Support records in JavaParsers (#16762)

This is a port of scala/scala#9551.

Fixes #14846.

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

@@ -688,6 +688,7 @@ class Definitions {
   @tu lazy val JavaCalendarClass: ClassSymbol = requiredClass("java.util.Calendar")
   @tu lazy val JavaDateClass: ClassSymbol = requiredClass("java.util.Date")
   @tu lazy val JavaFormattableClass: ClassSymbol = requiredClass("java.util.Formattable")
+  @tu lazy val JavaRecordClass: Symbol = getClassIfDefined("java.lang.Record")
 
   @tu lazy val JavaEnumClass: ClassSymbol = {
     val cls = requiredClass("java.lang.Enum")

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"
@@ -913,6 +914,10 @@ 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"
@@ -945,6 +950,8 @@ 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

@@ -20,7 +20,8 @@ import StdNames._
 import reporting._
 import dotty.tools.dotc.util.SourceFile
 import util.Spans._
-import scala.collection.mutable.ListBuffer
+
+import scala.collection.mutable.{ListBuffer, LinkedHashMap}
 
 object JavaParsers {
 
@@ -96,8 +97,12 @@ object JavaParsers {
     def javaLangDot(name: Name): Tree =
       Select(javaDot(nme.lang), name)
 
+    /** Tree representing `java.lang.Object` */
     def javaLangObject(): Tree = javaLangDot(tpnme.Object)
 
+    /** Tree representing `java.lang.Record` */
+    def javaLangRecord(): Tree = javaLangDot(tpnme.Record)
+
     def arrayOf(tpt: Tree): AppliedTypeTree =
       AppliedTypeTree(scalaDot(tpnme.Array), List(tpt))
 
@@ -555,6 +560,14 @@ object JavaParsers {
 
     def definesInterface(token: Int): Boolean = token == INTERFACE || token == AT
 
+    /** If the next token is the identifier "record", convert it into the RECORD token.
+      * This makes it easier to handle records in various parts of the code,
+      * in particular when a `parentToken` is passed to some functions.
+      */
+    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 +594,16 @@ 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 +740,11 @@ 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 =>
-        typeDecl(start, if (definesInterface(parentToken)) mods | Flags.JavaStatic else mods)
+    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) then mods | Flags.JavaStatic else mods)
       case _ =>
         termDecl(start, mods, parentToken, parentTParams)
-    }
 
     def makeCompanionObject(cdef: TypeDef, statics: List[Tree]): Tree =
       atSpan(cdef.span) {
@@ -804,6 +826,51 @@ 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))).to(LinkedHashMap)
+
+      for case DefDef(name, paramss, _, _) <- 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 =
+        DefDef(nme.CONSTRUCTOR, joinParams(tparams, List(header)), TypeTree(), EmptyTree)
+          .withMods(Modifiers(Flags.JavaDefined | Flags.Synthetic, mods.privateWithin))
+
+      // return the trees
+      val recordTypeDef = atSpan(start, nameOffset) {
+        TypeDef(name,
+          makeTemplate(
+            parents = superclass :: interfaces,
+            stats = canonicalConstructor :: accessors ::: body,
+            tparams = tparams,
+            true
+          )
+        ).withMods(mods)
+      }
+      addCompanionObject(statics, recordTypeDef)
+    end recordDecl
+
     def interfaceDecl(start: Offset, mods: Modifiers): List[Tree] = {
       accept(INTERFACE)
       val nameOffset = in.offset
@@ -846,7 +913,8 @@ object JavaParsers {
         else if (in.token == SEMI)
           in.nextToken()
         else {
-          if (in.token == ENUM || definesInterface(in.token)) mods |= Flags.JavaStatic
+          adaptRecordIdentifier()
+          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
@@ -947,13 +1015,13 @@ object JavaParsers {
       }
     }
 
-    def typeDecl(start: Offset, mods: Modifiers): List[Tree] = in.token match {
+    def typeDecl(start: Offset, mods: Modifiers): List[Tree] = in.token match
       case ENUM      => enumDecl(start, mods)
       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)
-    }
 
     def tryConstant: Option[Constant] = {
       val negate = in.token match {
@@ -1004,6 +1072,7 @@ object JavaParsers {
         if (in.token != EOF) {
           val start = in.offset
           val mods = modifiers(inInterface = false)
+          adaptRecordIdentifier() // needed for typeDecl
           buf ++= typeDecl(start, mods)
         }
       }

