fix(#17255): cannot find Scala companion module from Java

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

@@ -41,7 +41,10 @@ object ContextOps:
  else pre.findMember(name, pre, required, excluded)
  }
  else // we are in the outermost context belonging to a class; self is invisible here. See inClassContext.
- ctx.owner.findMember(name, ctx.owner.thisType, required, excluded)
+ if ctx.isJava then
+ javaFindMember(name, ctx.owner.thisType, lookInCompanion = true,required, excluded)
+ else
+ ctx.owner.findMember(name, ctx.owner.thisType, required, excluded)
  else
  ctx.scope.denotsNamed(name).filterWithFlags(required, excluded).toDenot(NoPrefix)
  }
@@ -55,11 +58,20 @@ object ContextOps:
  final def javaFindMember(name: Name, pre: Type, lookInCompanion: Boolean, required: FlagSet = EmptyFlags, excluded: FlagSet = EmptyFlags): Denotation =
  assert(ctx.isJava)
  inContext(ctx) {
-
+ import dotty.tools.dotc.core.NameOps.*
  val preSym = pre.typeSymbol
-
  // 1. Try to search in current type and parents.
- val directSearch = pre.findMember(name, pre, required, excluded)
+ val directSearch =
+ def asModule =
+ if name.isTypeName && name.endsWith(StdNames.str.MODULE_SUFFIX) then
+ pre.findMember(name.stripModuleClassSuffix.moduleClassName, pre, required, excluded) match
+ case NoDenotation => NoDenotation
+ case symDenot: SymDenotation =>
+ symDenot.companionModule.denot
+ else NoDenotation
+ pre.findMember(name, pre, required, excluded) match
+ case NoDenotation => asModule
+ case denot => denot
 
  // 2. Try to search in companion class if current is an object.
  def searchCompanionClass = if lookInCompanion && preSym.is(Flags.Module) then

compiler/test/dotc/pos-test-pickling.blacklist

@@ -29,6 +29,7 @@ i16649-irrefutable.scala
 strict-pattern-bindings-3.0-migration.scala
 i17186b.scala
 i11982a.scala
+i17255
 
 # Tree is huge and blows stack for printing Text
 i7034.scala

compiler/test/dotc/run-test-pickling.blacklist

@@ -44,3 +44,5 @@ t6138
 t6138-2
 i12656.scala
 trait-static-forwarder
+i17255
+

tests/pos/i17255/Bar.java

@@ -0,0 +1,6 @@
+package example;
+
+
+public class Bar {
+private static final example.Foo$ MOD = example.Foo$.MODULE$;
+}

tests/pos/i17255/Baz.java

@@ -0,0 +1,7 @@
+package example;
+
+import example.Foo$;
+
+public class Baz {
+private static final Foo$ MOD = Foo$.MODULE$;
+}

tests/pos/i17255/Foo.scala

@@ -0,0 +1,5 @@
+package example
+
+case class Foo(i: Int)
+
+object Foo

tests/run/i17255/J.java

@@ -0,0 +1,16 @@
+package p;
+
+public class J {
+public static J j = new J();
+public static p.J f() {
+return p.J.j;
+}
+public static Module$ module2() {
+return p.Module$.MODULE$;
+}
+public static p.Module$ module() {
+return p.Module$.MODULE$;
+}
+
+public String toString() { return "J"; }
+}

tests/run/i17255/Module.scala

@@ -0,0 +1,13 @@
+// scalajs: --skip
+
+package p {
+ object Module {
+ override def toString = "Module"
+ }
+}
+
+object Test extends App {
+ assert(p.J.f().toString == "J")
+ assert(p.J.module().toString == "Module")
+ assert(p.J.module2().toString == "Module")
+}