Extract map_theoryt base class from arrayst

[tautschnig]

Separate map-theoretic reasoning (index tracking, equality tracking, Ackermann constraints, read-over-weakeq, extensionality, CDCL(T) propagation, constraint counting) from array-specific encoding (with/if/of/comprehension constraints, lazy selects, 2D inlining).

Inheritance chain: arrayst -> map_theoryt -> equalityt -> prop_conv_solvert

Likely best reviewed commit-by-commit: the second commit introduces a lot of renaming, which impacts call sites. No (intended) functional changes in the second commit.

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• Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• n/a The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
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[Copilot]

Pull request overview

This PR introduces a new map_theoryt base class to factor out map-/array-theoretic reasoning infrastructure from arrayst, adjusting the inheritance chain to arrayst -> map_theoryt -> equalityt -> prop_conv_solvert.

Changes:

• Added map_theoryt (header + constructor TU) containing shared state and helpers for index/equality tracking, Ackermann constraints, and constraint counting.
• Updated arrayst to inherit from map_theoryt and removed now-shared members from arrays.h.
• Re-scoped several previously-arrayst helper methods to map_theoryt.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/solvers/flattening/map_theory.h	Introduces the new base class API and shared state for map/array reasoning.
src/solvers/flattening/map_theory.cpp	Adds map_theoryt constructor implementation.
src/solvers/flattening/arrays.h	Switches arrayst to inherit from map_theoryt and removes moved members.
src/solvers/flattening/arrays.cpp	Updates implementations to use map_theoryt for extracted functionality.

Comments suppressed due to low confidence (1)

src/solvers/flattening/arrays.cpp:47

• Several map_theoryt method implementations (e.g., record_array_index, collect_indices, collect_arrays, add_array_constraint, etc.) are now defined in arrays.cpp. This undermines the stated goal of separating map-theoretic reasoning from array-specific encoding and makes linkage/dependencies less clear. Consider moving map_theoryt method definitions into map_theory.cpp and leaving arrays.cpp to only implement arrayst-specific behavior.

void map_theoryt::record_array_index(const index_exprt &index)
{
  // we are not allowed to put the index directly in the
  //   entry for the root of the equivalence class
  //   because this map is accessed during building the error trace
  std::size_t number=arrays.number(index.array());
  if(index_map[number].insert(index.index()).second)
    update_indices.insert(number);
}

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[codecov]

Codecov Report

❌ Patch coverage is 79.44785% with 67 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.50%. Comparing base (beacad5) to head (52317c2).

Files with missing lines	Patch %	Lines
src/solvers/flattening/map_theory.cpp	71.59%	50 Missing ⚠️
src/solvers/flattening/arrays.cpp	88.23%	12 Missing ⚠️
src/solvers/flattening/map_theory.h	69.23%	4 Missing ⚠️
src/solvers/flattening/arrays.h	50.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8992      +/-   ##
===========================================
- Coverage    80.50%   80.50%   -0.01%     
===========================================
  Files         1704     1706       +2     
  Lines       188816   188809       -7     
  Branches        73       73              
===========================================
- Hits        152013   152006       -7     
  Misses       36803    36803              

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