+breaking: true
+new_feature: false
+bug_fix: false
+---
+Upgrade MSRV to Rust 1.78.0.

.github/workflows/ci.yml

@@ -38,7 +38,7 @@ on:
         required: false
 
 env:
-  rust_version: 1.76.0
+  rust_version: 1.78.0
   rust_toolchain_components: clippy,rustfmt
   ENCRYPTED_DOCKER_PASSWORD: ${{ secrets.ENCRYPTED_DOCKER_PASSWORD }}
   DOCKER_LOGIN_TOKEN_PASSPHRASE: ${{ secrets.DOCKER_LOGIN_TOKEN_PASSPHRASE }}

.github/workflows/claim-crate-names.yml

@@ -10,7 +10,7 @@ concurrency:
   cancel-in-progress: true
 
 env:
-  rust_version: 1.76.0
+  rust_version: 1.78.0
 
 name: Claim unpublished crate names on crates.io
 run-name: ${{ github.workflow }}

.github/workflows/github-pages.yml

@@ -8,7 +8,7 @@ on:
 name: Update GitHub Pages
 
 env:
-  rust_version: 1.76.0
+  rust_version: 1.78.0
 
 # Allow only one doc pages build to run at a time for the entire smithy-rs repo
 concurrency:

.github/workflows/release.yml

@@ -10,7 +10,7 @@ concurrency:
   cancel-in-progress: true
 
 env:
-  rust_version: 1.76.0
+  rust_version: 1.78.0
 
 name: Release smithy-rs
 on:

.github/workflows/update-sdk-next.yml

@@ -45,7 +45,7 @@ jobs:
     - name: Set up Rust
       uses: dtolnay/rust-toolchain@master
       with:
-        toolchain: 1.76.0
+        toolchain: 1.78.0
     - name: Delete old SDK
       run: |
     - name: Generate a fresh SDK

aws/rust-runtime/aws-credential-types/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "aws-credential-types"
-version = "1.2.0"
+version = "1.2.1"
 authors = ["AWS Rust SDK Team <[email protected]>"]
 description = "Types for AWS SDK credentials."
 edition = "2021"

aws/rust-runtime/aws-credential-types/src/credential_fn.rs

@@ -73,12 +73,7 @@ where
 #[cfg(test)]
 mod test {
     use crate::credential_fn::provide_credentials_fn;
-    use crate::{
-        provider::{future, ProvideCredentials},
-        Credentials,
-    };
-    use async_trait::async_trait;
-    use std::fmt::{Debug, Formatter};
+    use crate::{provider::ProvideCredentials, Credentials};
 
     fn assert_send_sync<T: Send + Sync>() {}
 
@@ -87,30 +82,6 @@ mod test {
         assert_send_sync::<Credentials>()
     }
 
-    #[async_trait]
-    trait AnotherTrait: Send + Sync {
-        async fn creds(&self) -> Credentials;
-    }
-
-    struct AnotherTraitWrapper<T> {
-        inner: T,
-    }
-
-    impl<T> Debug for AnotherTraitWrapper<T> {
-        fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
-            write!(f, "wrapper")
-        }
-    }
-
-    impl<T: AnotherTrait> ProvideCredentials for AnotherTraitWrapper<T> {
-        fn provide_credentials<'a>(&'a self) -> future::ProvideCredentials<'a>
-        where
-            Self: 'a,
-        {
-            future::ProvideCredentials::new(async move { Ok(self.inner.creds().await) })
-        }
-    }
-
     // Test that the closure passed to `provide_credentials_fn` is allowed to borrow things
     #[tokio::test]
     async fn provide_credentials_fn_closure_can_borrow() {

aws/rust-runtime/aws-credential-types/src/token_fn.rs

@@ -73,8 +73,6 @@ where
 mod test {
     use super::*;
     use crate::Token;
-    use async_trait::async_trait;
-    use std::fmt::{Debug, Formatter};
 
     fn assert_send_sync<T: Send + Sync>() {}
 
@@ -83,30 +81,6 @@ mod test {
         assert_send_sync::<Token>()
     }
 
-    #[async_trait]
-    trait AnotherTrait: Send + Sync {
-        async fn token(&self) -> Token;
-    }
-
-    struct AnotherTraitWrapper<T> {
-        inner: T,
-    }
-
-    impl<T> Debug for AnotherTraitWrapper<T> {
-        fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
-            write!(f, "wrapper")
-        }
-    }
-
-    impl<T: AnotherTrait> ProvideToken for AnotherTraitWrapper<T> {
-        fn provide_token<'a>(&'a self) -> future::ProvideToken<'a>
-        where
-            Self: 'a,
-        {
-            future::ProvideToken::new(async move { Ok(self.inner.token().await) })
-        }
-    }
-
     // Test that the closure passed to `provide_token_fn` is allowed to borrow things
     #[tokio::test]
     async fn provide_token_fn_closure_can_borrow() {

aws/rust-runtime/aws-inlineable/src/lib.rs

@@ -57,6 +57,7 @@ pub mod endpoint_discovery;
 mod serialization_settings;
 
 /// Parse the Expires and ExpiresString fields correctly
+#[allow(dead_code)]
 pub mod s3_expires_interceptor;
 
 // just so docs work

aws/rust-runtime/aws-runtime/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "aws-runtime"
-version = "1.4.1"
+version = "1.4.2"
 authors = ["AWS Rust SDK Team <[email protected]>"]
 description = "Runtime support code for the AWS SDK. This crate isn't intended to be used directly."
 edition = "2021"

aws/rust-runtime/aws-runtime/src/env_config/property.rs

@@ -166,7 +166,7 @@ impl Properties {
             .entry(properties_key.clone())
             .and_modify(|v| {
                 tracing::trace!("overwriting {properties_key}: was {v}, now {value}");
-                *v = value.clone();
+                v.clone_from(&value);
             })
             .or_insert(value);
     }

codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/CodegenDelegator.kt

@@ -46,7 +46,11 @@ interface ModuleDocProvider {
             }
             try {
                 when {
-                    module.documentationOverride != null -> writer.docs(module.documentationOverride)
+                    module.documentationOverride != null -> {
+                        if (module.documentationOverride.isNotEmpty()) {
+                            writer.docs(module.documentationOverride)
+                        }
+                    }
                     else -> provider?.docsWriter(module)?.also { writeTo -> writeTo(writer) }
                 }
             } catch (e: NotImplementedError) {

codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/testutil/Rust.kt

@@ -125,7 +125,7 @@ object TestWorkspace {
                 // help rust select the right version when we run cargo test
                 // TODO(https://github.com/smithy-lang/smithy-rs/issues/2048): load this from the msrv property using a
                 //  method as we do for runtime crate versions
-                "[toolchain]\nchannel = \"1.76.0\"\n",
+                "[toolchain]\nchannel = \"1.78.0\"\n",
             )
             // ensure there at least an empty lib.rs file to avoid broken crates
             newProject.resolve("src").mkdirs()

gradle.properties

@@ -4,7 +4,7 @@
 #
 
 # Rust MSRV (entered into the generated README)
-rust.msrv=1.76.0
+rust.msrv=1.78.0
 
 # To enable debug, swap out the two lines below.
 # When changing this value, be sure to run `./gradlew --stop` to kill the Gradle daemon.