GNU3 demangler: fix multi-level sr scope resolution without N prefix

GCC emits "sr St 6__and_I<T>E 5value" for std::__and_<T>::value in
enable_if expressions. The previous sr/else handler assumed exactly one
qualifier after the unresolved type, leaving trailing source-name
components unread and causing DemangleException in subsequent parsing.

Fix: loop over digit-started source names after the initial unresolved
type, treating each as an intermediate qualifier when it has template
args AND another source name follows, or as the final name otherwise.
Operator-name ("on") and destructor-name ("dn") final components fall
through to the existing DemangleBaseUnresolvedName() call.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: plafosse

demangler/gnu3/demangle_gnu3.cpp

@@ -1843,6 +1843,39 @@ string DemangleGNU3::DemangleExpression()
 		else
 		{
 			out += DemangleUnresolvedType().GetString() + "::";
+			// GCC may encode multi-level scoped names without the 'N' qualifier
+			// prefix, e.g. "sr St 6__and_I<T>E 5value" for std::__and_<T>::value.
+			// Process any digit-started names: if a name has template args AND
+			// another source name follows, it is an intermediate qualifier level;
+			// otherwise it is the final base-unresolved-name.
+			while (isdigit(m_reader.Peek()))
+			{
+				const string segName = DemangleSourceName();
+				if (m_reader.Peek() == 'I')
+				{
+					vector<string> args;
+					m_reader.Consume();
+					DemangleTemplateArgs(args);
+					if (isdigit(m_reader.Peek()))
+					{
+						// Another source name follows — intermediate qualifier.
+						out += segName + GetTemplateString(args) + "::";
+					}
+					else
+					{
+						// No more source names — this template-id is the final name.
+						out += segName + GetTemplateString(args);
+						return out;
+					}
+				}
+				else
+				{
+					// Plain source name with no template args — final base name.
+					out += segName;
+					return out;
+				}
+			}
+			// peek is not a digit: fall back for operator-names ("on") / destructor-names ("dn").
 			out += DemangleBaseUnresolvedName().GetString();
 		}
 		return out;