[flang] Adjust new warnings for extensions

Prevent messages from module files, respect the language feature
flags when enabling the relaxed PURE dummy argument checking, and
check that the new warnings are enabled.

Author: klausler

flang/lib/Semantics/check-declarations.cpp

@@ -730,15 +730,26 @@ void CheckHelper::CheckObjectEntity(
           }
         }
       } else if (!IsIntentInOut(symbol)) { // C1586
-        messages_.Say(
-            "non-POINTER dummy argument of pure %s must have INTENT() or VALUE attribute"_warn_en_US,
-            what);
+        if (!InModuleFile()) {
+          if (context_.IsEnabled(common::LanguageFeature::RelaxedPureDummy)) {
+            if (context_.ShouldWarn(
+                    common::LanguageFeature::RelaxedPureDummy)) {
+              messages_.Say(
+                  "non-POINTER dummy argument of pure %s should have INTENT() or VALUE attribute"_warn_en_US,
+                  what);
+            }
+          } else {
+            messages_.Say(
+                "non-POINTER dummy argument of pure %s must have INTENT() or VALUE attribute"_err_en_US,
+                what);
+          }
+        }
         ok = false;
       }
-      if (ok && InFunction()) {
+      if (ok && InFunction() && !InModuleFile()) {
         if (context_.IsEnabled(common::LanguageFeature::RelaxedPureDummy)) {
           if (context_.ShouldWarn(common::LanguageFeature::RelaxedPureDummy) &&
-              !InModuleFile() && !InElemental()) {
+              !InElemental()) {
             messages_.Say(
                 "non-POINTER dummy argument of pure function should be INTENT(IN) or VALUE"_warn_en_US);
           }

flang/test/Semantics/call10.f90

@@ -53,7 +53,7 @@ pure real function f02(a)
     real, value :: a ! ok
   end function
   pure real function f03(a) ! C1583
-    !ERROR: non-POINTER dummy argument of pure function must have INTENT() or VALUE attribute
+    !WARNING: non-POINTER dummy argument of pure function should have INTENT() or VALUE attribute
     real :: a
   end function
   pure real function f03a(a)
@@ -83,7 +83,7 @@ pure function f08() ! C1585
   end function
 
   pure subroutine s01(a) ! C1586
-    !ERROR: non-POINTER dummy argument of pure subroutine must have INTENT() or VALUE attribute
+    !WARNING: non-POINTER dummy argument of pure subroutine should have INTENT() or VALUE attribute
     real :: a
   end subroutine
   pure subroutine s01a(a)