Generate static inline accessors module

If a class `C` needs inline accessors that would be added top-level
or if the accessor is to a static member, we place it in a new
invisible module `C$inline$accessors`.

If the accessor location in the new scheme is not the same as the
previous location, we also generate the old accessor for backward binary
compatibility but do not use it.

Fixes #13215
Fixes #15413

Author: nicolasstucki

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

@@ -21,6 +21,7 @@ object StdNames {
     inline val AVOID_CLASH_SUFFIX       = "$_avoid_name_clash_$"
     inline val MODULE_SUFFIX            = "$"
     inline val TOPLEVEL_SUFFIX          = "$package"
+    inline val TOPLEVEL_INLINE_SUFFIX   = "$inline$accessors"
     inline val NAME_JOIN                = "$"
     inline val DEFAULT_GETTER           = "$default$"
     inline val LOCALDUMMY_PREFIX        = "<local "       // owner of local blocks

compiler/src/dotty/tools/dotc/inlines/PrepareInlineable.scala

@@ -2,6 +2,8 @@ package dotty.tools
 package dotc
 package inlines
 
+import scala.collection.mutable
+
 import dotty.tools.dotc.ast.{Trees, tpd, untpd}
 import Trees._
 import core._
@@ -22,14 +24,21 @@ import transform.SymUtils.*
 import config.Printers.inlining
 import util.Property
 import dotty.tools.dotc.transform.TreeMapWithStages._
+import dotty.tools.dotc.ast.desugar.packageObjectName
+import dotty.tools.dotc.core.StdNames.str
+import dotty.tools.dotc.util.{Spans, SrcPos}
+import dotty.tools.dotc.typer.TopLevelExtensionModules.newAccessorModule
 
 object PrepareInlineable {
   import tpd._
 
   private val InlineAccessorsKey = new Property.Key[InlineAccessors]
+  private val InlineAccessorsModuleKey = new Property.Key[mutable.Map[Symbol, Symbol]]
 
   def initContext(ctx: Context): Context =
-    ctx.fresh.setProperty(InlineAccessorsKey, new InlineAccessors)
+    ctx.fresh
+      .setProperty(InlineAccessorsKey, new InlineAccessors)
+      .setProperty(InlineAccessorsModuleKey, mutable.Map.empty)
 
   def makeInlineable(tree: Tree)(using Context): Tree =
     ctx.property(InlineAccessorsKey).get.makeInlineable(tree)
@@ -39,6 +48,19 @@ object PrepareInlineable {
       case Some(inlineAccessors) => inlineAccessors.addAccessorDefs(cls, body)
       case _ => body
 
+  def inlineAccessorsModule(topLevelClass: Symbol)(using Context): Symbol =
+    assert(topLevelClass.asClass.owner.is(Package), topLevelClass)
+    ctx.property(InlineAccessorsModuleKey).get.getOrElse(topLevelClass, NoSymbol)
+
+  def requiredInlineAccessorsModule(topLevelClass: Symbol)(using Context): Symbol =
+    assert(topLevelClass.asClass.owner.is(Package), topLevelClass)
+    ctx.property(InlineAccessorsModuleKey) match
+      case Some(inlineAccessorsModule) =>
+        inlineAccessorsModule.getOrElseUpdate(
+          topLevelClass,
+          newAccessorModule(str.TOPLEVEL_INLINE_SUFFIX))
+      case None => NoSymbol
+
   class InlineAccessors extends AccessProxies {
 
     /** If an inline accessor name wraps a unique inline name, this is taken as indication
@@ -99,20 +121,32 @@ object PrepareInlineable {
      *  advantage that we can re-use the receiver as is. But it is only
      *  possible if the receiver is essentially this or an outer this, which is indicated
      *  by the test that we can find a host for the accessor.
+     *
+     *  @param inlineSym symbol of the inline method
+     *  @param compat use inline accessor format of 3.0-3.2
      */
-    class MakeInlineableDirect(inlineSym: Symbol) extends MakeInlineableMap(inlineSym) {
+    class MakeInlineableDirect(inlineSym: Symbol, compat: Boolean) extends MakeInlineableMap(inlineSym) {
       def preTransform(tree: Tree)(using Context): Tree = tree match {
         case tree: RefTree if needsAccessor(tree.symbol) =>
           if tree.symbol.isConstructor then
             report.error("Implementation restriction: cannot use private constructors in inline methods", tree.srcPos)
             tree // TODO: create a proper accessor for the private constructor
-          else
+          else if compat then
+            // Generate the accessor for backwards compatibility with 3.0-3.3
             val nearestHost = AccessProxies.hostForAccessorOf(tree.symbol)
             val host = if nearestHost.is(Package) then ctx.owner.topLevelClass else nearestHost
             useAccessor(tree, host)
+          else
+            // Generate the accessor for 3.4+
+            val nearestHost = AccessProxies.hostForAccessorOf(tree.symbol)
+            if nearestHost.is(Package) || (tree.symbol.owner.isStaticOwner && !nearestHost.isStaticOwner) then
+              useAccessor(tree, requiredInlineAccessorsModule(ctx.owner.topLevelClass))
+            else
+              useAccessor(tree, nearestHost)
         case _ =>
           tree
       }
+
       override def ifNoHost(reference: RefTree)(using Context): Tree = reference
     }
 
