Restrict argument type of concat to be a concrete type for type saf…

…ety.
tarao · Nov 27, 2023 · da9dbf3 · da9dbf3
1 parent 67ed1ee
commit da9dbf3
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Showing 5 changed files with 72 additions and 2 deletions.
diff --git a/modules/core/src/main/scala/com/github/tarao/record4s/ArrayRecord.scala b/modules/core/src/main/scala/com/github/tarao/record4s/ArrayRecord.scala
@@ -243,6 +243,7 @@ object ArrayRecord extends ArrayRecord.Extensible[EmptyTuple] {
       other: R2,
     )(using c: Concat[R, R2]): c.Out =
       withPotentialTypingError {
+        summon[typing.Concrete[R2]]
         val vec = record
           .__fields
           .toVector

diff --git a/modules/core/src/main/scala/com/github/tarao/record4s/Macros.scala b/modules/core/src/main/scala/com/github/tarao/record4s/Macros.scala
@@ -19,6 +19,7 @@ package com.github.tarao.record4s
 import scala.annotation.nowarn
 
 import Record.newMapRecord
+import typing.Concrete
 import typing.Record.{Concat, Lookup, Select, Unselect}
 
 @nowarn("msg=unused local")
@@ -215,6 +216,27 @@ object Macros {
     }
   }
 
+  def derivedTypingConcreteImple[T: Type](using
+    Quotes,
+  ): Expr[Concrete[T]] = withInternal {
+    import quotes.reflect.*
+    import internal.*
+
+    if (TypeRepr.of[T].dealias.typeSymbol.isTypeParam)
+      errorAndAbort(
+        Seq(
+          s"A concrete type expected but type variable ${Type.show[T]} is given.",
+          "Did you forget to make the method inline?",
+        ).mkString("\n"),
+      )
+    else
+      '{
+        Concrete
+          .instance
+          .asInstanceOf[Concrete[T]]
+      }
+  }
+
   private def typeNameOfImpl[T: Type](using Quotes): Expr[String] = {
     import quotes.reflect.*
 

diff --git a/modules/core/src/main/scala/com/github/tarao/record4s/Record.scala b/modules/core/src/main/scala/com/github/tarao/record4s/Record.scala
@@ -129,6 +129,7 @@ object Record {
     inline def concat[R2: RecordLike, RR <: %](
       other: R2,
     )(using Concat.Aux[R, R2, RR]): RR = withPotentialTypingError {
+      summon[typing.Concrete[R2]]
       newMapRecord[RR](
         record
           .__iterable

diff --git a/modules/core/src/main/scala/com/github/tarao/record4s/typing/Typing.scala b/modules/core/src/main/scala/com/github/tarao/record4s/typing/Typing.scala
@@ -31,6 +31,14 @@ trait MaybeError {
   type Msg <: String
 }
 
+final class Concrete[T] private {}
+object Concrete {
+  private[record4s] val instance = new Concrete[Nothing]
+
+  transparent inline given [T]: Concrete[T] =
+    ${ Macros.derivedTypingConcreteImple }
+}
+
 private inline def showTypingError(using err: typing.MaybeError): Unit = {
   import scala.compiletime.{constValue, erasedValue, error}
 

diff --git a/modules/core/src/test/scala/com/github/tarao/record4s/TypeErrorSpec.scala b/modules/core/src/test/scala/com/github/tarao/record4s/TypeErrorSpec.scala
@@ -48,6 +48,22 @@ class TypeErrorSpec extends helper.UnitSpec {
             typing.Record.Concat.Aux[R, % { val name: String }, RR],
           ): RR = record ++ %(email = email)
         """ shouldNot typeCheck
+
+        def checkErrors(errs: List[Error]): Unit = {
+          errs should not be empty
+          errs.head.kind shouldBe ErrorKind.Typer
+          val _ = errs.exists(
+            _.message.startsWith(
+              "A concrete type expected",
+            ),
+          ) shouldBe true
+        }
+
+        checkErrors(typeCheckErrors("""
+          def concat[R1 <: %, R2 <: %, RR <: %](r1: R1, r2: R2)(using
+            typing.Record.Concat.Aux[R1, R2, RR],
+          ): RR = r1 ++ r2
+        """))
       }
     }
 
@@ -149,16 +165,38 @@ class TypeErrorSpec extends helper.UnitSpec {
 
       it("should detect wrong usage") {
         """
-          def addEmail[R, RR <: %](record: ArrayRecord[R], email: String)(using
+          def addEmail[R, RR <: ProductRecord](record: ArrayRecord[R], email: String)(using
             typing.ArrayRecord.Concat.Aux[R, Nothing, RR],
           ): RR = record ++ ArrayRecord(email = email)
         """ shouldNot typeCheck
 
         """
-          def addEmail[R, RR <: %](record: ArrayRecord[R], email: String)(using
+          def addEmail[R, RR <: ProductRecord](record: ArrayRecord[R], email: String)(using
             typing.ArrayRecord.Concat.Aux[R, ArrayRecord[("name", String) *: EmptyTuple], RR],
           ): RR = record ++ ArrayRecord(email = email)
         """ shouldNot typeCheck
+
+        """
+          def concat[R1, R2, RR <: ProductRecord](r1: ArrayRecord[R1], r2: ArrayRecord[R2])(using
+            typing.ArrayRecord.Concat.Aux[R1, R2, RR],
+          ): RR = r1 ++ r2
+        """ shouldNot typeCheck
+
+        def checkErrors(errs: List[Error]): Unit = {
+          errs should not be empty
+          errs.head.kind shouldBe ErrorKind.Typer
+          val _ = errs.exists(
+            _.message.startsWith(
+              "A concrete type expected",
+            ),
+          ) shouldBe true
+        }
+
+        checkErrors(typeCheckErrors("""
+          def concat[R1, R2 <: %, RR <: ProductRecord](r1: ArrayRecord[R1], r2: R2)(using
+            typing.ArrayRecord.Concat.Aux[R1, R2, RR],
+          ): RR = r1 ++ r2
+        """))
       }
     }