[Audit-Medium] valid service type shapes are mishandled

[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: valid service type shapes are mishandled — CONFIRMED

Affected code:

• src/IceRpc.ServiceGenerator/ServiceGenerator.cs:20-25 — syntax predicate is node is ClassDeclarationSyntax; the cast (ClassDeclarationSyntax)context.TargetNode reinforces the same assumption
• src/IceRpc.ServiceGenerator/Internal/Parser.cs:89-97 — ServiceClass is constructed from classSymbol.Name (bare name, no generic arity) and classDeclaration.Keyword.ValueText
• src/IceRpc.ServiceGenerator/Internal/Parser.cs:99-113 — the enclosing-container block handles only one level of nesting and then stops (the reassignment of parentNode = parentNode.Parent; at line 112 is the last statement of the if; there is no loop)
• src/IceRpc.ServiceGenerator/Internal/ContainerDefinition.cs:11 — the Enclosing linked list shape is correct; the parser just doesn't populate beyond one level
• src/IceRpc.ServiceGenerator/Internal/Emitter.cs:33-49 — builds the partial {keyword} {name} header from the data the parser supplied

Verification:

Confirmed on three distinct axes:

1. Records — [Service] on public partial record class Foo never triggers the generator because the syntax predicate only matches ClassDeclarationSyntax, not RecordDeclarationSyntax. No diagnostic, no generated file — silent failure.
2. Generics — classSymbol.Name is "Foo" for Foo<T>; the emitted partial class Foo { ... } doesn't merge with the user's partial class Foo<T> and the build fails with a type-not-partial error, pointing nowhere useful.
3. Multi-level nesting — class Outer { class Middle { [Service] class Leaf { } } } emits partial class Middle { partial class Leaf { ... } } without Outer, which the compiler rejects because the generated source declares Middle at the global/namespace scope rather than inside Outer.

Impact:

• Supported-looking service declarations silently fail to generate (records).
• Nested and generic services break compilation with malformed generated code.
• Failure points don't lead the developer back to the root cause.

Recommendation:

• Expand the syntax predicate to TypeDeclarationSyntax (or specifically ClassDeclarationSyntax or RecordDeclarationSyntax) and widen the cast accordingly.
• Capture the full type syntax for the service class (class Foo<T> where T : …) and for each enclosing container, including generic parameters and constraints.
• Iterate on parentNode in a loop so every enclosing type is captured.
• Add regression tests for record classes, multi-level nesting, and generic service types.

Status: Valid, Medium severity.

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Source report: src-IceRpc.ServiceGenerator-audit-2026-04-14.md (finding valid service type shapes are mishandled — **CONFIRMED**)

Severity (auditor-assigned): Medium