Non-functional miscellaneous improvements (#1445)

This commit contains non-functional (i.e. mostly stylistic, small
refactors, documentation and consistency) improvements that I've batched
and rolled up while working on #1342.

* Make `extraDependencies` from `InlineDependency` class private
* Miscellaneous improvements to `RustTypes.kt`
* Remove dead code from `RuntimeTypes.kt`
* Style change in `RuntimeTypes.kt`
* Miscellaneous improvements to `SymbolVisitor.kt`
* Miscellaneous improvements to `BuilderGenerator.kt`
    - Make it consistent with the `ServerBuilderGenerator` from #1342.
* Miscellaneous improvements to `TestHelpers.kt`
* Add docs to `headers_for_prefix` function
    - I keep rereading the implementation to see what this returns; it's
      not intuitive from the function name.

codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/rustlang/CargoDependency.kt

@@ -55,7 +55,7 @@ sealed class RustDependency(open val name: String) : SymbolDependencyContainer {
 class InlineDependency(
     name: String,
     val module: RustModule,
-    val extraDependencies: List<RustDependency> = listOf(),
+    private val extraDependencies: List<RustDependency> = listOf(),
     val renderer: (RustWriter) -> Unit
 ) : RustDependency(name) {
     override fun version(): String {

codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/rustlang/RustTypes.kt

@@ -91,11 +91,11 @@ sealed class RustType {
     }
 
     data class Reference(val lifetime: kotlin.String?, override val member: RustType) : RustType(), Container {
-        override val name: kotlin.String = member.name
+        override val name = member.name
     }
 
     data class Option(override val member: RustType) : RustType(), Container {
-        override val name: kotlin.String = "Option"
+        override val name = "Option"
         override val namespace = "std::option"
 
         /** Convert `Option<T>` to `Option<&T>` **/
@@ -105,7 +105,7 @@ sealed class RustType {
     }
 
     data class Box(override val member: RustType) : RustType(), Container {
-        override val name: kotlin.String = "Box"
+        override val name = "Box"
         override val namespace = "std::boxed"
     }
 
@@ -115,7 +115,7 @@ sealed class RustType {
     }
 
     data class Vec(override val member: RustType) : RustType(), Container {
-        override val name: kotlin.String = "Vec"
+        override val name = "Vec"
         override val namespace = "std::vec"
     }
 
@@ -148,25 +148,21 @@ fun RustType.asArgumentType(fullyQualified: Boolean = true): String {
 }
 
 /** Format this Rust type so that it may be used as an argument type in a function definition */
-fun RustType.asArgumentValue(name: String): String {
-    return when (this) {
-        is RustType.String,
-        is RustType.Box -> "$name.into()"
+fun RustType.asArgumentValue(name: String) =
+    when (this) {
+        is RustType.String, is RustType.Box -> "$name.into()"
         else -> name
     }
-}
 
 /**
  * For a given name, generate an `Argument` data class containing pre-formatted strings for using this type when
- * writing a Rust function
+ * writing a Rust function.
  */
-fun RustType.asArgument(name: String): Argument {
-    return Argument(
-        "$name: ${this.asArgumentType()}",
-        this.asArgumentValue(name),
-        this.render(),
-    )
-}
+fun RustType.asArgument(name: String) = Argument(
+    "$name: ${this.asArgumentType()}",
+    this.asArgumentValue(name),
+    this.render(),
+)
 
 /**
  * Render this type, including references and generic parameters.
@@ -298,7 +294,7 @@ data class RustMetadata(
         return this
     }
 
