Possible missing tests for legacy function properties

[gibson042]

ECMA-262 specifies presence of "caller" and "arguments" properties on Function.prototype that each use the single realm-global %ThrowTypeError% as both getter and setter, and does not specify such properties on function instances (where their absence is arguably expected). But, as observed at endojs/endo#2655 (comment) , implementations diverge.

• JSC and SM follow spec by defining them only on Function.prototype (but violate it by having distinct values for the 4 respective getter/setter functions).
• V8 violates the spec by additionally defining them on Function() and non-strict function(){…} instances (non-writable and non-configurable null-valued data properties).
• XS violates the spec by additionally defining caller [although correctly omitting arguments] on Function() and non-strict function(){…} instances (writable and configurable undefined-valued data properties).
• Hermes violates the spec by omitting them from Function.prototype, and additionally by defining them on strict function(){…} instances (non-configurable accessor properties with %ThrowTypeError% getter/setter functions).

…
And Hermes has an additional bug: in a module context, function(){} is treated differently from function(){ "use strict"; } (cf. Strict Mode Code, "Module code is always strict mode code") for both these function properties and for arguments.callee.

[anba]

Related:

• Add Function#caller and Function#arguments to Annex B ecma262#562
• https://github.com/claudepache/es-legacy-function-reflection

[jdorfman]

Hey @gibson042, this is a little out of my comfort zone, but I wanted to give it a shot since the help wanted label was on.

I'm not going to create a PR until you give me a 👍

Code: main...jdorfman:test262:jd/issue-4340

Results:

test262-harness test/built-ins/Function/prototype/caller-arguments/*.js
FAIL test/built-ins/Function/prototype/caller-arguments/strict-vs-nonstrict.js (default)
  non-strict function should not have own caller property

FAIL test/built-ins/Function/prototype/caller-arguments/cross-realm-behavior.js (default)
  Expected no error, got TypeError: otherRealm.evaluate is not a function

FAIL test/built-ins/Function/prototype/caller-arguments/cross-realm-behavior.js (strict mode)
  Expected no error, got TypeError: otherRealm.evaluate is not a function

FAIL test/built-ins/Function/prototype/caller-arguments/module-context.js (default)
  normal function should not have caller

Ran 7 tests
3 passed
4 failed

Feel free to close without explanation, I won't take it personally ;)

[gibson042]

@jdorfman that's a great start, you should open that PR so it can be formally reviewed.

[jdorfman]

Thanks @gibson042 done