Separate traversal and accumulation.

tarao · Nov 28, 2023 · 8008f4e · 8008f4e
1 parent 948017f
commit 8008f4e
Showing 1 changed file with 68 additions and 43 deletions.
diff --git a/modules/core/src/main/scala/com/github/tarao/record4s/InternalMacros.scala b/modules/core/src/main/scala/com/github/tarao/record4s/InternalMacros.scala
@@ -151,52 +151,47 @@ private[record4s] class InternalMacros(using
       )
     }
 
-  def schemaOfRecord[R: Type]: Schema = {
-    // Check if tpr represents Tag[T]: we need to check IsTag[Tag[T]] given instance
-    // because representation of opaque type varies among different package names such as
-    // Tag$package.Tag[T] or $proxyN.Tag[T].
-    def isTag(tpr: TypeRepr): Boolean =
-      tpr match {
-        case AppliedType(t, _) =>
-          tpr.asType match {
-            case '[tpe] => Expr.summon[Tag.IsTag[tpe]].nonEmpty
-          }
-        case _ =>
-          false
-      }
+  // Check if tpr represents Tag[T]: we need to check IsTag[Tag[T]] given instance
+  // because representation of opaque type varies among different package names such as
+  // Tag$package.Tag[T] or $proxyN.Tag[T].
+  private def isTag(tpr: TypeRepr): Boolean =
+    tpr match {
+      case AppliedType(_, _) =>
+        tpr.asType match {
+          case '[tpe] => Expr.summon[Tag.IsTag[tpe]].nonEmpty
+        }
+      case _ =>
+        false
+    }
 
+  def traverse[R: Type, Acc](acc: Acc, f: (Acc, Type[?]) => Acc): Acc = {
     def safeDealias(tpr: TypeRepr): TypeRepr =
       if (isTag(tpr)) tpr
       else tpr.dealias
 
     val nothing = TypeRepr.of[Nothing]
 
-    @tailrec def collectTupledFieldTypes(
+    @tailrec def traverseTuple(
       tpe: Type[?],
-      acc: Seq[(String, Type[?])],
-    ): Seq[(String, Type[?])] = tpe match {
+      acc: Acc,
+    ): Acc = tpe match {
       case '[(labelType, valueType) *: rest]
         // Type variable or Nothing always matches with `Nothing *: Nothing`
         if TypeRepr.of[labelType] != nothing
           && TypeRepr.of[valueType] != nothing
           && TypeRepr.of[rest] != nothing =>
-        TypeRepr.of[labelType] match {
-          case ConstantType(StringConstant(label)) =>
-            collectTupledFieldTypes(
-              Type.of[rest],
-              acc :+ (validatedLabel(label), Type.of[valueType]),
-            )
-          case _ =>
-            collectTupledFieldTypes(Type.of[rest], acc)
-        }
+        traverseTuple(
+          Type.of[rest],
+          f(acc, Type.of[(labelType, valueType)]),
+        )
       case _ =>
-        acc
+        f(acc, tpe)
     }
 
-    @tailrec def collectFieldTypesAndTags(
+    @tailrec def traverse1(
       reversed: List[TypeRepr],
-      acc: Schema,
-    ): Schema = reversed match {
+      acc: Acc,
+    ): Acc = reversed match {
       // base { label: valueType }
       // For example
       //   TypeRepr.of[%{val name: String; val age: Int}]
@@ -210,45 +205,75 @@ private[record4s] class InternalMacros(using
       //     "age",
       //     TypeRepr.of[Int]
       //   )
-      case Refinement(base, label, valueType) :: rest =>
-        collectFieldTypesAndTags(
+      case (tpr @ Refinement(base, _, _)) :: rest =>
+        traverse1(
           safeDealias(base) :: rest,
-          acc.copy(fieldTypes =
-            (validatedLabel(label), valueType.asType) +: acc.fieldTypes,
-          ),
+          f(acc, tpr.asType),
         )
 
       // tpr1 & tpr2
       case AndType(tpr1, tpr2) :: rest =>
-        collectFieldTypesAndTags(
+        traverse1(
           safeDealias(tpr2) :: safeDealias(tpr1) :: rest,
           acc,
         )
 
       // Tag[T]
-      case (head @ AppliedType(_, List(tpr))) :: rest if isTag(head) =>
-        collectFieldTypesAndTags(
+      case head :: rest if isTag(head) =>
+        traverse1(
           rest,
-          acc.copy(tags = tpr.asType +: acc.tags),
+          f(acc, head.asType),
         )
 
       // typically `%` in `% { ... }` or
       // (tp1, ...)
       // tp1 *: ...
       case head :: rest =>
-        collectFieldTypesAndTags(
+        traverse1(
           rest,
-          acc.copy(fieldTypes =
-            collectTupledFieldTypes(head.asType, Seq.empty) ++ acc.fieldTypes,
-          ),
+          traverseTuple(head.asType, acc),
         )
 
       // all done
       case Nil =>
         acc
     }
 
-    collectFieldTypesAndTags(List(safeDealias(TypeRepr.of[R])), Schema.empty)
+    traverse1(List(safeDealias(TypeRepr.of[R])), acc)
+  }
+
+  def schemaOfRecord[R: Type]: Schema = {
+    traverse[R, Schema](
+      Schema.empty,
+      (acc: Schema, tpe: Type[?]) => {
+        tpe match {
+          case '[(labelType, valueType)] =>
+            TypeRepr.of[labelType] match {
+              case ConstantType(StringConstant(label)) =>
+                acc.copy(fieldTypes =
+                  acc.fieldTypes :+ (validatedLabel(label), Type.of[valueType]),
+                )
+              case _ =>
+                acc
+            }
+
+          case '[tpe] =>
+            TypeRepr.of[tpe] match {
+              case Refinement(_, label, valueType) =>
+                acc.copy(fieldTypes =
+                  (validatedLabel(label), valueType.asType) +: acc.fieldTypes,
+                )
+
+              // Tag[T]
+              case tpr @ AppliedType(_, List(tag)) if isTag(tpr) =>
+                acc.copy(tags = tag.asType +: acc.tags)
+
+              case _ =>
+                acc
+            }
+        }
+      },
+    )
   }
 
   def schemaOf[R: Type](