fix #16499 (#16514)

lib/system/fatal.nim

@@ -30,16 +30,20 @@ elif (defined(nimQuirky) or defined(nimPanics)) and not defined(nimscript):
   proc name(t: typedesc): string {.magic: "TypeTrait".}
 
   proc sysFatal(exceptn: typedesc, message, arg: string) {.inline, noreturn.} =
-    writeStackTrace()
+    when nimvm:
-    var buf = newStringOfCap(200)
+      # TODO when doAssertRaises works in CT, add a test for it
-    add(buf, "Error: unhandled exception: ")
+      raise (ref exceptn)(msg: message & arg)
-    add(buf, message)
+    else:
-    add(buf, arg)
+      writeStackTrace()
-    add(buf, " [")
+      var buf = newStringOfCap(200)
-    add(buf, name exceptn)
+      add(buf, "Error: unhandled exception: ")
-    add(buf, "]\n")
+      add(buf, message)
-    cstderr.rawWrite buf
+      add(buf, arg)
-    quit 1
+      add(buf, " [")
+      add(buf, name exceptn)
+      add(buf, "]\n")
+      cstderr.rawWrite buf
+      quit 1
 
   proc sysFatal(exceptn: typedesc, message: string) {.inline, noreturn.} =
     sysFatal(exceptn, message, "")

tests/assert/tassert_c.nim

@@ -8,7 +8,7 @@ tassert_c.nim(35)        tassert_c
 tassert_c.nim(34)        foo
 assertions.nim(30)       failedAssertImpl
 assertions.nim(23)       raiseAssert
-fatal.nim(49)            sysFatal"""
+fatal.nim(53)            sysFatal"""
 
 proc tmatch(x, p: string): bool =
   var i = 0