From 7adb4784bf484f8cf57b5edb612d2c4f34388237 Mon Sep 17 00:00:00 2001
From: Paul Phillips <paulp@improving.org>
Date: Sun, 4 Dec 2011 10:06:28 -0800
Subject: Tweaked ident suggestions.

Rolled damaru-levenshtein algorithm back to my original "pure"
version.  Cut max distance to 1.  Turned on by default because
now it offers nothing unexpected, and removed short-lived
-Ysuggest-idents option.
---
 .../scala/tools/nsc/settings/ScalaSettings.scala   |  1 -
 .../scala/tools/nsc/typechecker/Typers.scala       |  2 +-
 src/compiler/scala/tools/util/EditDistance.scala   | 31 +++++++++++-----------
 3 files changed, 16 insertions(+), 18 deletions(-)

(limited to 'src')

diff --git a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
index 1f8fa5bbe2..6be15e4e98 100644
--- a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
@@ -178,7 +178,6 @@ trait ScalaSettings extends AbsScalaSettings
 
   val exposeEmptyPackage = BooleanSetting("-Yexpose-empty-package", "Internal only: expose the empty package.").internalOnly()
   val YnoProductN = BooleanSetting ("-Yno-productN", "Do not add ProductN to case classes")
-  val suggestIdents = BooleanSetting("-Ysuggest-idents", "Suggest alternatives for `not found` identifiers")
 
   def stop = stopAfter
 
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 30d10325be..7671ccbed7 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -3874,7 +3874,7 @@ trait Typers extends Modes with Adaptations with PatMatVirtualiser {
                 else {
                   val similar = (
                     // name length check to limit unhelpful suggestions for e.g. "x" and "b1"
-                    if (settings.suggestIdents.value && name.length > 2) {
+                    if (name.length > 2) {
                       val allowed = (
                         startingIdentContext.enclosingContextChain
                             flatMap (ctx => ctx.scope.toList ++ ctx.imports.flatMap(_.allImportedSymbols))
diff --git a/src/compiler/scala/tools/util/EditDistance.scala b/src/compiler/scala/tools/util/EditDistance.scala
index 704286d47e..a8d7408532 100644
--- a/src/compiler/scala/tools/util/EditDistance.scala
+++ b/src/compiler/scala/tools/util/EditDistance.scala
@@ -8,22 +8,22 @@ package util
 
 object EditDistance {
   def similarString(name: String, allowed: TraversableOnce[String]): String = {
-    val suggested = suggestions(name, allowed.toSeq, maxDistance = 2, maxSuggestions = 2)
-    if (suggested.isEmpty) "" 
+    val suggested = suggestions(name, allowed.toSeq, maxDistance = 1, maxSuggestions = 2)
+    if (suggested.isEmpty) ""
     else suggested.mkString(" (similar: ", ", ", ")")
   }
 
-  def suggestions(a: String, bs: Seq[String], maxDistance: Int = 3, maxSuggestions: Int = 3): Seq[String] =
-    bs.map { b => (b, distance(a, b) ) } filter (_._2 <= maxDistance) sortBy(_._2) take(maxSuggestions) map(_._1)
+  def suggestions(a: String, bs: Seq[String], maxDistance: Int, maxSuggestions: Int): Seq[String] = (
+    bs map (b => (b, distance(a, b)))
+      filter (_._2 <= maxDistance)
+      sortBy (_._2)
+      take   (maxSuggestions)
+      map    (_._1)
+  )
 
-  def distance(a: String, b: String): Int =
-    levenshtein(a, b, insertCost = 1, deleteCost = 1, subCost = 2, transposeCost = 1, matchCost = -1, true)
+  def distance(a: String, b: String): Int = levenshtein(a, b, transpositions = true)
 
-  /** Translated from the java version at
-  *    http://www.merriampark.com/ld.htm
-  *  which is declared to be public domain.
-  */
-  def levenshtein(s: String, t: String, insertCost: Int = 1, deleteCost: Int = 1, subCost: Int = 1, transposeCost: Int = 1, matchCost: Int = 0, transpositions: Boolean = false): Int = {
+  def levenshtein(s: String, t: String, transpositions: Boolean): Int = {
     val n = s.length
     val m = t.length
     if (n == 0) return m
@@ -35,18 +35,17 @@ object EditDistance {
 
     for (i <- 1 to n ; val s_i = s(i - 1) ; j <- 1 to m) {
       val t_j   = t(j - 1)
-      val cost  = if (s_i == t_j) matchCost else subCost
-      val tcost = if (s_i == t_j) matchCost else transposeCost
+      val cost  = if (s_i == t_j) 0 else 1
 
-      val c1 = d(i - 1)(j) + deleteCost
-      val c2 = d(i)(j - 1) + insertCost
+      val c1 = d(i - 1)(j) + 1
+      val c2 = d(i)(j - 1) + 1
       val c3 = d(i - 1)(j - 1) + cost
 
       d(i)(j) = c1 min c2 min c3
 
       if (transpositions) {
         if (i > 1 && j > 1 && s(i - 1) == t(j - 2) && s(i - 2) == t(j - 1))
-        d(i)(j) = d(i)(j) min (d(i - 2)(j - 2) + cost)
+          d(i)(j) = d(i)(j) min (d(i - 2)(j - 2) + cost)
       }
     }
 
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