Editorial: Better align ArrayBuffer.p.sliceToImmutable with slice

Author: gibson042

spec.emu

@@ -717,19 +717,20 @@ contributors: Mark S. Miller, Richard Gibson
             1. Let _O_ be the *this* value.
             1. Perform ? RequireInternalSlot(_O_, [[ArrayBufferData]]).
             1. If IsSharedArrayBuffer(_O_) is *true*, throw a *TypeError* exception.
-            1. TODO: Confirm inclusion of this redundant check.
             1. If IsDetachedBuffer(_O_) is *true*, throw a *TypeError* exception.
             1. Let _len_ be _O_.[[ArrayBufferByteLength]].
             1. Let _bounds_ be ? ResolveBounds(_len_, _start_, _end_).
             1. Let _first_ be _bounds_.[[From]].
             1. Let _final_ be _bounds_.[[To]].
-            1. TODO: Confirm this strictness vs. the conventional `max(_final_ - _first_, 0)`.
             1. Let _newLen_ be _final_ - _first_.
+            1. TODO: Confirm this strictness vs. `slice` (rejecting negative _newLen_ rather than clamping to 0).
             1. If _newLen_ < 0, throw a *RangeError* exception.
-            1. Let _copyLen_ be min(_newLen_, _len_).
-            1. NOTE: Side-effects of the above steps may have detached or resized _O_. This algorithm proceeds only when _O_ is not detached, even if _newLen_ is 0.
+            1. NOTE: Side-effects of the above steps may have detached or resized _O_.
             1. If IsDetachedBuffer(_O_) is *true*, throw a *TypeError* exception.
-            1. Let _newBuffer_ be ? AllocateImmutableArrayBuffer(%ArrayBuffer%, _newLen_, _O_.[[ArrayBufferData]], _first_, _copyLen_).
+            1. Let _fromBuf_ be _O_.[[ArrayBufferData]].
+            1. Let _currentLen_ be _O_.[[ArrayBufferByteLength]].
+            1. If _currentLen_ < _final_, throw a *RangeError* exception.
+            1. Let _newBuffer_ be ? AllocateImmutableArrayBuffer(%ArrayBuffer%, _newLen_, _fromBuf_, _first_, _newLen_).
             1. Return _newBuffer_.
           </emu-alg>
         </emu-clause>