Use semigroup to combine results in SemigroupalK derivation (#521)

typelevel · Apr 2, 2024 · ea36c08 · ea36c08
1 parent 39d1054
commit ea36c08
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Showing 6 changed files with 19 additions and 8 deletions.
diff --git a/core/src/main/scala-3/cats/tagless/macros/DeriveMacros.scala b/core/src/main/scala-3/cats/tagless/macros/DeriveMacros.scala
@@ -43,7 +43,7 @@ private class DeriveMacros[Q <: Quotes](using val q: Q):
       val lambdaType = MethodType(x :: Nil)(_ => tpe :: Nil, _ => resultType)
       val lambda = Lambda(method, lambdaType, (_, xs) => xf(tpe, xs.head.asExpr.asTerm))
       val result = Select.overloaded(arg, "map", resultType :: Nil, lambda :: Nil)
-      val repeatedType = AppliedType(defn.RepeatedParamClass.typeRef, resultType :: Nil)
+      val repeatedType = defn.RepeatedParamClass.typeRef.appliedTo(resultType)
       Typed(result, TypeTree.of(using repeatedType.asType))
 
     def transformArg(method: Symbol, paramAndArg: (Definition, Tree)): Tree =

diff --git a/core/src/main/scala-3/cats/tagless/macros/macroSemigroupalK.scala b/core/src/main/scala-3/cats/tagless/macros/macroSemigroupalK.scala
@@ -16,6 +16,7 @@
 
 package cats.tagless.macros
 
+import cats.Semigroup
 import cats.tagless.*
 import cats.data.Tuple2K
 
@@ -78,5 +79,9 @@ object MacroSemigroupalK:
             .unique(tpe.firstK.summonLambda[SemigroupalK](f), "productK")
             .appliedToTypes(List(F, G))
             .appliedTo(argf, argg)
+        case (tpe, argf :: argg :: Nil) =>
+          Implicits.search(TypeRepr.of[Semigroup].appliedTo(tpe)) match
+            case success: ImplicitSearchSuccess => Select.unique(success.tree, "combine").appliedTo(argf, argg)
+            case _ => argf
       }
     )
diff --git a/tests/src/test/scala-3/cats/tagless/tests/simple/ApplyKSpec.scala b/tests/src/test/scala-3/cats/tagless/tests/simple/ApplyKSpec.scala
@@ -51,7 +51,7 @@ class ApplyKSpec extends munit.FunSuite with Fixtures:
     assertEquals(tryInstance.tuple, Try(instance.tuple))
   }
 
-  test("DeriveMacro should not derive instance for a not simple algebra") {
+  test("DeriveMacro should derive instance for a not simple algebra") {
     assert(typeCheckErrors("Derive.applyK[NotSimpleService]").isEmpty)
   }
 

diff --git a/tests/src/test/scala-3/cats/tagless/tests/simple/Fixtures.scala b/tests/src/test/scala-3/cats/tagless/tests/simple/Fixtures.scala
@@ -31,7 +31,7 @@ trait Fixtures:
     def paranthesless: F[Int]
     def tuple: F[(Int, Long)]
 
-  def instance = new SimpleService[Id]:
+  object instance extends SimpleService[Id]:
     def id(): Id[Int] = 42
     def list(id: Int): Id[List[Int]] = List(id)
     def lists(id1: Int, id2: Int): Id[List[Int]] = List(id1, id2)
@@ -42,12 +42,16 @@ trait Fixtures:
     def id(): Int
     def list(id: Int): F[List[Int]]
 
+  object instancens extends NotSimpleService[Id]:
+    def id(): Int = 42
+    def list(id: Int): Id[List[Int]] = List(1, 2, 3)
+
   trait SimpleServiceC[F[_]] derives ContravariantK:
     def id(id: F[Int]): Int
     def ids(id1: F[Int], id2: F[Int]): Int
     def foldSpecialized(init: String)(f: (Int, String) => Int): Cokleisli[F, String, Int]
 
-  def instancec = new SimpleServiceC[Id]:
+  object instancec extends SimpleServiceC[Id]:
     def id(id: Id[Int]): Int = id
     def ids(id1: Id[Int], id2: Id[Int]): Int = id1 + id2
     def foldSpecialized(init: String)(f: (Int, String) => Int): Cokleisli[Id, String, Int] =

diff --git a/tests/src/test/scala-3/cats/tagless/tests/simple/InvariantKSpec.scala b/tests/src/test/scala-3/cats/tagless/tests/simple/InvariantKSpec.scala
@@ -50,7 +50,7 @@ class InvariantKSpec extends munit.FunSuite with Fixtures:
     assertEquals(invariantInstance.tuple, optionalInstance.tuple)
   }
 
-  test("DeriveMacro should not derive instance for a not simple algebra") {
+  test("DeriveMacro should derive instance for a not simple algebra") {
     assert(typeCheckErrors("Derive.invariantK[NotSimpleService]").isEmpty)
   }
 

diff --git a/tests/src/test/scala-3/cats/tagless/tests/simple/SemigroupalKSpec.scala b/tests/src/test/scala-3/cats/tagless/tests/simple/SemigroupalKSpec.scala
@@ -24,7 +24,6 @@ import cats.Id
 import cats.arrow.FunctionK
 import cats.data.Tuple2K
 
-import scala.compiletime.testing.*
 import scala.annotation.experimental
 
 @experimental
@@ -47,8 +46,11 @@ class SemigroupalKSpec extends munit.FunSuite with Fixtures:
     assertEquals(combinedInstance.tuple, Tuple2K(instance.tuple, optionalInstance.tuple))
   }
 
-  test("DeriveMacro should not derive instance for a not simple algebra") {
-    assert(typeCheckErrors("Derive.semigroupalK[NotSimpleService]").isEmpty)
+  test("DeriveMacro should derive instance for a not simple algebra") {
+    val semigroupalK = Derive.semigroupalK[NotSimpleService]
+    val combinedInstance = semigroupalK.productK(instancens, instancens)
+
+    assertEquals(combinedInstance.id(), 2 * instancens.id())
   }
 
   test("SemigroupalK derives syntax") {