update

Author: thomas-k-cameron

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

@@ -22,6 +22,7 @@ sealed class ModuleDocSection {
     data class ServiceDocs(val documentationTraitValue: String?) : ModuleDocSection()
     object CrateOrganization : ModuleDocSection()
     object Examples : ModuleDocSection()
+    object UnstableFeature : ModuleDocSection()
 }
 
 sealed class LibRsSection(name: String) : Section(name) {
@@ -62,6 +63,27 @@ class LibRsGenerator(
                 containerDocs(escape(defaultServiceDocs ?: settings.moduleName))
             }
 
+            // Unstable Feature
+            docSection(ModuleDocSection.UnstableFeature).also { docs ->
+                if (docs.isNotEmpty()) {
+                    containerDocs("\n## Unstable Features")
+                    val awsSdkUnstable = """
+                    Some highly experimental features requires passing `aws_sdk_unstable` to RUSTFLAGS.
+                    e.g.
+                    ```bash
+                    export RUSTFLAGS="--cfg aws_sdk_unstable"
+                    cargo build --features serde-serialize
+                    ```
+
+                    If you enable unstable features without enabling `RUSTFLAGS="--cfg aws_sdk_unstable"`, compilation will fail with a message detailing the reason.
+                    """.trimIndent()
+                    containerDocs(awsSdkUnstable)
+                    docs.forEach { writeTo ->
+                        writeTo(this)
+                    }
+                }
+            }
+
             // Crate Organization
             docSection(ModuleDocSection.CrateOrganization).also { docs ->
                 if (docs.isNotEmpty()) {