@@ -228,8 +262,12 @@ object PrepareInlineable {
         // so no accessors are needed for them.
         tree
       else
+        // Generate inline accessors for 3.0-3.3
+        new MakeInlineablePassing(inlineSym).transform(
+          new MakeInlineableDirect(inlineSym, compat = true).transform(tree))
+          // Generate and use inline accessors for 3.4+
         new MakeInlineablePassing(inlineSym).transform(
-          new MakeInlineableDirect(inlineSym).transform(tree))
+          new MakeInlineableDirect(inlineSym, compat = false).transform(tree))
     }
   }
 

compiler/src/dotty/tools/dotc/quoted/Interpreter.scala

@@ -349,9 +349,10 @@ object Interpreter:
       if !ctx.compilationUnit.isSuspendable then None
       else targetException match
         case _: NoClassDefFoundError | _: ClassNotFoundException =>
-          val className = targetException.getMessage
-          if className eq null then None
+          val msg = targetException.getMessage
+          if msg eq null then None
           else
+            val className = msg.stripSuffix(str.TOPLEVEL_INLINE_SUFFIX + str.MODULE_SUFFIX)
             val sym = staticRef(className.toTypeName).symbol
             if (sym.isDefinedInCurrentRun) Some(sym) else None
         case _ => None

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

@@ -0,0 +1,76 @@
+package dotty.tools.dotc.typer
+
+import dotty.tools.dotc.ast.*, untpd.*
+import dotty.tools.dotc.core.Contexts.*
+import dotty.tools.dotc.core.Flags.*
+import dotty.tools.dotc.core.Names.*
+import dotty.tools.dotc.core.Scopes.*
+import dotty.tools.dotc.core.StdNames.*
+import dotty.tools.dotc.core.Symbols.*
+
+/** Creation of top-level extension modules */
+object TopLevelExtensionModules:
+  import tpd.*
+
+  /** Creates the symbols for a new extension module associated with the current
+   *  top-level class. These definitions are invisible in the source code.
+   *
+   * ```scala
+   *  class C
+   *  // symbols generated by `newAccessorModule("$extension")`
+   *  lazy val C$extension = new C$extension$
+   *  class C$extension$
+   *  ```
+   *
+   *  @param suffix suffix that will be appended to the name of the top-level class
+   *  @return The class symbol of the new module
+   */
+  def newAccessorModule(suffix: String)(using Context): ClassSymbol =
+    val inlineAccessorObjectName: TermName =
+      assert(suffix.startsWith("$"), "suffix should start with $")
+      assert(suffix.size > 1, "suffix should start with $ followed by a name")
+      val fileName = ctx.source.file.name
+      val sourceName = ctx.owner.topLevelClass.name
+      (sourceName ++ suffix).toTermName
+
+    val mod = newNormalizedModuleSymbol(
+      ctx.owner.topLevelClass.owner,
+      inlineAccessorObjectName,
+      ModuleValCreationFlags & Invisible,
+      ModuleClassCreationFlags & Invisible,
+      List(defn.ObjectClass.typeRef),
+      newScope,
+      NoSymbol,
+      coord = ctx.owner.topLevelClass.span
+    )
+    val cls = mod.moduleClass.asClass
+    cls.enter(newConstructor(cls, Synthetic, Nil, Nil))
+    cls
+
+  /** Generate a list with the ValDef and TypeDef trees of an extension module (created with `newAccessorModule`).
+   *
+   * ```scala
+   *  // given the moduleClassSym for `C$extension$` and `body` this generates the trees
+   *  lazy val C$extension = new C$extension$
+   *  class C$extension$:
+   *    <body*>
+   *  ```
+   *  @param moduleClassSym class symbol of the extension module
+   *  @param body list of definitions in the extension module
+   */
+  def topLevelModuleDefTree(moduleClassSym: ClassSymbol, body: List[Tree])(using Context): List[Tree] =
+    assert(moduleClassSym.owner.is(Package))
+    val untpdCtr = untpd.DefDef(nme.CONSTRUCTOR, Nil, tpd.TypeTree(defn.UnitClass.typeRef), tpd.EmptyTree)
+    val ctr = ctx.typeAssigner.assignType(untpdCtr, moduleClassSym.primaryConstructor)
+
+    val parents = List(TypeTree(defn.ObjectClass.typeRef))
+    val clsDef =
+      tpd.ClassDefWithParents(moduleClassSym.asClass, ctr, parents, body)
+        .withSpan(moduleClassSym.span)
+
+    val newCls =
+      Apply(New(ref(moduleClassSym)).select(moduleClassSym.primaryConstructor), Nil)
+    val modVal =
+      ValDef(moduleClassSym.companionModule.asTerm, newCls).withSpan(clsDef.span)
+        .withSpan(moduleClassSym.companionModule.span)
+    List(modVal, clsDef)

