Remove SoftClassReference

They were `get` immediately, and it's unclear
what happens if a reference is GCed and reparsed
later (it may set fields of existing enclosing
classes).

pmd-java/src/main/java/net/sourceforge/pmd/lang/java/symbols/internal/asm/AsmSymbolResolver.java

@@ -31,19 +31,19 @@ public class AsmSymbolResolver implements SymbolResolver {
     private final Classpath classLoader;
     private final SignatureParser typeLoader;
 
-    private final ConcurrentMap<String, SoftClassReference> knownStubs = new ConcurrentHashMap<>();
+    private final ConcurrentMap<String, ClassStub> knownStubs = new ConcurrentHashMap<>();
 
     /**
      * Sentinel for when we fail finding a URL. This allows using a single map,
      * instead of caching failure cases separately.
      */
-    private final SoftClassReference failed;
+    private final ClassStub failed;
 
     public AsmSymbolResolver(TypeSystem ts, Classpath classLoader) {
         this.ts = ts;
         this.classLoader = classLoader;
         this.typeLoader = new SignatureParser(this);
-        this.failed = new SoftClassReference(this, "/*failed-lookup*/", FailedLoader.INSTANCE, 0);
+        this.failed = new ClassStub(this, "/*failed-lookup*/", FailedLoader.INSTANCE, 0);
     }
 
     @Override
@@ -52,25 +52,23 @@ public class AsmSymbolResolver implements SymbolResolver {
 
         String internalName = getInternalName(binaryName);
 
-        SoftClassReference found = knownStubs.computeIfAbsent(internalName, iname -> {
+        ClassStub found = knownStubs.computeIfAbsent(internalName, iname -> {
             @Nullable URL url = getUrlOfInternalName(iname);
             if (url == null) {
                 return failed;
             }
 
-            return new SoftClassReference(this, iname, new UrlLoader(url), ClassStub.UNKNOWN_ARITY);
+            return new ClassStub(this, iname, new UrlLoader(url), ClassStub.UNKNOWN_ARITY);
         });
 
-        if (found == failed) { // NOPMD CompareObjectsWithEquals
-            return null;
-        }
-        ClassStub stub = found.get();
-        if (!stub.hasCanonicalName()) {
+        if (!found.hasCanonicalName()) {
+            // note: this check needs to be done outside of computeIfAbsent
+            //  to prevent recursive updates of the knownStubs map.
             knownStubs.put(internalName, failed);
-            return null;
+            found = failed;
         }
 
-        return stub;
+        return found == failed ? null : found; // NOPMD CompareObjectsWithEquals
     }
 
     SignatureParser getSigParser() {
@@ -131,7 +129,7 @@ public class AsmSymbolResolver implements SymbolResolver {
             }
             @Nullable URL url = getUrlOfInternalName(iname);
             Loader loader = url == null ? FailedLoader.INSTANCE : new UrlLoader(url);
-            return new SoftClassReference(this, iname, loader, observedArity);
-        }).get();
+            return new ClassStub(this, iname, loader, observedArity);
+        });
     }
 }

pmd-java/src/main/java/net/sourceforge/pmd/lang/java/symbols/internal/asm/SoftClassReference.java

@@ -1,44 +0,0 @@
-/*
- * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
- */
-
-package net.sourceforge.pmd.lang.java.symbols.internal.asm;
-
-
-import java.lang.ref.SoftReference;
-
-import org.checkerframework.checker.nullness.qual.NonNull;
-
-/**
- * A soft reference over a (possibly loaded class stub).
- */
-final class SoftClassReference {
-
-    private final Loader loader;
-    private final String internalName;
-    private final int observedArity;
-    private final AsmSymbolResolver resolver;
-    private SoftReference<ClassStub> ref;
-
-    SoftClassReference(AsmSymbolResolver resolver, String internalName, Loader loader, int observedArity) {
-        this.resolver = resolver;
-        this.loader = loader;
-        this.internalName = internalName;
-        this.observedArity = observedArity;
-    }
-
-    @SuppressWarnings("PMD.AssignmentInOperand")
-    @NonNull ClassStub get() {
-        ClassStub c;
-        if (ref == null || (c = ref.get()) == null) { // SUPPRESS CHECKSTYLE NOW
-            c = new ClassStub(resolver, internalName, loader, observedArity);
-            ref = new SoftReference<>(c);
-        }
-        return c;
-    }
-
-    @Override
-    public String toString() {
-        return internalName + " " + loader;
-    }
-}