Incorporated reviewer feedback.

Made things a little more consistent and self-apparent.

2 files changed, 20 insertions, 17 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Contexts.scala b/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
index fc1db32a2d..21c33aad0d 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
@@ -365,6 +365,7 @@ trait Contexts { self: Analyzer =>
     @inline final def withinSuperInit[T](op: => T): T                      = withMode(enabled = SuperInit)(op)
     @inline final def withinSecondTry[T](op: => T): T                      = withMode(enabled = SecondTry)(op)
     @inline final def withinTypeConstructor[T](op: => T): T                = withMode(enabled = TypeConstructor)(op)
+    @inline final def withinPatAlternative[T](op: => T): T                 = withMode(enabled = PatternAlternative)(op)
 
     /* TODO - consolidate returnsSeen (which seems only to be used by checkDead)
      * and ReturnExpr.
@@ -374,14 +375,8 @@ trait Contexts { self: Analyzer =>
       withMode(enabled = ReturnExpr)(op)
     }
 
-    /** TODO: The "sticky modes" are EXPRmode, PATTERNmode, TYPEmode.
-     *  To mimick the sticky mode behavior, when captain stickyfingers
-     *  comes around we need to propagate those modes but forget the other
-     *  context modes which were once mode bits; those being so far the
-     *  ones listed here.
-     */
-    @inline final def withOnlyStickyModes[T](op: => T): T =
-      withMode(disabled = PatternAlternative | StarPatterns | SuperInit | SecondTry | ReturnExpr | TypeConstructor | TypeApplication)(op)
+    // See comment on FormerNonStickyModes.
+    @inline final def withOnlyStickyModes[T](op: => T): T = withMode(disabled = FormerNonStickyModes)(op)
 
     /** @return true if the `expr` evaluates to true within a silent Context that incurs no errors */
     @inline final def inSilentMode(expr: => Boolean): Boolean = {
@@ -1389,6 +1384,16 @@ object ContextMode {
    */
   final val TypeApplication: ContextMode          = 1 << 17
 
+  /** TODO: The "sticky modes" are EXPRmode, PATTERNmode, TYPEmode.
+   *  To mimick the sticky mode behavior, when captain stickyfingers
+   *  comes around we need to propagate those modes but forget the other
+   *  context modes which were once mode bits; those being so far the
+   *  ones listed here.
+   */
+  final val FormerNonStickyModes: ContextMode = (
+    PatternAlternative | StarPatterns | SuperInit | SecondTry | ReturnExpr | TypeConstructor | TypeApplication
+  )
+
   final val DefaultMode: ContextMode      = MacrosEnabled
 
   private val contextModeNameMap = Map(
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index eeae7da94f..5cce4865cc 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -3039,7 +3039,7 @@ trait Typers extends Adaptations with Tags {
     }
 
     def typedArg(arg: Tree, mode: Mode, newmode: Mode, pt: Type): Tree = {
-      val typedMode = mode stickyPlus newmode
+      val typedMode = mode.onlySticky | newmode
       val t = withCondConstrTyper(mode.inSccMode)(_.typed(arg, typedMode, pt))
       checkDead.inMode(typedMode, t)
     }
@@ -3062,7 +3062,7 @@ trait Typers extends Adaptations with Tags {
           // No formals left or * indicates varargs.
           val isVarArgs = formals.isEmpty || formals.tail.isEmpty && isRepeatedParamType(formals.head)
           val isByName  = formals.nonEmpty && isByNameParamType(formals.head)
-          def typedMode = mode stickyPlus ( if (isByName) NOmode else BYVALmode )
+          def typedMode = if (isByName) mode.onlySticky else mode.onlySticky | BYVALmode
           def body = typedArg(args.head, mode, typedMode, adapted.head)
           def arg1 = if (isVarArgs) context.withinStarPatterns(body) else body
 
@@ -4984,13 +4984,11 @@ trait Typers extends Adaptations with Tags {
         newTyper(context.makeNewScope(ddef, sym)).constrTyperIf(isConstrDefaultGetter)
       }
 
-      def typedAlternative(alt: Alternative) = {
-        val saved = context.inPatAlternative
-        context.inPatAlternative = true
-        try treeCopy.Alternative(tree, alt.trees mapConserve (alt => typed(alt, mode, pt))) setType pt
-        finally context.inPatAlternative = saved
-      }
-
+      def typedAlternative(alt: Alternative) = (
+        context withinPatAlternative (
+          treeCopy.Alternative(tree, alt.trees mapConserve (alt => typed(alt, mode, pt))) setType pt
+        )
+      )
       def typedStar(tree: Star) = {
         if (!context.starPatterns && !isPastTyper)
           StarPatternWithVarargParametersError(tree)