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

@@ -34,6 +34,8 @@ import util.Spans._
 import util.common._
 import util.{Property, SimpleIdentityMap, SrcPos}
 import Applications.{tupleComponentTypes, wrapDefs, defaultArgument}
+import TopLevelExtensionModules.topLevelModuleDefTree
+
 
 import collection.mutable
 import annotation.tailrec
@@ -2713,6 +2715,16 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
           pkg.moduleClass.info.decls.lookup(topLevelClassName).ensureCompleted()
           var stats1 = typedStats(tree.stats, pkg.moduleClass)._1
           if (!ctx.isAfterTyper)
+            val inlineAccessorClasses = stats1.view.collect {
+              case tdef @ TypeDef(name, rhs) if tdef.symbol.isClass && PrepareInlineable.inlineAccessorsModule(tdef.symbol).exists =>
+                val inlineAccessorsModuleClass = PrepareInlineable.inlineAccessorsModule(tdef.symbol)
+                topLevelModuleDefTree(
+                  inlineAccessorsModuleClass.asClass,
+                  addAccessorDefs(inlineAccessorsModuleClass, Nil)
+                )
+            }.flatten
+            stats1 = stats1 ++ inlineAccessorClasses
+
             stats1 = stats1 ++ typedBlockStats(MainProxies.proxies(stats1))._1
           cpy.PackageDef(tree)(pid1, stats1).withType(pkg.termRef)
         }

compiler/test/dotty/tools/backend/jvm/DottyBytecodeTests.scala

@@ -1682,6 +1682,83 @@ class DottyBytecodeTests extends DottyBytecodeTest {
       assertSameCode(instructions, expected)
     }
   }
+
+  @Test
+  def i13215(): Unit = {
+    val code =
+      """package foo:
+        |  trait Bar:
+        |    inline def baz = Baz
+        |  private[foo] object Baz
+      """.stripMargin
+    checkBCode(code) { dir =>
+      val privateAccessors = Opcodes.ACC_PRIVATE | Opcodes.ACC_PROTECTED
+
+      // For 3.0-3.3 compat
+      val barClass = loadClassNode(dir.subdirectoryNamed("foo").lookupName("Bar.class", directory = false).input, skipDebugInfo = false)
+      val accessorOld  = getMethod(barClass, "foo$Bar$$inline$Baz")
+      assert(accessorOld.signature == "()Lfoo/Baz$;", accessorOld.signature)
+      assert((accessorOld.access & privateAccessors) == 0)
+
+      // For 3.4+
+      val accessorsClass = loadClassNode(dir.subdirectoryNamed("foo").lookupName("Bar$inline$accessors.class", directory = false).input, skipDebugInfo = false)
+      val accessorNew  = getMethod(accessorsClass, "inline$Baz")
+      assert(accessorNew.signature == "()Lfoo/Baz$;", accessorNew.signature)
+      assert((accessorNew.access & privateAccessors) == 0)
+    }
+  }
+
+  @Test
+  def i15413(): Unit = {
+    val code =
+      """import scala.quoted.*
+        |class Macro:
+        |  inline def foo = Macro.fooImpl
+        |object Macro:
+        |  private def fooImpl = {}
+      """.stripMargin
+    checkBCode(code) { dir =>
+      val privateAccessors = Opcodes.ACC_PRIVATE | Opcodes.ACC_PROTECTED
+
+      // For 3.0-3.3 compat
+      val macroClass = loadClassNode(dir.lookupName("Macro.class", directory = false).input, skipDebugInfo = false)
+      val accessorOld  = getMethod(macroClass, "Macro$$inline$fooImpl")
+      assert(accessorOld.signature == "()V")
+      assert((accessorOld.access & privateAccessors) == 0)
+
+      // For 3.4+
+      val accessorsClass = loadClassNode(dir.lookupName("Macro$inline$accessors.class", directory = false).input, skipDebugInfo = false)
+      val accessorNew  = getMethod(accessorsClass, "inline$fooImpl")
+      assert(accessorNew.signature == "()V")
+      assert((accessorNew.access & privateAccessors) == 0)
+    }
+  }
+
+  @Test
+  def i15413b(): Unit = {
+    val code =
+      """package foo
+        |class C:
+        |  inline def baz = D.bazImpl
+        |object D:
+        |  private[foo] def bazImpl = {}
+      """.stripMargin
+    checkBCode(code) { dir =>
+      val privateAccessors = Opcodes.ACC_PRIVATE | Opcodes.ACC_PROTECTED
+
+      // For 3.0-3.3 compat
+      val barClass = loadClassNode(dir.subdirectoryNamed("foo").lookupName("C.class", directory = false).input, skipDebugInfo = false)
+      val accessorOld  = getMethod(barClass, "inline$bazImpl$i1")
+      assert(accessorOld.desc == "(Lfoo/D$;)V", accessorOld.desc)
+      assert((accessorOld.access & privateAccessors) == 0)
+
+      // For 3.4+
+      val accessorsClass = loadClassNode(dir.subdirectoryNamed("foo").lookupName("C$inline$accessors.class", directory = false).input, skipDebugInfo = false)
+      val accessorNew  = getMethod(accessorsClass, "inline$bazImpl")
+      assert(accessorNew.signature == "()V", accessorNew.signature)
+      assert((accessorNew.access & privateAccessors) == 0)
+    }
+  }
 }
 
