Extract parts of defDefSig (& completeConstructor)

Author: dwijnand

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

@@ -1526,13 +1526,7 @@ class Namer { typer: Typer =>
       index(constr)
       index(rest)(using localCtx)
 
-      symbolOfTree(constr).info.stripPoly match // Completes constr symbol as a side effect
-        case mt: MethodType if cls.is(Case) && mt.isParamDependent =>
-          // See issue #8073 for background
-          report.error(
-              em"""Implementation restriction: case classes cannot have dependencies between parameters""",
-              cls.srcPos)
-        case _ =>
+      checkCaseClassParamDependencies(symbolOfTree(constr).info, cls) // Completes constr symbol as a side effect
 
       tempInfo = denot.asClass.classInfo.integrateOpaqueMembers.asInstanceOf[TempClassInfo]
       denot.info = savedInfo
@@ -1860,31 +1854,6 @@ class Namer { typer: Typer =>
     // Beware: ddef.name need not match sym.name if sym was freshened!
     val isConstructor = sym.name == nme.CONSTRUCTOR
 
-    // A map from context-bounded type parameters to associated evidence parameter names
-    val witnessNamesOfParam = mutable.Map[TypeDef, List[TermName]]()
-    if !ddef.name.is(DefaultGetterName) && !sym.is(Synthetic) then
-      for params <- ddef.paramss; case tdef: TypeDef <- params do
-        for case WitnessNamesAnnot(ws) <- tdef.mods.annotations do
-          witnessNamesOfParam(tdef) = ws
-
-    /** Is each name in `wnames` defined somewhere in the longest prefix of all `params`
-     *  that have been typed ahead (i.e. that carry the TypedAhead attachment)?
-     */
-    def allParamsSeen(wnames: List[TermName], params: List[MemberDef]) =
-      (wnames.toSet[Name] -- params.takeWhile(_.hasAttachment(TypedAhead)).map(_.name)).isEmpty
-
-    /** Enter and typecheck parameter list.
-     *  Once all witness parameters for a context bound are seen, create a
-     *  context bound companion for it.
-     */
-    def completeParams(params: List[MemberDef])(using Context): Unit =
-      index(params)
-      for param <- params do
-        typedAheadExpr(param)
-        for (tdef, wnames) <- witnessNamesOfParam do
-          if wnames.contains(param.name) && allParamsSeen(wnames, params) then
-            addContextBoundCompanionFor(symbolOfTree(tdef), wnames, params.map(symbolOfTree))
-
     // The following 3 lines replace what was previously just completeParams(tparams).
     // But that can cause bad bounds being computed, as witnessed by
     // tests/pos/paramcycle.scala. The problematic sequence is this:
@@ -1914,33 +1883,10 @@ class Namer { typer: Typer =>
       for tparam <- ddef.leadingTypeParams yield typedAheadExpr(tparam).symbol
     if completedTypeParams.forall(_.isType) then
       completer.setCompletedTypeParams(completedTypeParams.asInstanceOf[List[TypeSymbol]])
-    ddef.trailingParamss.foreach(completeParams)
+    completeTrailingParamss(ddef, sym)
     val paramSymss = normalizeIfConstructor(ddef.paramss.nestedMap(symbolOfTree), isConstructor)
     sym.setParamss(paramSymss)
 
-    /** Under x.modularity, we add `tracked` to context bound witnesses
-     *  that have abstract type members
-     */
-    def needsTracked(sym: Symbol, param: ValDef)(using Context) =
-      !sym.is(Tracked)
-      && param.hasAttachment(ContextBoundParam)
-      && sym.info.memberNames(abstractTypeNameFilter).nonEmpty
-
-    /** Under x.modularity, set every context bound evidence parameter of a class to be tracked,
-     *  provided it has a type that has an abstract type member. Reset private and local flags
-     *  so that the parameter becomes a `val`.
-     */
-    def setTracked(param: ValDef): Unit =
-      val sym = symbolOfTree(param)
-      sym.maybeOwner.maybeOwner.infoOrCompleter match
-        case info: TempClassInfo if needsTracked(sym, param) =>
-          typr.println(i"set tracked $param, $sym: ${sym.info} containing ${sym.info.memberNames(abstractTypeNameFilter).toList}")
-          for acc <- info.decls.lookupAll(sym.name) if acc.is(ParamAccessor) do
-            acc.resetFlag(PrivateLocal)
-            acc.setFlag(Tracked)
-            sym.setFlag(Tracked)
-        case _ =>
-
     def wrapMethType(restpe: Type): Type =
       instantiateDependent(restpe, paramSymss)
       methodType(paramSymss, restpe, ddef.mods.is(JavaDefined))
@@ -1966,6 +1912,68 @@ class Namer { typer: Typer =>
       valOrDefDefSig(ddef, sym, paramSymss, wrapMethType)
   end defDefSig
 
