Support records in JavaParsers

This is a port of scala/scala#9551

compiler/src/dotty/tools/dotc/core/StdNames.scala

@@ -204,6 +204,7 @@ object StdNames {
     final val Null: N                = "Null"
     final val Object: N              = "Object"
     final val FromJavaObject: N      = "<FromJavaObject>"
+    final val Record: N              = "Record"
     final val Product: N             = "Product"
     final val PartialFunction: N     = "PartialFunction"
     final val PrefixType: N          = "PrefixType"
@@ -912,6 +913,10 @@ object StdNames {
     final val VOLATILEkw: N     = kw("volatile")
     final val WHILEkw: N        = kw("while")
 
+    final val RECORDid: N         = "record"
+    final val VARid: N            = "var"
+    final val YIELDid: N          = "yield"
+
     final val BoxedBoolean: N       = "java.lang.Boolean"
     final val BoxedByte: N          = "java.lang.Byte"
     final val BoxedCharacter: N     = "java.lang.Character"
@@ -944,6 +949,8 @@ object StdNames {
     final val JavaSerializable: N    = "java.io.Serializable"
   }
 
+
+
   class JavaTermNames extends JavaNames[TermName] {
     protected def fromString(s: String): TermName = termName(s)
   }

compiler/src/dotty/tools/dotc/parsing/JavaParsers.scala

@@ -98,6 +98,8 @@ object JavaParsers {
 
     def javaLangObject(): Tree = javaLangDot(tpnme.Object)
 
+    def javaLangRecord(): Tree = javaLangDot(tpnme.Record)
+
     def arrayOf(tpt: Tree): AppliedTypeTree =
       AppliedTypeTree(scalaDot(tpnme.Array), List(tpt))
 
@@ -555,6 +557,10 @@ object JavaParsers {
 
     def definesInterface(token: Int): Boolean = token == INTERFACE || token == AT
 
+    def adaptRecordIdentifier(): Unit =
+      if in.token == IDENTIFIER && in.name == jnme.RECORDid then
+        in.token = RECORD
+
     def termDecl(start: Offset, mods: Modifiers, parentToken: Int, parentTParams: List[TypeDef]): List[Tree] = {
       val inInterface = definesInterface(parentToken)
       val tparams = if (in.token == LT) typeParams(Flags.JavaDefined | Flags.Param) else List()
@@ -581,6 +587,16 @@ object JavaParsers {
                    TypeTree(), methodBody()).withMods(mods)
           }
         }
+      } else if (in.token == LBRACE && rtptName != nme.EMPTY && parentToken == RECORD) {
+        /*
+        record RecordName(T param1, ...) {
+          RecordName { // <- here
+            // methodBody
+          }
+        }
+        */
+        methodBody()
+        Nil
       }
       else {
         var mods1 = mods
@@ -717,12 +733,11 @@ object JavaParsers {
       ValDef(name, tpt2, if (mods.is(Flags.Param)) EmptyTree else unimplementedExpr).withMods(mods1)
     }
 
-    def memberDecl(start: Offset, mods: Modifiers, parentToken: Int, parentTParams: List[TypeDef]): List[Tree] = in.token match {
-      case CLASS | ENUM | INTERFACE | AT =>
+    def memberDecl(start: Offset, mods: Modifiers, parentToken: Int, parentTParams: List[TypeDef]): List[Tree] = in.token match
+      case CLASS | ENUM | RECORD | INTERFACE | AT =>
         typeDecl(start, if (definesInterface(parentToken)) mods | Flags.JavaStatic else mods)
       case _ =>
         termDecl(start, mods, parentToken, parentTParams)
-    }
 
     def makeCompanionObject(cdef: TypeDef, statics: List[Tree]): Tree =
       atSpan(cdef.span) {
@@ -804,6 +819,48 @@ object JavaParsers {
       addCompanionObject(statics, cls)
     }
 
+    def recordDecl(start: Offset, mods: Modifiers): List[Tree] =
+      accept(RECORD)
+      val nameOffset = in.offset
+      val name = identForType()
+      val tparams = typeParams()
+      val header = formalParams()
+      val superclass = javaLangRecord() // records always extend java.lang.Record
+      val interfaces = interfacesOpt() // records may implement interfaces
+      val (statics, body) = typeBody(RECORD, name, tparams)
+
+      // We need to generate accessors for every param, if no method with the same name is already defined
+
+      var fieldsByName = header.map(v => (v.name, (v.tpt, v.mods.annotations))).toMap
+
+      for case DefDef(name, paramss, tpt, rhs) <- body
+      if paramss.isEmpty && fieldsByName.contains(name)
+      do
+        fieldsByName -= name
+      end for
+
+      val accessors =
+        (for (name, (tpt, annots)) <- fieldsByName yield
+          DefDef(name, Nil, tpt, unimplementedExpr).withMods(Modifiers(Flags.JavaDefined | Flags.Method | Flags.Synthetic))
+        ).toList
+
+      // generate the canonical constructor
+      val canonicalConstructor = makeConstructor(header, tparams)
+
+      // return the trees, probably with addCompanionObject (like classDecl)
+      val recordTypeDef = atSpan(start, nameOffset) {
+        TypeDef(name,
+          makeTemplate(
+            parents = superclass :: interfaces,
+            stats = canonicalConstructor :: accessors ::: body,
+            tparams = tparams,
+            false
+          )
+        )
+      }
+      addCompanionObject(statics, recordTypeDef)
+    end recordDecl
+
     def interfaceDecl(start: Offset, mods: Modifiers): List[Tree] = {
       accept(INTERFACE)
       val nameOffset = in.offset
@@ -846,7 +903,7 @@ object JavaParsers {
         else if (in.token == SEMI)
           in.nextToken()
         else {
-          if (in.token == ENUM || definesInterface(in.token)) mods |= Flags.JavaStatic
+          if (in.token == ENUM || in.token == RECORD || definesInterface(in.token)) mods |= Flags.JavaStatic
           val decls = memberDecl(start, mods, parentToken, parentTParams)
           (if (mods.is(Flags.JavaStatic) || inInterface && !(decls exists (_.isInstanceOf[DefDef])))
             statics
@@ -952,6 +1009,7 @@ object JavaParsers {
       case INTERFACE => interfaceDecl(start, mods)
       case AT        => annotationDecl(start, mods)
       case CLASS     => classDecl(start, mods)
+      case RECORD    => recordDecl(start, mods)
       case _         => in.nextToken(); syntaxError(em"illegal start of type declaration", skipIt = true); List(errorTypeTree)
     }
 

compiler/src/dotty/tools/dotc/parsing/JavaTokens.scala

@@ -22,6 +22,7 @@ object JavaTokens extends TokensCommon {
   inline val INTERFACE = 105;        enter(INTERFACE, "interface")
   inline val ENUM = 106;             enter(ENUM, "enum")
   inline val IMPLEMENTS = 107;       enter(IMPLEMENTS, "implements")
+  inline val RECORD = 108;           enter(RECORD, "record")
 
   /** modifiers */
   inline val PUBLIC = 110;           enter(PUBLIC, "public")