[gcc r14-4694] c++: accepts-invalid with =delete("") [PR111840]

[Marek Polacek <mpolacek@gcc.gnu.org>]

https://gcc.gnu.org/g:1fbb7d75abbb050f790d8b43422602ee4b152608

commit r14-4694-g1fbb7d75abbb050f790d8b43422602ee4b152608
Author: Marek Polacek <polacek@redhat.com>
Date:   Tue Oct 17 16:11:11 2023 -0400

    c++: accepts-invalid with =delete("") [PR111840]
    
    r6-2367 added a DECL_INITIAL check to cp_parser_simple_declaration
    so that we don't emit multiple errors in g++.dg/parse/error57.C.
    But that means we don't diagnose
    
      int f1() = delete("george_crumb");
    
    anymore, because fn decls often have error_mark_node in their
    DECL_INITIAL.  (The code may be allowed one day via https://wg21.link/P2573R0.)
    
    I was hoping I could use cp_parser_error_occurred but that would
    regress error57.C.
    
            PR c++/111840
    
    gcc/cp/ChangeLog:
    
            * parser.cc (cp_parser_simple_declaration): Do cp_parser_error
            for FUNCTION_DECLs.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/parse/error65.C: New test.

Diff:
---
 gcc/cp/parser.cc                     | 14 +++++++-------
 gcc/testsuite/g++.dg/parse/error65.C | 10 ++++++++++
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index 59b9852895ec..57b62fb73631 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -15669,6 +15669,7 @@ cp_parser_simple_declaration (cp_parser* parser,
 					maybe_range_for_decl,
 					&init_loc,
 					&auto_result);
+      const bool fndecl_p = TREE_CODE (decl) == FUNCTION_DECL;
       /* If an error occurred while parsing tentatively, exit quickly.
 	 (That usually happens when in the body of a function; each
 	 statement is treated as a declaration-statement until proven
@@ -15682,16 +15683,13 @@ cp_parser_simple_declaration (cp_parser* parser,
 	     init-declarator, they shall all form declarations of
 	     variables.  */
 	  if (auto_function_declaration == NULL_TREE)
-	    auto_function_declaration
-	      = TREE_CODE (decl) == FUNCTION_DECL ? decl : error_mark_node;
-	  else if (TREE_CODE (decl) == FUNCTION_DECL
-		   || auto_function_declaration != error_mark_node)
+	    auto_function_declaration = fndecl_p ? decl : error_mark_node;
+	  else if (fndecl_p || auto_function_declaration != error_mark_node)
 	    {
 	      error_at (decl_specifiers.locations[ds_type_spec],
 			"non-variable %qD in declaration with more than one "
 			"declarator with placeholder type",
-			TREE_CODE (decl) == FUNCTION_DECL
-			? decl : auto_function_declaration);
+			fndecl_p ? decl : auto_function_declaration);
 	      auto_function_declaration = error_mark_node;
 	    }
 	}
@@ -15763,7 +15761,9 @@ cp_parser_simple_declaration (cp_parser* parser,
 	  /* If we have already issued an error message we don't need
 	     to issue another one.  */
 	  if ((decl != error_mark_node
-	       && DECL_INITIAL (decl) != error_mark_node)
+	       /* grokfndecl sets DECL_INITIAL to error_mark_node for
+		  functions.  */
+	       && (fndecl_p || DECL_INITIAL (decl) != error_mark_node))
 	      || cp_parser_uncommitted_to_tentative_parse_p (parser))
 	    cp_parser_error (parser, "expected %<,%> or %<;%>");
 	  /* Skip tokens until we reach the end of the statement.  */
diff --git a/gcc/testsuite/g++.dg/parse/error65.C b/gcc/testsuite/g++.dg/parse/error65.C
new file mode 100644
index 000000000000..d9e0a4bfbcba
--- /dev/null
+++ b/gcc/testsuite/g++.dg/parse/error65.C
@@ -0,0 +1,10 @@
+// PR c++/111840
+// { dg-do compile { target c++11 } }
+
+// NB: =delete("reason") may be allowed via P2573.
+int f1() = delete("should have a reason"); // { dg-error "expected" }
+int f2() = delete[""]; // { dg-error "expected" }
+int f3() = delete{""}; // { dg-error "expected" }
+int f4() = delete""; // { dg-error "expected" }
+int f5() = delete[{'a'""; // { dg-error "expected" }
+int i = f5();