+  def completeTrailingParamss(ddef: DefDef, sym: Symbol)(using Context): Unit =
+    // A map from context-bounded type parameters to associated evidence parameter names
+    val witnessNamesOfParam = mutable.Map[TypeDef, List[TermName]]()
+    if !ddef.name.is(DefaultGetterName) && !sym.is(Synthetic) then
+      for params <- ddef.paramss; case tdef: TypeDef <- params do
+        for case WitnessNamesAnnot(ws) <- tdef.mods.annotations do
+          witnessNamesOfParam(tdef) = ws
+
+    /** Is each name in `wnames` defined somewhere in the longest prefix of all `params`
+     *  that have been typed ahead (i.e. that carry the TypedAhead attachment)?
+     */
+    def allParamsSeen(wnames: List[TermName], params: List[MemberDef]) =
+      (wnames.toSet[Name] -- params.takeWhile(_.hasAttachment(TypedAhead)).map(_.name)).isEmpty
+
+    /** Enter and typecheck parameter list.
+     *  Once all witness parameters for a context bound are seen, create a
+     *  context bound companion for it.
+     */
+    def completeParams(params: List[MemberDef])(using Context): Unit =
+      index(params)
+      for param <- params do
+        typedAheadExpr(param)
+        for (tdef, wnames) <- witnessNamesOfParam do
+          if wnames.contains(param.name) && allParamsSeen(wnames, params) then
+            addContextBoundCompanionFor(symbolOfTree(tdef), wnames, params.map(symbolOfTree))
+
+    ddef.trailingParamss.foreach(completeParams)
+  end completeTrailingParamss
+
+  /** Checks an implementation restriction on case classes. */
+  def checkCaseClassParamDependencies(mt: Type, cls: Symbol)(using Context): Unit =
+    mt.stripPoly match
+      case mt: MethodType if cls.is(Case) && mt.isParamDependent =>
+        // See issue #8073 for background
+        report.error(
+            em"""Implementation restriction: case classes cannot have dependencies between parameters""",
+            cls.srcPos)
+      case _ =>
+
+  /** Under x.modularity, we add `tracked` to context bound witnesses
+   *  that have abstract type members
+   */
+  def needsTracked(sym: Symbol, param: ValDef)(using Context) =
+    !sym.is(Tracked)
+    && param.hasAttachment(ContextBoundParam)
+    && sym.info.memberNames(abstractTypeNameFilter).nonEmpty
+
+  /** Under x.modularity, set every context bound evidence parameter of a class to be tracked,
+   *  provided it has a type that has an abstract type member. Reset private and local flags
+   *  so that the parameter becomes a `val`.
+   */
+  def setTracked(param: ValDef)(using Context): Unit =
+    val sym = symbolOfTree(param)
+    sym.maybeOwner.maybeOwner.infoOrCompleter match
+      case info: TempClassInfo if needsTracked(sym, param) =>
+        typr.println(i"set tracked $param, $sym: ${sym.info} containing ${sym.info.memberNames(abstractTypeNameFilter).toList}")
+        for acc <- info.decls.lookupAll(sym.name) if acc.is(ParamAccessor) do
+          acc.resetFlag(PrivateLocal)
+          acc.setFlag(Tracked)
+          sym.setFlag(Tracked)
+      case _ =>
+
   def inferredResultType(
       mdef: ValOrDefDef,
       sym: Symbol,