Improve / add freeze checking helper functions

- Add an override of isDeepFrozen that can take an Asset, and thus an
  MPTIssue. The MPT version just calls isFrozen, since they're
  equivalent for MPTs.
- Add wrappers checkFrozen and checkDeepFrozen that return the
  appropriate TER code, so the Asset type doesn't have to be checked
  at every #*%@ing caller.
- Convert the Loan* transactors to use these functions.

src/xrpld/app/tx/detail/LoanBrokerCoverDeposit.cpp

@@ -89,15 +89,11 @@ LoanBrokerCoverDeposit::preclaim(PreclaimContext const& ctx)
     auto const pseudoAccountID = sleBroker->at(sfAccount);
 
     // Cannot transfer a frozen Asset
-    if (isFrozen(ctx.view, account, vaultAsset))
-        return vaultAsset.holds<Issue>() ? tecFROZEN : tecLOCKED;
-    if (vaultAsset.holds<Issue>())
-    {
-        auto const issue = vaultAsset.get<Issue>();
-        if (isDeepFrozen(
-                ctx.view, pseudoAccountID, issue.currency, issue.account))
-            return tecFROZEN;
-    }
+    if (auto const ret = checkFrozen(ctx.view, account, vaultAsset))
+        return ret;
+    // Pseudo-account cannot receive if asset is deep frozen
+    if (auto const ret = checkDeepFrozen(ctx.view, pseudoAccountID, vaultAsset))
+        return ret;
 
     if (accountHolds(
             ctx.view,

src/xrpld/app/tx/detail/LoanBrokerCoverWithdraw.cpp

@@ -90,18 +90,11 @@ LoanBrokerCoverWithdraw::preclaim(PreclaimContext const& ctx)
     auto const pseudoAccountID = sleBroker->at(sfAccount);
 
     // Cannot transfer a frozen Asset
-    /*
-    if (isFrozen(ctx.view, account, vaultAsset))
-        return vaultAsset.holds<Issue>() ? tecFROZEN : tecLOCKED;
-    */
-    if (isFrozen(ctx.view, pseudoAccountID, vaultAsset))
-        return vaultAsset.holds<Issue>() ? tecFROZEN : tecLOCKED;
-    if (vaultAsset.holds<Issue>())
-    {
-        auto const issue = vaultAsset.get<Issue>();
-        if (isDeepFrozen(ctx.view, account, issue.currency, issue.account))
-            return tecFROZEN;
-    }
+    if (auto const ret = checkFrozen(ctx.view, pseudoAccountID, vaultAsset))
+        return ret;
+    // Account cannot receive if asset is deep frozen
+    if (auto const ret = checkDeepFrozen(ctx.view, account, vaultAsset))
+        return ret;
 
     auto const coverAvail = sleBroker->at(sfCoverAvailable);
     // Cover Rate is in 1/10 bips units

src/xrpld/app/tx/detail/LoanDraw.cpp

@@ -131,19 +131,16 @@ LoanDraw::preclaim(PreclaimContext const& ctx)
         return tecINSUFFICIENT_FUNDS;
     }
 
-    if (isFrozen(ctx.view, brokerPseudoAccount, asset))
+    if (auto const ret = checkFrozen(ctx.view, brokerPseudoAccount, asset))
     {
         JLOG(ctx.j.warn()) << "Loan Broker pseudo-account is frozen.";
-        return asset.holds<Issue>() ? tecFROZEN : tecLOCKED;
+        return ret;
     }
-    if (asset.holds<Issue>())
+    if (auto const ret = checkDeepFrozen(ctx.view, account, asset))
     {
-        auto const issue = asset.get<Issue>();
-        if (isDeepFrozen(ctx.view, account, issue.currency, issue.account))
-        {
-            JLOG(ctx.j.warn()) << "Borrower account is frozen.";
-            return tecFROZEN;
-        }
+        JLOG(ctx.j.warn())
+            << "Borrower account cannot receive funds (deep frozen).";
+        return ret;
     }
 
     if (hasExpired(ctx.view, loanSle->at(sfNextPaymentDueDate)))

src/xrpld/app/tx/detail/LoanPay.cpp

@@ -131,19 +131,16 @@ LoanPay::preclaim(PreclaimContext const& ctx)
         return tecWRONG_ASSET;
     }
 
-    if (isFrozen(ctx.view, brokerPseudoAccount, asset))
+    if (auto const ret = checkFrozen(ctx.view, account, asset))
     {
-        JLOG(ctx.j.warn()) << "Loan Broker pseudo-account is frozen.";
-        return asset.holds<Issue>() ? tecFROZEN : tecLOCKED;
+        JLOG(ctx.j.warn()) << "Borrower account is frozen.";
+        return ret;
     }
-    if (asset.holds<Issue>())
+    if (auto const ret = checkDeepFrozen(ctx.view, brokerPseudoAccount, asset))
     {
-        auto const issue = asset.get<Issue>();
-        if (isDeepFrozen(ctx.view, account, issue.currency, issue.account))
-        {
-            JLOG(ctx.j.warn()) << "Borrower account is frozen.";
-            return tecFROZEN;
-        }
+        JLOG(ctx.j.warn()) << "Loan Broker pseudo-account can not receive "
+                              "funds (deep frozen).";
+        return ret;
     }
 
     return tesSUCCESS;

src/xrpld/app/tx/detail/LoanSet.cpp

@@ -204,19 +204,25 @@ LoanSet::preclaim(PreclaimContext const& ctx)
     if (auto const ter = canAddHolding(ctx.view, asset))
         return ter;
 
