work around incorrectly unexpanded names

src/compiler/scala/tools/nsc/transform/Constructors.scala

@@ -474,15 +474,21 @@ abstract class Constructors extends Statics with Transform with TypingTransforme
     def usesSpecializedField = intoConstructor.usesSpecializedField
 
     // The constructor parameter corresponding to an accessor
-    def parameter(acc: Symbol): Symbol = parameterNamed(acc.unexpandedName.getterName)
+    def parameter(acc: Symbol): Symbol = {
+      import scala.util.Try
+      //works around the edge case where unexpandedName over-unexpands shenanigans like literal $$ or `$#`
+      def unexpanded = parameterNamed(acc.unexpandedName.getterName)
+      def expanded = parameterNamed(acc.getterName)
+      unexpanded.orElse(expanded).swap.map(abort).merge
+    }
 
-    // The constructor parameter with given name. This means the parameter
-    // has given name, or starts with given name, and continues with a `$` afterwards.
-    def parameterNamed(name: Name): Symbol =
+    // The constructor parameter with given getter name. This means the parameter name
+    // decodes to the same name that the getter decodes to
+    def parameterNamed(name: Name): Either[String, Symbol] =  
       primaryConstrParams.filter(_.name.decodedName == name.decodedName) match {
-        case List(p) => p
-        case Nil     => abort(s"$name not in $primaryConstrParams")
-        case ps      => abort(s"$name matches multiple constructor paramters $ps")
+        case List(p) => Right(p)
+        case Nil     => Left(s"No constructor parameter named $name (decoded to ${name.decodedName}) found in list of constructor parameters $primaryConstrParams (decoded to ${primaryConstrParams.map(_.decodedName)})")
+        case ps      => Left(s"$name matches multiple constructor parameters $ps")
       }
 
     // A transformer for expressions that go into the constructor
@@ -529,7 +535,7 @@ abstract class Constructors extends Statics with Transform with TypingTransforme
           else if (canBeSupplanted(tree.symbol))
             gen.mkAttributedIdent(parameter(tree.symbol)) setPos tree.pos
           else if (tree.symbol.outerSource == clazz && !isDelayedInitSubclass)
-            gen.mkAttributedIdent(parameterNamed(nme.OUTER)) setPos tree.pos
+            gen.mkAttributedIdent(parameterNamed(nme.OUTER).fold(abort, identity)).setPos(tree.pos)
           else
             super.transform(tree)
 

src/reflect/scala/reflect/internal/StdNames.scala

@@ -437,6 +437,9 @@ trait StdNames {
      *  Look backward from the end of the string for "$$", and take the
      *  part of the string after that; but if the string is "$$$" or longer,
      *  be sure to retain the extra dollars.
+     *  If the name happens to be a back quoted name containing literal $$
+     *  or $ followed by an operator that gets encoded, go directly to compiler
+     *  crash. Do not pass go and don't even think about collecting any $$
      */
     def unexpandedName(name: Name): Name = name lastIndexOf "$$" match {
       case 0 | -1 => name

test/files/run/t10625.check

@@ -0,0 +1,3 @@
+1
+1
+Some(1)

test/files/run/t10625.scala

@@ -0,0 +1,8 @@
+case class WhyNot(`^$#`: Int)
+object Test extends App {
+  val wn = WhyNot(1)
+  println(wn.`^$#`)
+  val WhyNot(i) = wn
+  println(i)
+  println(WhyNot.unapply(wn))
+}