Merge pull request scala#7876 from retronym/topic/tailrec-patrol

Tailrec patrol

Author: retronym

src/compiler/scala/reflect/macros/compiler/Errors.scala

@@ -14,6 +14,7 @@ package scala.reflect.macros
 package compiler
 
 import java.lang.System.{lineSeparator => EOL}
+import scala.annotation.tailrec
 import scala.reflect.macros.util.Traces
 
 trait Errors extends Traces {
@@ -104,6 +105,7 @@ trait Errors extends Traces {
     private def checkConforms(slot: String, rtpe: Type, atpe: Type) = {
       val verbose = macroDebugVerbose
 
+      @tailrec
       def check(rtpe: Type, atpe: Type): Boolean = {
         def success() = { if (verbose) println(f"$rtpe <: $atpe?%ntrue"); true }
         (rtpe, atpe) match {

src/compiler/scala/reflect/reify/codegen/GenUtils.scala

@@ -13,6 +13,8 @@
 package scala.reflect.reify
 package codegen
 
+import scala.annotation.tailrec
+
 trait GenUtils {
   self: Reifier =>
 
@@ -112,7 +114,8 @@ trait GenUtils {
     case _ => false
   }
 
-  def isCrossStageTypeBearer(tree: Tree): Boolean = tree match {
+  @tailrec
+  final def isCrossStageTypeBearer(tree: Tree): Boolean = tree match {
     case TypeApply(hk, _) => isCrossStageTypeBearer(hk)
     case Select(sym @ Select(_, ctor), nme.apply) if ctor == nme.WeakTypeTag || ctor == nme.TypeTag || ctor == nme.Expr => true
     case _ => false

src/compiler/scala/reflect/reify/phases/Reshape.scala

@@ -13,6 +13,7 @@
 package scala.reflect.reify
 package phases
 
+import scala.annotation.tailrec
 import scala.tools.nsc.symtab.Flags._
 
 trait Reshape {
@@ -189,6 +190,7 @@ trait Reshape {
       CompoundTypeTree(Template(parents1, self, stats1))
     }
 
+    @tailrec
     private def toPreTyperTypedOrAnnotated(tree: Tree): Tree = tree match {
       case ty @ Typed(expr1, tpt) =>
         if (reifyDebug) println("reify typed: " + tree)
@@ -197,6 +199,7 @@ trait Reshape {
           case tpt => tpt
         }
         val annotatedArg = {
+          @tailrec
           def loop(tree: Tree): Tree = tree match {
             case annotated1 @ Annotated(ann, annotated2 @ Annotated(_, _)) => loop(annotated2)
             case annotated1 @ Annotated(ann, arg) => arg

src/compiler/scala/tools/cmd/CommandLineParser.scala

@@ -49,6 +49,7 @@ object CommandLineParser {
       while (!done && !terminal) pos += 1
       !done
     }
+    @tailrec
     def skipToDelim(): Boolean =
       cur match {
         case q @ (DQ | SQ)        => { qpos += pos; bump(); skipToQuote(q) } && { qpos += pos; bump(); skipToDelim() }

src/compiler/scala/tools/nsc/Global.scala

@@ -41,6 +41,7 @@ import scala.tools.nsc.classpath._
 import scala.tools.nsc.profile.Profiler
 import scala.util.control.NonFatal
 import java.io.Closeable
+import scala.annotation.tailrec
 
 class Global(var currentSettings: Settings, reporter0: LegacyReporter)
     extends SymbolTable
@@ -1381,7 +1382,8 @@ class Global(var currentSettings: Settings, reporter0: LegacyReporter)
     // NOTE: Early initialized members temporarily typechecked before the enclosing class, see typedPrimaryConstrBody!
     //       Here we work around that wrinkle by claiming that a pre-initialized member is compiled in
     //       *every* run. This approximation works because this method is exclusively called with `this` == `currentRun`.
-    def compiles(sym: Symbol): Boolean =
+    @tailrec
+    final def compiles(sym: Symbol): Boolean =
       if (sym == NoSymbol) false
       else if (symSource.isDefinedAt(sym)) true
       else if (!sym.isTopLevel) compiles(sym.originalEnclosingTopLevelClassOrDummy)
@@ -1642,6 +1644,7 @@ class Global(var currentSettings: Settings, reporter0: LegacyReporter)
 
