__evaluatePureFunction doesn't properly validate arguments

[NTillmann]

Prepacking the following crashes Prepack.

__evaluatePureFunction("boo");

In the implementation, it shouldn't check via an invariant that the argument is a proper value, but instead it should throw a user-level exception or emit a CompilerDiagnostics error.

[rahilvora]

Hey @NTillmann I am very new to open source contribution and I would love to work on this issue. Should I go ahead with it?

[NTillmann]

This one should be easy! Give it a try.

[rahilvora]

Sure. Will try it :)

[rahilvora]

PR for this issue: #2403

[rahilvora]

@NTillmann Can you please tell which error message I should add for this issues which will help a developer to understand the error https://github.com/facebook/prepack/wiki/Prepack-diagnostics

[NTillmann]

Just make up a new PP number that isn't used yet. Propose a wiki text in your PR, and then we'll create the wiki page for you when landing the PR.