Andreas Kling 63d8a1821e LibJS: Don't overwrite cached this value on async/generator reentry ...

When resuming execution of a suspended function, we must not overwrite
any cached `this` value with something from the ExecutionContext.

This was causing an empty JS::Value to leak into the VM when resuming
an async arrow function, since the "this mode" for such functions is
lexical and thus ExecutionContext will have an empty `this`.

It became a problem due to the bytecode optimization where we allow
ourselves to assume that `this` remains cached after we've executed a
ResolveThisBinding in this (or the first) basic block of the executable.

Fixes https://github.com/LadybirdBrowser/ladybird/issues/138

(cherry picked from commit a91bb72dabe54849657720e36e19a3d3b737055f)

2024-06-24 16:38:47 +02:00

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