Avoid indiscriminate import from collection

Author: som-snytt

src/compiler/scala/reflect/reify/utils/SymbolTables.scala

@@ -13,7 +13,7 @@
 package scala.reflect.reify
 package utils
 
-import scala.collection._
+import scala.collection.{immutable, mutable}, mutable.{ArrayBuffer, ListBuffer}
 import java.lang.System.{lineSeparator => EOL}
 
 trait SymbolTables {
@@ -22,7 +22,7 @@ trait SymbolTables {
   import global._
 
   class SymbolTable private[SymbolTable] (
-    private[SymbolTable] val symtab: immutable.ListMap[Symbol, Tree] = immutable.ListMap[Symbol, Tree](),
+    private[SymbolTable] val symtab: immutable.ListMap[Symbol, Tree] = immutable.ListMap.empty[Symbol, Tree],
     private[SymbolTable] val aliases: List[(Symbol, TermName)] = List[(Symbol, TermName)](),
     private[SymbolTable] val original: Option[List[Tree]] = None) {
 
@@ -166,8 +166,8 @@ trait SymbolTables {
       reifier.state.symtab = symtab0.asInstanceOf[reifier.SymbolTable]
       def currtab = reifier.symtab.asInstanceOf[SymbolTable]
       try {
-        val cumulativeSymtab = mutable.ArrayBuffer[Tree](symtab0.symtab.values.toList: _*)
-        val cumulativeAliases = mutable.ArrayBuffer[(Symbol, TermName)](symtab0.aliases: _*)
+        val cumulativeSymtab = ArrayBuffer[Tree](symtab0.symtab.values.toList: _*)
+        val cumulativeAliases = ArrayBuffer[(Symbol, TermName)](symtab0.aliases: _*)
 
         def fillInSymbol(sym: Symbol): Tree = {
           if (reifyDebug) println("Filling in: %s (%s)".format(sym, sym.accurateKindString))
@@ -203,7 +203,7 @@ trait SymbolTables {
         }
 
         val withAliases = cumulativeSymtab flatMap (entry => {
-          val result = mutable.ListBuffer[Tree]()
+          val result = ListBuffer[Tree]()
           result += entry
           val sym = reifyBinding(entry).symbol
           if (sym != NoSymbol)

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

@@ -15,7 +15,7 @@ package transform
 
 import symtab._
 import Flags._
-import scala.collection._
+import scala.collection.mutable, mutable.{Buffer, ListBuffer}
 import scala.tools.nsc.Reporting.WarningCategory
 import scala.util.chaining._
 
@@ -35,8 +35,8 @@ abstract class CleanUp extends Statics with Transform with ast.TreeDSL {
     new CleanUpTransformer(unit)
 
   class CleanUpTransformer(unit: CompilationUnit) extends StaticsTransformer {
-    private val newStaticMembers      = mutable.Buffer.empty[Tree]
-    private val newStaticInits        = mutable.Buffer.empty[Tree]
+    private val newStaticMembers      = Buffer.empty[Tree]
+    private val newStaticInits        = Buffer.empty[Tree]
     private val symbolsStoredAsStatic = mutable.Map.empty[String, Symbol]
     private var transformListApplyLimit = 8
     private def reducingTransformListApply[A](depth: Int)(body: => A): A = {
@@ -438,7 +438,7 @@ abstract class CleanUp extends Statics with Transform with ast.TreeDSL {
          * resulting switch may need to correspond to a single case body.
          */
 
-        val labels = mutable.ListBuffer.empty[LabelDef]
+        val labels = ListBuffer.empty[LabelDef]
         var defaultCaseBody = Throw(New(MatchErrorClass.tpe_*, selArg)): Tree
 
