Module segment_borrow 

Segment-level borrow registry for fine-grained access control.

The account-level BorrowRegistry prevents aliasing across entire accounts. This module adds segment-level conflict detection: two borrows of the same account are allowed when their byte ranges don’t overlap, or when both are read-only.

Conflict Rules

Existing	New	Overlapping?	Allowed
Read	Read	yes	✅
Read	Write	yes	❌
Write	Read	yes	❌
Write	Write	yes	❌
any	any	no	✅

Zero-Cost Design

• Fixed-capacity array (no heap)
• Inline conflict checks
• Deterministic iteration (bounded loop)

Structs

SegmentBorrow

A single active segment borrow.

SegmentBorrowGuard

RAII guard that releases a segment borrow when dropped.

SegmentBorrowRegistry

Instruction-scoped segment borrow registry.

Enums

AccessKind

Read or write access intent for a segment borrow.

Constants

MAX_SEGMENT_BORROWS

Maximum simultaneous segment borrows per instruction.