Reported by André Bargull in
<https://bugzilla.mozilla.org/show_bug.cgi?id=1464758>.

`function nan() { return /* expression to compute NaN */ }` may not return the same implementation-distinguishable NaN value before and after JIT compilation.

Fixes gh-1476
Closes gh-1484

This reverts commit a01de4a7.

Because Proxies no longer allow to return duplicate property keys.

These tests are not helpful for their respective APIs being tested.

They don't add any coverage for the built-in apis and basically check
behaviors that might conflict with a implementation defined global.

This script is intended to identify common test file formatting errors
prior to their acceptance into the project. It is designed to support
future extensions for additional validation rules.

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>

Fix 850

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>

Some popular JavaScript engines display violation of invariants about
property attributes for some non-standard but “web-reality” object
properties. Add tests against such violations

Closes #653
Fixes #649

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>

* Add tests for prototype realm inference

* Add tests for miscellaneous realm concerns

* Add tests for realm of spec-created Errors

In some cases, Error objects produced by the specification are
observable from ECMAScript code. Among these cases, some are further
differentiated in that they occur outside of any built-in function and
may be triggered through syntactic production directly. The current
realm record is commonly interpreted incorrectly under these
circumstances.

Add tests asserting that the expected realm record is used when
constructing such Error objects.

* Add tests for realm use in ArraySpeciesCreate

* Add tests for function realm retrieval

* Add tests for cross-realm behaviors of Symbols

* Add tests for GetValue and PutValue

* Add tests for realm of spec-created Arrays

In some cases, Arrays produced by CreateArrayFromList are observable
from ECMAScript code. Among these cases, two occur outside of any
built-in function and may be triggered through syntactic production
directly. The current realm record is commonly interpreted incorrectly
under these circumstances.

Add tests asserting that the expected realm record is used when
constructing arrays.

* Add test for spec-created object

* fixup! Add tests for realm of spec-created Errors

* fixup! Add tests for realm of spec-created Errors

* fixup! Add tests for prototype realm inference

* fixup! Add tests for miscellaneous realm concerns

Per https://github.com/tc39/ecma262/pull/593

Fixes gh-683
Ref gh-648
Ref tc39/ecma262#353

The global isNaN is not precise at all, and Number.isNaN is an ES6 feature that makes it preferrable to use assert's sameValue for NaN values, as it handles it internally using the comparison.