-    fun renderVisibility(writer: RustWriter): RustMetadata {
+    private fun renderVisibility(writer: RustWriter): RustMetadata {
         writer.writeInline(
             when (visibility) {
                 Visibility.PRIVATE -> ""

codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/RuntimeTypes.kt

@@ -172,7 +172,6 @@ data class RuntimeType(val name: String?, val dependency: RustDependency?, val n
         val Display = stdfmt.member("Display")
         val From = RuntimeType("From", dependency = null, namespace = "std::convert")
         val TryFrom = RuntimeType("TryFrom", dependency = null, namespace = "std::convert")
-        val Infallible = RuntimeType("Infallible", dependency = null, namespace = "std::convert")
         val PartialEq = std.member("cmp::PartialEq")
         val StdError = RuntimeType("Error", dependency = null, namespace = "std::error")
         val String = RuntimeType("String", dependency = null, namespace = "std::string")
@@ -235,17 +234,14 @@ data class RuntimeType(val name: String?, val dependency: RustDependency?, val n
         val HttpRequestBuilder = Http("request::Builder")
         val HttpResponseBuilder = Http("response::Builder")
 
-        val Hyper = CargoDependency.Hyper.asType()
-
         fun eventStreamReceiver(runtimeConfig: RuntimeConfig): RuntimeType =
             RuntimeType(
                 "Receiver",
                 dependency = CargoDependency.SmithyHttp(runtimeConfig),
                 "aws_smithy_http::event_stream"
             )
 
-        fun jsonErrors(runtimeConfig: RuntimeConfig) =
-            forInlineDependency(InlineDependency.jsonErrors(runtimeConfig))
+        fun jsonErrors(runtimeConfig: RuntimeConfig) = forInlineDependency(InlineDependency.jsonErrors(runtimeConfig))
 
         val IdempotencyToken by lazy { forInlineDependency(InlineDependency.idempotencyToken()) }
 

codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/SymbolVisitor.kt

@@ -113,7 +113,9 @@ fun Symbol.mapRustType(f: (RustType) -> RustType): Symbol {
 /** Set the symbolLocation for this symbol builder */
 fun Symbol.Builder.locatedIn(symbolLocation: SymbolLocation): Symbol.Builder {
     val currentRustType = this.build().rustType()
-    check(currentRustType is RustType.Opaque) { "Only Opaque can have their namespace updated" }
+    check(currentRustType is RustType.Opaque) {
+        "Only `Opaque` can have their namespace updated"
+    }
     val newRustType = currentRustType.copy(namespace = "crate::${symbolLocation.namespace}")
     return this.definitionFile("src/${symbolLocation.filename}")
         .namespace("crate::${symbolLocation.namespace}", "::")
@@ -148,6 +150,18 @@ fun SymbolProvider.wrapOptional(member: MemberShape, value: String): String = va
  */
 fun SymbolProvider.toOptional(member: MemberShape, value: String): String = value.letIf(!toSymbol(member).isOptional()) { "Some($value)" }
 
+/**
+ * Services can rename their contained shapes. See https://awslabs.github.io/smithy/1.0/spec/core/model.html#service
+ * specifically, `rename`
+ */
+fun Shape.contextName(serviceShape: ServiceShape?): String {
+    return if (serviceShape != null) {
+        id.getName(serviceShape)
+    } else {
+        id.name
+    }
+}
+
 /**
  * Base converter from `Shape` to `Symbol`. Shapes are the direct contents of the `Smithy` model. `Symbols` carry information
  * about Rust types, namespaces, dependencies, metadata as well as other information required to render a symbol.
@@ -168,18 +182,6 @@ class SymbolVisitor(
         return shape.accept(this)
     }
 
