Move DisableTracing helper classes to bottom of class; clear debugWriter

Author: DSouzaM

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/metadata/MetadataTracer.java

@@ -139,6 +139,7 @@ private void shutdown() {
 
         if (debugWriter != null) {
             debugWriter.close();
+            debugWriter = null;
         }
     }
 
@@ -409,37 +410,6 @@ private void debugMethod(ConfigurationTypeDescriptor typeDescriptor, String meth
         debug("method registered for reflection", typeDescriptor + "." + methodName + internalSignature);
     }
 
-    /**
-     * Disables tracing on the current thread from instantiation until {@link #close}.
-     */
-    public sealed interface DisableTracing extends AutoCloseable {
-        @Override
-        void close();
-    }
-
-    private final class DisableTracingImpl implements DisableTracing {
-        final String oldReason;
-
-        private DisableTracingImpl(String reason) {
-            this.oldReason = disableTracingReason.get();
-            disableTracingReason.set(reason);
-        }
-
-        @Override
-        public void close() {
-            disableTracingReason.set(oldReason);
-        }
-    }
-
-    private static final class DisableTracingNoOp implements DisableTracing {
-        private static final DisableTracingNoOp INSTANCE = new DisableTracingNoOp();
-
-        @Override
-        public void close() {
-            // do nothing
-        }
-    }
-
     /**
      * Disables tracing on the current thread from instantiation until {@link DisableTracing#close}.
      * Should be used in a try-with-resources block.
@@ -541,6 +511,37 @@ static RuntimeSupport.Hook checkImproperOptionUsageHook() {
             }
         };
     }
+
+    /**
+     * Disables tracing on the current thread from instantiation until {@link #close}.
+     */
+    public sealed interface DisableTracing extends AutoCloseable {
+        @Override
+        void close();
+    }
+
+    private final class DisableTracingImpl implements DisableTracing {
+        final String oldReason;
+
+        private DisableTracingImpl(String reason) {
+            this.oldReason = disableTracingReason.get();
+            disableTracingReason.set(reason);
+        }
+
+        @Override
+        public void close() {
+            disableTracingReason.set(oldReason);
+        }
+    }
+
+    private static final class DisableTracingNoOp implements DisableTracing {
+        private static final DisableTracingNoOp INSTANCE = new DisableTracingNoOp();
+
+        @Override
+        public void close() {
+            // do nothing
+        }
+    }
 }
 
 record TraceOptions(Path path, boolean merge, Path debugLog) {