Traverse all of bindings to compute reference counts of bindings

We used to traverse only the RHS of bindings, but this misses references
that are part of the binding's type.

Author: odersky

compiler/src/dotty/tools/dotc/typer/Inliner.scala

@@ -579,19 +579,13 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(implicit ctx: Context) {
     }
     val countRefs = new TreeTraverser {
       override def traverse(t: Tree)(implicit ctx: Context) = {
+        def updateRefCount(sym: Symbol, inc: Int) =
+          for (x <- refCount.get(sym)) refCount(sym) = x + inc
         t match {
-          case t: RefTree =>
-            refCount.get(t.symbol) match {
-              case Some(x) => refCount(t.symbol) = x + 1
-              case none =>
-            }
+          case t: RefTree => updateRefCount(t.symbol, 1)
           case _: New | _: TypeTree =>
             t.tpe.foreachPart {
-              case ref: TermRef =>
-                refCount.get(ref.symbol) match {
-                  case Some(x) => refCount(ref.symbol) = x + 2
-                  case none =>
-                }
+              case ref: TermRef => updateRefCount(ref.symbol, 2) // can't be inlined, so make sure refCount is at least 2
               case _ =>
             }
           case _ =>
@@ -600,7 +594,7 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(implicit ctx: Context) {
       }
     }
     countRefs.traverse(tree)
-    for (binding <- bindings) countRefs.traverse(binding.rhs)
+    for (binding <- bindings) countRefs.traverse(binding)
     val inlineBindings = new TreeMap {
       override def transform(t: Tree)(implicit ctx: Context) =
         super.transform {