SI-7228, bug in weak subtyping.

Another in the category of bugs which involve narrowing,
widening, mediuming, dealiasing, weakening, normalizing,
denormalizing, supernormalizing, subnormalizing, and
double-bounded supersubnormalizing.

This is probably not the ideal fix, but it is an improvement.

1 files changed, 10 insertions, 13 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
index 2331f82a58..29d4c8423b 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
@@ -268,7 +268,7 @@ trait Implicits {
    */
   object Function1 {
     val Sym = FunctionClass(1)
-    def unapply(tp: Type) = tp match {
+    def unapply(tp: Type) = tp baseType Sym match {
       case TypeRef(_, Sym, arg1 :: arg2 :: _) => Some((arg1, arg2))
       case _                                  => None
     }
@@ -431,10 +431,8 @@ trait Implicits {
       val start = if (Statistics.canEnable) Statistics.startTimer(matchesPtNanos) else null
       val result = normSubType(tp, pt) || isView && {
         pt match {
-          case TypeRef(_, Function1.Sym, arg1 :: arg2 :: Nil) =>
-            matchesPtView(tp, arg1, arg2, undet)
-          case _ =>
-            false
+          case Function1(arg1, arg2) => matchesPtView(tp, arg1, arg2, undet)
+          case _                     => false
         }
       }
       if (Statistics.canEnable) Statistics.stopTimer(matchesPtNanos, start)
@@ -576,20 +574,19 @@ trait Implicits {
 
       def fail(reason: String): SearchResult = failure(itree, reason)
       try {
-        val itree1 =
-          if (isView) {
-            val arg1 :: arg2 :: _ = pt.typeArgs
+        val itree1 = pt match {
+          case Function1(arg1, arg2) if isView =>
             typed1(
               atPos(itree.pos)(Apply(itree, List(Ident("<argument>") setType approximate(arg1)))),
               EXPRmode,
               approximate(arg2)
             )
-          }
-          else
-            typed1(itree, EXPRmode, wildPt)
-
-        if (context.hasErrors)
+          case _ => typed1(itree, EXPRmode, wildPt)
+        }
+        if (context.hasErrors) {
+          log("implicit adapt failed: " + context.errBuffer.head.errMsg)
           return fail(context.errBuffer.head.errMsg)
+        }
 
         if (Statistics.canEnable) Statistics.incCounter(typedImplicits)