Followups from #896 (#907)

* Simplify parameterProperties and parameterProperties

* Match only on synthetic constructors

* Limit synthetic constructor keeps to kotlin classes

kotlin/codegen/src/main/java/com/squareup/moshi/kotlin/codegen/api/AdapterGenerator.kt

@@ -36,8 +36,8 @@ import com.squareup.moshi.JsonReader
 import com.squareup.moshi.JsonWriter
 import com.squareup.moshi.Moshi
 import com.squareup.moshi.internal.Util
-import java.lang.reflect.Constructor
 import com.squareup.moshi.kotlin.codegen.JsonClassCodegenProcessor
+import java.lang.reflect.Constructor
 import java.lang.reflect.Type
 
 private val MOSHI_UTIL = Util::class.asClassName()
@@ -226,13 +226,8 @@ internal class AdapterGenerator(
     result.addStatement("%N.endObject()", readerParam)
 
     var separator = "\n"
-    var useDefaultsConstructor = false
-    val parameterProperties = propertyList.asSequence()
-        .filter { it.hasConstructorParameter }
-        .onEach {
-          useDefaultsConstructor = useDefaultsConstructor || it.hasDefault
-        }
-        .toList()
+    val parameterProperties = propertyList.filter { it.hasConstructorParameter }
+    val useDefaultsConstructor = parameterProperties.any { it.hasDefault }
 
     val resultName = nameAllocator.newName("result")
     val hasNonConstructorProperties = nonTransientProperties.any { !it.hasConstructorParameter }

moshi/src/main/resources/META-INF/proguard/moshi.pro

@@ -22,8 +22,8 @@
 # We can't _just_ keep the defaults constructor because Proguard/R8's spec doesn't allow wildcard
 # matching preceding parameters.
 -keepnames class kotlin.jvm.internal.DefaultConstructorMarker
--keepclassmembers @com.squareup.moshi.JsonClass class * {
-    <init>(...);
+-keepclassmembers @com.squareup.moshi.JsonClass @kotlin.Metadata class * {
+    synthetic <init>(...);
 }
 
 # Retain generated JsonAdapters if annotated type is retained.