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.

8 files changed, 22 insertions, 28 deletions

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)
       }
     }
 
diff --git a/test/files/neg/nopredefs.check b/test/files/neg/nopredefs.check
index 0a0ab34482..e6c1af78a0 100644
--- a/test/files/neg/nopredefs.check
+++ b/test/files/neg/nopredefs.check
@@ -1,4 +1,4 @@
-nopredefs.scala:5: error: not found: value Set
+nopredefs.scala:5: error: not found: value Set (similar: Seq)
   val y = Set(3)
           ^
 one error found
diff --git a/test/files/neg/suggest-similar.check b/test/files/neg/suggest-similar.check
index 320c7d0092..0a858aaf2e 100644
--- a/test/files/neg/suggest-similar.check
+++ b/test/files/neg/suggest-similar.check
@@ -1,13 +1,10 @@
 suggest-similar.scala:8: error: not found: value flippitx (similar: flippity)
   flippitx = 123
   ^
-suggest-similar.scala:9: error: not found: value identipoo (similar: identity)
-  Nil map identipoo
+suggest-similar.scala:9: error: not found: value identiyt (similar: identity)
+  Nil map identiyt
           ^
 suggest-similar.scala:10: error: not found: type Bingus (similar: Dingus)
   new Bingus
       ^
-suggest-similar.scala:11: error: value bap is not a member of object Nil
-  Nil bap identity
-      ^
-four errors found
+three errors found
diff --git a/test/files/neg/suggest-similar.flags b/test/files/neg/suggest-similar.flags
deleted file mode 100644
index 66bb23c396..0000000000
--- a/test/files/neg/suggest-similar.flags
+++ /dev/null
@@ -1 +0,0 @@
--Ysuggest-idents
\ No newline at end of file
diff --git a/test/files/neg/suggest-similar.scala b/test/files/neg/suggest-similar.scala
index ae18c6ea62..ff327478fe 100644
--- a/test/files/neg/suggest-similar.scala
+++ b/test/files/neg/suggest-similar.scala
@@ -6,6 +6,6 @@ import Dingus._
 
 class A {
   flippitx = 123
-  Nil map identipoo
+  Nil map identiyt
   new Bingus
 }
diff --git a/test/files/neg/t2870.check b/test/files/neg/t2870.check
index 6577577d3f..72bc0d98a1 100644
--- a/test/files/neg/t2870.check
+++ b/test/files/neg/t2870.check
@@ -1,4 +1,4 @@
-t2870.scala:1: error: not found: type Jar
+t2870.scala:1: error: not found: type Jar (similar: Jars)
 class Jars(jar: Jar)
                 ^
 t2870.scala:6: error: illegal cyclic reference involving value <import>