fix(csharp): recover arity-sibling base types dropped by the self-loop guard

[vitali87]

Problem

C# overloads type names by generic arity: public sealed class PredicateBuilder : PredicateBuilder<object> declares a base that is a different type sharing the simple name. cgr's name resolution lands on the declaring type itself, and the deferred-inherits self-loop guard then drops the edge (dotted module-anchored remainder) or externalizes it. On Polly this silently lost 6 INHERITS edges (RetryStrategyOptions, CircuitBreakerStrategyOptions, PredicateBuilder, BrokenCircuitException<TResult>, ITtlStrategy, ExecuteParameters).

Fix

When a deferred C# base resolves to the child itself, recover the arity sibling before falling back:

1. Package tier: a unique other type declaration (Class/Interface/Enum) with the same simple name under the module's parent package — the conventional Foo.cs + Foo.TResult.cs sibling layout.
2. Project-wide tier: only when the package tier finds zero candidates (the pair can span projects: Polly's legacy BrokenCircuitException<TResult> : BrokenCircuitException inherits from Polly.Core), accept a project-wide unique declaration.

Ambiguity at either tier keeps the no-edge answer rather than guessing, and the recovery is gated to C# — only C# can legally name a different type with the declaring type's own simple name, so other languages keep the existing shadowed-name semantics (e.g. thrift's pub enum Error implementing std Error).

Validation

RED → GREEN in commit history: failing tests first for the same-directory pair (class and interface variants), then the cross-directory pair.

On Polly, INHERITS false negatives drop from 5 to 2 (tp 192 → 195, F1 0.9253 → 0.9330). The two remaining misses have distinct root causes, out of scope here:

• PredicateBuilder<TResult> is partial across two files, so the package tier sees two candidates and correctly refuses to guess; the opt-in Roslyn hybrid frontend's partial-group merge is the semantic answer for that shape.
• ExecuteParameters<T> : ExecuteParameters nests both types in one class, so their qualified names collide (the known duplicate-QN limitation; tracked separately).

Full suite: 5224 passed, 10 skipped.

[gemini-code-assist]

Code Review

This pull request introduces support for C# arity overloading resolution during class ingestion. Specifically, it adds a helper method _csharp_arity_sibling to recover generic sibling types when a base class resolves to the declaring type itself (e.g., class Foo : Foo<object>), preventing the self-loop guard from dropping the inheritance edge. Unit tests have also been added to cover these scenarios. Feedback on the PR points out potential issues with the package-level sibling matching logic when dealing with root modules (no namespace) or subpackages, and provides a robust suggestion to compare exact parent packages instead.

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[greptile-apps]

Greptile Summary

This PR updates C# inheritance resolution for generic-arity sibling types. The main changes are:

• Recover a unique same-name C# type declaration when deferred base resolution points back to the child type.
• Prefer a unique sibling under the module parent package before falling back to a project-wide unique declaration.
• Keep ambiguous matches as no-edge results instead of guessing.
• Add tests for same-directory class and interface pairs, plus cross-directory sibling recovery.

Confidence Score: 5/5

Safe to merge with minimal risk.

The change is narrowly scoped to C# self-loop recovery, preserves existing fallback behavior for other languages and ambiguous matches, and adds focused tests for the new paths.

No files require special attention.

T-Rex Logs

What T-Rex did

• Attempted the narrow C# inheritance pytest validation for codebase_rag/tests/test_csharp_inheritance.py.
• Dependency setup blocked before pytest collection because pymgclient==1.5.1 could not build without cmake.
• Tool availability check showed uv was present, but cmake3 and cmake were unavailable.
• Pytest environment activity shows uv created a virtual environment and dependency resolution started, then building pymgclient==1.5.1 failed due to missing suitable cmake, so validation remains inconclusive.

_{Ran code and verified through T-Rex}

Important Files Changed

Filename	Overview
codebase_rag/parsers/class_ingest/mixin.py	Adds C#-only deferred inheritance recovery for arity-sibling base types when self-loop resolution would otherwise drop the edge.
codebase_rag/tests/test_csharp_inheritance.py	Adds tests for same-directory class/interface arity siblings and cross-directory project-wide recovery.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
A[Deferred C# base resolution] --> B{parent_qn == child_qn?}
B -- No --> C[Existing deferred parent resolution]
B -- Yes --> D{Language is C#?}
D -- No --> E[Existing self-loop fallback]
D -- Yes --> F[Find same-simple-name type declarations]
F --> G{Unique candidate under module parent package?}
G -- Yes --> H[Emit INHERITS to package sibling]
G -- Multiple --> I[Emit no edge]
G -- None --> J{Unique project-wide candidate?}
J -- Yes --> K[Emit INHERITS to project-wide sibling]
J -- No --> I

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flowchart TD
A[Deferred C# base resolution] --> B{parent_qn == child_qn?}
B -- No --> C[Existing deferred parent resolution]
B -- Yes --> D{Language is C#?}
D -- No --> E[Existing self-loop fallback]
D -- Yes --> F[Find same-simple-name type declarations]
F --> G{Unique candidate under module parent package?}
G -- Yes --> H[Emit INHERITS to package sibling]
G -- Multiple --> I[Emit no edge]
G -- None --> J{Unique project-wide candidate?}
J -- Yes --> K[Emit INHERITS to project-wide sibling]
J -- No --> I

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_{Reviews (1): Last reviewed commit: "fix(csharp): fall back to a project-wide..." | Re-trigger Greptile}