fix: prevent variable shadowing in event derive macro

[Princetimix69]

Summary

Fixes a variable shadowing issue in the derive(starknet::Event) macro where struct members named keys or data would collide with the generated deserialize function arguments.

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Type of change

Please check one:

• Bug fix (fixes incorrect behavior)
• New feature
• Performance improvement
• Documentation change with concrete technical impact
• Style, wording, formatting, or typo-only change

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Why is this change needed?

When a user defines a Starknet Event struct with members named keys or data, the generated deserialize function creates local variables with the same names. These local variables shadow the ref keys and ref data arguments required for the deserialization process, causing compilation errors or incorrect behavior.

By prefixing the local variables for deserialized values (e.g., using __val_keys instead of keys), this PR ensures that the function arguments remain accessible throughout the function body.

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What was the behavior or documentation before?

The derive(starknet::Event) macro generated variable names identical to their struct member names. If a member was named keys or data, it would shadow the deserialization buffer arguments keys and data.

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What is the behavior or documentation after?

The macro now generates local variables with a __val_ prefix (e.g., __val_membername). This prevents any collision with the fixed argument names keys and data, allowing Event structs to safely use these names as member fields.

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Related issue or discussion (if any)

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Additional context

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This change is 

[orizi]

@orizi made 1 comment.
Reviewable status: 0 of 1 files reviewed, 1 unresolved discussion (waiting on @Princetimix69).

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