     /** Reset package class to state at typer (not sure what this is needed for?)
      */
+    @tailrec
     private def resetPackageClass(pclazz: Symbol): Unit = if (typerPhase != NoPhase) {
       enteringPhase(firstPhase) {
         pclazz.setInfo(enteringPhase(typerPhase)(pclazz.info))

src/compiler/scala/tools/nsc/ast/DocComments.scala

@@ -13,6 +13,7 @@
 package scala.tools.nsc
 package ast
 
+import scala.annotation.tailrec
 import symtab._
 import util.DocStrings._
 import scala.collection.mutable
@@ -302,7 +303,8 @@ trait DocComments { self: Global =>
    *  @param vble  The variable for which a definition is searched
    *  @param site  The class for which doc comments are generated
    */
-  def lookupVariable(vble: String, site: Symbol): Option[String] = site match {
+  @tailrec
+  final def lookupVariable(vble: String, site: Symbol): Option[String] = site match {
     case NoSymbol => None
     case _        =>
       val searchList =
@@ -311,7 +313,8 @@ trait DocComments { self: Global =>
 
       searchList collectFirst { case x if defs(x) contains vble => defs(x)(vble) } match {
         case Some(str) if str startsWith "$" => lookupVariable(str.tail, site)
-        case res                             => res orElse lookupVariable(vble, site.owner)
+        case s @ Some(str)                   => s
+        case None                            => lookupVariable(vble, site.owner)
       }
   }
 
@@ -326,6 +329,7 @@ trait DocComments { self: Global =>
   protected def expandVariables(initialStr: String, sym: Symbol, site: Symbol): String = {
     val expandLimit = 10
 
+    @tailrec
     def expandInternal(str: String, depth: Int): String = {
       if (depth >= expandLimit)
         throw new ExpansionLimitExceeded(str)
@@ -528,6 +532,7 @@ trait DocComments { self: Global =>
               (typeRef(NoPrefix, alias, Nil), false)
           }
 
+      @tailrec
       def subst(sym: Symbol, from: List[Symbol], to: List[(Type, Boolean)]): (Type, Boolean) =
         if (from.isEmpty) (sym.tpe, false)
         else if (from.head == sym) to.head

src/compiler/scala/tools/nsc/ast/TreeBrowsers.scala

@@ -24,6 +24,7 @@ import javax.swing.event.TreeModelListener
 import javax.swing.tree._
 
 import java.util.concurrent.locks._
+import scala.annotation.tailrec
 
 /**
  * Tree browsers can show the AST in a graphical and interactive
@@ -683,6 +684,7 @@ object TreeBrowsers {
     def format(width: Int, writer: Writer): Unit = {
       type FmtState = (Int, Boolean, Document)
 
+      @tailrec
       def fits(w: Int, state: List[FmtState]): Boolean = state match {
         case _ if w < 0 =>
           false
@@ -713,6 +715,7 @@ object TreeBrowsers {
         if (rem == 1)     { writer write " " }
       }
 
+      @tailrec
       def fmt(k: Int, state: List[FmtState]): Unit = state match {
         case List() => ()
         case (_, _, DocNil) :: z =>

src/compiler/scala/tools/nsc/ast/TreeGen.scala

@@ -13,6 +13,7 @@
 package scala.tools.nsc
 package ast
 
+import scala.annotation.tailrec
 import scala.collection.mutable.ListBuffer
 import symtab.Flags._
 import scala.reflect.internal.util.FreshNameCreator
@@ -265,6 +266,7 @@ abstract class TreeGen extends scala.reflect.internal.TreeGen with TreeDSL {
 
   // used to create the lifted method that holds a function's body
   def mkLiftedFunctionBodyMethod(localTyper: global.analyzer.Typer)(owner: global.Symbol, fun: global.Function) = {
+    @tailrec
     def nonLocalEnclosingMember(sym: Symbol): Symbol = {
       if (sym.isLocalDummy) sym.enclClass.primaryConstructor
       else if (sym.isLocalToBlock) nonLocalEnclosingMember(sym.originalOwner)

src/compiler/scala/tools/nsc/ast/TreeInfo.scala

@@ -95,7 +95,7 @@ abstract class TreeInfo extends scala.reflect.internal.TreeInfo with MacroAnnoti
     case _ => super.isInterfaceMember(tree)
   }
 
-  override def isConstructorWithDefault(t: Tree) = t match {
+  override def isConstructorWithDefault(t: Tree): Boolean = t match {
     case DocDef(_, definition) => isConstructorWithDefault(definition)
     case _ => super.isConstructorWithDefault(t)
   }

src/compiler/scala/tools/nsc/ast/parser/Parsers.scala

@@ -18,9 +18,10 @@ package ast.parser
 
 import scala.collection.mutable
 import mutable.ListBuffer
-import scala.reflect.internal.{ Precedence, ModifierFlags => Flags }
+import scala.reflect.internal.{Precedence, ModifierFlags => Flags}
 import scala.reflect.internal.util.{ SourceFile, Position, FreshNameCreator, ListOfNil }
 import Tokens._
+import scala.annotation.tailrec
 
