[refactor] add error message to all new Error() calls (#15609)

It's treated a bad practices to create exceptions without error message.

Motivation:

Even if it seems that the error can never happen, it still can - for
example, when someone adds an enum value and forgets to update all
switches.

Modification:

Replaced all calls of `new Error()` by `new Error("Unexpected something:
" + value)`.

Author: asolntsev

buffer/src/main/java/io/netty/buffer/AbstractReferenceCountedByteBuf.java

@@ -23,6 +23,7 @@
 import io.netty.util.internal.AtomicReferenceCountUpdater;
 import io.netty.util.internal.PlatformDependent;
 import io.netty.util.internal.ReferenceCountUpdater;
+import io.netty.util.internal.ReferenceCountUpdater.UpdaterType;
 import io.netty.util.internal.UnsafeReferenceCountUpdater;
 import io.netty.util.internal.VarHandleReferenceCountUpdater;
 
@@ -39,7 +40,8 @@ public abstract class AbstractReferenceCountedByteBuf extends AbstractByteBuf {
     private static final ReferenceCountUpdater<AbstractReferenceCountedByteBuf> updater;
 
     static {
-        switch (ReferenceCountUpdater.updaterTypeOf(AbstractReferenceCountedByteBuf.class, "refCnt")) {
+        UpdaterType updaterType = ReferenceCountUpdater.updaterTypeOf(AbstractReferenceCountedByteBuf.class, "refCnt");
+        switch (updaterType) {
             case Atomic:
                 AIF_UPDATER = newUpdater(AbstractReferenceCountedByteBuf.class, "refCnt");
                 REFCNT_FIELD_OFFSET = -1;
@@ -75,7 +77,7 @@ protected VarHandle varHandle() {
                 };
                 break;
             default:
-                throw new Error("Unknown updater type for AbstractReferenceCountedByteBuf");
+                throw new Error("Unexpected updater type for AbstractReferenceCountedByteBuf: " + updaterType);
         }
     }
 

buffer/src/main/java/io/netty/buffer/AdaptivePoolingAllocator.java

@@ -1119,7 +1119,8 @@ private static class Chunk implements ReferenceCounted, ChunkInfo {
         private static final ReferenceCountUpdater<Chunk> updater;
 
         static {
-            switch (ReferenceCountUpdater.updaterTypeOf(Chunk.class, "refCnt")) {
+            ReferenceCountUpdater.UpdaterType updaterType = ReferenceCountUpdater.updaterTypeOf(Chunk.class, "refCnt");
+            switch (updaterType) {
                 case Atomic:
                     AIF_UPDATER = newUpdater(Chunk.class, "refCnt");
                     REFCNT_FIELD_OFFSET = -1;
@@ -1155,7 +1156,7 @@ protected VarHandle varHandle() {
                     };
                     break;
                 default:
-                    throw new Error("Unknown updater type for Chunk");
+                    throw new Error("Unexpected updater type for Chunk: " + updaterType);
             }
         }
 

buffer/src/main/java/io/netty/buffer/PoolArena.java

@@ -272,7 +272,7 @@ void freeChunk(PoolChunk<T> chunk, long handle, int normCapacity, SizeClass size
                         ++deallocationsSmall;
                         break;
                     default:
-                        throw new Error();
+                        throw new Error("Unexpected size class: " + sizeClass);
                 }
             }
             destroyChunk = !chunk.parent.free(chunk, handle, normCapacity, nioBuffer);

buffer/src/main/java/io/netty/buffer/PoolThreadCache.java

@@ -193,7 +193,7 @@ private MemoryRegionCache<?> cache(PoolArena<?> area, int sizeIdx, SizeClass siz
         case Small:
             return cacheForSmall(area, sizeIdx);
         default:
-            throw new Error();
+            throw new Error("Unexpected size class: " + sizeClass);
         }
     }
 

buffer/src/test/java/io/netty/buffer/ByteBufDerivationTest.java

@@ -175,7 +175,8 @@ public void testMixture() throws Exception {
         Random rnd = new Random();
         for (int i = 0; i < buf.capacity(); i ++) {
             ByteBuf newDerived;
-            switch (rnd.nextInt(4)) {
+            int randomNumber = rnd.nextInt(4);
+            switch (randomNumber) {
             case 0:
                 newDerived = derived.slice(1, derived.capacity() - 1);
                 break;
@@ -190,7 +191,7 @@ public void testMixture() throws Exception {
                 newDerived = Unpooled.unmodifiableBuffer(derived);
                 break;
             default:
-                throw new Error();
+                throw new Error("Unexpected random number: " + randomNumber);
             }
 
