[flang] Don't crash on not-yet-implemented feature (#91368)

A procedure pointer can be initialized in a DATA statement, but
semantics crashes if the initializer is the name of an intrinsic
function. This patch fixes that crash so that compilation survives to
the point where lowering admits that it doesn't yet support the feature.

Addresses #91295.

Author: klausler

flang/lib/Semantics/data-to-inits.cpp

@@ -903,7 +903,13 @@ void ConstructInitializer(const Symbol &symbol,
       if (const auto *procDesignator{
               std::get_if<evaluate::ProcedureDesignator>(&expr->u)}) {
         CHECK(!procDesignator->GetComponent());
-        mutableProc.set_init(DEREF(procDesignator->GetSymbol()));
+        if (const auto *intrin{procDesignator->GetSpecificIntrinsic()}) {
+          const Symbol *intrinSymbol{
+              symbol.owner().FindSymbol(SourceName{intrin->name})};
+          mutableProc.set_init(DEREF(intrinSymbol));
+        } else {
+          mutableProc.set_init(DEREF(procDesignator->GetSymbol()));
+        }
       } else {
         CHECK(evaluate::IsNullProcedurePointer(*expr));
         mutableProc.set_init(nullptr);