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

@@ -41,6 +41,9 @@ object JavaTokens extends TokensCommon {
   inline val SWITCH = 133;           enter(SWITCH, "switch")
   inline val ASSERT = 134;           enter(ASSERT, "assert")
 
+  /** contextual keywords (turned into keywords in certain conditions, see JLS 3.9 of Java 9+) */
+  inline val RECORD = 135;           enter(RECORD, "record")
+
   /** special symbols */
   inline val EQEQ = 140
   inline val BANGEQ = 141

compiler/src/dotty/tools/dotc/typer/Namer.scala

@@ -862,7 +862,6 @@ class Namer { typer: Typer =>
      *  with a user-defined method in the same scope with a matching type.
      */
     private def invalidateIfClashingSynthetic(denot: SymDenotation): Unit =
-
       def isCaseClassOrCompanion(owner: Symbol) =
         owner.isClass && {
           if (owner.is(Module)) owner.linkedClass.is(CaseClass)
@@ -879,10 +878,19 @@ class Namer { typer: Typer =>
             !sd.symbol.is(Deferred) && sd.matches(denot)))
 
       val isClashingSynthetic =
-        denot.is(Synthetic, butNot = ConstructorProxy)
-        && desugar.isRetractableCaseClassMethodName(denot.name)
-        && isCaseClassOrCompanion(denot.owner)
-        && (definesMember || inheritsConcreteMember)
+        denot.is(Synthetic, butNot = ConstructorProxy) &&
+        (
+          (desugar.isRetractableCaseClassMethodName(denot.name)
+            && isCaseClassOrCompanion(denot.owner)
+            && (definesMember || inheritsConcreteMember)
+          )
+          ||
+          // remove synthetic constructor of a java Record if it clashes with a non-synthetic constructor
+          (denot.isConstructor
+            && denot.owner.is(JavaDefined) && denot.owner.derivesFrom(defn.JavaRecordClass)
+            && denot.owner.unforcedDecls.lookupAll(denot.name).exists(c => c != denot.symbol && c.info.matches(denot.info))
+          )
+        )
 
       if isClashingSynthetic then
         typr.println(i"invalidating clashing $denot in ${denot.owner}")

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -2441,11 +2441,17 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
   }
 
   def typedDefDef(ddef: untpd.DefDef, sym: Symbol)(using Context): Tree = {
-    if (!sym.info.exists) { // it's a discarded synthetic case class method, drop it
-      assert(sym.is(Synthetic) && desugar.isRetractableCaseClassMethodName(sym.name))
+    def canBeInvalidated(sym: Symbol): Boolean =
+      sym.is(Synthetic)
+      && (desugar.isRetractableCaseClassMethodName(sym.name) ||
+        (sym.isConstructor && sym.owner.derivesFrom(defn.JavaRecordClass)))
+
+    if !sym.info.exists then
+      // it's a discarded method (synthetic case class method or synthetic java record constructor), drop it
+      assert(canBeInvalidated(sym))
       sym.owner.info.decls.openForMutations.unlink(sym)
       return EmptyTree
-    }
+
     // TODO: - Remove this when `scala.language.experimental.erasedDefinitions` is no longer experimental.
     //       - Modify signature to `erased def erasedValue[T]: T`
     if sym.eq(defn.Compiletime_erasedValue) then
@@ -3598,7 +3604,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
     adapt(tree, pt, ctx.typerState.ownedVars)
 
   private def adapt1(tree: Tree, pt: Type, locked: TypeVars)(using Context): Tree = {
-    assert(pt.exists && !pt.isInstanceOf[ExprType] || ctx.reporter.errorsReported)
+    assert(pt.exists && !pt.isInstanceOf[ExprType] || ctx.reporter.errorsReported, i"tree: $tree, pt: $pt")
     def methodStr = err.refStr(methPart(tree).tpe)
 
