From 5f4011ef2969e4c4ac93f570bef45e9afb65bb9a Mon Sep 17 00:00:00 2001
From: Jason Zaugg <jzaugg@gmail.com>
Date: Wed, 9 Oct 2013 13:10:28 +0200
Subject: [backport] SI-7902 Fix spurious kind error due to an unitialized
 symbol

Tracked down this error:

    <none> is invariant, but type Y2 is declared covariant
    <none>'s bounds<notype> are stricter than type X2's declared bounds >: Nothing <: Any, <none>'s bounds<notype> are stricter than type Y2's declared bounds >: Nothing <: Any

to `Symbol#typeParams` returning `List(NoSymbol)` if the symbol
was not initialized.

This happends in the enclosed test for:

    // checkKindBoundsHK()
    hkArgs   = List(type M3)
    hkParams = List(type M2)

This commit forces the symbol of the higher-kinded type argument
before checking kind conformance.

A little backstory:

The `List(NoSymbol)` arises from:

    class PolyTypeCompleter... {
      // @M. If `owner` is an abstract type member, `typeParams` are all NoSymbol (see comment in `completerOf`),
      // otherwise, the non-skolemized (external) type parameter symbols
      override val typeParams = tparams map (_.symbol)

The variation that triggers this problem gets into the kind
conformance checks quite early on, during naming of:

    private[this] val x = ofType[InSeq]

The inferred type of which is forced during:

    def addDerivedTrees(typer: Typer, stat: Tree): List[Tree] = stat match {
      case vd @ ValDef(mods, name, tpt, rhs) if !noFinishGetterSetter(vd) =>
        // If we don't save the annotations, they seem to wander off.
        val annotations = stat.symbol.initialize.annotations

(cherry picked from commit 03a06e02483eaf442158339c2edd6bcfd99847a3)
---
 src/reflect/scala/reflect/internal/Kinds.scala | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/reflect/scala/reflect/internal/Kinds.scala b/src/reflect/scala/reflect/internal/Kinds.scala
index 08686832ef..3ab7b20ecd 100644
--- a/src/reflect/scala/reflect/internal/Kinds.scala
+++ b/src/reflect/scala/reflect/internal/Kinds.scala
@@ -184,6 +184,7 @@ trait Kinds {
           )
         }
         else {
+          hkarg.initialize // SI-7902 otherwise hkarg.typeParams yields List(NoSymbol)!
           debuglog("checkKindBoundsHK recursing to compare params of "+ hkparam +" with "+ hkarg)
           kindErrors ++= checkKindBoundsHK(
             hkarg.typeParams,
@@ -229,4 +230,4 @@ trait Kinds {
       }
     }
   }
-}
\ No newline at end of file
+}
-- 
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