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What this means

mutation invalidates outstanding iterator borrows

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Metadata

  • Code: E4012
  • Default level: Error
  • Phase: Borrow Check
  • Canonical docs URL: https://docs.brim-lang.com/diagnostics/E4012
  • Tags: borrow, iterator

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How to fix

  • collect first
  • avoid mutating backing collection during iteration

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Typical output

E4012: iterator invalidation pattern
note: mutation invalidates outstanding iterator borrows