             assertThat(nestLevel(newDerived)).isLessThanOrEqualTo(3);

codec-base/src/main/java/io/netty/handler/codec/AsciiHeadersEncoder.java

@@ -90,7 +90,7 @@ public void encode(Entry<CharSequence, CharSequence> entry) {
                 buf.setByte(offset ++, ' ');
                 break;
             default:
-                throw new Error();
+                throw new Error("Unexpected separator type: " + separatorType);
         }
 
         writeAscii(buf, offset, value);
@@ -105,7 +105,7 @@ public void encode(Entry<CharSequence, CharSequence> entry) {
                 buf.setByte(offset ++, '\n');
                 break;
             default:
-                throw new Error();
+                throw new Error("Unexpected newline type: " + newlineType);
         }
 
         buf.writerIndex(offset);

codec-base/src/main/java/io/netty/handler/codec/LengthFieldPrepender.java

@@ -195,7 +195,7 @@ protected void encode(ChannelHandlerContext ctx, ByteBuf msg, List<Object> out)
             out.add(ctx.alloc().buffer(8).order(byteOrder).writeLong(length));
             break;
         default:
-            throw new Error("should not reach here");
+            throw new Error("Unexpected length field length: " + lengthFieldLength);
         }
         out.add(msg.retain());
     }

codec-classes-quic/src/main/java/io/netty/handler/codec/quic/QuicheQuicSslContext.java

@@ -323,7 +323,7 @@ private static int boringSSLVerifyModeForServer(ClientAuth mode) {
             case OPTIONAL:
                 return BoringSSL.SSL_VERIFY_PEER;
             default:
-                throw new Error(mode.toString());
+                throw new Error("Unexpected mode: " + mode);
         }
     }
 

codec-classes-quic/src/main/java/io/netty/handler/codec/quic/QuicheQuicStreamChannel.java

@@ -980,13 +980,14 @@ void recv() {
                         while (!finReceived && continueReading) {
                             byteBuf = allocHandle.allocate(allocator);
                             allocHandle.attemptedBytesRead(byteBuf.writableBytes());
-                            switch (parent.streamRecv(streamId(), byteBuf)) {
+                            QuicheQuicChannel.StreamRecvResult result = parent.streamRecv(streamId(), byteBuf);
+                            switch (result) {
                                 case DONE:
                                     // Nothing left to read;
                                     readable = false;
                                     break;
                                 case FIN:
-                                    // If we received a FIN we also should mark the channel as non readable as
+                                    // If we received a FIN we also should mark the channel as non-readable as
                                     // there is nothing left to read really.
                                     readable = false;
                                     finReceived = true;
@@ -995,7 +996,7 @@ void recv() {
                                 case OK:
                                     break;
                                 default:
-                                    throw new Error();
+                                    throw new Error("Unexpected StreamRecvResult: " + result);
                             }
                             allocHandle.lastBytesRead(byteBuf.readableBytes());
                             if (allocHandle.lastBytesRead() <= 0) {

codec-compression/src/main/java/io/netty/handler/codec/compression/ZlibUtil.java

@@ -41,43 +41,32 @@ static CompressionException deflaterException(Deflater z, String message, int re
     }
 
     static JZlib.WrapperType convertWrapperType(ZlibWrapper wrapper) {
-        JZlib.WrapperType convertedWrapperType;
         switch (wrapper) {
         case NONE:
-            convertedWrapperType = JZlib.W_NONE;
-            break;
+            return JZlib.W_NONE;
         case ZLIB:
-            convertedWrapperType = JZlib.W_ZLIB;
-            break;
+            return JZlib.W_ZLIB;
         case GZIP:
-            convertedWrapperType = JZlib.W_GZIP;
-            break;
+            return JZlib.W_GZIP;
         case ZLIB_OR_NONE:
-            convertedWrapperType = JZlib.W_ANY;
-            break;
+            return JZlib.W_ANY;
         default:
-            throw new Error();
+            throw new Error("Unexpected wrapper type: " + wrapper);
         }
-        return convertedWrapperType;
     }
 
     static int wrapperOverhead(ZlibWrapper wrapper) {
-        int overhead;
         switch (wrapper) {
         case NONE:
-            overhead = 0;
-            break;
+            return 0;
         case ZLIB:
         case ZLIB_OR_NONE:
-            overhead = 2;
-            break;
+            return 2;
         case GZIP:
-            overhead = 10;
-            break;
+            return 10;
         default:
-            throw new Error();
+            throw new Error("Unexpected wrapper type: " + wrapper);
         }
-        return overhead;
     }
 
     private ZlibUtil() {