Add test for truthiness.

As compiled by Adobe Animate CC 2020, this test appears to only use `iffalse`. However, both `op_is_false` and `op_is_true` coerce in the same manner, so I'm not entirely sure this is a problem for now.

core/tests/regression_tests.rs

@@ -273,6 +273,7 @@ swf_tests! {
     (as3_es4_interfaces, "avm2/es4_interfaces", 1),
     (as3_istype, "avm2/istype", 1),
     (as3_instanceof, "avm2/instanceof", 1),
+    (as3_truthiness, "avm2/truthiness", 1),
 }
 
 // TODO: These tests have some inaccuracies currently, so we use approx_eq to test that numeric values are close enough.

core/tests/swfs/avm2/truthiness/Test.as

@@ -0,0 +1,57 @@
+package {
+	public class Test {
+	}
+}
+
+function assert_truthiness(val) {
+	if (val) {
+		trace("Value is truthy");
+	} else {
+		trace("Value is falsy");
+	}
+}
+
+trace("//if (true)");
+assert_truthiness(true);
+
+trace("//if (false)");
+assert_truthiness(false);
+
+trace("//if (null)");
+assert_truthiness(null);
+
+trace("//if (undefined)");
+assert_truthiness(undefined);
+
+trace("//if (\"\")");
+assert_truthiness("");
+
+trace("//if (\"str\")");
+assert_truthiness("str");
+
+trace("//if (\"true\")");
+assert_truthiness("true");
+
+trace("//if (\"false\")");
+assert_truthiness("false");
+
+trace("//if (0.0)");
+assert_truthiness(0.0);
+
+trace("//if (NaN)");
+assert_truthiness(NaN);
+
+trace("//if (-0.0)");
+assert_truthiness(-0.0);
+
+trace("//if (Infinity)");
+assert_truthiness(Infinity);
+
+trace("//if (1.0)");
+assert_truthiness(1.0);
+
+trace("//if (-1.0)");
+assert_truthiness(-1.0);
+
+trace("//if (new Object())");
+assert_truthiness({});

core/tests/swfs/avm2/truthiness/output.txt

@@ -0,0 +1,30 @@
+//if (true)
+Value is truthy
+//if (false)
+Value is falsy
+//if (null)
+Value is falsy
+//if (undefined)
+Value is falsy
+//if ("")
+Value is falsy
+//if ("str")
+Value is truthy
+//if ("true")
+Value is truthy
+//if ("false")
+Value is truthy
+//if (0.0)
+Value is falsy
+//if (NaN)
+Value is falsy
+//if (-0.0)
+Value is falsy
+//if (Infinity)
+Value is truthy
+//if (1.0)
+Value is truthy
+//if (-1.0)
+Value is truthy
+//if (new Object())
+Value is truthy