Merge pull request #4919 from retronym/ticket/9630

Pattern Matching analysis improvements

4 files changed, 16 insertions, 9 deletions

diff --git a/src/compiler/scala/reflect/macros/contexts/Parsers.scala b/src/compiler/scala/reflect/macros/contexts/Parsers.scala
index f4584f3627..cc3f01e53b 100644
--- a/src/compiler/scala/reflect/macros/contexts/Parsers.scala
+++ b/src/compiler/scala/reflect/macros/contexts/Parsers.scala
@@ -16,8 +16,9 @@ trait Parsers {
       val tree = gen.mkTreeOrBlock(parser.parseStatsOrPackages())
       sreporter.infos.foreach {
         case sreporter.Info(pos, msg, sreporter.ERROR) => throw ParseException(pos, msg)
+        case _ =>
       }
       tree
     } finally global.reporter = oldReporter
   }
-}
\ No newline at end of file
+}
diff --git a/src/compiler/scala/tools/nsc/transform/patmat/Logic.scala b/src/compiler/scala/tools/nsc/transform/patmat/Logic.scala
index 1a4df9973e..8b2e09495f 100644
--- a/src/compiler/scala/tools/nsc/transform/patmat/Logic.scala
+++ b/src/compiler/scala/tools/nsc/transform/patmat/Logic.scala
@@ -691,7 +691,7 @@ trait ScalaLogic extends Interface with Logic with TreeAndTypeAnalysis {
           // if X is mutable.
           freshExistentialSubtype(t.tpe)
         }
-        else trees find (a => a.correspondsStructure(t)(sameValue)) match {
+        else trees find (a => equivalentTree(a, t)) match {
           case Some(orig) =>
             debug.patmat("unique tp for tree: " + ((orig, orig.tpe)))
             orig.tpe
diff --git a/src/compiler/scala/tools/nsc/transform/patmat/MatchAnalysis.scala b/src/compiler/scala/tools/nsc/transform/patmat/MatchAnalysis.scala
index affbcf9ec8..ab3b25e76b 100644
--- a/src/compiler/scala/tools/nsc/transform/patmat/MatchAnalysis.scala
+++ b/src/compiler/scala/tools/nsc/transform/patmat/MatchAnalysis.scala
@@ -84,11 +84,15 @@ trait TreeAndTypeAnalysis extends Debugging {
     tp <:< tpImpliedNormalizedToAny
   }
 
-  // TODO: improve, e.g., for constants
-  def sameValue(a: Tree, b: Tree): Boolean = (a eq b) || ((a, b) match {
-    case (_ : Ident, _ : Ident) => a.symbol eq b.symbol
-    case _                      => false
-  })
+  def equivalentTree(a: Tree, b: Tree): Boolean = (a, b) match {
+    case (Select(qual1, _), Select(qual2, _)) => equivalentTree(qual1, qual2) && a.symbol == b.symbol
+    case (Ident(_), Ident(_)) => a.symbol == b.symbol
+    case (Literal(c1), Literal(c2)) => c1 == c2
+    case (This(_), This(_)) => a.symbol == b.symbol
+    case (Apply(fun1, args1), Apply(fun2, args2)) => equivalentTree(fun1, fun2) && args1.corresponds(args2)(equivalentTree)
+    // Those are the only cases we need to handle in the pattern matcher
+    case _ => false
+  }
 
   trait CheckableTreeAndTypeAnalysis {
     val typer: Typer
@@ -172,6 +176,8 @@ trait TreeAndTypeAnalysis extends Debugging {
               filterChildren(subclasses)
             })
           }
+        case sym if sym.isCase =>
+          List(List(tp))
 
         case sym =>
           debug.patmat("enum unsealed "+ ((tp, sym, sym.isSealed, isPrimitiveValueClass(sym))))
@@ -276,7 +282,7 @@ trait MatchApproximation extends TreeAndTypeAnalysis with ScalaLogic with MatchT
 
       // hashconsing trees (modulo value-equality)
       def unique(t: Tree, tpOverride: Type = NoType): Tree =
-        trees find (a => a.correspondsStructure(t)(sameValue)) match {
+        trees find (a => equivalentTree(a, t)) match {
           case Some(orig) =>
             // debug.patmat("unique: "+ (t eq orig, orig))
             orig
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 84af9233e1..bf64ed9baa 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -1860,7 +1860,7 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
       clazz.annotations.map(_.completeInfo())
       if (templ.symbol == NoSymbol)
         templ setSymbol clazz.newLocalDummy(templ.pos)
-      val self1 = templ.self match {
+      val self1 = (templ.self: @unchecked) match {
         case vd @ ValDef(_, _, tpt, EmptyTree) =>
           val tpt1 = checkNoEscaping.privates(
             clazz.thisSym,