miniscript: don't check for top level validity at parsing time

Letting the caller perform the checks allows for finer-grained error
reporting.

Author: darosior

src/script/miniscript.h

@@ -953,7 +953,11 @@ void BuildBack(const Ctx& ctx, Fragment nt, std::vector<NodeRef<Key>>& construct
     }
 }
 
-//! Parse a miniscript from its textual descriptor form.
+/**
+ * Parse a miniscript from its textual descriptor form.
+ * This does not check whether the script is valid, let alone sane. The caller is expected to use
+ * the `IsValidTopLevel()` and `IsSaneTopLevel()` to check for these properties on the node.
+ */
 template<typename Key, typename Ctx>
 inline NodeRef<Key> Parse(Span<const char> in, const Ctx& ctx)
 {
@@ -1255,9 +1259,7 @@ inline NodeRef<Key> Parse(Span<const char> in, const Ctx& ctx)
     // Sanity checks on the produced miniscript
     assert(constructed.size() == 1);
     if (in.size() > 0) return {};
-    const NodeRef<Key> tl_node = std::move(constructed.front());
-    if (!tl_node->IsValidTopLevel()) return {};
-    return tl_node;
+    return std::move(constructed.front());
 }
 
 /** Decode a script into opcode/push pairs.

src/test/miniscript_tests.cpp

@@ -276,7 +276,7 @@ BOOST_AUTO_TEST_CASE(fixed_tests)
     // (for now) have 'd:' be 'u'. This tests we can't use a 'd:' wrapper for a thresh, which requires
     // its subs to all be 'u' (taken from https://github.com/rust-bitcoin/rust-miniscript/discussions/341).
     const auto ms_minimalif = miniscript::FromString("thresh(3,c:pk_k(03d30199d74fb5a22d47b6e054e2f378cedacffcb89904a61d75d0dbd407143e65),sc:pk_k(03fff97bd5755eeea420453a14355235d382f6472f8568a18b2f057a1460297556),sc:pk_k(0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798),sdv:older(32))", CONVERTER);
-    BOOST_CHECK(!ms_minimalif);
+    BOOST_CHECK(ms_minimalif && !ms_minimalif->IsValid());
     // A Miniscript with duplicate keys is not sane
     const auto ms_dup1 = miniscript::FromString("and_v(v:pk(03d30199d74fb5a22d47b6e054e2f378cedacffcb89904a61d75d0dbd407143e65),pk(03d30199d74fb5a22d47b6e054e2f378cedacffcb89904a61d75d0dbd407143e65))", CONVERTER);
     BOOST_CHECK(ms_dup1);