[vala/staging] tests: Add invalid "unary decrement" test to increase coverage

[Rico Tzschichholz <ricotz src gnome org>]

commit dadfb89c2f454545fab0df762de17e9251dbf017
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Sat Oct 23 15:27:12 2021 +0200

    tests: Add invalid "unary decrement" test to increase coverage

 tests/Makefile.am                               | 1 +
 tests/semantic/unary-unsupported-decrement.test | 9 +++++++++
 2 files changed, 10 insertions(+)
---
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 0edea24ac..6ba6e3b43 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -1172,6 +1172,7 @@ TESTS = \
        semantic/type-argument-ownership-mismatch.test \
        semantic/unary-invalid-instance-member-access.test \
        semantic/unary-unsupported-complement.test \
+       semantic/unary-unsupported-decrement.test \
        semantic/unary-unsupported-increment.test \
        semantic/unary-unsupported-minus.test \
        semantic/unary-unsupported-negation.test \
diff --git a/tests/semantic/unary-unsupported-decrement.test b/tests/semantic/unary-unsupported-decrement.test
new file mode 100644
index 000000000..1cbd523ba
--- /dev/null
+++ b/tests/semantic/unary-unsupported-decrement.test
@@ -0,0 +1,9 @@
+Invalid Code
+
+int foo () {
+       return 23;
+}
+
+void main () {
+       ++foo ();
+}