Fix regex in KMP for visiting inner classes

Summary:
The old regex alone was accepting all inner classes per each inner class instead of just the next inner class in the hierarchy, therefore the analysis was blowing up and visiting classes an unnesessarily huge amount of times.
Now the visits happen only to the classes that have not been previously visited, therefore there is no additional branching happening.

Author: olesya.subbotina

kmp-library/src/main/java/com/guardsquare/proguard/kotlin/printer/KotlinMetadataPrinter.java

@@ -58,6 +58,8 @@
 import proguard.classfile.kotlin.visitor.filter.KotlinTypeFilter;
 import proguard.classfile.util.ClassUtil;
 import proguard.classfile.visitor.ClassCounter;
+import proguard.classfile.visitor.ClassPoolFiller;
+import proguard.classfile.visitor.ClassPresenceFilter;
 import proguard.classfile.visitor.MultiClassVisitor;
 import proguard.classfile.visitor.MultiMemberVisitor;
 import com.guardsquare.proguard.kotlin.printer.internal.visitor.KotlinTypeVisitorWrapper;
@@ -95,7 +97,7 @@ public class KotlinMetadataPrinter
     private       int                           indentation;
     private Context context;
     private final boolean excludeEmbedded;
-
+    private final ClassPool visitedNestedClassPool = new ClassPool();
 
     public KotlinMetadataPrinter(ClassPool programClassPool)
     {
@@ -326,6 +328,7 @@ else if (classCounter.getCount() > 0)
             });
 
             kotlinClassKindMetadata.nestedClassesAccept(false,
+                new MultiClassVisitor(new ClassPoolFiller(visitedNestedClassPool),
                 new ReferencedKotlinMetadataVisitor(
                 new KotlinMetadataVisitorWrapper(
                     (i, metadata) -> {
@@ -336,7 +339,11 @@ else if (classCounter.getCount() > 0)
                             println();
                         }
                     },
-                    MyKotlinSourceMetadataPrinter.this)));
+                    MyKotlinSourceMetadataPrinter.this))));
+
+            if (kotlinClassKindMetadata.referencedCompanionClass != null) {
+                visitedNestedClassPool.removeClass(kotlinClassKindMetadata.referencedCompanionClass);
+            }
 
             visitChildClasses(clazz);
 
@@ -1079,11 +1086,15 @@ private void visitChildClasses(Clazz clazz)
         {
             // Cache the synthetic class string, as we might have already visited them, so the string will be empty.
             pushStringBuilder();
+            // Only visit the classes that have not yet been visited in the previous nested classes visits.
             programClassPool.classesAccept(
-                    clazz.getName() + TypeConstants.INNER_CLASS_SEPARATOR + "[^$]+",
-                    new ReferencedKotlinMetadataVisitor(MyKotlinSourceMetadataPrinter.this));
+                clazz.getName() + TypeConstants.INNER_CLASS_SEPARATOR + "*",
+                new ClassPresenceFilter(
+                    visitedNestedClassPool,
+                    null,
+                    new ReferencedKotlinMetadataVisitor(MyKotlinSourceMetadataPrinter.this)));
             String innerClassesString = popStringBuilder();
-            if (innerClassesString.length() > 0)
+            if (!innerClassesString.isEmpty())
             {
                 println();
                 println("// Synthetic inner classes - these were generated by the Kotlin compiler from e.g. lambdas", true);
@@ -1326,7 +1337,7 @@ private String valueParameterFlags(KotlinValueParameterFlags flags)
             (flags.isNoInline      ? "noinline "    : "") +
             (flags.hasDefaultValue ? ""  : "");
     }
-    
+
     private enum ValueParameterType
     {
         NORMAL, VAR, VAL