     def readapt(tree: Tree)(using Context) = adapt(tree, pt, locked)

compiler/test/dotty/tools/dotc/CompilationTests.scala

@@ -29,7 +29,7 @@ class CompilationTests {
 
   @Test def pos: Unit = {
     implicit val testGroup: TestGroup = TestGroup("compilePos")
-    aggregateTests(
+    var tests = List(
       compileFile("tests/pos/nullarify.scala", defaultOptions.and("-Ycheck:nullarify")),
       compileFile("tests/pos-special/utf8encoded.scala", explicitUTF8),
       compileFile("tests/pos-special/utf16encoded.scala", explicitUTF16),
@@ -65,8 +65,13 @@ class CompilationTests {
       compileFile("tests/pos-special/extend-java-enum.scala", defaultOptions.and("-source", "3.0-migration")),
       compileFile("tests/pos-custom-args/help.scala", defaultOptions.and("-help", "-V", "-W", "-X", "-Y")),
       compileFile("tests/pos-custom-args/i13044.scala", defaultOptions.and("-Xmax-inlines:33")),
-      compileFile("tests/pos-custom-args/jdk-8-app.scala", defaultOptions.and("-release:8")),
-    ).checkCompile()
+      compileFile("tests/pos-custom-args/jdk-8-app.scala", defaultOptions.and("-release:8"))
+    )
+
+    if scala.util.Properties.isJavaAtLeast("16") then
+      tests ::= compileFilesInDir("tests/pos-java16+", defaultOptions.and("-Ysafe-init"))
+
+    aggregateTests(tests*).checkCompile()
   }
 
   @Test def rewrites: Unit = {

tests/pos-java16+/java-records/FromScala.scala

@@ -0,0 +1,43 @@
+object C:
+  def useR1: Unit =
+    // constructor signature
+    val r = R1(123, "hello")
+
+    // accessors
+    val i: Int = r.i
+    val s: String = r.s
+
+    // methods
+    val iRes: Int = r.getInt()
+    val sRes: String = r.getString()
+
+    // supertype
+    val record: java.lang.Record = r
+
+  def useR2: Unit =
+    // constructor signature
+    val r2 = R2.R(123, "hello")
+
+    // accessors signature
+    val i: Int = r2.i
+    val s: String = r2.s
+
+    // method
+    val i2: Int = r2.getInt
+
+    // supertype
+    val isIntLike: IntLike = r2
+    val isRecord: java.lang.Record = r2
+
+  def useR3 =
+    // constructor signature
+    val r3 = R3(123, 42L, "hi")
+    new R3("hi", 123)
+    // accessors signature
+    val i: Int = r3.i
+    val l: Long = r3.l
+    val s: String = r3.s
+    // method
+    val l2: Long = r3.l(43L, 44L)
+    // supertype
+    val isRecord: java.lang.Record = r3

tests/pos-java16+/java-records/IntLike.scala

@@ -0,0 +1,2 @@
+trait IntLike:
+  def getInt: Int

tests/pos-java16+/java-records/R1.java

@@ -0,0 +1,9 @@
+public record R1(int i, String s) {
+  public String getString() {
+    return s + i;
+  }
+
+  public int getInt() {
+    return 0;
+  }
+}

tests/pos-java16+/java-records/R2.java

@@ -0,0 +1,13 @@
+public class R2 {
+    final record R(int i, String s) implements IntLike {
+        public int getInt() {
+            return i;
+        }
+
+        // Canonical constructor
+        public R(int i, java.lang.String s) {
+            this.i = i;
+            this.s = s.intern();
+        }
+    }
+}

tests/pos-java16+/java-records/R3.java

@@ -0,0 +1,22 @@
+public record R3(int i, long l, String s) {
+
+    // User-specified accessor
+    public int i() {
+        return i + 1; // evil >:)
+    }
+
+    // Not an accessor - too many parameters
+    public long l(long a1, long a2) {
+        return a1 + a2;
+    }
+
+    // Secondary constructor
+    public R3(String s, int i) {
+        this(i, 42L, s);
+    }
+
+    // Compact constructor
+    public R3 {
+        s = s.intern();
+    }
+}