[flang] Add missing source location to a semantic error message

[klausler]

Summary

Ensure that the semantic error "An allocatable or pointer component
reference must be applied to a scalar base" is emitted with a source
code location.

[PeteSteinfeld]

All builds and tests correctly and looks good.

flang/lib/Semantics/expression.cpp

if (sym->detailsIf<semantics::TypeParamDetails>()) {
             "A type parameter inquiry must be applied to "
             "a designator"_err_en_US);
       }
     } else if (!dtSpec || !dtSpec->scope()) {
       CHECK(context_.AnyFatalError() || !foldingContext_.messages().empty());
       return std::nullopt;
     } else if (std::optional<DataRef> dataRef{
                    ExtractDataRef(std::move(*dtExpr))}) {
+      auto restorer{GetContextualMessages().SetLocation(name)};
       if (auto component{
               CreateComponent(std::move(*dataRef), *sym, *dtSpec->scope())}) {
         return Designate(DataRef{std::move(*component)});
       } else {
         Say(name, "Component is not in scope of derived TYPE(%s)"_err_en_US,
             dtSpec->typeSymbol().name());
       }
     } else {

flang/test/Semantics/expr-errors04.f90

 ! RUN: %python %S/test_errors.py %s %flang_fc1
 ! Regression test for more than one part-ref with nonzero rank
 
 program m
   interface
     function real_info1(i)
     end
     subroutine real_info2()
     end
     subroutine real_generic()
     end
   end interface
   type mt
     complex :: c, c2(2)
     integer :: x, x2(2)
     character(10) :: s, s2(2)
+    real, pointer :: p
+    real, allocatable :: a
    contains
     procedure, nopass :: info1 => real_info1
     procedure, nopass :: info2 => real_info2
     procedure, nopass :: real_generic
     generic :: g1 => real_generic
   end type
   type mt2
     type(mt) :: t1(2,2)
program m
 
   !ERROR: Reference to rank-2 object 't1' has 1 subscripts
   call sub0(t%t3%t2%t1(1:)%info1(i))
   !ERROR: Reference to rank-2 object 't1' has 1 subscripts
   call t%t3%t2%t1(1:)%info2
   !ERROR: Reference to rank-2 object 't1' has 1 subscripts
   call t%t3%t2%t1(1:)%g1
 
+  !ERROR: An allocatable or pointer component reference must be applied to a scalar base
+  print *, t(1)%t3(1)%t2(1)%t1%p
+  !ERROR: An allocatable or pointer component reference must be applied to a scalar base
+  print *, t%t3(1)%t2(1)%t1(1,1)%p
+  !ERROR: An allocatable or pointer component reference must be applied to a scalar base
+  print *, t(1)%t3(1)%t2(1)%t1%a
+  !ERROR: An allocatable or pointer component reference must be applied to a scalar base
+  print *, t%t3(1)%t2(1)%t1(1,1)%a
+  !ERROR: An allocatable or pointer component reference must be applied to a scalar base
+  t(1)%t3(1)%t2(1)%t1%p => null()
+  !ERROR: An allocatable or pointer component reference must be applied to a scalar base
+  t%t3(1)%t2(1)%t1(1,1)%p => null()
+
 end