[Basic] NFC: Factor out _FILENAME_FOR_ASSERT macro

Author: hamishknight

include/swift/Basic/Assertions.h

@@ -24,6 +24,13 @@
 #define ASSERT_UNLIKELY(expression) ((expression))
 #endif
 
+// Visual Studio doesn't have __FILE_NAME__
+#ifdef __FILE_NAME__
+#define _FILENAME_FOR_ASSERT __FILE_NAME__
+#else
+#define _FILENAME_FOR_ASSERT __FILE__
+#endif
+
 // ================================ Mandatory Asserts ================================
 
 // `ASSERT(expr)`:
@@ -41,27 +48,13 @@
 // that are more expensive than you think.  You can switch those to
 // `CONDITIONAL_ASSERT` or `DEBUG_ASSERT` as needed.
 
-// Visual Studio doesn't have __FILE_NAME__
-#ifdef __FILE_NAME__
-
-#define ASSERT(expr) \
-  do { \
-    if (ASSERT_UNLIKELY(!(expr))) {			   \
-      ASSERT_failure(#expr, __FILE_NAME__, __LINE__, __func__); \
-    } \
-  } while (0)
-
-#else
-
-#define ASSERT(expr) \
-  do { \
-    if (ASSERT_UNLIKELY(!(expr))) {			   \
-      ASSERT_failure(#expr, __FILE__, __LINE__, __func__); \
-    } \
+#define ASSERT(expr)                                                           \
+  do {                                                                         \
+    if (ASSERT_UNLIKELY(!(expr))) {                                            \
+      ASSERT_failure(#expr, _FILENAME_FOR_ASSERT, __LINE__, __func__);         \
+    }                                                                          \
   } while (0)
 
-#endif
-
 // Function that reports the actual failure when it occurs.
 void ASSERT_failure(const char *expr, const char *file, int line, const char *func);