Add memoize utility function

scalafix/rules/src/main/scala/rsc/rules/semantics/Scopes.scala

@@ -3,6 +3,7 @@
 package rsc.rules.semantics
 
 import rsc.rules.semantics.Scope.MemberKey
+import rsc.rules.util.memoize
 import scala.collection.mutable
 import scala.meta._
 import scala.meta.internal.{semanticdb => s}
@@ -15,12 +16,10 @@ sealed trait Scope {
 
   def getRename(name: n.Name): String = ""
 
-  private val _cache = new java.util.HashMap[MemberKey, String]
-
   protected def member(symtab: Symtab, sym: String, name: n.Name): String =
-    _cache.computeIfAbsent(MemberKey(symtab, sym, name), _member)
+    _member(MemberKey(symtab, sym, name))
 
-  private def _member(key: MemberKey): String = {
+  private val _member: MemberKey => String = memoize { key: MemberKey =>
     val MemberKey(symtab, sym, name) = key
 
     def getInfo(desc: Descriptor): Option[s.SymbolInformation] =

scalafix/rules/src/main/scala/rsc/rules/util/MemoizeUtil.scala

@@ -0,0 +1,14 @@
+package rsc.rules.util
+
+trait MemoizeUtil {
+
+  /**
+   * Memoize the results of a function call to prevent repeated calls
+   */
+  def memoize[I, O](f: I => O): I => O = {
+    val _cache = new java.util.HashMap[I, O]
+
+    key =>
+      _cache.computeIfAbsent(key, _ => f(key))
+  }
+}

scalafix/rules/src/main/scala/rsc/rules/util/package.scala

@@ -0,0 +1,3 @@
+package rsc.rules
+
+package object util extends MemoizeUtil