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HashSet model: deterministic Object[]-backed set - #45

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HashSet model: deterministic Object[]-backed set#45
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Depends-on: #42 (first commit in this PR)

Executable model of java.util.HashSet over a duplicate-free Object[]
prefix: add/remove/contains/size/isEmpty/clear, addAll/removeAll/
retainAll/containsAll, toArray, and iterator() via
CProverArrayLikeIterator (snapshot semantics). Iteration is storage
order, conformant with HashSet's unspecified-order contract. Null
elements are supported per the JDK. A package-private wrapping
constructor exposes a pre-existing storage prefix so map models can
build keySet()/entrySet() views without copying.

Co-authored-by: Kiro kiro-agent@users.noreply.github.com

tautschnig and others added 2 commits July 28, 2026 23:53
…eneric-element annotation

Three top-level org.cprover support classes for collection models'
iterator()/enhanced-for support. They are inert until collection models
reference them (none in this repo do yet -- the javadoc describes intended
usage); landing them separately keeps the model changes reviewable.

- CProverArrayLikeIterator<E>: generic snapshot iterator over an
  Object[]-backed collection; captures (storage, size) at iterator()
  time. Top-level rather than an inner class deliberately: a non-static
  inner class's implicit this$0 creates a Collection <-> Iterator
  lazy-class-loading cycle that aborts JBMC's nondet initialisation of
  abstract collection parameters. The class javadoc carries the full
  design rationale (snapshot-vs-fail-fast trade-off, iteration-order
  conformance, and the documented opt-in future paths for CME modelling
  and Iterator.remove()).

  next() past the end throws NoSuchElementException per the JDK contract.
  An assume() guard on the precondition would be unsound here: it would
  prune exactly the executions in which target code over-iterates,
  hiding those bugs behind vacuously-passing paths; modelling the throw
  keeps them observable with the correct exception type.

- CProverMapEntry<K, V>: read-only snapshot Map.Entry for entrySet()
  views of parallel-array map models. Deliberately final; entry-driven
  mutation calls for a separate write-through entry class (documented),
  not subclassing.

- @CProverGenericArrayElement: marks an Object[] field as holding a
  model class's generic-parameter elements, so JBMC's nondet object
  factory can specialise the element type.

Co-authored-by: Kiro <kiro-agent@users.noreply.github.com>
Executable model of java.util.HashSet over a duplicate-free Object[]
prefix: add/remove/contains/size/isEmpty/clear, addAll/removeAll/
retainAll/containsAll, toArray, and iterator() via
CProverArrayLikeIterator (snapshot semantics). Iteration is storage
order, conformant with HashSet's unspecified-order contract. Null
elements are supported per the JDK. A package-private wrapping
constructor exposes a pre-existing storage prefix so map models can
build keySet()/entrySet() views without copying.

Co-authored-by: Kiro <kiro-agent@users.noreply.github.com>
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