[flang] Fix crash in statement function semantics (bug #80532) (#82702)

When statement function expressions are analyzed, ensure that the
semantics context has a valid location set, otherwise a type spec (like
"integer::") can lead to a crash.

Fixes #80532.

flang/lib/Semantics/expression.cpp

@@ -4613,8 +4613,9 @@ evaluate::Expr<evaluate::SubscriptInteger> AnalyzeKindSelector(
     SemanticsContext &context, common::TypeCategory category,
     const std::optional<parser::KindSelector> &selector) {
   evaluate::ExpressionAnalyzer analyzer{context};
+  CHECK(context.location().has_value());
   auto restorer{
-      analyzer.GetContextualMessages().SetLocation(context.location().value())};
+      analyzer.GetContextualMessages().SetLocation(*context.location())};
   return analyzer.AnalyzeKindSelector(category, selector);
 }
 

flang/lib/Semantics/resolve-names.cpp

@@ -8475,6 +8475,7 @@ void ResolveNamesVisitor::FinishSpecificationPart(
     if (const auto *statement{std::get_if<
             parser::Statement<common::Indirection<parser::StmtFunctionStmt>>>(
             &decl.u)}) {
+      messageHandler().set_currStmtSource(statement->source);
       AnalyzeStmtFunctionStmt(statement->statement.value());
     }
   }