[flang] Fix CONTIGUOUS attribute checking

[klausler]

Summary

A CONTIGUOUS entity must be an array pointer, assumed-shape dummy array,
or assumed-rank dummy argument (C752, C830). As currently implemented,
f18 only implements the array requirement if the entity is a pointer.
Combine these checks and start issuing citations to scalars.

flang/lib/Semantics/check-declarations.cpp

void CheckHelper::Check(const Symbol &symbol) {
   }
   if (symbol.attrs().test(Attr::BIND_C)) {
     CheckBindC(symbol);
   }
   if (symbol.attrs().test(Attr::SAVE) &&
       !symbol.implicitAttrs().test(Attr::SAVE)) {
     CheckExplicitSave(symbol);
   }
+  const auto *object{symbol.detailsIf<ObjectEntityDetails>()};
+  if (symbol.attrs().test(Attr::CONTIGUOUS)) {
+    if ((!object && !symbol.has<UseDetails>()) ||
+        !((IsPointer(symbol) && symbol.Rank() > 0) || IsAssumedShape(symbol) ||
+            evaluate::IsAssumedRank(symbol))) {
+      if (symbol.owner().IsDerivedType()) { // C752
+        messages_.Say(
+            "A CONTIGUOUS component must be an array with the POINTER attribute"_err_en_US);
+      } else { // C830
+        messages_.Say(
+            "CONTIGUOUS entity must be an array pointer, assumed-shape, or assumed-rank"_err_en_US);
+      }
+    }
+  }
   CheckGlobalName(symbol);
   if (isDone) {
     return; // following checks do not apply
   }
+
   if (symbol.attrs().test(Attr::PROTECTED)) {
     if (symbol.owner().kind() != Scope::Kind::Module) { // C854
       messages_.Say(
           "A PROTECTED entity must be in the specification part of a module"_err_en_US);
     }
     if (!evaluate::IsVariable(symbol) && !IsProcedurePointer(symbol)) { // C855
       messages_.Say(
           "A PROTECTED entity must be a variable or pointer"_err_en_US);
if (type) { // Section 7.2, paragraph 7; C795
     bool isChar{type->category() == DeclTypeSpec::Character};
     bool canHaveAssumedParameter{(isChar && IsNamedConstant(symbol)) ||
         (IsAssumedLengthCharacter(symbol) && // C722
             (IsExternal(symbol) ||
                 ClassifyProcedure(symbol) ==
                     ProcedureDefinitionClass::Dummy)) ||
         symbol.test(Symbol::Flag::ParentComp)};
     if (!IsStmtFunctionDummy(symbol)) { // C726
-      if (const auto *object{symbol.detailsIf<ObjectEntityDetails>()}) {
+      if (object) {
         canHaveAssumedParameter |= object->isDummy() ||
             (isChar && object->isFuncResult()) ||
             IsStmtFunctionResult(symbol); // Avoids multiple messages
       } else {
         canHaveAssumedParameter |= symbol.has<AssocEntityDetails>();
       }
     }
     if (IsProcedurePointer(symbol) && symbol.HasExplicitInterface()) {
if (const Symbol *result{FindFunctionResult(symbol)}) {
       messages_.Say(
           "A dummy procedure pointer should not have assumed-length CHARACTER(*) result type"_port_en_US);
       // The non-dummy case is a hard error that's caught elsewhere.
     }
   }
   if (symbol.attrs().test(Attr::VALUE)) {
     CheckValue(symbol, derived);
   }
-  if (symbol.attrs().test(Attr::CONTIGUOUS) && IsPointer(symbol) &&
-      symbol.Rank() == 0) { // C830
-    messages_.Say("CONTIGUOUS POINTER must be an array"_err_en_US);
-  }
   if (IsDummy(symbol)) {
     if (IsNamedConstant(symbol)) {
       messages_.Say(
           "A dummy argument may not also be a named constant"_err_en_US);
     }
   } else if (IsFunctionResult(symbol)) {
     if (IsNamedConstant(symbol)) {
       messages_.Say(
           "A function result may not also be a named constant"_err_en_US);
     }
     CheckBindCFunctionResult(symbol);
   }
-  if (symbol.owner().IsDerivedType() &&
-      (symbol.attrs().test(Attr::CONTIGUOUS) &&
-          !(IsPointer(symbol) && symbol.Rank() > 0))) { // C752
-    messages_.Say(
-        "A CONTIGUOUS component must be an array with the POINTER attribute"_err_en_US);
-  }
   if (symbol.owner().IsModule() && IsAutomatic(symbol)) {
     messages_.Say(
         "Automatic data object '%s' may not appear in the specification part"
         " of a module"_err_en_US,
         symbol.name());
   }
   if (IsProcedure(symbol) && !symbol.HasExplicitInterface()) {
     if (IsAllocatable(symbol)) {

flang/test/Semantics/call07.f90

contains
   subroutine s03(p)
     real, pointer, intent(in) :: p(:)
   end subroutine
   subroutine s04(p)
     real, pointer :: p
   end subroutine
 
   subroutine test
-    !ERROR: CONTIGUOUS POINTER must be an array
+    !ERROR: CONTIGUOUS entity must be an array pointer, assumed-shape, or assumed-rank
     real, pointer, contiguous :: a01 ! C830
     real, pointer :: a02(:)
     real, target :: a03(10)
     real :: a04(10) ! not TARGET
+    !ERROR: CONTIGUOUS entity must be an array pointer, assumed-shape, or assumed-rank
+    real, contiguous :: scalar
     call s01(a03) ! ok
     !WARNING: Target of CONTIGUOUS pointer association is not known to be contiguous
     call s01(a02)
     !ERROR: CONTIGUOUS pointer may not be associated with a discontiguous target
     call s01(a03(::2))
     call s02(a02) ! ok
     call s03(a03) ! ok
     !ERROR: Actual argument associated with POINTER dummy argument 'p=' must also be POINTER unless INTENT(IN)