Run PatternMatcher earlier, in the group before ExplicitOuter

compiler/src/dotty/tools/dotc/Compiler.scala

@@ -73,10 +73,10 @@ class Compiler {
          new ByNameClosures,         // Expand arguments to by-name parameters to closures
          new HoistSuperArgs,         // Hoist complex arguments of supercalls to enclosing scope
          new SpecializeApplyMethods, // Adds specialized methods to FunctionN
-         new RefChecks) ::           // Various checks mostly related to abstract members and overriding
-    List(new ElimOpaque,             // Turn opaque into normal aliases
+         new RefChecks,              // Various checks mostly related to abstract members and overriding
          new TryCatchPatterns,       // Compile cases in try/catch
-         new PatternMatcher,         // Compile pattern matches
+         new PatternMatcher) ::      // Compile pattern matches
+    List(new ElimOpaque,             // Turn opaque into normal aliases
          new sjs.ExplicitJSClasses,  // Make all JS classes explicit (Scala.js only)
          new ExplicitOuter,          // Add accessors to outer classes from nested ones.
          new ExplicitSelf,           // Make references to non-trivial self types explicit as casts

compiler/src/dotty/tools/dotc/transform/ExplicitOuter.scala

@@ -40,10 +40,8 @@ class ExplicitOuter extends MiniPhase with InfoTransformer { thisPhase =>
 
   override def phaseName: String = ExplicitOuter.name
 
-  /** List of names of phases that should have finished their processing of all compilation units
-    * before this phase starts
-    */
-  override def runsAfter: Set[String] = Set(PatternMatcher.name, HoistSuperArgs.name)
+  override def runsAfter:         Set[String] = Set(HoistSuperArgs.name)
+  override def runsAfterGroupsOf: Set[String] = Set(PatternMatcher.name)
 
   override def changesMembers: Boolean = true // the phase adds outer accessors
 

tests/run/i13096.scala

@@ -0,0 +1,10 @@
+class C1 {
+  private class C2
+  new C2 match {
+    case c: C2 =>
+  }
+}
+
+object Test extends App {
+  new C1
+}