Rename productArity in pattern matcher to prodArity

productArity is a method defined in ProductN which is inherited from
case classes. It is possible that it will be usewd in the implementation
of pattern matching in the future. The previous implementation used
the same name to mean something else: Not the arity of the case class
itself but the arity of the pattern/type it represented.

Renaming to prodArity avoids the confusion.

Author: odersky

src/dotty/tools/dotc/transform/PatternMatcher.scala

@@ -1376,8 +1376,8 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {thisTrans
 
       def subPatTypes: List[Type] = typedPatterns map (_.tpe)
 
-      // there are `productArity` non-seq elements in the tuple.
-      protected def firstIndexingBinder = productArity
+      // there are `prodArity` non-seq elements in the tuple.
+      protected def firstIndexingBinder = prodArity
       protected def expectedLength      = elementArity
       protected def lastIndexingBinder  = totalArity - starArity - 1
 
@@ -1535,7 +1535,7 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {thisTrans
       // the trees that select the subpatterns on the extractor's result, referenced by `binder`
       // require (totalArity > 0 && (!lastIsStar || isSeq))
       protected def subPatRefs(binder: Symbol, subpatBinders: List[Symbol], binderTypeTested: Type): List[Tree] = {
-        if(aligner.isSingle && aligner.extractor.productArity == 1 && defn.isTupleType(binder.info)) {
+        if(aligner.isSingle && aligner.extractor.prodArity == 1 && defn.isTupleType(binder.info)) {
           // special case for extractor
           // comparing with scalac additional assertions added
           val subpw = subpatBinders.head.info.widen
@@ -1577,13 +1577,13 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {thisTrans
     *
     *  Here Pm/Fi is the last pattern to match the fixed arity section.
     *
-    *    productArity: the value of i, i.e. the number of non-sequence types in the extractor
+    *    prodArity: the value of i, i.e. the number of non-sequence types in the extractor
     *    nonStarArity: the value of j, i.e. the number of non-star patterns in the case definition
     *    elementArity: j - i, i.e. the number of non-star patterns which must match sequence elements
     *       starArity: 1 or 0 based on whether there is a star (sequence-absorbing) pattern
     *      totalArity: nonStarArity + starArity, i.e. the number of patterns in the case definition
     *
-    *  Note that productArity is a function only of the extractor, and
+    *  Note that prodArity is a function only of the extractor, and
     *  nonStar/star/totalArity are all functions of the patterns. The key
     *  value for aligning and typing the patterns is elementArity, as it
     *  is derived from both sets of information.
@@ -1651,7 +1651,7 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {thisTrans
     final case class Extractor(whole: Type, fixed: List[Type], repeated: Repeated) {
       require(whole != NoType, s"expandTypes($whole, $fixed, $repeated)")
 
-      def productArity = fixed.length
+      def prodArity    = fixed.length
       def hasSeq       = repeated.exists
       def elementType  = repeated.elementType
       def sequenceType = repeated.sequenceType
@@ -1681,8 +1681,8 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {thisTrans
       *  < 0: There are more products than patterns: compile time error.
       */
     final case class Aligned(patterns: Patterns, extractor: Extractor) {
-      def elementArity = patterns.nonStarArity - productArity
-      def productArity = extractor.productArity
+      def elementArity = patterns.nonStarArity - prodArity
+      def prodArity    = extractor.prodArity
       def starArity    = patterns.starArity
       def totalArity   = patterns.totalArity
 
@@ -1693,15 +1693,15 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {thisTrans
       def typedNonStarPatterns = products ::: elements
       def typedPatterns        = typedNonStarPatterns ::: stars
 
-      def isBool   = !isSeq && productArity == 0
+      def isBool   = !isSeq && prodArity == 0
       def isSingle = !isSeq && totalArity == 1
       def isStar   = patterns.hasStar
       def isSeq    = extractor.hasSeq
 
       private def typedAsElement(pat: Pattern)  = TypedPat(pat, extractor.elementType)
       private def typedAsSequence(pat: Pattern) = TypedPat(pat, extractor.sequenceType)
-      private def productPats = patterns.fixed take productArity
-      private def elementPats = patterns.fixed drop productArity
+      private def productPats = patterns.fixed take prodArity
+      private def elementPats = patterns.fixed drop prodArity
       private def products    = (productPats, productTypes).zipped map TypedPat
       private def elements    = elementPats map typedAsElement
       private def stars       = patterns.starPatterns map typedAsSequence
@@ -1710,7 +1710,7 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {thisTrans
       |Aligned {
       |   patterns  $patterns
       |  extractor  $extractor
-      |    arities  $productArity/$elementArity/$starArity  // product/element/star
+      |    arities  $prodArity/$elementArity/$starArity  // product/element/star
       |      typed  ${typedPatterns mkString ", "}
       |}""".stripMargin.trim
     }
@@ -1826,7 +1826,7 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {thisTrans
         def offering      = extractor.offeringString
         def symString     = tree.symbol.showLocated
         def offerString   = if (extractor.isErroneous) "" else s" offering $offering"
-        def arityExpected = ( if (extractor.hasSeq) "at least " else "" ) + productArity
+        def arityExpected = ( if (extractor.hasSeq) "at least " else "" ) + prodArity
 
         def err(msg: String)         = ctx.error(msg, tree.pos)
         def warn(msg: String)        = ctx.warning(msg, tree.pos)
@@ -1871,12 +1871,12 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {thisTrans
           *  process, we will tuple the extractor before creation Aligned so that
           *  it contains known good values.
           */
-        def productArity    = extractor.productArity
+        def prodArity       = extractor.prodArity
         def acceptMessage   = if (extractor.isErroneous) "" else s" to hold ${extractor.offeringString}"
-        val requiresTupling = isUnapply && patterns.totalArity == 1 && productArity > 1
+        val requiresTupling = isUnapply && patterns.totalArity == 1 && prodArity > 1
 
         //if (requiresTupling && effectivePatternArity(args) == 1)
-        //  currentUnit.deprecationWarning(sel.pos, s"${sel.symbol.owner} expects $productArity patterns$acceptMessage but crushing into $productArity-tuple to fit single pattern (SI-6675)")
+        //  currentUnit.deprecationWarning(sel.pos, s"${sel.symbol.owner} expects $prodArity patterns$acceptMessage but crushing into $prodArity-tuple to fit single pattern (SI-6675)")
 
         val normalizedExtractor =
           if (requiresTupling)