Fortran: catch invalid kind in character conversion [PR69636,PR103779]

gcc/fortran/ChangeLog:

	PR fortran/69636
	PR fortran/103779
	* intrinsic.cc (gfc_convert_chartype): Recover on invalid character
	kind in conversion instead of generating an internal error.

gcc/testsuite/ChangeLog:

	PR fortran/69636
	PR fortran/103779
	* gfortran.dg/pr103779.f90: New test.

Co-authored-by: Steven G. Kargl <kargl@gcc.gnu.org>

gcc/fortran/intrinsic.cc

@@ -5419,7 +5419,8 @@ gfc_convert_chartype (gfc_expr *expr, gfc_typespec *ts)
   gcc_assert (expr->ts.type == BT_CHARACTER && ts->type == BT_CHARACTER);
 
   sym = find_char_conv (&expr->ts, ts);
-  gcc_assert (sym);
+  if (sym == NULL)
+    return false;
 
   /* Insert a pre-resolved function call to the right function.  */
   old_where = expr->where;

gcc/testsuite/gfortran.dg/pr103779.f90

@@ -0,0 +1,18 @@
+! { dg-do compile }
+! PR fortran/69636
+! PR fortran/103779
+! Contributed by G.Steinmetz
+
+character(1,) function f() ! { dg-error "Expected initialization expression" }
+  f = 'a'
+end
+
+character(1,kind=) function g() ! { dg-error "Expected initialization expression" }
+  g = 'a'
+end
+
+character(1,n) function h() ! { dg-error "has not been declared" }
+  h = 'a'
+end
+
+! { dg-prune-output "Bad kind expression" }