Keep inlined nodes until backend phase

Refactoring of inlined nodes to simplify the work on #17055.
This work is based on #18229.

Author: Tetchki

compiler/src/dotty/tools/backend/jvm/BCodeBodyBuilder.scala

@@ -25,6 +25,7 @@ import dotty.tools.dotc.core.Contexts._
 import dotty.tools.dotc.core.Phases._
 import dotty.tools.dotc.core.Decorators.em
 import dotty.tools.dotc.report
+import dotty.tools.dotc.inlines.Inlines
 
 /*
  *
@@ -479,6 +480,10 @@ trait BCodeBodyBuilder extends BCodeSkelBuilder {
         case t: TypeApply => // dotty specific
           generatedType = genTypeApply(t)
 
+        case inlined @ Inlined(_, _, _) => 
+          genLoadTo(Inlines.dropInlined(inlined) , expectedType, dest)
+          generatedDest = dest
+
         case _ => abort(s"Unexpected tree in genLoad: $tree/${tree.getClass} at: ${tree.span}")
       }
 

compiler/src/dotty/tools/backend/sjs/JSCodeGen.scala

@@ -36,6 +36,7 @@ import dotty.tools.dotc.transform.sjs.JSSymUtils._
 
 import JSEncoding._
 import ScopedVar.withScopedVars
+import dotty.tools.dotc.inlines.Inlines
 
 /** Main codegen for Scala.js IR.
  *
@@ -1930,6 +1931,9 @@ class JSCodeGen()(using genCtx: Context) {
       case EmptyTree =>
         js.Skip()
 
+      case inlined @ Inlined(_, _, _) =>
+        genStatOrExpr(Inlines.dropInlined(inlined), isStat)
+
       case _ =>
         throw new FatalError("Unexpected tree in genExpr: " +
             tree + "/" + tree.getClass + " at: " + (tree.span: Position))

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

@@ -897,7 +897,7 @@ object Erasure {
 
     override def typedInlined(tree: untpd.Inlined, pt: Type)(using Context): Tree =
       super.typedInlined(tree, pt) match {
-        case tree: Inlined => Inlines.dropInlined(tree)
+        case tree: Inlined => tree //Inlines.dropInlined(tree)
       }
 
     override def typedValDef(vdef: untpd.ValDef, sym: Symbol)(using Context): Tree =

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

@@ -17,6 +17,7 @@ import Names._
 import NameKinds._
 import NameOps._
 import ast.Trees._
+import dotty.tools.dotc.inlines.Inlines
 
 object Mixin {
   val name: String = "mixin"
@@ -221,6 +222,7 @@ class Mixin extends MiniPhase with SymTransformer { thisPhase =>
             case _ =>
           }
           (scall, stats ::: inits, args)
+      case inlined @ Inlined(_, _, _) => transformConstructor(Inlines.dropInlined(inlined) )
       case _ =>
         val Apply(sel @ Select(New(_), nme.CONSTRUCTOR), args) = tree: @unchecked
         val (callArgs, initArgs) = if (tree.symbol.owner.is(Trait)) (Nil, args) else (args, Nil)