Merge pull request scala#3524 from paulp/pr/8280

SI-8280 regression in implicit selection.

Author: adriaanm

src/compiler/scala/tools/nsc/typechecker/Implicits.scala

@@ -306,7 +306,10 @@ trait Implicits {
    */
   object Function1 {
     val Sym = FunctionClass(1)
-    def unapply(tp: Type) = tp baseType Sym match {
+    // It is tempting to think that this should be inspecting "tp baseType Sym"
+    // rather than tp. See test case run/t8280 and the commit message which
+    // accompanies it for explanation why that isn't done.
+    def unapply(tp: Type) = tp match {
       case TypeRef(_, Sym, arg1 :: arg2 :: _) => Some((arg1, arg2))
       case _                                  => None
     }

test/files/run/t8280.check

@@ -0,0 +1,9 @@
+Int
+Int
+Int
+Int
+Int
+Int
+Int
+Int
+Int

test/files/run/t8280.scala

@@ -0,0 +1,82 @@
+import scala.language.implicitConversions
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    Moop1.ob1
+    Moop1.ob2
+    Moop1.ob3
+    Moop2.ob1
+    Moop2.ob2
+    Moop2.ob3
+    Moop3.ob1
+    Moop3.ob2
+    Moop3.ob3
+  }
+}
+
+// int object vs.
+object Moop1 {
+  object ob1 {
+    implicit object f1 extends (Int => String) { def apply(x: Int): String = "Int" }
+    implicit object f2 extends (Long => String) { def apply(x: Long): String = "Long" }
+
+    println(5: String)
+  }
+  object ob2 {
+    implicit object f1 extends (Int => String) { def apply(x: Int): String = "Int" }
+    implicit def f2(x: Long): String = "Long"
+
+    println(5: String)
+  }
+  object ob3 {
+    implicit object f1 extends (Int => String) { def apply(x: Int): String = "Int" }
+    implicit val f2: Long => String = _ => "Long"
+
+    println(5: String)
+  }
+}
+
+// int def vs.
+object Moop2 {
+  object ob1 {
+    implicit def f1(x: Int): String = "Int"
+    implicit object f2 extends (Long => String) { def apply(x: Long): String = "Long" }
+
+    println(5: String)
+  }
+  object ob2 {
+    implicit def f1(x: Int): String = "Int"
+    implicit def f2(x: Long): String = "Long"
+
+    println(5: String)
+  }
+  object ob3 {
+    implicit def f1(x: Int): String = "Int"
+    implicit val f2: Long => String = _ => "Long"
+
+    println(5: String)
+  }
+}
+
+// int val vs.
+object Moop3 {
+  object ob1 {
+    implicit val f1: Int => String  = _ => "Int"
+    implicit object f2 extends (Long => String) { def apply(x: Long): String = "Long" }
+
+    println(5: String)
+  }
+  object ob2 {
+    implicit val f1: Int => String  = _ => "Int"
+    implicit def f2(x: Long): String = "Long"
+
+    println(5: String)
+  }
+  object ob3 {
+    implicit val f1: Int => String  = _ => "Int"
+    implicit val f2: Long => String = _ => "Long"
+
+    println(5: String)
+  }
+}
+