Move trait inlining into Inlining phase

Author: timotheeandres

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

@@ -56,7 +56,7 @@ object Inlines:
 
   /** Can a call to method `meth` be inlined? */
   def isInlineable(meth: Symbol)(using Context): Boolean =
-    meth.is(Inline) && meth.hasAnnotation(defn.BodyAnnot) && !inInlineMethod
+    meth.isInlineMethod && meth.hasAnnotation(defn.BodyAnnot) && !inInlineMethod
 
   def isInlineableFromInlineTrait(inlinedTraitSym: ClassSymbol, member: tpd.Tree)(using Context): Boolean =
     !(member.isInstanceOf[tpd.TypeDef] && inlinedTraitSym.typeParams.contains(member.symbol))
@@ -72,15 +72,19 @@ object Inlines:
       )
       && !ctx.typer.hasInliningErrors
       && !ctx.base.stopInlining
+      && !ctx.owner.isInlineTrait
 
     tree match
       case Block(_, expr) =>
         needsInlining(expr)
       case tdef @ TypeDef(_, impl: Template) =>
-        !tdef.symbol.isInlineTrait && impl.parents.exists(_.symbol.isInlineTrait) && isInlineableInCtx
+        !tdef.symbol.isInlineTrait && impl.parents.map(symbolFromParent).exists(_.isInlineTrait) && isInlineableInCtx
       case _ =>
         isInlineable(tree.symbol) && !tree.tpe.widenTermRefExpr.isInstanceOf[MethodOrPoly] && isInlineableInCtx
 
+  private def symbolFromParent(parent: Tree)(using Context): Symbol =
+    if parent.symbol.isConstructor then parent.symbol.owner else parent.symbol
+
   private def needsTransparentInlining(tree: Tree)(using Context): Boolean =
     tree.symbol.is(Transparent)
     || ctx.mode.is(Mode.ForceInline)
@@ -184,10 +188,22 @@ object Inlines:
     tree2
   end inlineCall
 
-  def inlineParentTrait(parent: tpd.Tree, overriddenDecls: Set[Symbol])(using Context): List[Tree] =
-    val traitSym = if parent.symbol.isConstructor then parent.symbol.owner else parent.symbol
-    if traitSym.isInlineTrait then InlineParentTrait(parent, traitSym.asClass).expandDefs(overriddenDecls)
-    else Nil
+  def inlineParentInlineTraits(cls: Tree)(using Context): Tree =
+    cls match {
+      case cls @ TypeDef(_, impl: Template) =>
+        val overriddenSyms = cls.symbol.info.decls.toList.flatMap(_.allOverriddenSymbols).toSet
+        val inlineDefs = impl.parents.flatMap(
+          parent =>
+            if symbolFromParent(parent).isInlineTrait then
+              InlineParentTrait(parent)(using ctx.withOwner(cls.symbol)).expandDefs(overriddenSyms)
+            else
+              Nil
+        )
+        val impl1 = cpy.Template(impl)(body = inlineDefs ::: impl.body)
+        cpy.TypeDef(cls)(rhs = impl1)
+      case _ =>
+        cls
+    }
 
   /** Try to inline a pattern with an inline unapply method. Fail with error if the maximal
    *  inline depth is exceeded.
@@ -480,10 +496,12 @@ object Inlines:
     end expand
   end InlineCall
 
-  private class InlineParentTrait(parent: tpd.Tree, parentSym: ClassSymbol)(using Context) extends Inliner(parent):
+  private class InlineParentTrait(parent: tpd.Tree)(using Context) extends Inliner(parent):
     import tpd._
     import Inlines.*
 
+    private val parentSym = symbolFromParent(parent)
+
     private val thisInlineTrait = ThisType.raw(TypeRef(ctx.owner.prefix, ctx.owner))
 
     def expandDefs(overriddenDecls: Set[Symbol]): List[Tree] =

compiler/src/dotty/tools/dotc/transform/Inlining.scala

@@ -72,6 +72,10 @@ class Inlining extends MacroTransform {
 
     override def transform(tree: Tree)(using Context): Tree = {
       tree match
+        case tree: TypeDef if Inlines.needsInlining(tree) =>
+          val tree1 = super.transform(tree)
+          if tree1.tpe.isError then tree1
+          else Inlines.inlineParentInlineTraits(tree1)
         case tree: MemberDef =>
           if tree.symbol.is(Inline) then tree
           else if tree.symbol.is(Param) then super.transform(tree)

compiler/src/dotty/tools/dotc/transform/PostTyper.scala

@@ -388,6 +388,8 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer { thisPhase
           val tree1 = cpy.DefDef(tree)(rhs = normalizeErasedRhs(tree.rhs, tree.symbol))
           processValOrDefDef(superAcc.wrapDefDef(tree1)(super.transform(tree1).asInstanceOf[DefDef]))
         case tree: TypeDef =>
+          if tree.symbol.isInlineTrait then
+            ctx.compilationUnit.needsInlining = true
           registerIfHasMacroAnnotations(tree)
           val sym = tree.symbol
           if (sym.isClass)

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

@@ -2653,13 +2653,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
       cdef.withType(UnspecifiedErrorType)
     else {
       val dummy = localDummy(cls, impl)
-      val inlineTraitDefs =
-        if ctx.isAfterTyper || cls.isInlineTrait then
-          Nil
-        else
-          val overriddenSyms = cls.info.decls.toList.flatMap(_.allOverriddenSymbols).toSet
-          parents1.flatMap(parent => Inlines.inlineParentTrait(parent, overriddenSyms))
-      val body1 = addAccessorDefs(cls, typedStats(impl.body, dummy)(using ctx.inClassContext(self1.symbol))._1) ::: inlineTraitDefs
+      val body1 = addAccessorDefs(cls, typedStats(impl.body, dummy)(using ctx.inClassContext(self1.symbol))._1)
 
       if !ctx.isAfterTyper && cls.isInlineTrait then
         val membersToInline = body1.filter(member => Inlines.isInlineableFromInlineTrait(cls, member))