Merge pull request #9121 from dotty-staging/fix-static-cycle

Avoid cycle between Java static class and outer class

Author: liufengyun

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

@@ -2202,7 +2202,10 @@ object SymDenotations {
       if (companion.isClass && !isAbsent(canForce = false) && !companion.isAbsent(canForce = false))
         myCompanion = companion
 
-    override def registeredCompanion(implicit ctx: Context) = { ensureCompleted(); myCompanion }
+    override def registeredCompanion(implicit ctx: Context) =
+      if !myCompanion.exists then
+        ensureCompleted()
+      myCompanion
     override def registeredCompanion_=(c: Symbol) = { myCompanion = c }
 
     private var myNestingLevel = -1

compiler/src/dotty/tools/dotc/core/classfile/ClassfileParser.scala

@@ -180,17 +180,19 @@ class ClassfileParser(
 
       for (i <- 0 until in.nextChar) parseMember(method = false)
       for (i <- 0 until in.nextChar) parseMember(method = true)
+
+      classRoot.registerCompanion(moduleRoot.symbol)
+      moduleRoot.registerCompanion(classRoot.symbol)
+
+      setClassInfo(moduleRoot, staticInfo, fromScala2 = false)
+
       classInfo = parseAttributes(classRoot.symbol, classInfo)
       if (isAnnotation)
         // classInfo must be a TempClassInfoType and not a TempPolyType,
         // because Java annotations cannot have type parameters.
         addAnnotationConstructor(classInfo.asInstanceOf[TempClassInfoType])
 
-      classRoot.registerCompanion(moduleRoot.symbol)
-      moduleRoot.registerCompanion(classRoot.symbol)
-
       setClassInfo(classRoot, classInfo, fromScala2 = false)
-      setClassInfo(moduleRoot, staticInfo, fromScala2 = false)
     }
     else if (result == Some(NoEmbedded))
       for (sym <- List(moduleRoot.sourceModule, moduleRoot.symbol, classRoot.symbol)) {
@@ -916,7 +918,7 @@ class ClassfileParser(
     }
 
     /** Return the class symbol for `entry`. It looks it up in its outer class.
-     *  Forces all outer class symbols to be completed.
+     *  This might force outer class symbols.
      */
     def classSymbol(entry: InnerClassEntry)(implicit ctx: Context): Symbol = {
       def getMember(sym: Symbol, name: Name)(implicit ctx: Context): Symbol =

tests/pos-java-interop-separate/static-cycle/A_1.java

@@ -0,0 +1,5 @@
+class Foo<T extends Foo<T>> {}
+
+public class A_1 extends Foo<A_1.InnerClass> {
+  public static class InnerClass extends Foo<A_1.InnerClass> {}
+}

tests/pos-java-interop-separate/static-cycle/B_2.scala

@@ -0,0 +1,3 @@
+object B {
+  val a = new A_1
+}