a68: avoid coalescing of stmt_lists in a68_lower_unit_list

At it happens, a68_lower_unit_list collects units as members of a
stmt_list, lowering them and appending them.  Problem is, stmt_lists
get coalesced when appended (or prepended) to another stmt_list.

One of the units that may lower in a stmt_list are generators, and the
coalescing manifests itself when the generators are found in
collateral clauses.

This patch puts in place a temporary workaround for this, which is to
wrap the stmt_list into a NOP_EXPR.  This avoid the coalescing, but a
less hackish solution will probably consist on changing the way
unit_lists get collected instead.

Signed-off-by: Jose E. Marchesi <jemarch@gnu.org>

gcc/algol68/ChangeLog

	* a68-low-generator.cc (a68_low_generator): Wrap the resulting
	stmt_list into a nop_expr.

gcc/testsuite/ChangeLog

	* algol68/execute/gen-in-constructor-1.a68: New test.
	* algol68/execute/gen-in-constructor-2.a68: Likewise.

gcc/algol68/a68-low-generator.cc

diff --git a/gcc/algol68/a68-low-generator.cc b/gcc/algol68/a68-low-generator.cc
index e321b7d..e619b04 100644
--- a/gcc/algol68/a68-low-generator.cc
+++ b/gcc/algol68/a68-low-generator.cc
@@ -509,6 +509,9 @@
       tree_stmt_iterator bounds_iter = tsi_start (bounds);
       tree gen = gen_mode (mode, &bounds_iter,
 			   heap ? a68_lower_malloc : a68_lower_alloca);
+      /* XXX ugly hack to avoid the resulting stmt_list to be coalesced
+	 on the current stmt_list in a68_lower_unit_list.  */
+      gen = build1 (NOP_EXPR, TREE_TYPE (gen), gen);
       return gen;
     }
 }

gcc/testsuite/algol68/execute/gen-in-constructor-1.a68

diff --git a/gcc/testsuite/algol68/execute/gen-in-constructor-1.a68 b/gcc/testsuite/algol68/execute/gen-in-constructor-1.a68
new file mode 100644
index 0000000..6cf40f4
--- /dev/null
+++ b/gcc/testsuite/algol68/execute/gen-in-constructor-1.a68
@@ -0,0 +1,7 @@
+begin mode Foo = struct (ref[]int lala, bool sign);
+      Foo zero = (heap[3:10]int, true);
+      assert(sign'zero = true);
+      assert(UPB lala'zero = 10);
+      assert(LWB lala'zero = 3);
+      skip
+end

gcc/testsuite/algol68/execute/gen-in-constructor-2.a68

diff --git a/gcc/testsuite/algol68/execute/gen-in-constructor-2.a68 b/gcc/testsuite/algol68/execute/gen-in-constructor-2.a68
new file mode 100644
index 0000000..9e67620
--- /dev/null
+++ b/gcc/testsuite/algol68/execute/gen-in-constructor-2.a68
@@ -0,0 +1,7 @@
+begin mode Foo = struct (bool sign, ref[]int lala);
+      Foo zero = (false, heap[0:-1]int);
+      assert(sign'zero = false);
+      assert(UPB lala'zero = -1);
+      assert(LWB lala'zero = 0);
+      skip
+end