Make Taproot spends standard + policy limits

This adds a `TxoutType::WITNESS_V1_TAPROOT` for P2TR outputs, and permits spending
them in standardness rules. No corresponding `CTxDestination` is added for it,
as that isn't needed until we want wallet integration. The taproot validation flags
are also enabled for mempool transactions, and standardness rules are added
(stack item size limit, no annexes).

1 files changed, 7 insertions, 1 deletions

diff --git a/src/script/standard.cpp b/src/script/standard.cpp
index 96a3d311a..f2f81664f 100644
--- a/src/script/standard.cpp
+++ b/src/script/standard.cpp
@@ -55,6 +55,7 @@ std::string GetTxnOutputType(TxoutType t)
     case TxoutType::NULL_DATA: return "nulldata";
     case TxoutType::WITNESS_V0_KEYHASH: return "witness_v0_keyhash";
     case TxoutType::WITNESS_V0_SCRIPTHASH: return "witness_v0_scripthash";
+    case TxoutType::WITNESS_V1_TAPROOT: return "witness_v1_taproot";
     case TxoutType::WITNESS_UNKNOWN: return "witness_unknown";
     } // no default case, so the compiler can warn about missing cases
     assert(false);
@@ -130,6 +131,11 @@ TxoutType Solver(const CScript& scriptPubKey, std::vector<std::vector<unsigned c
             vSolutionsRet.push_back(witnessprogram);
             return TxoutType::WITNESS_V0_SCRIPTHASH;
         }
+        if (witnessversion == 1 && witnessprogram.size() == WITNESS_V1_TAPROOT_SIZE) {
+            vSolutionsRet.push_back(std::vector<unsigned char>{(unsigned char)witnessversion});
+            vSolutionsRet.push_back(std::move(witnessprogram));
+            return TxoutType::WITNESS_V1_TAPROOT;
+        }
         if (witnessversion != 0) {
             vSolutionsRet.push_back(std::vector<unsigned char>{(unsigned char)witnessversion});
             vSolutionsRet.push_back(std::move(witnessprogram));
@@ -203,7 +209,7 @@ bool ExtractDestination(const CScript& scriptPubKey, CTxDestination& addressRet)
         std::copy(vSolutions[0].begin(), vSolutions[0].end(), hash.begin());
         addressRet = hash;
         return true;
-    } else if (whichType == TxoutType::WITNESS_UNKNOWN) {
+    } else if (whichType == TxoutType::WITNESS_UNKNOWN || whichType == TxoutType::WITNESS_V1_TAPROOT) {
         WitnessUnknown unk;
         unk.version = vSolutions[0][0];
         std::copy(vSolutions[1].begin(), vSolutions[1].end(), unk.program);