Implement GenIso.unit

Author: liufengyun

compiler/src/dotty/tools/dotc/tastyreflect/TypeOrBoundsOpsImpl.scala

@@ -25,6 +25,8 @@ trait TypeOrBoundsOpsImpl extends scala.tasty.reflect.TypeOrBoundsOps with CoreI
 
     def typeSymbol(implicit ctx: Context): Symbol = tpe.typeSymbol
 
+    def isSingleton(implicit ctx: Context): Boolean = tpe.isSingleton
+
     def memberType(member: Symbol)(implicit ctx: Context): Type =
       member.info.asSeenFrom(tpe, member.owner)
   }

library/src/scala/tasty/reflect/TypeOrBoundsOps.scala

@@ -55,6 +55,7 @@ trait TypeOrBoundsOps extends Core {
     def widen(implicit ctx: Context): Type
     def classSymbol(implicit ctx: Context): Option[ClassSymbol]
     def typeSymbol(implicit ctx: Context): Symbol
+    def isSingleton(implicit ctx: Context): Boolean
     def memberType(member: Symbol)(implicit ctx: Context): Type
   }
 

tests/run-with-compiler/i5941/macro_1.scala

@@ -128,6 +128,41 @@ object Iso {
       apply(from)(to)
     }
   }
+
+  def implUnit[S: Type](implicit refl: Reflection): Expr[Iso[S, Unit]] = {
+    import refl._
+    import util._
+    import quoted.Toolbox.Default._
+
+    val tpS = typeOf[S]
+
+    if (tpS.isSingleton) {
+      val ident = Term.Ident(tpS.asInstanceOf[TermRef]).seal[S]
+      '{
+        Iso[S, Unit](Function.const(~ident))(Function.const(()))
+      }
+    }
+    else if (tpS.classSymbol.flatMap(cls => if (cls.flags.is(Flags.Case)) Some(true) else None).nonEmpty) {
+      val cls = tpS.classSymbol.get
+
+      if (cls.caseFields.size != 0)
+        throw new QuoteError("Use GenIso.fields for case classes more than one parameter")
+
+      val companion = tpS match {
+        case Type.SymRef(sym, prefix)   => Type.TermRef(prefix, sym.name)
+        case Type.TypeRef(name, prefix) => Type.TermRef(prefix, name)
+      }
+
+      val obj = Term.Select.overloaded(Term.Ident(companion), "apply", Nil, Nil).seal[S]
+
+      '{
+        Iso[S, Unit](Function.const(~obj))(Function.const(()))
+      }
+    }
+    else {
+      throw new QuoteError("Only support generation for case classes or singleton types")
+    }
+  }
 }
 
 object GenIso {
@@ -141,7 +176,7 @@ object GenIso {
   inline def apply[S, A]: Iso[S, A] = ~Iso.impl[S, A]
 
   inline def fields[S, A]: Iso[S, A] = ???
-  inline def unit[S]: Iso[S, Unit] = ???
+  inline def unit[S]: Iso[S, Unit] = ~Iso.implUnit[S]
 }
 
 trait Prism[S, A] {

tests/run-with-compiler/i5941/usage_2.scala

@@ -30,5 +30,7 @@ object Test {
     // assert(jStr(JStr("world")) == JStr("world"))
 
     assert(GenIso[JStr, String].to(JStr("Hello")) == "Hello")
+    assert(GenIso.unit[JNull.type].to(JNull) == (()))
+    assert(GenIso.unit[JNull.type].from(()) == JNull)
   }
 }