Merge pull request #2127 from dotty-staging/fix/variable-pattern-access

Fix desugaring of variable pattern leaking into API

Author: smarter

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -557,7 +557,7 @@ object desugar {
    *   val/var/lazy val p = e  ==>  val/var/lazy val x_1 = (e: @unchecked) match (case p => (x_1))
    *
    *   in case there are zero or more than one variables in pattern
-   *   val/var/lazy p = e  ==>  private synthetic [lazy] val t$ = (e: @unchecked) match (case p => (x_1, ..., x_N))
+   *   val/var/lazy p = e  ==>  private[this] synthetic [lazy] val t$ = (e: @unchecked) match (case p => (x_1, ..., x_N))
    *                   val/var/def x_1 = t$._1
    *                   ...
    *                   val/var/def x_N = t$._N
@@ -586,7 +586,8 @@ object desugar {
           derivedValDef(original, named, tpt, matchExpr, mods)
         case _ =>
           val tmpName = ctx.freshName().toTermName
-          val patMods = mods & (AccessFlags | Lazy) | Synthetic
+          val patMods =
+            mods & Lazy | Synthetic | (if (ctx.owner.isClass) PrivateLocal else EmptyFlags)
           val firstDef =
             ValDef(tmpName, TypeTree(), matchExpr)
               .withPos(pat.pos.union(rhs.pos)).withMods(patMods)

tests/run/variable-pattern-access.check

@@ -0,0 +1,7 @@
+# Fields of A:
+private final int A.a$$local
+private final int A.b$$local
+private final scala.Tuple2 A.$1$
+# Methods of A:
+public int A.a()
+public int A.b()

tests/run/variable-pattern-access.scala

@@ -0,0 +1,16 @@
+class A {
+  val (a, b) = (1, 2)
+}
+object Test {
+  def printFields(cls: Class[_]) =
+    println(cls.getDeclaredFields.map(_.toString).sorted.deep.mkString("\n"))
+  def printMethods(cls: Class[_]) =
+    println(cls.getDeclaredMethods.map(_.toString).sorted.deep.mkString("\n"))
+
+  def main(args: Array[String]): Unit = {
+    println("# Fields of A:")
+    printFields(classOf[A])
+    println("# Methods of A:")
+    printMethods(classOf[A])
+  }
+}