Merge pull request #982 from adriaanm/ticket-wolfcry

SI-5930 SI-5897 reduce redundant warnings in matches, fix flags usage

5 files changed, 20 insertions, 14 deletions

diff --git a/src/compiler/scala/tools/nsc/ast/TreeGen.scala b/src/compiler/scala/tools/nsc/ast/TreeGen.scala
index be5909a67f..144fb0d5ec 100644
--- a/src/compiler/scala/tools/nsc/ast/TreeGen.scala
+++ b/src/compiler/scala/tools/nsc/ast/TreeGen.scala
@@ -72,8 +72,6 @@ abstract class TreeGen extends reflect.internal.TreeGen with TreeDSL {
     Annotated(Ident(nme.synthSwitch), expr)
   }
 
-  def hasSynthCaseSymbol(t: Tree) = (t.symbol ne null) && (t.symbol hasFlag (CASE | SYNTHETIC))
-
   // TODO: would be so much nicer if we would know during match-translation (i.e., type checking)
   // whether we should emit missingCase-style apply (and isDefinedAt), instead of transforming trees post-factum
   class MatchMatcher {
@@ -94,13 +92,13 @@ abstract class TreeGen extends reflect.internal.TreeGen with TreeDSL {
       case Apply(Apply(TypeApply(Select(tgt, nme.runOrElse), targs), List(scrut)), List(matcher)) if opt.virtPatmat => // println("virt match: "+ (tgt, targs, scrut, matcher) + "for:\n"+ matchExpr )
         caseVirtualizedMatch(matchExpr, tgt, targs, scrut, matcher)
       // optimized version of virtpatmat
-      case Block(stats, matchEndDef) if opt.virtPatmat && (stats forall hasSynthCaseSymbol) =>
+      case Block(stats, matchEndDef) if opt.virtPatmat && (stats forall treeInfo.hasSynthCaseSymbol) =>
         // the assumption is once we encounter a case, the remainder of the block will consist of cases
         // the prologue may be empty, usually it is the valdef that stores the scrut
         val (prologue, cases) = stats span (s => !s.isInstanceOf[LabelDef])
         caseVirtualizedMatchOpt(matchExpr, prologue, cases, matchEndDef, identity)
       // optimized version of virtpatmat
-      case Block(outerStats, orig@Block(stats, matchEndDef)) if opt.virtPatmat && (stats forall hasSynthCaseSymbol) =>
+      case Block(outerStats, orig@Block(stats, matchEndDef)) if opt.virtPatmat && (stats forall treeInfo.hasSynthCaseSymbol) =>
         val (prologue, cases) = stats span (s => !s.isInstanceOf[LabelDef])
         caseVirtualizedMatchOpt(matchExpr, prologue, cases, matchEndDef, m => copyBlock(matchExpr, outerStats, m))
       case other =>
diff --git a/src/compiler/scala/tools/nsc/transform/TailCalls.scala b/src/compiler/scala/tools/nsc/transform/TailCalls.scala
index 492273dfdc..770aa8b7ac 100644
--- a/src/compiler/scala/tools/nsc/transform/TailCalls.scala
+++ b/src/compiler/scala/tools/nsc/transform/TailCalls.scala
@@ -36,7 +36,7 @@ abstract class TailCalls extends Transform {
     }
   }
 
-  import gen.hasSynthCaseSymbol
+  import treeInfo.hasSynthCaseSymbol
 
   /**
    * A Tail Call Transformer
diff --git a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala
index cf5c7265ad..a4457936c8 100644
--- a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala
@@ -113,7 +113,6 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
   import definitions._
   import analyzer._ //Typer
 
-  val SYNTH_CASE = Flags.CASE | SYNTHETIC
 
   case class DefaultOverrideMatchAttachment(default: Tree)
 
@@ -241,7 +240,8 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
       // append the default to the list of cases and suppress the unreachable case error that may arise (once we detect that...)
       val matchFailGenOverride = match_.attachments.get[DefaultOverrideMatchAttachment].map{case DefaultOverrideMatchAttachment(default) => ((scrut: Tree) => default)}
 
-      val selectorSym  = freshSym(selector.pos, pureType(selectorTp)) setFlag SYNTH_CASE
+      val selectorSym  = freshSym(selector.pos, pureType(selectorTp)) setFlag treeInfo.SYNTH_CASE_FLAGS
+
       // pt = Any* occurs when compiling test/files/pos/annotDepMethType.scala  with -Xexperimental
       val combined = combineCases(selector, selectorSym, cases map translateCase(selectorSym, pt), pt, matchOwner, matchFailGenOverride)
 
