Add hard todo for non default component lower bounds

Author: jeanPerier

flang/lib/Lower/ConvertType.cpp

@@ -263,6 +263,20 @@ struct TypeBuilder {
     return ty;
   }
 
+  /// Does \p component has non deferred lower bounds that are not compile time
+  /// constant 1.
+  static bool componentHasNonDefaultLowerBounds(
+      const Fortran::semantics::Symbol &component) {
+    if (const auto *objDetails =
+            component.detailsIf<Fortran::semantics::ObjectEntityDetails>())
+      for (const auto &bounds : objDetails->shape())
+        if (auto lb = bounds.lbound().GetExplicit())
+          if (auto constant = Fortran::evaluate::ToInt64(*lb))
+            if (!constant || *constant != 1)
+              return true;
+    return false;
+  }
+
   mlir::Type genDerivedType(const Fortran::semantics::DerivedTypeSpec &tySpec) {
     std::vector<std::pair<std::string, mlir::Type>> ps;
     std::vector<std::pair<std::string, mlir::Type>> cs;
@@ -278,6 +292,11 @@ struct TypeBuilder {
     // (1) The data components.
     for (const auto &field :
          Fortran::semantics::OrderedComponentIterator(tySpec)) {
+      // Lowering is assuming non deferred component lower bounds are always 1.
+      // Catch any situations where this is not true for now.
+      if (componentHasNonDefaultLowerBounds(field))
+        TODO(converter.genLocation(field.name()),
+             "lowering derived type components with non default lower bounds");
       auto ty = genSymbolType(field);
       // Do not add the parent component (component of the parents are
       // added and should be sufficient, the parent component would