Fix #947

src/dotty/tools/dotc/ast/Desugar.scala

@@ -517,6 +517,12 @@ object desugar {
       }
   }
 
+  /** Expand variable identifier x to x @ _ */
+  def patternVar(tree: Tree)(implicit ctx: Context) = {
+    val Ident(name) = tree
+    Bind(name, Ident(nme.WILDCARD)).withPos(tree.pos)
+  }
+
   def defTree(tree: Tree)(implicit ctx: Context): Tree = tree match {
     case tree: ValDef => valDef(tree)
     case tree: TypeDef => if (tree.isClassDef) classDef(tree) else typeDef(tree)

src/dotty/tools/dotc/typer/Typer.scala

@@ -253,8 +253,8 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
     if (ctx.mode is Mode.Pattern) {
       if (name == nme.WILDCARD)
         return tree.withType(pt)
-      if (isVarPattern(tree))
-        return typed(untpd.Bind(name, untpd.Ident(nme.WILDCARD)).withPos(tree.pos), pt)
+      if (isVarPattern(tree) && name.isTermName)
+        return typed(desugar.patternVar(tree), pt)
     }
 
     val saved = importedFromRoot
@@ -848,7 +848,12 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
         args = args.take(tparams.length)
       }
       def typedArg(arg: untpd.Tree, tparam: Symbol) = {
-        val arg1 = typed(arg, if (ctx.mode is Mode.Pattern) tparam.info else WildcardType)
+        val (desugaredArg, argPt) =
+          if (ctx.mode is Mode.Pattern)
+            (if (isVarPattern(arg)) desugar.patternVar(arg) else arg, tparam.info)
+          else
+            (arg, WildcardType)
+        val arg1 = typed(desugaredArg, argPt)
         adaptTypeArg(arg1, if (tparam.isCompleted) tparam.info else WildcardType)
       }
       val args1 = args.zipWithConserve(tparams)(typedArg(_, _)).asInstanceOf[List[Tree]]

test/dotc/scala-collections.whitelist

@@ -86,6 +86,8 @@
 #./scala-scala/src/library/scala/collection/mutable/IndexedSeq.scala
 #./scala-scala/src/library/scala/collection/mutable/ListBuffer.scala
 
+./scala-scala/src/library/scala/collection/mutable/ArrayBuilder.scala
+
 ./scala-scala/src/library/scala/collection/immutable/Stack.scala
 ./scala-scala/src/library/scala/collection/immutable/StringLike.scala
 ./scala-scala/src/library/scala/collection/immutable/StringOps.scala
@@ -167,7 +169,7 @@
 ./scala-scala/src/library/scala/collection/SeqExtractors.scala
 
 # https://github.com/lampepfl/dotty/issues/945
-#./scala-scala/src/library/scala/collection/SeqLike.scala
+./scala-scala/src/library/scala/collection/SeqLike.scala
 
 ./scala-scala/src/library/scala/collection/SeqProxy.scala
 ./scala-scala/src/library/scala/collection/SeqProxyLike.scala

tests/pos/i947.scala

@@ -0,0 +1,16 @@
+object Test {
+
+  class c {
+
+    private var x: Int = 0
+
+    override def equals(other: Any) = other match {
+      case o: c => x == o.x
+      case xs: List[c] => false
+      case ys: List[d18383] => false
+      case _ => false
+    }
+
+
+  }
+}

tests/pos/implicits2.scala

@@ -16,4 +16,10 @@ object implicits2 {
 
   val x: scala.collection.immutable.WrappedString = "abc"
 
+  implicit val (xx: String, y: Int) = ("a", 22)
+
+  def main(args: Array[String]) = {
+    println(implicitly[String])
+    println(implicitly[Int])
+  }
 }