@@ -1317,6 +1317,9 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
     def freshSym(pos: Position, tp: Type = NoType, prefix: String = "x") =
       NoSymbol.newTermSymbol(freshName(prefix), pos) setInfo tp
 
+    def newSynthCaseLabel(name: String) =
+      NoSymbol.newLabel(freshName(name), NoPosition) setFlag treeInfo.SYNTH_CASE_FLAGS
+
     // codegen relevant to the structure of the translation (how extractors are combined)
     trait AbsCodegen {
       def matcher(scrut: Tree, scrutSym: Symbol, restpe: Type)(cases: List[Casegen => Tree], matchFailGen: Option[Tree => Tree]): Tree
@@ -1487,7 +1490,7 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
     case object FalseCond extends Cond {override def toString = "F"}
 
     case class AndCond(a: Cond, b: Cond) extends Cond {override def toString = a +"/\\"+ b}
-    case class OrCond(a: Cond, b: Cond) extends Cond  {override def toString = "("+a+") \\/ ("+ b +")"}
+    case class OrCond(a: Cond, b: Cond)  extends Cond {override def toString = "("+a+") \\/ ("+ b +")"}
 
     object EqualityCond {
       private val uniques = new collection.mutable.HashMap[(Tree, Tree), EqualityCond]
@@ -3109,7 +3112,7 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
           }
       }
 
-      private val defaultLabel: Symbol =  NoSymbol.newLabel(freshName("default"), NoPosition) setFlag SYNTH_CASE
+      private val defaultLabel: Symbol =  newSynthCaseLabel("default")
 
       /** Collapse guarded cases that switch on the same constant (the last case may be unguarded).
        *
@@ -3477,11 +3480,11 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
        * if keepGoing is false, the result Some(x) of the naive translation is encoded as matchRes == x
        */
       def matcher(scrut: Tree, scrutSym: Symbol, restpe: Type)(cases: List[Casegen => Tree], matchFailGen: Option[Tree => Tree]): Tree = {
-        val matchEnd = NoSymbol.newLabel(freshName("matchEnd"), NoPosition) setFlag SYNTH_CASE
+        val matchEnd = newSynthCaseLabel("matchEnd")
         val matchRes = NoSymbol.newValueParameter(newTermName("x"), NoPosition, SYNTHETIC) setInfo restpe.withoutAnnotations //
         matchEnd setInfo MethodType(List(matchRes), restpe)
 
-        def newCaseSym = NoSymbol.newLabel(freshName("case"), NoPosition) setInfo MethodType(Nil, restpe) setFlag SYNTH_CASE
+        def newCaseSym = newSynthCaseLabel("case") setInfo MethodType(Nil, restpe)
         var _currCase = newCaseSym
 
         val caseDefs = cases map { (mkCase: Casegen => Tree) =>
diff --git a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
index 9501998152..29ed8e6013 100644
--- a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
@@ -1541,7 +1541,8 @@ abstract class RefChecks extends InfoTransform with reflect.internal.transform.R
           transform(qual)
 
       case Apply(fn, args) =>
-        checkSensible(tree.pos, fn, args)
+        // sensicality should be subsumed by the unreachability/exhaustivity/irrefutability analyses in the pattern matcher
+        if (!inPattern) checkSensible(tree.pos, fn, args)
         currentApplication = tree
         tree
     }
@@ -1718,7 +1719,7 @@ abstract class RefChecks extends InfoTransform with reflect.internal.transform.R
             val pat1 = transform(pat)
             inPattern = false
             treeCopy.CaseDef(tree, pat1, transform(guard), transform(body))
-          case LabelDef(_, _, _) if gen.hasSynthCaseSymbol(result) =>
+          case LabelDef(_, _, _) if treeInfo.hasSynthCaseSymbol(result) =>
             val old = inPattern
             inPattern = true
             val res = deriveLabelDef(result)(transform)
diff --git a/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala b/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala
index 38c2c5f719..74c51ece9f 100644
--- a/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala
@@ -401,7 +401,11 @@ trait TypeDiagnostics {
 
     object checkDead {
       private var expr: Symbol = NoSymbol
-      private def exprOK = expr != Object_synchronized
+
+      private def exprOK =
+        (expr != Object_synchronized) &&
+        !(expr.isLabel && treeInfo.isSynthCaseSymbol(expr)) // it's okay to jump to matchEnd (or another case) with an argument of type nothing
+
       private def treeOK(tree: Tree) = tree.tpe != null && tree.tpe.typeSymbol == NothingClass
 
       def updateExpr(fn: Tree) = {