[Audit-Medium] derived service operations can be silently dropped whe…

[pepone]

AI-generated audit finding — this issue was opened from an automated security/correctness audit. It has not been triaged by a human yet; verify the reasoning, reproducibility, and severity before acting on it.

Medium: derived service operations can be silently dropped when a base service already uses the same operation name — CONFIRMED

Affected code:

• src/IceRpc.ServiceGenerator/Internal/Parser.cs:61-87 — GetServiceMethods(classSymbol.AllInterfaces).Except(baseServiceMethods) then the duplicate-name diagnostic loop
• src/IceRpc.ServiceGenerator/Internal/ServiceMethod.cs:18-33 — Equals and GetHashCode both defined solely in terms of OperationName

Verification:

Confirmed. Two problems stacked on each other:

1. ServiceMethod.Equals is OperationName == other.OperationName only — two methods with the same operation name are equal even if they dispatch to different C# methods with different IDL shapes.
2. Except(baseServiceMethods) therefore strips any derived method whose operation name collides with a base method, silently. The duplicate-name diagnostic at line 75-83 runs on the already-filtered set, so the collision is never reported. The derived dispatcher then omits the operation entirely, and requests for that operation dispatch to the base class's implementation.

For a developer who meant to override a base operation with a differently-shaped IDL method (e.g. Slice override of an Ice operation), the generated dispatch quietly ignores their override.

Impact:

• Dispatch tables diverge from the declared service contract.
• Override and collision mistakes are hidden instead of diagnosed.

Recommendation:

• Check for duplicate operation names across both derived and inherited sets before the Except filter, and report DuplicateOperationNames for any collision.
• Make ServiceMethod.Equals consider the full method identity (concrete subtype + declaring interface + signature) so that only genuinely inherited methods get removed by Except.

Status: Valid, Medium severity.

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Source report: src-IceRpc.ServiceGenerator-audit-2026-04-14.md (finding derived service operations can be silently dropped when a base service already uses the same operation name — **CONFIRMED**)

Severity (auditor-assigned): Medium