[flang] Downgrade inappropriate error message to a warning

[klausler]

Summary

It may not be great practice to pass a procedure (or procedure pointer)
with an implicit interface as an actual argument to correspond with
a dummy procedure (pointer), but it's not an error. Change to a
warning, and modify tests accordingly.

[jeanPerier]

The LLVM build bot seems to have had weird issues applying the patch, but the patch looks good to me.

flang/lib/Semantics/check-call.cpp

if (auto argChars{characteristics::DummyArgument::FromActual(
                 messages.Say(
                     "Actual procedure argument has interface incompatible with %s"_err_en_US,
                     dummyName);
                 return;
               } else {
                 messages.Say(
                     "Actual procedure argument has an implicit interface "
                     "which is not known to be compatible with %s which has an "
-                    "explicit interface"_err_en_US,
+                    "explicit interface"_en_US,
                     dummyName);
-                return;
               }
             }
           } else { // 15.5.2.9(2,3)
             if (interface.IsSubroutine() && argInterface.IsFunction()) {
               messages.Say(
                   "Actual argument associated with procedure %s is a function but must be a subroutine"_err_en_US,
                   dummyName);
             } else if (interface.IsFunction()) {

flang/test/Semantics/call09.f90

function intprocptr()
     intprocptr => intfunc
   end function
 
   subroutine test1 ! 15.5.2.9(5)
     intrinsic :: sin
     procedure(realfunc), pointer :: p
     procedure(intfunc), pointer :: ip
     integer, pointer :: intPtr
-    external :: extfunc
-    external :: extfuncPtr
-    pointer :: extfuncPtr
     p => realfunc
     ip => intfunc
     call s01(realfunc) ! ok
     !ERROR: Actual procedure argument has interface incompatible with dummy argument 'p='
     call s01(intfunc)
     call s01(p) ! ok
     call s01(procptr()) ! ok
     !ERROR: Actual procedure argument has interface incompatible with dummy argument 'p='
     call s01(intprocptr())
     call s01(null()) ! ok
     call s01(null(p)) ! ok
     !ERROR: Actual procedure argument has interface incompatible with dummy argument 'p='
     call s01(null(ip))
     call s01(sin) ! ok
     !ERROR: Actual argument associated with procedure dummy argument 'p=' is not a procedure
     call s01(null(intPtr))
     !ERROR: Actual argument associated with procedure dummy argument 'p=' is typeless
     call s01(B"0101")
-    !ERROR: Actual procedure argument has an implicit interface which is not known to be compatible with dummy argument 'p=' which has an explicit interface
-    call s01(extfunc)
     !ERROR: Actual argument associated with procedure pointer dummy argument 'p=' must be a POINTER unless INTENT(IN)
     call s02(realfunc)
     call s02(p) ! ok
     !ERROR: Actual procedure argument has interface incompatible with dummy argument 'p='
     call s02(ip)
     !ERROR: Actual argument associated with procedure pointer dummy argument 'p=' must be a POINTER unless INTENT(IN)
     call s02(procptr())
     !ERROR: Actual argument associated with procedure pointer dummy argument 'p=' must be a POINTER unless INTENT(IN)
     call s02(null())
     !ERROR: Actual argument associated with procedure pointer dummy argument 'p=' must be a POINTER unless INTENT(IN)
     call s02(null(p))
     !ERROR: Actual argument associated with procedure pointer dummy argument 'p=' must be a POINTER unless INTENT(IN)
     call s02(sin)
-    !ERROR: Actual procedure argument has an implicit interface which is not known to be compatible with dummy argument 'p=' which has an explicit interface
-    call s02(extfunc)
-    !ERROR: Actual procedure argument has an implicit interface which is not known to be compatible with dummy argument 'p=' which has an explicit interface
-    call s03(extfuncPtr)
   end subroutine
 
   subroutine callsub(s)
     call s
   end subroutine
   subroutine takesrealfunc1(f)
     external f
     real f

flang/test/Semantics/call21.f90

+! RUN: %flang -fsyntax-only 2>&1 %s | FileCheck %s
+! Verifies that warnings issue when actual arguments with implicit
+! interfaces are associated with dummy procedures and dummy procedure
+! pointers whose interfaces are explicit.
+module m
+ contains
+  real function realfunc(x)
+    real, intent(in) :: x
+    realfunc = x
+  end function
+  subroutine s00(p0)
+    procedure(realfunc) :: p0
+  end subroutine
+  subroutine s01(p1)
+    procedure(realfunc), pointer, intent(in) :: p1
+  end subroutine
+  subroutine s02(p2)
+    procedure(realfunc), pointer :: p2
+  end subroutine
+  subroutine test
+    external :: extfunc
+    external :: extfuncPtr
+    pointer :: extfuncPtr
+    !CHECK: Actual procedure argument has an implicit interface which is not known to be compatible with dummy argument 'p0=' which has an explicit interface
+    call s00(extfunc)
+    !CHECK: Actual procedure argument has an implicit interface which is not known to be compatible with dummy argument 'p1=' which has an explicit interface
+    call s01(extfunc)
+    !CHECK: Actual procedure argument has an implicit interface which is not known to be compatible with dummy argument 'p2=' which has an explicit interface
+    call s02(extfuncPtr)
+  end subroutine
+end module