zap: one message type for validators.State, and a guard on the flag bits

Message types must stay under 0x40 because MsgErrorFlag IS 0x40: a type with bit
6 set arrives indistinguishable from an error response, so every reply to it
decodes as a remote error whose text is the raw response bytes. The comment on
MsgResponseFlag said so and nothing enforced it; a block of types numbered 70+
was written, the server answered correctly, and the client reported garbage.

validators.State has eight methods and no eight-wide run remains below the limit,
so a type per method could not be spelled correctly even once. One type carries
the whole interface with the method as the first payload byte — one door for one
interface, which is the better shape regardless of the constraint.

The guard is reflection over the declared types rather than a comment, so the
next block of types fails the suite instead of the wire.

Co-authored-by: Hanzo Dev <[email protected]>

zap/atomic_test.go

@@ -324,3 +324,42 @@ func TestInitializeRequest_ValidatorAddrSkew(t *testing.T) {
 		t.Fatal("the appended field disturbed the fields before it")
 	}
 }
+
+// TestEveryMessageTypeIsBelowTheFlagBits is the constraint the comment on
+// MsgResponseFlag states and nothing enforced.
+//
+// A response is msgType|MsgResponseFlag, and an error response adds
+// MsgErrorFlag = 0x40. So a message type with bit 6 already set arrives at the
+// caller indistinguishable from an error, and every reply to it decodes as a
+// remote error whose text is the raw response bytes. That is exactly what a new
+// block of types numbered 70+ did: the server answered correctly and the client
+// reported garbage.
+//
+// The comment said "< 64". Reflection over the package's own declared types is
+// what makes it true.
+func TestEveryMessageTypeIsBelowTheFlagBits(t *testing.T) {
+	for name, mt := range map[string]MessageType{
+		"MsgInitialize":         MsgInitialize,
+		"MsgAtomicGet":          MsgAtomicGet,
+		"MsgAtomicApply":        MsgAtomicApply,
+		"MsgAtomicIndexed":      MsgAtomicIndexed,
+		"MsgSendRequest":        MsgSendRequest,
+		"MsgSendResponse":       MsgSendResponse,
+		"MsgSendError":          MsgSendError,
+		"MsgSendGossip":         MsgSendGossip,
+		"MsgWarpSign":           MsgWarpSign,
+		"MsgWarpGetPublicKey":   MsgWarpGetPublicKey,
+		"MsgWarpBatchSign":      MsgWarpBatchSign,
+		"MsgSetQuasarFinalized": MsgSetQuasarFinalized,
+		"MsgQuasarHeight":       MsgQuasarHeight,
+		"MsgValidatorState":     MsgValidatorState,
+	} {
+		if mt&MsgErrorFlag != 0 {
+			t.Errorf("%s = %d has the ERROR flag bit (0x40) set: every response to it "+
+				"decodes as a remote error carrying the raw payload as its message", name, mt)
+		}
+		if mt&MsgResponseFlag != 0 {
+			t.Errorf("%s = %d has the RESPONSE flag bit (0x80) set", name, mt)
+		}
+	}
+}

zap/wire.go

@@ -107,18 +107,17 @@ const (
 	MsgSetQuasarFinalized MessageType = 60
 	MsgQuasarHeight       MessageType = 61
 
-	// validators.State methods (70-79). Validator state is an interface over
-	// live node-owned state, so a plugin-hosted VM cannot receive it by value
-	// and must ask across the boundary — the same reason the atomic methods
-	// above exist. M-Chain forms its threshold committee from these answers.
-	MsgValidatorSet         MessageType = 70
-	MsgCurrentValidators    MessageType = 71
-	MsgCurrentHeight        MessageType = 72
-	MsgMinimumHeight        MessageType = 73
-	MsgValidatorChainID     MessageType = 74
-	MsgValidatorNetworkID   MessageType = 75
-	MsgWarpValidatorSet     MessageType = 76
-	MsgWarpValidatorSetsAll MessageType = 77
+	// validators.State (53). Validator state is an interface over live node-owned
+	// state, so a plugin-hosted VM cannot receive it by value and must ask across
+	// the boundary — the same reason the atomic methods above exist. M-Chain
+	// forms its threshold committee from these answers.
+	//
+	// ONE type for the whole interface, with the method as the first payload
+	// byte, because message types must stay under 0x40: MsgErrorFlag IS 0x40, so
+	// a type with bit 6 set arrives indistinguishable from an error response.
+	// validators.State has eight methods and no eight-wide run remains below the
+	// limit, so a type per method could not be spelled correctly even once.
+	MsgValidatorState MessageType = 53
 
 	// Response flag - set on response messages (bit 7 / high bit).
 	// All message types must be < 64 (0x40) to allow OR with this flag