Fix Java record problems (#19578) and (#19386) (#19583)

This is a dependency of #19577 and should be reviewed and merged first.

fixes #18639
fixes #19386
fixes #19578

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

@@ -854,13 +854,13 @@ object JavaParsers {
 
       val accessors =
         (for (name, (tpt, annots)) <- fieldsByName yield
-          DefDef(name, Nil, tpt, unimplementedExpr)
+          DefDef(name, List(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)
+        DefDef(nme.CONSTRUCTOR, joinParams(Nil, List(header)), TypeTree(), EmptyTree)
           .withMods(Modifiers(Flags.JavaDefined | Flags.Synthetic, mods.privateWithin))
 
       // return the trees
@@ -872,7 +872,7 @@ object JavaParsers {
             tparams = tparams,
             needsDummyConstr = true
           )
-        ).withMods(mods)
+        ).withMods(mods.withFlags(Flags.JavaDefined | Flags.Final))
       }
       addCompanionObject(statics, recordTypeDef)
     end recordDecl

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

@@ -879,6 +879,10 @@ class Namer { typer: Typer =>
      *  with a user-defined method in the same scope with a matching type.
      */
     private def invalidateIfClashingSynthetic(denot: SymDenotation): Unit =
+
+      def isJavaRecord(owner: Symbol) =
+        owner.is(JavaDefined) && owner.derivesFrom(defn.JavaRecordClass)
+
       def isCaseClassOrCompanion(owner: Symbol) =
         owner.isClass && {
           if (owner.is(Module)) owner.linkedClass.is(CaseClass)
@@ -902,9 +906,9 @@ class Namer { typer: Typer =>
             && (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)
+          // remove synthetic constructor or method of a java Record if it clashes with a non-synthetic constructor
+          (isJavaRecord(denot.owner)
+            && denot.is(Method)
             && denot.owner.unforcedDecls.lookupAll(denot.name).exists(c => c != denot.symbol && c.info.matches(denot.info))
           )
         )

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

@@ -2548,10 +2548,10 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
     def canBeInvalidated(sym: Symbol): Boolean =
       sym.is(Synthetic)
       && (desugar.isRetractableCaseClassMethodName(sym.name) ||
-        (sym.isConstructor && sym.owner.derivesFrom(defn.JavaRecordClass)))
+         (sym.owner.is(JavaDefined) && sym.owner.derivesFrom(defn.JavaRecordClass) && sym.is(Method)))
 
     if !sym.info.exists then
-      // it's a discarded method (synthetic case class method or synthetic java record constructor), drop it
+      // it's a discarded method (synthetic case class method or synthetic java record constructor or overriden member), drop it
       assert(canBeInvalidated(sym))
       sym.owner.info.decls.openForMutations.unlink(sym)
       return EmptyTree

tests/pos-java16+/i19386/FromScala.scala

@@ -0,0 +1,2 @@
+def test(r: R1): Unit =
+  val i: Int = r.i()

tests/pos-java16+/i19386/R1.java

@@ -0,0 +1 @@
+public record R1(int i) {}

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

@@ -1,4 +1,8 @@
 object C:
+
+  def useR0: Unit =
+    val r = R0()
+
   def useR1: Unit =
     // constructor signature
     val r = R1(123, "hello")
@@ -41,3 +45,7 @@ object C:
     val l2: Long = r3.l(43L, 44L)
     // supertype
     val isRecord: java.lang.Record = r3
+
+  def useR4: Unit =
+    val r4 = R4(1)
+    val i: Int = r4.t

tests/pos-java16+/java-records/R0.java

@@ -0,0 +1 @@
+public record R0() {}

tests/pos-java16+/java-records/R4.java

@@ -0,0 +1 @@
+public record R4<T>(T t) {}