deprecate sequtils.delete and add an overload with saner semantics consistent with system.delete (#18487)

* deprecate sequtils.delete and add an overload with saner semantics
* AssertionDefect => IndexDefect
* improve tsequtils
* add tests; use splice in js for optimization

lib/pure/collections/sequtils.nim

@@ -509,12 +509,51 @@ proc keepIf*[T](s: var seq[T], pred: proc(x: T): bool {.closure.})
       inc(pos)
   setLen(s, pos)
 
-func delete*[T](s: var seq[T]; first, last: Natural) =
+func delete*[T](s: var seq[T]; slice: Slice[int]) =
+  ## Deletes the items `s[slice]`, raising `IndexDefect` if the slice contains
+  ## elements out of range.
+  ##
+  ## This operation moves all elements after `s[slice]` in linear time.
+  runnableExamples:
+    var a = @[10, 11, 12, 13, 14]
+    doAssertRaises(IndexDefect): a.delete(4..5)
+    assert a == @[10, 11, 12, 13, 14]
+    a.delete(4..4)
+    assert a == @[10, 11, 12, 13]
+    a.delete(1..2)
+    assert a == @[10, 13]
+    a.delete(1..<1) # empty slice
+    assert a == @[10, 13]
+  when compileOption("boundChecks"):
+    if not (slice.a < s.len and slice.a >= 0 and slice.b < s.len):
+      raise newException(IndexDefect, $(slice: slice, len: s.len))
+  if slice.b >= slice.a:
+    template defaultImpl =
+      var i = slice.a
+      var j = slice.b + 1
+      var newLen = s.len - j + i
+      while i < newLen:
+        when defined(gcDestructors):
+          s[i] = move(s[j])
+        else:
+          s[i].shallowCopy(s[j])
+        inc(i)
+        inc(j)
+      setLen(s, newLen)
+    when nimvm: defaultImpl()
+    else:
+      when defined(js):
+        let n = slice.b - slice.a + 1
+        let first = slice.a
+        {.emit: "`s`.splice(`first`, `n`);".}
+      else:
+        defaultImpl()
+
+func delete*[T](s: var seq[T]; first, last: Natural) {.deprecated: "use `delete(s, first..last)`".} =
   ## Deletes the items of a sequence `s` at positions `first..last`
   ## (including both ends of the range).
   ## This modifies `s` itself, it does not return a copy.
-  ##
-  runnableExamples:
+  runnableExamples("--warning:deprecated:off"):
     let outcome = @[1, 1, 1, 1, 1, 1, 1, 1]
     var dest = @[1, 1, 1, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1]
     dest.delete(3, 8)