-    /**
-     * Services can rename their contained shapes. See https://awslabs.github.io/smithy/1.0/spec/core/model.html#service
-     * specifically, `rename`
-     */
-    private fun Shape.contextName(): String {
-        return if (serviceShape != null) {
-            id.getName(serviceShape)
-        } else {
-            id.name
-        }
-    }
-
     /**
      * Return the name of a given `enum` variant. Note that this refers to `enum` in the Smithy context
      * where enum is a trait that can be applied to [StringShape] and not in the Rust context of an algebraic data type.
@@ -238,7 +240,8 @@ class SymbolVisitor(
     override fun doubleShape(shape: DoubleShape): Symbol = simpleShape(shape)
     override fun stringShape(shape: StringShape): Symbol {
         return if (shape.hasTrait<EnumTrait>()) {
-            symbolBuilder(shape, RustType.Opaque(shape.contextName().toPascalCase())).locatedIn(Models).build()
+            val rustType = RustType.Opaque(shape.contextName(serviceShape).toPascalCase())
+            symbolBuilder(shape, rustType).locatedIn(Models).build()
         } else {
             simpleShape(shape)
         }
@@ -285,7 +288,7 @@ class SymbolVisitor(
         return symbolBuilder(
             shape,
             RustType.Opaque(
-                shape.contextName()
+                shape.contextName(serviceShape)
                     .replaceFirstChar { it.uppercase() }
             )
         )
@@ -305,7 +308,7 @@ class SymbolVisitor(
         val isError = shape.hasTrait<ErrorTrait>()
         val isInput = shape.hasTrait<SyntheticInputTrait>()
         val isOutput = shape.hasTrait<SyntheticOutputTrait>()
-        val name = shape.contextName().toPascalCase().letIf(isError && config.renameExceptions) {
+        val name = shape.contextName(serviceShape).toPascalCase().letIf(isError && config.renameExceptions) {
             it.replace("Exception", "Error")
         }
         val builder = symbolBuilder(shape, RustType.Opaque(name))
@@ -318,7 +321,7 @@ class SymbolVisitor(
     }
 
     override fun unionShape(shape: UnionShape): Symbol {
-        val name = shape.contextName().toPascalCase()
+        val name = shape.contextName(serviceShape).toPascalCase()
         val builder = symbolBuilder(shape, RustType.Opaque(name)).locatedIn(Models)
 
         return builder.build()
@@ -355,9 +358,7 @@ private const val SHAPE_KEY = "shape"
 private const val SYMBOL_DEFAULT = "symboldefault"
 private const val RENAMED_FROM_KEY = "renamedfrom"
 
-fun Symbol.Builder.rustType(rustType: RustType): Symbol.Builder {
-    return this.putProperty(RUST_TYPE_KEY, rustType)
-}
+fun Symbol.Builder.rustType(rustType: RustType): Symbol.Builder = this.putProperty(RUST_TYPE_KEY, rustType)
 
 fun Symbol.Builder.renamedFrom(name: String): Symbol.Builder {
     return this.putProperty(RENAMED_FROM_KEY, name)
@@ -366,9 +367,7 @@ fun Symbol.Builder.renamedFrom(name: String): Symbol.Builder {
 fun Symbol.renamedFrom(): String? = this.getProperty(RENAMED_FROM_KEY, String::class.java).orNull()
 
 fun Symbol.defaultValue(): Default = this.getProperty(SYMBOL_DEFAULT, Default::class.java).orElse(Default.NoDefault)
-fun Symbol.Builder.setDefault(default: Default): Symbol.Builder {
-    return this.putProperty(SYMBOL_DEFAULT, default)
-}
+fun Symbol.Builder.setDefault(default: Default): Symbol.Builder = this.putProperty(SYMBOL_DEFAULT, default)
 
 /**
  * Type representing the default value for a given type. (eg. for Strings, this is `""`)
@@ -406,7 +405,7 @@ fun Symbol.extractSymbolFromOption(): Symbol = this.mapRustType { it.stripOuter<
 fun Symbol.isRustBoxed(): Boolean = rustType().stripOuter<RustType.Option>() is RustType.Box
 
 // Symbols should _always_ be created with a Rust type & shape attached
-fun Symbol.rustType(): RustType = this.getProperty(RUST_TYPE_KEY, RustType::class.java).get()
+fun Symbol.rustType(): RustType = this.expectProperty(RUST_TYPE_KEY, RustType::class.java)
 fun Symbol.shape(): Shape = this.expectProperty(SHAPE_KEY, Shape::class.java)
 
 /**