-    if (isFrozen(ctx.view, brokerOwner, asset) ||
-        isFrozen(ctx.view, brokerPseudo, asset))
+    if (auto const ret = checkFrozen(ctx.view, brokerOwner, asset))
     {
-        JLOG(ctx.j.warn()) << "One of the affected accounts is frozen.";
-        return asset.holds<Issue>() ? tecFROZEN : tecLOCKED;
+        JLOG(ctx.j.warn()) << "Broker owner account is frozen.";
+        return ret;
     }
-    if (asset.holds<Issue>())
+    if (auto const ret = checkFrozen(ctx.view, brokerPseudo, asset))
     {
-        auto const issue = asset.get<Issue>();
-        if (isDeepFrozen(ctx.view, borrower, issue.currency, issue.account))
-            return tecFROZEN;
-        if (isDeepFrozen(ctx.view, brokerPseudo, issue.currency, issue.account))
-            return tecFROZEN;
+        JLOG(ctx.j.warn()) << "Broker pseudo-account account is frozen.";
+        return ret;
+    }
+    if (auto const ret = checkDeepFrozen(ctx.view, borrower, asset))
+    {
+        JLOG(ctx.j.warn()) << "Borrower account is deep frozen.";
+        return ret;
+    }
+    if (auto const ret = checkDeepFrozen(ctx.view, brokerPseudo, asset))
+    {
+        JLOG(ctx.j.warn()) << "Broker pseudo-account account is deep frozen.";
+        return ret;
     }
 
     auto const principalRequested = tx[sfPrincipalRequested];

src/xrpld/ledger/View.h

@@ -175,6 +175,29 @@ isFrozen(
         asset.value());
 }
 
+[[nodiscard]] inline TER
+checkFrozen(ReadView const& view, AccountID const& account, Issue const& issue)
+{
+    return isFrozen(view, account, issue) ? (TER)tecFROZEN : (TER)tesSUCCESS;
+}
+
+[[nodiscard]] inline TER
+checkFrozen(
+    ReadView const& view,
+    AccountID const& account,
+    MPTIssue const& mptIssue)
+{
+    return isFrozen(view, account, mptIssue) ? (TER)tecLOCKED : (TER)tesSUCCESS;
+}
+
+[[nodiscard]] inline TER
+checkFrozen(ReadView const& view, AccountID const& account, Asset const& asset)
+{
+    return std::visit(
+        [&](auto const& issue) { return checkFrozen(view, account, issue); },
+        asset.value());
+}
+
 [[nodiscard]] bool
 isAnyFrozen(
     ReadView const& view,
@@ -220,6 +243,80 @@ isDeepFrozen(
     Currency const& currency,
     AccountID const& issuer);
 
+[[nodiscard]] inline bool
+isDeepFrozen(
+    ReadView const& view,
+    AccountID const& account,
+    Issue const& issue,
+    int = 0 /*ignored*/)
+{
+    return isDeepFrozen(view, account, issue.currency, issue.account);
+}
+
+[[nodiscard]] inline bool
+isDeepFrozen(
+    ReadView const& view,
+    AccountID const& account,
+    MPTIssue const& mptIssue,
+    int depth = 0)
+{
+    // Unlike IOUs, frozen / locked MPTs are not allowed to send or receive
+    // funds, so checking "deep frozen" is the same as checking "frozen".
+    return isFrozen(view, account, mptIssue, depth);
+}
+
+/**
+ *   isFrozen check is recursive for MPT shares in a vault, descending to
+ *   assets in the vault, up to maxAssetCheckDepth recursion depth. This is
+ *   purely defensive, as we currently do not allow such vaults to be created.
+ */
+[[nodiscard]] inline bool
+isDeepFrozen(
+    ReadView const& view,
+    AccountID const& account,
+    Asset const& asset,
+    int depth = 0)
+{
+    return std::visit(
+        [&](auto const& issue) {
+            return isDeepFrozen(view, account, issue, depth);
+        },
+        asset.value());
+}
+
+[[nodiscard]] inline TER
+checkDeepFrozen(
+    ReadView const& view,
+    AccountID const& account,
+    Issue const& issue)
+{
+    return isDeepFrozen(view, account, issue) ? (TER)tecFROZEN
+                                              : (TER)tesSUCCESS;
+}
+
+[[nodiscard]] inline TER
+checkDeepFrozen(
+    ReadView const& view,
+    AccountID const& account,
+    MPTIssue const& mptIssue)
+{
+    return isDeepFrozen(view, account, mptIssue) ? (TER)tecLOCKED
+                                                 : (TER)tesSUCCESS;
+}
+
+[[nodiscard]] inline TER
+checkDeepFrozen(
+    ReadView const& view,
+    AccountID const& account,
+    Asset const& asset)
+{
+    return std::visit(
+        [&](auto const& issue) {
+            return checkDeepFrozen(view, account, issue);
+        },
+        asset.value());
+}
+
 [[nodiscard]] bool
 isLPTokenFrozen(
     ReadView const& view,