From c44bb8d0d95aac5af6f01ea284309f86876574f3 Mon Sep 17 00:00:00 2001
From: "Chris (Krzysztof) Pado" <povder@gmail.com>
Date: Sun, 29 Oct 2023 20:38:32 -0700
Subject: [PATCH] First impl attempt

---
 .../tools/dotc/parsing/JavaParsers.scala      | 46 ++++++++++++++++++-
 .../dotc/parsing/JavaJep445ParserTest.scala   | 26 ++++++++++-
 .../UnnamedStartsWithAnnotatedField.java      |  5 ++
 3 files changed, 74 insertions(+), 3 deletions(-)
 create mode 100644 tests/pos-java21+/jep445/UnnamedStartsWithAnnotatedField.java

diff --git a/compiler/src/dotty/tools/dotc/parsing/JavaParsers.scala b/compiler/src/dotty/tools/dotc/parsing/JavaParsers.scala
index 6ec896dcb200..bdcf190f590c 100644
--- a/compiler/src/dotty/tools/dotc/parsing/JavaParsers.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/JavaParsers.scala
@@ -826,6 +826,27 @@ object JavaParsers {
       addCompanionObject(statics, cls)
     }
 
+    def unnamedClassDecl(priorTypes: List[Tree], start: Offset): List[Tree] = {
+      val name = source.name.replaceAll("\\.java$", "").nn.toTypeName
+      val (statics, body) = typeBodyDecls(CLASS, name, Nil)
+      
+      val (priorStatics, priorBody) = priorTypes.partition {
+        case t: TypeDef => t.mods.is(Flags.JavaStatic)
+        case _: ModuleDef => true
+        case _ => false
+      }
+
+      val cls = atSpan(start, 0) {
+        TypeDef(name, makeTemplate(
+          parents = Nil,
+          stats = priorBody ::: body,
+          tparams = Nil, 
+          needsDummyConstr = true)
+        ).withMods(Modifiers(Flags.Private | Flags.Final))
+      }
+      addCompanionObject(priorStatics ::: statics, cls)
+    }
+
     def recordDecl(start: Offset, mods: Modifiers): List[Tree] =
       accept(RECORD)
       val nameOffset = in.offset
@@ -1067,16 +1088,37 @@ object JavaParsers {
       val buf = new ListBuffer[Tree]
       while (in.token == IMPORT)
         buf ++= importDecl()
+
+      val afterImports = in.offset
+      val typesBuf = new ListBuffer[Tree]
+      
       while (in.token != EOF && in.token != RBRACE) {
         while (in.token == SEMI) in.nextToken()
         if (in.token != EOF) {
           val start = in.offset
           val mods = modifiers(inInterface = false)
           adaptRecordIdentifier() // needed for typeDecl
-          buf ++= typeDecl(start, mods)
+
+          in.token match {
+            case ENUM | INTERFACE | AT | CLASS | RECORD => typesBuf ++= typeDecl(start, mods)
+            case _ =>
+              if (thisPackageName == tpnme.EMPTY_PACKAGE) {
+                // upon encountering non-types directly at a compilation unit level in an unnamed package,
+                // the entire compilation unit is treated as a JEP-445 unnamed class
+                //TODO support @annotated members of unnamed class
+                val cls = unnamedClassDecl(priorTypes = typesBuf.toList, start = afterImports)
+                typesBuf.clear()
+                typesBuf ++= cls
+              } else {
+                in.nextToken()
+                syntaxError(em"illegal start of type declaration", skipIt = true)
+                List(errorTypeTree)
+              }
+          }
         }
       }
-      val unit = atSpan(start) { PackageDef(pkg, buf.toList) }
+      
+      val unit = atSpan(start) { PackageDef(pkg, (buf ++ typesBuf).toList) }
       accept(EOF)
       unit match
         case PackageDef(Ident(nme.EMPTY_PACKAGE), Nil) => EmptyTree
diff --git a/compiler/test/dotty/tools/dotc/parsing/JavaJep445ParserTest.scala b/compiler/test/dotty/tools/dotc/parsing/JavaJep445ParserTest.scala
index 240df42acb06..c2bd1fa50532 100644
--- a/compiler/test/dotty/tools/dotc/parsing/JavaJep445ParserTest.scala
+++ b/compiler/test/dotty/tools/dotc/parsing/JavaJep445ParserTest.scala
@@ -21,7 +21,8 @@ class JavaJep445ParserTest extends DottyTest {
          |import some.pkg.*;
          |
          |private volatile int x = 0;
-         |private String s = "s";
+         |@Magic
+         |protected String s = "s";
          |
          |void main() {}
          |""".stripMargin
@@ -44,6 +45,29 @@ class JavaJep445ParserTest extends DottyTest {
          |
          |interface Inner {}
          |
+         |static class InnerStatic {}
+         |
+         |void main() {}
+         |""".stripMargin
+
+    val parser =
+      JavaParsers.JavaParser(SourceFile.virtual("MyUnnamed.java", code))
+    val tree = parser.parse()
+
+    println(tree.show)
+
+    fail("TODO")
+  }
+  
+  @Test def `treats leading top-level annotated vars as members of unnamed class`: Unit = {
+    val code =
+      s"""
+         |
+         |import some.pkg.*;
+         |
+         |@MyAnnotation
+         |int x = 0;
+         |
          |void main() {}
          |""".stripMargin
 
diff --git a/tests/pos-java21+/jep445/UnnamedStartsWithAnnotatedField.java b/tests/pos-java21+/jep445/UnnamedStartsWithAnnotatedField.java
new file mode 100644
index 000000000000..ae7df0e58509
--- /dev/null
+++ b/tests/pos-java21+/jep445/UnnamedStartsWithAnnotatedField.java
@@ -0,0 +1,5 @@
+
+@MyAnnotation
+int myInt = 10;
+
+void main() {}