662822 - Clarify behavior when EvaluateInFrame introduces new variables

Status: RESOLVED DUPLICATE of bug 662826

(Core :: JavaScript Engine, defect)

Description

[Brian Hackett [Laid off!]]

The bytecode, bytecode emitter and the rest of the JS VM have a lot of optimizations which depend on knowing the variables declared by each script.  These will deoptimize appropriately if a direct eval() exists which could introduce new variable bindings, but assume the debugger is not used to EvaluateInFrame and introduce new variable bindings in scripts which do not contain direct eval().

If the EvaluateInFrame does introduce new bindings, it adds a call object and puts the properties there, and whether those properties are actually observed by the running script depends on whether the bytecode name optimizations were used in that script or not.  I don't know what the right thing to do here is (throw an error?), but inconsistently ignoring things doesn't seem like good behavior.