close #9901 add testcase (#16662)

* close #9901 add testcase

* follow advice

tests/misc/tproveinit.nim

@@ -0,0 +1,18 @@
+discard """
+  joinable: false
+"""
+
+{.warningAsError[ProveInit]:on.}
+template main() =
+  proc fn(): var int =
+    discard
+  discard fn()
+doAssert not compiles(main())
+
+# bug #9901
+import std/[sequtils, times]
+proc parseMyDates(line: string): DateTime =
+  result = parse(line, "yyyy-MM-dd")
+var dateStrings = @["2018-12-01", "2018-12-02", "2018-12-03"]
+var parsed = dateStrings.map(parseMyDates)
+discard parsed