Scala.js: Properly call default param getters for nested JS ctors

Forward port of
scala-js/scala-js@491176f

Author: sjrd

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

@@ -1140,9 +1140,14 @@ class JSCodeGen()(using genCtx: Context) {
 
   private def genSecondaryJSClassCtor(dd: DefDef): SplitSecondaryJSCtor = {
     val sym = dd.symbol
-    val Block(stats, _) = dd.rhs
     assert(!sym.isPrimaryConstructor, s"called with primary ctor $sym")
 
+    def flattenBlocks(t: Tree): List[Tree] = t match {
+      case Block(stats, expr) => (stats :+ expr).flatMap(flattenBlocks)
+      case _                  => t :: Nil
+    }
+    val stats = flattenBlocks(dd.rhs)
+
     val beforeThisCall = List.newBuilder[js.Tree]
     var thisCall: Option[(Symbol, List[js.Tree])] = None
     val afterThisCall = List.newBuilder[js.Tree]
@@ -1167,6 +1172,8 @@ class JSCodeGen()(using genCtx: Context) {
       }
     }
 
+    assert(thisCall.isDefined,
+        i"could not find the this() call in secondary JS constructor at ${dd.sourcePos}:\n${stats.map(_.show).mkString("\n")}")
     val Some((targetCtor, ctorArgs)) = thisCall
 
     val params = dd.paramss.flatten.map(_.symbol)
@@ -1175,16 +1182,18 @@ class JSCodeGen()(using genCtx: Context) {
         ctorArgs, afterThisCall.result())
   }
 
-  private def genJSClassCtorDispatch(sym: Symbol, allParams: List[Symbol],
+  private def genJSClassCtorDispatch(ctorSym: Symbol, allParamSyms: List[Symbol],
       overloadNum: Int): (jsExportsGen.Exported, List[js.ParamDef]) = {
 
-    implicit val pos: SourcePosition = sym.sourcePos
+    implicit val pos: SourcePosition = ctorSym.sourcePos
+
+    val allParamsAndInfos = allParamSyms.zip(ctorSym.jsParamInfos)
 
     /* `allParams` are the parameters as seen from inside the constructor body,
      * i.e., the ones generated by the trees in the constructor body.
      */
     val (captureParamsAndInfos, normalParamsAndInfos) =
-      allParams.zip(sym.jsParamInfos).partition(_._2.capture)
+      allParamsAndInfos.partition(_._2.capture)
 
     /* For class captures, we need to generate different names than the ones
      * used by the constructor body. This is necessary so that we can forward
@@ -1203,13 +1212,14 @@ class JSCodeGen()(using genCtx: Context) {
 
     val normalInfos = normalParamsAndInfos.map(_._2).toIndexedSeq
 
-    val jsExport = new jsExportsGen.Exported(sym, normalInfos) {
+    val jsExport = new jsExportsGen.Exported(ctorSym, normalInfos) {
       def genBody(formalArgsRegistry: jsExportsGen.FormalArgsRegistry): js.Tree = {
         val paramAssigns = for {
           ((param, info), i) <- normalParamsAndInfos.zipWithIndex
         } yield {
-          val rhs = jsExportsGen.genScalaArg(this, i, formalArgsRegistry, info, static = true)(
-              prevArgsCount => allParams.take(prevArgsCount).map(genVarRef(_)))
+          val rhs = jsExportsGen.genScalaArg(this, i, formalArgsRegistry, info, static = true,
+              captures = captureParamsAndInfos.map(pi => genVarRef(pi._1)))(
+              prevArgsCount => normalParamsAndInfos.take(prevArgsCount).map(pi => genVarRef(pi._1)))
 
           js.Assign(genVarRef(param), rhs)
         }
@@ -3511,7 +3521,7 @@ class JSCodeGen()(using genCtx: Context) {
   }
 
   /** Gen a statically linked call to an instance method. */
-  private def genApplyMethodMaybeStatically(receiver: js.Tree, method: Symbol,
+  def genApplyMethodMaybeStatically(receiver: js.Tree, method: Symbol,
       arguments: List[js.Tree])(implicit pos: Position): js.Tree = {
     if (method.isPrivate || method.isClassConstructor)
       genApplyMethodStatically(receiver, method, arguments)

