some test cleanups & category reorganization (#22010)

* clean up some test categories

* mention exact slice issue

* magics into system

* move trangechecks into overflow

* move tmemory to system

* try fix CI

* try fix CI

* final CI fix

tests/init/tinitchecks_v2.nim

@@ -57,3 +57,27 @@ proc currentlyValid(x: out int; y: out string; cond: bool) =
   y = "abc" # <-- error: not every path initializes 'y'
 
 currentlyValid gl, gs, false
+
+block: # previously effects/toutparam
+  proc gah[T](x: out T) =
+    x = 3
+
+  proc arr1 =
+    var a: array[2, int]
+    var x: int
+    gah(x)
+    a[0] = 3
+    a[x] = 3
+    echo x
+
+  arr1()
+
+  proc arr2 =
+    var a: array[2, int]
+    var x: int
+    a[0] = 3
+    a[x] = 3 #[tt.Warning
+      ^ use explicit initialization of 'x' for clarity [Uninit] ]#
+    echo x
+
+  arr2()

tests/init/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