[flang][openacc][NFC] Issue better error message when directive is wrong (#69034)

Author: clementval

flang/lib/Parser/openacc-parsers.cpp

@@ -150,11 +150,12 @@ TYPE_PARSER(sourced(construct<AccLoopDirective>(
 TYPE_PARSER(construct<AccBeginLoopDirective>(
     sourced(Parser<AccLoopDirective>{}), Parser<AccClauseList>{}))
 
-TYPE_PARSER(construct<AccEndLoop>(startAccLine >> "END LOOP"_tok))
+TYPE_PARSER(construct<AccEndLoop>("END LOOP"_tok))
 
 TYPE_PARSER(construct<OpenACCLoopConstruct>(
     sourced(Parser<AccBeginLoopDirective>{} / endAccLine),
-    maybe(Parser<DoConstruct>{}), maybe(Parser<AccEndLoop>{} / endAccLine)))
+    maybe(Parser<DoConstruct>{}),
+    maybe(startAccLine >> Parser<AccEndLoop>{} / endAccLine)))
 
 // 2.15.1 Routine directive
 TYPE_PARSER(sourced(construct<OpenACCRoutineConstruct>(verbatim("ROUTINE"_tok),
@@ -227,22 +228,25 @@ TYPE_PARSER(construct<OpenACCStandaloneConstruct>(
 TYPE_PARSER(construct<OpenACCStandaloneDeclarativeConstruct>(
     sourced(Parser<AccDeclarativeDirective>{}), Parser<AccClauseList>{}))
 
-TYPE_PARSER(
-    startAccLine >> first(sourced(construct<OpenACCDeclarativeConstruct>(
-                              Parser<OpenACCStandaloneDeclarativeConstruct>{})),
-                        sourced(construct<OpenACCDeclarativeConstruct>(
-                            Parser<OpenACCRoutineConstruct>{}))))
+TYPE_PARSER(startAccLine >>
+    withMessage("expected OpenACC directive"_err_en_US,
+        first(sourced(construct<OpenACCDeclarativeConstruct>(
+                  Parser<OpenACCStandaloneDeclarativeConstruct>{})),
+            sourced(construct<OpenACCDeclarativeConstruct>(
+                Parser<OpenACCRoutineConstruct>{})))))
 
 // OpenACC constructs
 TYPE_CONTEXT_PARSER("OpenACC construct"_en_US,
     startAccLine >>
-        first(construct<OpenACCConstruct>(Parser<OpenACCBlockConstruct>{}),
-            construct<OpenACCConstruct>(Parser<OpenACCCombinedConstruct>{}),
-            construct<OpenACCConstruct>(Parser<OpenACCLoopConstruct>{}),
-            construct<OpenACCConstruct>(Parser<OpenACCStandaloneConstruct>{}),
-            construct<OpenACCConstruct>(Parser<OpenACCCacheConstruct>{}),
-            construct<OpenACCConstruct>(Parser<OpenACCWaitConstruct>{}),
-            construct<OpenACCConstruct>(Parser<OpenACCAtomicConstruct>{})))
+        withMessage("expected OpenACC directive"_err_en_US,
+            first(construct<OpenACCConstruct>(Parser<OpenACCBlockConstruct>{}),
+                construct<OpenACCConstruct>(Parser<OpenACCCombinedConstruct>{}),
+                construct<OpenACCConstruct>(Parser<OpenACCLoopConstruct>{}),
+                construct<OpenACCConstruct>(
+                    Parser<OpenACCStandaloneConstruct>{}),
+                construct<OpenACCConstruct>(Parser<OpenACCCacheConstruct>{}),
+                construct<OpenACCConstruct>(Parser<OpenACCWaitConstruct>{}),
+                construct<OpenACCConstruct>(Parser<OpenACCAtomicConstruct>{}))))
 
 TYPE_PARSER(startAccLine >>
     sourced(construct<AccEndCombinedDirective>(sourced("END"_tok >>

flang/test/Semantics/OpenACC/acc-error.f90

@@ -0,0 +1,15 @@
+! RUN: %python %S/../test_errors.py %s %flang -fopenacc
+
+! Check parser specific error for OpenACC
+
+
+subroutine test(a, n)
+    integer :: a(n)
+    !ERROR: expected OpenACC directive
+    !$acc p
+    integer :: i,j
+ 
+    i = 0
+    !ERROR: expected OpenACC directive
+    !$acc p
+  end subroutine