Fix debug bound on 0.55.x (#2630)

## Motivation and Context
- #2577 added a `Debug` bound on `ResolveEndpoint`, but this was a
semver-incompatible change

## Description
This removes that bound but re-adds a Debug implementation in areas that
we need them

## Testing
- CI

- [ ] Backport this commit to main

----

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

Author: rcoh

codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/client/smithy/generators/config/ServiceConfigGenerator.kt

@@ -228,12 +228,25 @@ class ServiceConfigGenerator(private val customizations: List<ConfigCustomizatio
         }
 
         writer.docs("Builder for creating a `Config`.")
-        writer.raw("#[derive(Clone, Debug, Default)]")
+        writer.raw("#[derive(Clone, Default)]")
         writer.rustBlock("pub struct Builder") {
             customizations.forEach {
                 it.section(ServiceConfig.BuilderStruct)(this)
             }
         }
+
+        // Custom implementation for Debug so we don't need to enforce Debug down the chain
+        writer.rustBlock("impl std::fmt::Debug for Builder") {
+            writer.rustTemplate(
+                """
+                fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+                    let mut config = f.debug_struct("Builder");
+                    config.finish()
+                }
+                """,
+            )
+        }
+
         writer.rustBlock("impl Builder") {
             writer.docs("Constructs a config builder.")
             writer.rustTemplate("pub fn new() -> Self { Self::default() }")

rust-runtime/aws-smithy-http/src/endpoint.rs

@@ -9,7 +9,7 @@ use crate::endpoint::error::InvalidEndpointError;
 use crate::operation::error::BuildError;
 use http::uri::{Authority, Uri};
 use std::borrow::Cow;
-use std::fmt::Debug;
+use std::fmt::{Debug, Formatter};
 use std::result::Result as StdResult;
 use std::str::FromStr;
 use std::sync::Arc;
@@ -23,7 +23,7 @@ pub use error::ResolveEndpointError;
 pub type Result = std::result::Result<aws_smithy_types::endpoint::Endpoint, ResolveEndpointError>;
 
 /// Implementors of this trait can resolve an endpoint that will be applied to a request.
-pub trait ResolveEndpoint<Params>: Debug + Send + Sync {
+pub trait ResolveEndpoint<Params>: Send + Sync {
     /// Given some endpoint parameters, resolve an endpoint or return an error when resolution is
     /// impossible.
     fn resolve_endpoint(&self, params: &Params) -> Result;
@@ -38,9 +38,15 @@ impl<T> ResolveEndpoint<T> for &'static str {
 }
 
 /// Endpoint Resolver wrapper that may be shared
-#[derive(Clone, Debug)]
+#[derive(Clone)]
 pub struct SharedEndpointResolver<T>(Arc<dyn ResolveEndpoint<T>>);
 
+impl<T> Debug for SharedEndpointResolver<T> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("SharedEndpointResolver").finish()
+    }
+}
+
 impl<T> SharedEndpointResolver<T> {
     /// Create a new `SharedEndpointResolver` from `ResolveEndpoint`
     pub fn new(resolve_endpoint: impl ResolveEndpoint<T> + 'static) -> Self {
@@ -60,7 +66,7 @@ impl<T> From<Arc<dyn ResolveEndpoint<T>>> for SharedEndpointResolver<T> {
     }
 }
 
-impl<T: Debug> ResolveEndpoint<T> for SharedEndpointResolver<T> {
+impl<T> ResolveEndpoint<T> for SharedEndpointResolver<T> {
     fn resolve_endpoint(&self, params: &T) -> Result {
         self.0.resolve_endpoint(params)
     }