Add previously failing pad(cast(lit)) example as a test case

* Previously, this test failed whenever InlineCasts was run

1 files changed, 29 insertions, 0 deletions

diff --git a/src/test/scala/firrtlTests/InlineCastsSpec.scala b/src/test/scala/firrtlTests/InlineCastsSpec.scala
new file mode 100644
index 00000000..1bf36b33
--- /dev/null
+++ b/src/test/scala/firrtlTests/InlineCastsSpec.scala
@@ -0,0 +1,29 @@
+// See LICENSE for license details.
+
+package firrtlTests
+
+import firrtl.transforms.InlineCastsTransform
+import firrtl.testutils.FirrtlFlatSpec
+
+/*
+ * Note: InlineCasts is still part of mverilog, so this test must both:
+ * - Test that the InlineCasts fix is effective given the current mverilog
+ * - Provide a test that will be robust if and when InlineCasts is no longer run in mverilog
+ *
+ * This is why the test passes InlineCasts as a custom transform: to future-proof it so that
+ * it can do real LEC against no-InlineCasts. It currently is just a sanity check that the
+ * emitted Verilog is legal, but it will automatically become a more meaningful test when
+ * InlineCasts is not run in mverilog.
+ */
+class InlineCastsEquivalenceSpec extends FirrtlFlatSpec {
+  "InlineCastsTransform" should "not produce broken Verilog" in {
+    val input =
+      s"""circuit literalsel_fir:
+         |  module literalsel_fir:
+         |    input i: UInt<4>
+         |    output o: SInt<8>
+         |    o <= pad(asSInt(UInt<2>("h1")), 8)
+         |""".stripMargin
+    firrtlEquivalenceTest(input, Seq(new InlineCastsTransform))
+  }
+}