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

@@ -13,6 +13,7 @@ import Denotations._
 import Flags._
 import Names._
 import NameKinds.DefaultGetterName
+import NameOps._
 import Periods._
 import Phases._
 import StdNames._
@@ -681,7 +682,7 @@ final class JSExportsGen(jsCodeGen: JSCodeGen)(using Context) {
     val varDefs = new mutable.ListBuffer[js.VarDef]
 
     for ((param, i) <- exported.params.zipWithIndex) {
-      val rhs = genScalaArg(exported, i, formalArgsRegistry, param, static)(
+      val rhs = genScalaArg(exported, i, formalArgsRegistry, param, static, captures = Nil)(
           prevArgsCount => varDefs.take(prevArgsCount).toList.map(_.ref))
 
       varDefs += js.VarDef(freshLocalIdent("prep" + i), NoOriginalName, rhs.tpe, mutable = false, rhs)
@@ -698,7 +699,7 @@ final class JSExportsGen(jsCodeGen: JSCodeGen)(using Context) {
    *  (unboxing and default parameter handling).
    */
   def genScalaArg(exported: Exported, paramIndex: Int, formalArgsRegistry: FormalArgsRegistry,
-      param: JSParamInfo, static: Boolean)(
+      param: JSParamInfo, static: Boolean, captures: List[js.Tree])(
       previousArgsValues: Int => List[js.Tree])(
       implicit pos: SourcePosition): js.Tree = {
 
@@ -713,7 +714,7 @@ final class JSExportsGen(jsCodeGen: JSCodeGen)(using Context) {
       if (exported.hasDefaultAt(paramIndex)) {
         // If argument is undefined and there is a default getter, call it
         js.If(js.BinaryOp(js.BinaryOp.===, jsArg, js.Undefined()), {
-          genCallDefaultGetter(exported.sym, paramIndex, static)(previousArgsValues)
+          genCallDefaultGetter(exported.sym, paramIndex, static, captures)(previousArgsValues)
         }, {
           unboxedArg
         })(unboxedArg.tpe)
@@ -724,7 +725,8 @@ final class JSExportsGen(jsCodeGen: JSCodeGen)(using Context) {
     }
   }
 
-  private def genCallDefaultGetter(sym: Symbol, paramIndex: Int, static: Boolean)(
+  private def genCallDefaultGetter(sym: Symbol, paramIndex: Int,
+      static: Boolean, captures: List[js.Tree])(
       previousArgsValues: Int => List[js.Tree])(
       implicit pos: SourcePosition): js.Tree = {
 
@@ -735,9 +737,30 @@ final class JSExportsGen(jsCodeGen: JSCodeGen)(using Context) {
     assert(!defaultGetterDenot.isOverloaded, i"found overloaded default getter $defaultGetterDenot")
     val defaultGetter = defaultGetterDenot.symbol
 
-    val targetTree =
-      if (sym.isClassConstructor || static) genLoadModule(targetSym)
-      else js.This()(encodeClassType(targetSym))
+    val targetTree = {
+      if (sym.isClassConstructor || static) {
+        if (targetSym.isStatic) {
+          assert(captures.isEmpty, i"expected empty captures for ${targetSym.fullName} at $pos")
+          genLoadModule(targetSym)
+        } else {
+          assert(captures.sizeIs == 1, "expected exactly one capture")
+
+          // Find the module accessor.
+          val outer = targetSym.originalOwner
+          val name = atPhase(typerPhase)(targetSym.name.unexpandedName).sourceModuleName
+          val modAccessor = outer.info.memberBasedOnFlags(name, required = Module).symbol
+          assert(modAccessor.exists, i"could not find module accessor for ${targetSym.fullName} at $pos")
+
+          val receiver = captures.head
+          if (outer.isJSType)
+            genApplyJSClassMethod(receiver, modAccessor, Nil)
+          else
+            genApplyMethodMaybeStatically(receiver, modAccessor, Nil)
+        }
+      } else {
+        js.This()(encodeClassType(targetSym))
+      }
+    }
 
     // Pass previous arguments to defaultGetter
     val defaultGetterArgs = previousArgsValues(defaultGetter.info.paramInfoss.head.size)