sys_core_fold: Suppress warnings better

86fbd6d76d strengthened type optimization in lets. As a result of
the stronger optimizations, special care had to be taken to
suppress false warnings.

It turns out that false warnings can still slip through. Slapping
on a 'compiler_generated' annotation at the top-level of a
complex term such as #c_tuple{} may not suppress all warnings.

We will need to go deeper into the term to eliminate all warnings.

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/compiler/test/warnings_SUITE.erl b/lib/compiler/test/warnings_SUITE.erl
index e996a55db6..f6ba75577d 100644
--- a/lib/compiler/test/warnings_SUITE.erl
+++ b/lib/compiler/test/warnings_SUITE.erl
@@ -733,6 +733,12 @@ no_warnings(Config) when is_list(Config) ->
 	          false -> Var;
                   true -> []
                 end.
+
+              c() ->
+                R0 = {r,\"abc\",undefined,os:timestamp()}, %No warning.
+                case R0 of
+	          {r,V1,_V2,V3} -> {r,V1,\"def\",V3}
+                end.
            ">>,
            [],
            []}],