Add test case for running on fictional platform where unreachable gets triggered

Author: ammaraskar

test-data/unit/check-unreachable-code.test

@@ -383,9 +383,21 @@ def foo(self) -> int:
 [builtins fixtures/ops.pyi]
 [out]
 
+[case testSysPlatformEarlyReturnActualUnreachableCodeForPlatform]
+# flags: --warn-unreachable --platform fictional
+import sys
+
+def foo() -> int:
+    if sys.platform != 'fictional':
+        return 1
+    return 0
+    return 0 + 1  # E: Statement is unreachable
+[builtins fixtures/ops.pyi]
+[out]
+
 -- TODO: We currently suppress unreachability warnings past semantic
--- reachability checks. This should be enabled and fixed.
-[case testSysPlatformInFunctionEarlyReturnWithActualUnreachableCode-skip]
+-- reachability checks. Need to decide if this should be fixed and enabled.
+[case testSysPlatformEarlyReturnActualUnreachableCodeNotForPlatform-skip]
 # flags: --warn-unreachable
 import sys