[flang] Don't complain about dummy subroutine under IMPLICIT NONE

[klausler]

Summary

The compiler emits a bogus 'No explicit type declared for...' error
when a dummy procedure turns out to be a subroutine (or at least not
a function or object) under control of IMPLICIT NONE.

Fixes https://github.com/llvm/llvm-project/issues/60224

[PeteSteinfeld]

Things build OK, but I get errors in check-flang:

FAIL: Flang :: Semantics/implicit13.f90 (1508 of 2183)
******************** TEST 'Flang :: Semantics/implicit13.f90' FAILED ********************
Script:
--
: 'RUN: at line 1';   "/usr/bin/python3.6" /local/home/psteinfeld/main/814/flang/test/Semantics/test_errors.py /local/home/psteinfeld/main/814/flang/test/Semantics/implicit13.f90 /local/home/psteinfeld/main/814/build/bin/flang-new -fc1
--
Exit Code: 1

Command Output (stdout):
--
--- 
+++ 
@@ -1,2 +1,2 @@

actual at 2: No explicit type declared for 'func'
actual at 2: No explicit type declared for 'obj'
expect at 6: No explicit type declared for 'func'
expect at 8: No explicit type declared for 'obj'

[klausler]

Update test.

[klausler]

Test fixed; please take another look.

[PeteSteinfeld]

All builds and tests correctly and looks good.

flang/lib/Semantics/resolve-names.cpp

if (IsIntrinsic(symbol.name(), functionOrSubroutineFlag)) {
       // type will be determined in expression semantics
       AcquireIntrinsicProcedureFlags(symbol);
       return;
     }
   }
   if (allowForwardReference && ImplicitlyTypeForwardRef(symbol)) {
     return;
   }
+  if (const auto *entity{symbol.detailsIf<EntityDetails>()};
+      entity && entity->isDummy()) {
+    // Dummy argument, no declaration or reference; if it turns
+    // out to be a subroutine, it's fine, and if it is a function
+    // or object, it'll be caught later.
+    return;
+  }
   if (!context().HasError(symbol)) {
     Say(symbol.name(), "No explicit type declared for '%s'"_err_en_US);
     context().SetError(symbol);
   }
 }
 
 // Extension: Allow forward references to scalar integer dummy arguments
 // or variables in COMMON to appear in specification expressions under

flang/test/Semantics/implicit13.f90

+! RUN: %python %S/test_errors.py %s %flang_fc1
+!ERROR: No explicit type declared for 'func'
+!ERROR: No explicit type declared for 'obj'
+subroutine implicit_none(func, sub, obj)
+  implicit none
+  call sub ! ok
+  print *, func()
+  print *, obj
+end