 /** Historical note: JavaParsers started life as a direct copy of Parsers
  *  but at a time when that Parsers had been replaced by a different one.
@@ -519,7 +520,8 @@ self =>
       t
     }
 
-    def isWildcard(t: Tree): Boolean = t match {
+    @tailrec
+    final def isWildcard(t: Tree): Boolean = t match {
       case Ident(name1) => !placeholderParams.isEmpty && name1 == placeholderParams.head.name
       case Typed(t1, _) => isWildcard(t1)
       case Annotated(t1, _) => isWildcard(t1)
@@ -955,6 +957,7 @@ self =>
       if (samePrecedence)
         checkHeadAssoc(leftAssoc)
 
+      @tailrec
       def loop(top: Tree): Tree = if (canReduce) {
         val info = popOpInfo()
         if (!isExpr && info.targs.nonEmpty) {
@@ -1087,7 +1090,8 @@ self =>
         val point      = if (name == tpnme.ERROR) hashOffset else nameOffset
         atPos(t.pos.start, point)(SelectFromTypeTree(t, name))
       }
-      def simpleTypeRest(t: Tree): Tree = in.token match {
+      @tailrec
+      final def simpleTypeRest(t: Tree): Tree = in.token match {
         case HASH     => simpleTypeRest(typeProjection(t))
         case LBRACKET => simpleTypeRest(atPos(t.pos.start, t.pos.point)(AppliedTypeTree(t, typeArgs())))
         case _        => t
@@ -1249,7 +1253,8 @@ self =>
       t
     }
 
-    def selectors(t: Tree, typeOK: Boolean, dotOffset: Offset): Tree =
+    @tailrec
+    final def selectors(t: Tree, typeOK: Boolean, dotOffset: Offset): Tree =
       if (typeOK && in.token == TYPE) {
         in.nextToken()
         atPos(t.pos.start, dotOffset) { SingletonTypeTree(t) }
@@ -1682,6 +1687,7 @@ self =>
       val start = in.offset
       val base  = opstack
 
+      @tailrec
       def loop(top: Tree): Tree = if (!isIdent) top else {
         pushOpInfo(reduceExprStack(base, top))
         newLineOptWhenFollowing(isExprIntroToken)
@@ -1762,7 +1768,8 @@ self =>
       simpleExprRest(t, canApply = canApply)
     }
 
-    def simpleExprRest(t: Tree, canApply: Boolean): Tree = {
+    @tailrec
+    final def simpleExprRest(t: Tree, canApply: Boolean): Tree = {
       if (canApply) newLineOptWhenFollowedBy(LBRACE)
       in.token match {
         case DOT =>
@@ -2047,6 +2054,7 @@ self =>
           )
           case _ => EmptyTree
         }
+        @tailrec
         def loop(top: Tree): Tree = reducePatternStack(base, top) match {
           case next if isIdent && !isRawBar => pushOpInfo(next) ; loop(simplePattern(() => badPattern3()))
           case next                         => next
@@ -2171,6 +2179,7 @@ self =>
     /** Drop `private` modifier when followed by a qualifier.
      *  Contract `abstract` and `override` to ABSOVERRIDE
      */
+    @tailrec
     private def normalizeModifiers(mods: Modifiers): Modifiers =
       if (mods.isPrivate && mods.hasAccessBoundary)
         normalizeModifiers(mods &~ Flags.PRIVATE)
@@ -2235,6 +2244,7 @@ self =>
      *  }}}
      */
     def modifiers(): Modifiers = normalizeModifiers {
+      @tailrec
       def loop(mods: Modifiers): Modifiers = in.token match {
         case PRIVATE | PROTECTED =>
           loop(accessQualifierOpt(addMod(mods, flagTokens(in.token), tokenRange(in))))
@@ -2255,6 +2265,7 @@ self =>
      *  }}}
      */
     def localModifiers(): Modifiers = {
+      @tailrec
       def loop(mods: Modifiers): Modifiers =
         if (isLocalModifier) loop(addMod(mods, flagTokens(in.token), tokenRange(in)))
         else mods

src/compiler/scala/tools/nsc/ast/parser/Scanners.scala

@@ -439,6 +439,7 @@ trait Scanners extends ScannersCommon {
 
     /** read next token, filling TokenData fields of Scanner.
      */
+    @tailrec
     protected final def fetchToken(): Unit = {
       offset = charOffset - 1
       (ch: @switch) match {
@@ -682,6 +683,7 @@ trait Scanners extends ScannersCommon {
       else syntaxError("unclosed quoted identifier")
     }
 