 object invocationReceiversTestCode {

tests/pos-macros/i15413/Macro_1.scala

@@ -0,0 +1,7 @@
+import scala.quoted.*
+
+class Macro:
+  inline def foo = ${ Macro.fooImpl }
+
+object Macro:
+  private def fooImpl(using Quotes) = '{}

tests/pos-macros/i15413/Test_2.scala

@@ -0,0 +1,2 @@
+def test =
+  new Macro().foo

tests/pos-macros/i15413b/Macro_1.scala

@@ -0,0 +1,5 @@
+import scala.quoted.*
+
+inline def foo = ${ fooImpl }
+
+private def fooImpl(using Quotes) = '{}

tests/pos-macros/i15413b/Test_2.scala

@@ -0,0 +1 @@
+def test = foo

tests/pos-macros/i15413c/Macro.scala

@@ -0,0 +1,7 @@
+import scala.quoted.*
+
+class Macro:
+  inline def foo = ${ Macro.fooImpl }
+
+object Macro:
+  private def fooImpl(using Quotes) = '{}

tests/pos-macros/i15413c/Test.scala

@@ -0,0 +1,2 @@
+def test =
+  new Macro().foo

tests/pos-macros/i15413d/Macro.scala

@@ -0,0 +1,5 @@
+import scala.quoted.*
+
+inline def foo = ${ fooImpl }
+
+private def fooImpl(using Quotes) = '{}

tests/pos-macros/i15413d/Test.scala

@@ -0,0 +1 @@
+def test = foo

tests/run-macros/i13215-compat-3.1/A_1_c3.1.0.scala

@@ -0,0 +1,6 @@
+package foo
+
+trait Bar:
+  inline def baz = Baz
+
+private[foo] object Baz

tests/run-macros/i13215-compat-3.1/A_3.scala

@@ -0,0 +1,6 @@
+package foo
+
+trait Bar:
+  inline def baz = Baz
+
+private[foo] object Baz

tests/run-macros/i13215-compat-3.1/B_2.scala

@@ -0,0 +1,22 @@
+// We first compile A using 3.1 to generate the old accessors
+// Then we compile this file to link against the old accessors
+// Finally we recompile A using the current compiler to generate a version
+// of A that contains the new accessors (and the old for backwards compat)
+
+@main def Test =
+  val bar: foo.Bar = new foo.Bar{}
+  bar.baz // test that old accessor links in 3.4+
+
+  // Check that both accessors exist in the bytecode
+  val barMethods =
+    java.lang.Class.forName("foo.Bar").getMethods()
+      .filter(_.getName().contains("inline"))
+      .filter(x => (x.getModifiers() & java.lang.reflect.Modifier.STATIC) == 0)
+      .map(_.getName())
+  val barObjectMethods =
+    java.lang.Class.forName("foo.Bar$inline$accessors").getMethods()
+    .filter(_.getName().contains("inline"))
+    .map(_.getName())
+
+  println("3.0-3.3 inline accessor: " + barMethods.toList)
+  println("3.4+ inline accessor: " + barObjectMethods.toList)

tests/run-macros/i15413-compat-3.1.check

@@ -0,0 +1,2 @@
+3.0-3.3 inline accessor: List(Macro$$inline$fooImpl)
+3.4+ inline accessor: List(inline$fooImpl)

tests/run-macros/i15413-compat-3.1/Macro_1_c3.1.0.scala

@@ -0,0 +1,7 @@
+import scala.quoted.*
+
+class Macro:
+  inline def foo = /*${*/ Macro.fooImpl /*}*/
+
+object Macro:
+  private def fooImpl/*(using Quotes)*/ = {}