         def LABEL(name: String) = currentOwner.newLabel(unit.freshTermName(name), swPos).setFlag(SYNTH_CASE_FLAGS)
@@ -523,7 +523,7 @@ abstract class CleanUp extends Statics with Transform with ast.TreeDSL {
               gen.evalOnce(classTagEvidence, currentOwner, unit) { ev =>
                 val arr = typedWithPos(tree.pos)(gen.mkMethodCall(classTagEvidence, definitions.ClassTagClass.info.decl(nme.newArray), Nil, Literal(Constant(elems.size)) :: Nil))
                 gen.evalOnce(arr, currentOwner, unit) { arr =>
-                  val stats = mutable.ListBuffer[Tree]()
+                  val stats = ListBuffer[Tree]()
                   foreachWithIndex(elems) { (elem, i) =>
                     stats += gen.mkMethodCall(gen.mkAttributedRef(definitions.ScalaRunTimeModule), currentRun.runDefinitions.arrayUpdateMethod,
                                               Nil, arr() :: Literal(Constant(i)) :: elem :: Nil)

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

@@ -15,7 +15,7 @@ package transform
 
 import symtab._
 import Flags._
-import scala.collection._
+import scala.collection.mutable
 
 /**
   * This transformer is responsible for preparing Function nodes for runtime,
@@ -68,7 +68,7 @@ abstract class Delambdafy extends Transform with TypingTransformers with ast.Tre
   class DelambdafyTransformer(unit: CompilationUnit) extends TypingTransformer(unit) {
     // we need to know which methods refer to the 'this' reference so that we can determine which lambdas need access to it
     // TODO: this looks expensive, so I made it a lazy val. Can we make it more pay-as-you-go / optimize for common shapes?
-    private[this] lazy val methodReferencesThis: Set[Symbol] =
+    private[this] lazy val methodReferencesThis: collection.Set[Symbol] =
       (new ThisReferringMethodsTraverser).methodReferencesThisIn(unit.body)
 
     private def mkLambdaMetaFactoryCall(fun: Function, target: Symbol, functionalInterface: Symbol, samUserDefined: Symbol, userSamCls: Symbol, isSpecialized: Boolean): Tree = {
@@ -360,12 +360,12 @@ abstract class Delambdafy extends Transform with TypingTransformers with ast.Tre
   // finds all methods that reference 'this'
   class ThisReferringMethodsTraverser extends InternalTraverser {
     // the set of methods that refer to this
-    private val thisReferringMethods = mutable.Set[Symbol]()
+    private val thisReferringMethods = mutable.Set.empty[Symbol]
 
     // the set of lifted lambda body methods that each method refers to
-    private val liftedMethodReferences = mutable.Map[Symbol, mutable.Set[Symbol]]()
+    private val liftedMethodReferences = mutable.Map.empty[Symbol, mutable.Set[Symbol]]
 
-    def methodReferencesThisIn(tree: Tree) = {
+    def methodReferencesThisIn(tree: Tree): collection.Set[Symbol] = {
       traverse(tree)
       liftedMethodReferences.keys foreach refersToThis
 

src/scaladoc/scala/tools/nsc/doc/base/CommentFactoryBase.scala

@@ -16,7 +16,7 @@ package base
 
 import base.comment._
 import scala.annotation.{nowarn, tailrec}
-import scala.collection._
+import scala.collection.mutable, mutable.ListBuffer
 import scala.reflect.internal.util.Position
 import scala.tools.nsc.Reporting.WarningCategory
 import scala.util.matching.Regex.{quoteReplacement, Match}
@@ -239,7 +239,7 @@ trait CommentFactoryBase { this: MemberLookupBase =>
       * @param inCodeBlock Whether the next line is part of a code block (in which no tags must be read). */
     def parse0 (
       docBody: StringBuilder,
-      tags: immutable.Map[TagKey, List[String]],
+      tags: Map[TagKey, List[String]],
       lastTagKey: Option[TagKey],
       remaining: List[String],
       inCodeBlock: Boolean
@@ -414,7 +414,7 @@ trait CommentFactoryBase { this: MemberLookupBase =>
         com
     }
 
-    parse0(new StringBuilder(comment.length), immutable.Map.empty, None, clean(comment), inCodeBlock = false)
+    parse0(new StringBuilder(comment.length), Map.empty, None, clean(comment), inCodeBlock = false)
 
