[flang] Allow for user-defined intrinsic operators (regression)

[klausler]

Summary

The recent code that uses an iterative rather than recursive walk
over the parse tree when processing expressions needs to allow for
the rare case in which an intrinsic operator (e.g., +) is extended
by a generic interface in the program.

flang/include/flang/Semantics/semantics.h

     return *this;
   }
 
+  bool anyDefinedIntrinsicOperator() const {
+    return anyDefinedIntrinsicOperator_;
+  }
+  SemanticsContext &set_anyDefinedIntrinsicOperator(bool yes = true) {
+    anyDefinedIntrinsicOperator_ = yes;
+    return *this;
+  }
+
   const DeclTypeSpec &MakeNumericType(TypeCategory, int kind = 0);
   const DeclTypeSpec &MakeLogicalType(int kind = 0);
 

   const Scope *builtinsScope_{nullptr}; // module __Fortran_builtins
   std::list<parser::Program> modFileParseTrees_;
   std::unique_ptr<CommonBlockMap> commonBlockMap_;
+  bool anyDefinedIntrinsicOperator_{false};
 };
 
 class Semantics {

flang/lib/Semantics/expression.cpp

     if (expr.typedExpr) {
       return expr.typedExpr->v;
     }
-    if (!wasIterativelyAnalyzing) {
+    if (!wasIterativelyAnalyzing && !context_.anyDefinedIntrinsicOperator()) {
       iterativelyAnalyzingSubexpressions_ = true;
       result = IterativelyAnalyzeSubexpressions(expr);
     }

flang/lib/Semantics/resolve-names.cpp

   if (auto *symbol{FindInScope(GenericSpecInfo{x}.symbolName())}) {
     SetGenericSymbol(*symbol);
   }
+  if (const auto *opr{std::get_if<parser::DefinedOperator>(&x.u)}; opr &&
+      std::holds_alternative<parser::DefinedOperator::IntrinsicOperator>(
+          opr->u)) {
+    context().set_anyDefinedIntrinsicOperator(true);
+  }
   return false;
 }