E4020: cannot mutate immutable binding

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What this means

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Metadata

• Code: E4020
• Default level: Error
• Phase: Borrow Check
• Canonical docs URL: https://docs.brim-lang.com/diagnostics/E4020
• Tags: borrow, mut

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How to fix

• declare mut
• interior mutability

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Typical output

E4020: cannot mutate immutable binding
note: mutation requires mutable binding