   }
 
@@ -503,14 +503,14 @@ trait CommentFactoryBase { this: MemberLookupBase =>
       /** Consumes all list item blocks (possibly with nested lists) of the
         * same list and returns the list block. */
       def listLevel(indent: Int, style: String): Block = {
-        val lines = mutable.ListBuffer.empty[Block]
+        val lines = ListBuffer.empty[Block]
         var line: Option[Block] = listLine(indent, style)
         while (line.isDefined) {
           lines += line.get
           line = listLine(indent, style)
         }
         val constructor = listStyles(style)
-        constructor(lines)
+        constructor(lines.toList)
       }
 
       val indent = countWhitespace

src/scaladoc/scala/tools/nsc/doc/base/comment/Body.scala

@@ -15,7 +15,7 @@ package doc
 package base
 package comment
 
-import scala.collection._
+import scala.collection.immutable.SortedMap
 
 /** A body of text. A comment has a single body, which is composed of
   * at least one block. Inside every body is exactly one summary.

src/scaladoc/scala/tools/nsc/doc/base/comment/Comment.scala

@@ -15,7 +15,7 @@ package doc
 package base
 package comment
 
-import scala.collection._
+import scala.collection.mutable.ListBuffer
 
 /** A Scaladoc comment and all its tags.
   *
@@ -29,7 +29,7 @@ abstract class Comment {
   def body: Body
 
   private def closeHtmlTags(inline: Inline): Inline = {
-    val stack = mutable.ListBuffer.empty[HtmlTag]
+    val stack = ListBuffer.empty[HtmlTag]
     def scan(i: Inline): Unit = {
       i match {
         case Chain(list) =>

src/scaladoc/scala/tools/nsc/doc/doclet/Generator.scala

@@ -13,7 +13,7 @@
 package scala.tools.nsc.doc
 package doclet
 
-import scala.collection._
+import scala.collection.mutable
 
 /** Custom Scaladoc generators must implement the `Generator` class. A custom generator can be selected in Scaladoc
   * using the `-doc-generator` command line option.

src/scaladoc/scala/tools/nsc/doc/html/HtmlFactory.scala

@@ -17,7 +17,7 @@ package html
 import model._
 import java.io.{ File => JFile }
 import io.{ Streamable, Directory }
-import scala.collection._
+import scala.collection.mutable
 import page.diagram._
 import scala.reflect.internal.Reporter
 

src/scaladoc/scala/tools/nsc/doc/model/CommentFactory.scala

@@ -16,7 +16,7 @@ package model
 
 import base.comment._
 
-import scala.collection._
+import scala.collection.mutable
 import scala.reflect.internal.util.Position
 
 /** The comment parser transforms raw comment strings into `Comment` objects.

src/scaladoc/scala/tools/nsc/doc/model/ModelFactoryTypeSupport.scala

@@ -17,7 +17,7 @@ package model
 import base._
 import diagram._
 import scala.annotation.nowarn
-import scala.collection._
+import scala.collection.{immutable, mutable}
 
 /** This trait extracts all required information for documentation from compilation units */
 trait ModelFactoryTypeSupport {

src/scaladoc/scala/tools/nsc/doc/model/TreeEntity.scala

@@ -14,8 +14,7 @@ package scala.tools.nsc
 package doc
 package model
 
-import scala.collection._
-
+import scala.collection.immutable.SortedMap
 
 /** A fragment of code. */
 abstract class TreeEntity {

src/scaladoc/scala/tools/nsc/doc/model/TreeFactory.scala

@@ -14,7 +14,7 @@ package scala.tools.nsc
 package doc
 package model
 
-import scala.collection._
+import scala.collection.immutable
 import scala.reflect.internal.util.{RangePosition, SourceFile}
 
 /** The goal of this trait is, using makeTree,

src/scaladoc/scala/tools/nsc/doc/model/TypeEntity.scala

@@ -14,7 +14,7 @@ package scala.tools.nsc
 package doc
 package model
 
-import scala.collection._
+import scala.collection.immutable.SortedMap
 
 /** A type. Note that types and templates contain the same information only for the simplest types. For example, a type
   * defines how a template's type parameters are instantiated (as in `List[Cow]`), what the template's prefix is