miniscript: split ValidSatisfactions from IsSane

This makes IsSane clearer. It is useful to differentiate between 'potential non-malleable satisfactions are valid' and 'such satisfactions exist' for testing.

Co-authored-by: Pieter Wuille <[email protected]>

Author: darosior

src/script/miniscript.h

@@ -779,8 +779,11 @@ struct Node {
     //! Check whether there is no satisfaction path that contains both timelocks and heightlocks
     bool CheckTimeLocksMix() const { return GetType() << "k"_mst; }
 
-    //! Do all sanity checks.
-    bool IsSane() const { return IsValid() && IsNonMalleable() && CheckTimeLocksMix() && CheckOpsLimit() && CheckStackSize(); }
+    //! Whether successful non-malleable satisfactions are guaranteed to be valid.
+    bool ValidSatisfactions() const { return IsValid() && CheckOpsLimit() && CheckStackSize(); }
+
+    //! Whether the apparent policy of this node matches its script semantics.
+    bool IsSane() const { return ValidSatisfactions() && IsNonMalleable() && CheckTimeLocksMix(); }
 
     //! Check whether this node is safe as a script on its own.
     bool IsSaneTopLevel() const { return IsValidTopLevel() && IsSane() && NeedsSignature(); }