Emit argument array for contiguous numbered arguments

For strings which match, this reduces the generated bytecode impact.
Each argument 'put' operation in the map required:

    36: aload         6
    38: ldc           #99                 // String 0
    40: aload_1
    41: invokevirtual #30                 // Method android/util/ArrayMap.put:(Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;
    44: pop

plus the associated string pool constant's size.

In the array, storage requires fewer bytecodes and bytecodes with fewer arguments reducing their size:

    32: aload         7
    34: iconst_0
    35: aload_1
    36: aastore

Creating the map used to cost 10 bytes and require invoking the ArrayMap constructor:

    26: new           #23                 // class android/util/ArrayMap
    29: dup
    30: iconst_5
    31: invokespecial #26                 // Method android/util/ArrayMap."<init>":(I)V
    34: astore        6

But the array requires only 5 bytes and zero method calls:

    27: anewarray     #4                  // class java/lang/Object
    30: astore        7

Finally, previously, the `Map` property of the `FormattedResource` class required an explicit cast inside the generated code:

     89: new           #32                // class app/cash/gingham/FormattedResource
     92: dup
     93: ldc           #108               // int 2131689631
     95: aload         6
     97: checkcast     #35                // class java/util/Map
    100: invokespecial #38                // Method app/cash/gingham/FormattedResource."<init>":(ILjava/util/Map;)V
    103: areturn

But with the property changing to `Any` (i.e., `Object`) the cast is no longer required for either the array-based or map-based generated code:

    69: new           #32                 // class app/cash/gingham/FormattedResource
    72: dup
    73: ldc           #96                 // int 2131689631
    75: aload         6
    77: invokespecial #36                 // Method app/cash/gingham/FormattedResource."<init>":(ILjava/lang/Object;)V
    80: areturn

plugin/src/main/java/app/cash/gingham/plugin/ResourceWriter.kt

@@ -53,10 +53,22 @@ private fun TokenizedResource.toFunSpec(packageStringsType: TypeName): FunSpec {
     .apply { if (description != null) addKdoc(description) }
     .apply { tokens.forEach { addParameter(it.toParameterSpec()) } }
     .returns(Types.FormattedResource)
-    .addStatement("val arguments = %T(%L)", Types.ArrayMap.parameterizedBy(STRING, ANY), tokens.size)
     .apply {
-      for (token in tokens) {
-        addStatement("arguments.put(%S, %L)", token.argumentName, token.toParameterCodeBlock())
+      if (hasContiguousNumberedTokens) {
+        addCode(
+          buildCodeBlock {
+            add("val arguments = arrayOf(⇥\n")
+            for (token in tokens) {
+              addStatement("%L,", token.toParameterCodeBlock())
+            }
+            add("⇤)\n")
+          }
+        )
+      } else {
+        addStatement("val arguments = %T(%L)", Types.ArrayMap.parameterizedBy(STRING, ANY), tokens.size)
+        for (token in tokens) {
+          addStatement("arguments.put(%S, %L)", token.argumentName, token.toParameterCodeBlock())
+        }
       }
     }
     .addCode(

plugin/src/main/java/app/cash/gingham/plugin/model/TokenizedResource.kt

@@ -11,6 +11,10 @@ internal data class TokenizedResource(
   val description: String?,
   val tokens: List<Token>,
 ) {
+  /* True when the tokens represent a contiguous set of integers counting from 0. */
+  val hasContiguousNumberedTokens: Boolean =
+    tokens.indices.toList() == tokens.map { (it as? Token.NumberedToken)?.number }
+
   sealed interface Token {
     val type: KClass<*>
 

plugin/src/test/java/app/cash/gingham/plugin/ResourceWriterTest.kt

@@ -83,7 +83,6 @@ class ResourceWriterTest {
       // Do not edit this file directly. Instead, edit the string resources in the source file.
       package com.gingham.test
 
-      import android.util.ArrayMap
       import app.cash.gingham.FormattedResource
       import com.gingham.test.R
       import java.time.Instant
@@ -104,12 +103,13 @@ class ResourceWriterTest {
           arg3: Number,
           arg4: String,
         ): FormattedResource {
-          val arguments = ArrayMap<String, Any>(5)
-          arguments.put("0", arg0)
-          arguments.put("1", Date.from(arg1))
-          arguments.put("2", arg2)
-          arguments.put("3", arg3)
-          arguments.put("4", arg4)
+          val arguments = arrayOf(
+            arg0,
+            Date.from(arg1),
+            arg2,
+            arg3,
+            arg4,
+          )
           return FormattedResource(
             id = R.string.test_numbered,
             arguments = arguments

runtime/src/main/java/app/cash/gingham/FormattedResource.kt

@@ -1,6 +1,7 @@
 // Copyright Square, Inc.
 package app.cash.gingham
 
+import android.icu.text.MessageFormat
 import androidx.annotation.StringRes
 
 /**
@@ -23,5 +24,10 @@ import androidx.annotation.StringRes
  * - The R.string.detective_has_suspects resource ID
  * - An integer value for the suspects argument
  * - A string value for the detective argument
+ *
+ * @property arguments Arguments passed directly to [MessageFormat.format].
  */
-data class FormattedResource(@StringRes val id: Int, val arguments: Map<String, Any>)
+data class FormattedResource constructor(
+  @StringRes val id: Int,
+  val arguments: Any,
+)

runtime/src/main/java/app/cash/gingham/FormattedResources.kt

@@ -16,4 +16,4 @@ fun Context.getString(formattedResource: FormattedResource): String =
  * Resolves and returns the final formatted version of the given formatted string.
  */
 fun Resources.getString(formattedResource: FormattedResource): String =
-  MessageFormat.format(getString(formattedResource.id), formattedResource.arguments)
+  MessageFormat(getString(formattedResource.id)).format(formattedResource.arguments)