+    @tailrec
     private def getIdentRest(): Unit = (ch: @switch) match {
       case 'A' | 'B' | 'C' | 'D' | 'E' |
            'F' | 'G' | 'H' | 'I' | 'J' |
@@ -716,6 +718,7 @@ trait Scanners extends ScannersCommon {
         }
     }
 
+    @tailrec
     private def getOperatorRest(): Unit = (ch: @switch) match {
       case '~' | '!' | '@' | '#' | '%' |
            '^' | '*' | '+' | '-' | '<' |
@@ -1484,6 +1487,7 @@ trait Scanners extends ScannersCommon {
     var tabSeen = false
 
     def line(offset: Offset): Int = {
+      @tailrec
       def findLine(lo: Int, hi: Int): Int = {
         val mid = (lo + hi) / 2
         if (offset < lineStart(mid)) findLine(lo, mid - 1)

src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala

@@ -13,7 +13,7 @@
 package scala.tools.nsc
 package backend.jvm
 
-import scala.annotation.switch
+import scala.annotation.{switch, tailrec}
 import scala.reflect.internal.Flags
 import scala.tools.asm
 import scala.tools.asm.Opcodes
@@ -692,6 +692,7 @@ abstract class BCodeBodyBuilder extends BCodeSkelBuilder {
               // Check if the Apply tree has an InlineAnnotatedAttachment, added by the typer
               // for callsites marked `f(): @inline/noinline`. For nullary calls, the attachment
               // is on the Select node (not on the Apply node added by UnCurry).
+              @tailrec
               def recordInlineAnnotated(t: Tree): Unit = {
                 if (t.hasAttachment[InlineAnnotatedAttachment]) lastInsn match {
                   case m: MethodInsnNode =>
@@ -1115,6 +1116,7 @@ abstract class BCodeBodyBuilder extends BCodeSkelBuilder {
     }
 
     /* Emit code to compare the two top-most stack values using the 'op' operator. */
+    @tailrec
     private def genCJUMP(success: asm.Label, failure: asm.Label, op: TestOp, tk: BType, targetIfNoJump: asm.Label, negated: Boolean = false): Unit = {
       if (targetIfNoJump == success) genCJUMP(failure, success, op.negate, tk, targetIfNoJump, negated = !negated)
       else {
@@ -1136,6 +1138,7 @@ abstract class BCodeBodyBuilder extends BCodeSkelBuilder {
     }
 
     /* Emits code to compare (and consume) stack-top and zero using the 'op' operator */
+    @tailrec
     private def genCZJUMP(success: asm.Label, failure: asm.Label, op: TestOp, tk: BType, targetIfNoJump: asm.Label, negated: Boolean = false): Unit = {
       if (targetIfNoJump == success) genCZJUMP(failure, success, op.negate, tk, targetIfNoJump, negated = !negated)
       else {

src/compiler/scala/tools/nsc/backend/jvm/BCodeHelpers.scala

@@ -21,6 +21,7 @@ import scala.tools.nsc.backend.jvm.BCodeHelpers.ScalaSigBytes
 import scala.tools.nsc.reporters.NoReporter
 
 import PartialFunction.cond
+import scala.annotation.tailrec
 
 /*
  *  Traits encapsulating functionality to convert Scala AST Trees into ASM ClassNodes.
@@ -131,7 +132,8 @@ abstract class BCodeHelpers extends BCodeIdiomatic {
     }
   }
 
-  def nextEnclosingClass(sym: Symbol): Symbol =
+  @tailrec
+  final def nextEnclosingClass(sym: Symbol): Symbol =
     if (sym.isClass) sym
     else nextEnclosingClass(nextEnclosing(sym))
 
@@ -173,6 +175,7 @@ abstract class BCodeHelpers extends BCodeIdiomatic {
       exitingPickler(enclCls.isDerivedValueClass) && method.owner != enclCls
     }
 
+    @tailrec
     def enclosingMethod(sym: Symbol): Option[Symbol] = {
       if (sym.isClass || sym == NoSymbol) None
       else if (sym.isMethod && !sym.isGetter) {
@@ -226,7 +229,8 @@ abstract class BCodeHelpers extends BCodeIdiomatic {
    *   object T { def f { object U } }
    * the owner of U is T, so UModuleClass.isStatic is true. Phase travel does not help here.
    */
-  def isOriginallyStaticOwner(sym: Symbol): Boolean =
+  @tailrec
+  final def isOriginallyStaticOwner(sym: Symbol): Boolean =
     sym.isPackageClass || sym.isModuleClass && isOriginallyStaticOwner(sym.originalOwner)
 
   /**