Resolve generic property types in KotlinJsonAdapter.

kotlin/src/main/java/com/squareup/moshi/kotlin/KotlinJsonAdapter.kt

@@ -225,8 +225,9 @@ class KotlinJsonAdapterFactory : JsonAdapter.Factory {
       }
 
       val name = jsonAnnotation?.name ?: property.name
+      val resolvedPropertyType = Types.resolve(type, rawType, property.returnType.javaType)
       val adapter = moshi.adapter<Any>(
-          property.returnType.javaType, Util.jsonAnnotations(allAnnotations.toTypedArray()))
+          resolvedPropertyType, Util.jsonAnnotations(allAnnotations.toTypedArray()))
 
       bindingsByName[property.name] =
           KotlinJsonAdapter.Binding(name, adapter, property as KProperty1<Any, Any?>, parameter)

kotlin/src/test/java/com/squareup/moshi/kotlin/KotlinJsonAdapterTest.kt

@@ -21,6 +21,7 @@ import com.squareup.moshi.JsonDataException
 import com.squareup.moshi.JsonQualifier
 import com.squareup.moshi.Moshi
 import com.squareup.moshi.ToJson
+import com.squareup.moshi.Types
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.Assert.fail
 import org.junit.Test
@@ -763,7 +764,53 @@ class KotlinJsonAdapterTest {
       var v26: Int, var v27: Int, var v28: Int, var v29: Int, var v30: Int,
       var v31: Int, var v32: Int, var v33: Int)
 
-  // TODO(jwilson): resolve generic types?
+  data class Box<out T>(val data: T)
+
+  @Test fun genericTypes() {
+    val moshi = Moshi.Builder().add(KotlinJsonAdapterFactory()).build()
+    val stringBoxAdapter = moshi.adapter<Box<String>>(
+        Types.newParameterizedTypeWithOwner(KotlinJsonAdapterTest::class.java, Box::class.java,
+            String::class.java))
+    assertThat(stringBoxAdapter.fromJson("""{"data":"hello"}""")).isEqualTo(Box("hello"))
+    assertThat(stringBoxAdapter.toJson(Box("hello"))).isEqualTo("""{"data":"hello"}""")
+  }
+
+  data class NestedGenerics<R, C, out V>(val value: Map<R, Map<C, List<V>>>)
+
+  @Test fun nestedGenericTypes() {
+    val moshi = Moshi.Builder().add(KotlinJsonAdapterFactory()).build()
+    val type = Types.newParameterizedTypeWithOwner(
+        KotlinJsonAdapterTest::class.java,
+        NestedGenerics::class.java,
+        String::class.java,
+        Int::class.javaObjectType,
+        Types.newParameterizedTypeWithOwner(
+            KotlinJsonAdapterTest::class.java,
+            Box::class.java,
+            String::class.java
+        )
+    )
+    val adapter = moshi.adapter<NestedGenerics<String, Int, Box<String>>>(type).indent("  ")
+    val json = """
+      |{
+      |  "value": {
+      |    "hello": {
+      |      "1": [
+      |        {
+      |          "data": " "
+      |        },
+      |        {
+      |          "data": "world!"
+      |        }
+      |      ]
+      |    }
+      |  }
+      |}
+      """.trimMargin()
+    val value = NestedGenerics(mapOf("hello" to mapOf(1 to listOf(Box(" "), Box("world!")))))
+    assertThat(adapter.fromJson(json)).isEqualTo(value)
+    assertThat(adapter.toJson(value)).isEqualTo(json)
+  }
 
   @Retention(RUNTIME)
   @JsonQualifier

moshi/src/main/java/com/squareup/moshi/Types.java

@@ -373,7 +373,8 @@ public final class Types {
     return new Type[] { Object.class, Object.class };
   }
 
-  static Type resolve(Type context, Class<?> contextRawType, Type toResolve) {
+  @CheckReturnValue // TODO(eric): Move this to internal Utils.
+  public static Type resolve(Type context, Class<?> contextRawType, Type toResolve) {
     // This implementation is made a little more complicated in an attempt to avoid object-creation.
     while (true) {
       if (toResolve instanceof TypeVariable) {