[PATCH] Fortran: error recovery on invalid CLASS(), PARAMETER declarations [PR105243]

[Harald Anlauf <anlauf@gmx.de>]

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Dear all,

a CLASS entity cannot have the PARAMETER attribute.
This is detected in some situations, but in others
we ICE because we never reach the existing check.
Adding a similar check when handling the declaration
improves error recovery.

The initial patch is by Steve.  I adjusted and moved
it slightly so that it also handles CLASS(*)
(unlimited polymorphic) at the same time.

Regtested on x86_64-pc-linux-gnu.  OK for mainline?

This patch actually addresses multiple PRs, some of
which are marked as regressions.  As I consider the
patch safe, I would like to backport to open branches
as far as it seems appropriate.

Thanks,
Harald


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From e0d5aeadd218f21e450db6601956691293210156 Mon Sep 17 00:00:00 2001
From: Harald Anlauf <anlauf@gmx.de>
Date: Wed, 29 Jun 2022 21:36:17 +0200
Subject: [PATCH] Fortran: error recovery on invalid CLASS(), PARAMETER
 declarations [PR105243]

gcc/fortran/ChangeLog:

	PR fortran/103137
	PR fortran/103138
	PR fortran/103693
	PR fortran/105243
	* decl.cc (gfc_match_data_decl): Reject CLASS entity declaration
	when it is given the PARAMETER attribute.

gcc/testsuite/ChangeLog:

	PR fortran/103137
	PR fortran/103138
	PR fortran/103693
	PR fortran/105243
	* gfortran.dg/class_58.f90: Fix test.
	* gfortran.dg/class_73.f90: New test.
---
 gcc/fortran/decl.cc                    |  8 ++++++++
 gcc/testsuite/gfortran.dg/class_58.f90 |  2 +-
 gcc/testsuite/gfortran.dg/class_73.f90 | 17 +++++++++++++++++
 3 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gfortran.dg/class_73.f90

diff --git a/gcc/fortran/decl.cc b/gcc/fortran/decl.cc
index 26ff54d4684..339f8b15035 100644
--- a/gcc/fortran/decl.cc
+++ b/gcc/fortran/decl.cc
@@ -6262,6 +6262,14 @@ gfc_match_data_decl (void)
       goto cleanup;
     }

+  /* F2018:C708.  */
+  if (current_ts.type == BT_CLASS && current_attr.flavor == FL_PARAMETER)
+    {
+      gfc_error ("CLASS entity at %C cannot have the PARAMETER attribute");
+      m = MATCH_ERROR;
+      goto cleanup;
+    }
+
   if (current_ts.type == BT_CLASS
 	&& current_ts.u.derived->attr.unlimited_polymorphic)
     goto ok;
diff --git a/gcc/testsuite/gfortran.dg/class_58.f90 b/gcc/testsuite/gfortran.dg/class_58.f90
index 20b601a2f51..fceb575432d 100644
--- a/gcc/testsuite/gfortran.dg/class_58.f90
+++ b/gcc/testsuite/gfortran.dg/class_58.f90
@@ -9,5 +9,5 @@ subroutine s
   end type
   class(t), parameter :: x = t()  ! { dg-error "cannot have the PARAMETER attribute" }
   class(t), parameter :: y = x    ! { dg-error "cannot have the PARAMETER attribute" }
-  class(t) :: z = x               ! { dg-error "must be dummy, allocatable or pointer" }
+  class(t) :: z = t()             ! { dg-error "must be dummy, allocatable or pointer" }
 end
diff --git a/gcc/testsuite/gfortran.dg/class_73.f90 b/gcc/testsuite/gfortran.dg/class_73.f90
new file mode 100644
index 00000000000..c11ee38c086
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/class_73.f90
@@ -0,0 +1,17 @@
+! { dg-do compile }
+! Error recovery on invalid CLASS(), PARAMETER declarations
+! PR fortran/103137
+! PR fortran/103138
+! PR fortran/103693
+! PR fortran/105243
+! Contributed by G.Steinmetz
+
+program p
+  type t
+     character(3) :: c = '(a)'
+  end type
+  class(t), parameter :: x = 1.  ! { dg-error "PARAMETER attribute" }
+  class(*), parameter :: y = t() ! { dg-error "PARAMETER attribute" }
+  class(*), parameter :: z = 1   ! { dg-error "PARAMETER attribute" }
+  print x%c                      ! { dg-error "Syntax error" }
+end
--
2.35.3