[Patch, fortran] Fix default type bugs in gfortran [PR99139, PR99368]

[Paul Richard Thomas <paul.richard.thomas@gmail.com>]

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The attached patch incorporates two of Steve's "Orphaned Patches" -
https://gcc.gnu.org/pipermail/fortran/2023-June/059423.html

They have in common that they both involve faults in use of default
type and that I was the ultimate cause of the bugs.

The patch regtests with the attached testcases.

I will commit in the next 24 hours unless there are any objections.

Paul

Fortran: Fix default type bugs in gfortran [PR99139, PR99368]

2023-07-08  Steve Kargl  <sgk@troutmask.apl.washington.edu>

gcc/fortran
PR fortran/99139
PR fortran/99368
* match.cc (gfc_match_namelist): Check for host associated or
defined types before applying default type.
(gfc_match_select_rank): Apply default type to selector of
unlnown type if possible.
* resolve.cc (resolve_fl_variable): Do not apply local default
initialization to assumed rank entities.

gcc/testsuite/
PR fortran/999139
* gfortran.dg/pr99139.f90 : New test

PR fortran/99368
* gfortran.dg/pr99368.f90 : New test

Fortran: Fix default type bugs in gfortran [PR99139, PR99368]

2023-07-08  Steve Kargl  <sgk@troutmask.apl.washington.edu>

gcc/fortran
PR fortran/99139
PR fortran/99368
* match.cc (gfc_match_namelist): Check for host associated or
defined types before applying default type.
(gfc_match_select_rank): Apply default type to selector of
unlnown type if possible.
* resolve.cc (resolve_fl_variable): Do not apply local default
initialization to assumed rank entities.

gcc/testsuite/
PR fortran/999139
* gfortran.dg/pr99139.f90 : New test

PR fortran/99368
* gfortran.dg/pr99368.f90 : New test

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! { dg-do compile }
! { dg-options "-finit-local-zero" }
!
! Contributed by Gerhard Steinmetz  <gscfq@t-online.de>
!
! Original implicitly typed 'x' gave a bad symbol ICE
subroutine s1(x)
   target :: x(..)
   select rank (y => x)
   rank (1)
   rank (2)
   end select
end

! Comment #2: Failed with above option
subroutine s2(x, z)
   real, target :: x(..)
   real :: z(10)
   select rank (y => x) ! Error was:Assumed-rank variable y at (1) may only be
                        ! used as actual argument
   rank (1)
   rank (2)
   end select
end

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! { dg-do compile }
!
! Contributed by Gerhard Steinmetz  <gscfq@t-online.de>
!
program p
   type y ! { dg-error "Derived type" }
   end type
contains
   subroutine s1
      namelist /x/ y ! { dg-error "conflicts with namelist object" }
      character(3) y
   end
   subroutine s2
      namelist /z/ y ! { dg-error "conflicts with namelist object" }
      character(3) y
   end
end

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diff --git a/gcc/fortran/match.cc b/gcc/fortran/match.cc
index ca64e59029e..a778bae0b9f 100644
--- a/gcc/fortran/match.cc
+++ b/gcc/fortran/match.cc
@@ -5622,10 +5622,32 @@ gfc_match_namelist (void)
 		  gfc_error_check ();
 		}
 	      else
-		/* If the type is not set already, we set it here to the
-		   implicit default type.  It is not allowed to set it
-		   later to any other type.  */
-		gfc_set_default_type (sym, 0, gfc_current_ns);
+		{
+		  /* Before the symbol is given an implicit type, check to
+		     see if the symbol is already available in the namespace,
+		     possibly through host association.  Importantly, the
+		     symbol may be a user defined type.  */
+
+		  gfc_symbol *tmp;
+
+		  gfc_find_symbol (sym->name, NULL, 1, &tmp);
+		  if (tmp
+		      && tmp->attr.generic
+		      && (tmp = gfc_find_dt_in_generic (tmp)))
+		    {
+		      if (tmp->attr.flavor == FL_DERIVED)
+			{
+			  gfc_error ("Derived type %qs at %L conflicts with "
+				     "namelist object %qs at %C",
+				     tmp->name, &tmp->declared_at, sym->name);
+			  goto error;
+			}
+		    }
+
+		  /* Set type of the symbol to its implicit default type.  It is
+		     not allowed to set it later to any other type.  */
+		  gfc_set_default_type (sym, 0, gfc_current_ns);
+		}
 	    }
 	  if (sym->attr.in_namelist == 0
 	      && !gfc_add_in_namelist (&sym->attr, sym->name, NULL))
@@ -6805,8 +6827,20 @@ gfc_match_select_rank (void)
 
   gfc_current_ns = gfc_build_block_ns (ns);
   m = gfc_match (" %n => %e", name, &expr2);
+
   if (m == MATCH_YES)
     {
+      /* If expr2 corresponds to an implicitly typed variable, then the
+	 actual type of the variable may not have been set.  Set it here.  */
+      if (!gfc_current_ns->seen_implicit_none
+	  && expr2->expr_type == EXPR_VARIABLE
+	  && expr2->ts.type == BT_UNKNOWN
+	  && expr2->symtree && expr2->symtree->n.sym)
+	{
+	  gfc_set_default_type (expr2->symtree->n.sym, 0, gfc_current_ns);
+	  expr2->ts.type = expr2->symtree->n.sym->ts.type;
+	}
+
       expr1 = gfc_get_expr ();
       expr1->expr_type = EXPR_VARIABLE;
       expr1->where = expr2->where;
diff --git a/gcc/fortran/resolve.cc b/gcc/fortran/resolve.cc
index 8e018b6e7e8..f7cfdfc133f 100644
--- a/gcc/fortran/resolve.cc
+++ b/gcc/fortran/resolve.cc
@@ -13510,7 +13510,8 @@ resolve_fl_variable (gfc_symbol *sym, int mp_flag)
 	}
     }
 
-  if (sym->value == NULL && sym->attr.referenced)
+  if (sym->value == NULL && sym->attr.referenced
+      && !(sym->as && sym->as->type == AS_ASSUMED_RANK))
     apply_default_init_local (sym); /* Try to apply a default initialization.  */
 
   /* Determine if the symbol may not have an initializer.  */