Infer generic class types from class MethodDataSource rows using shared runtime support

A generic test class whose only type information comes from a class-level MethodDataSource silently disappears in generated discovery. Enable declared-row and constructor-based type inference once the sibling runtime support is merged, so both discovery modes run the same tests or report an actionable discovery failure.

Scope and owned files

src/TUnit.Core.SourceGenerator/Generators/TestMetadataGenerator.cs and src/TUnit.Core.SourceGenerator/CodeGenerators/Helpers/InstanceFactoryGenerator.cs.
tests/TUnit.Core.SourceGenerator.Tests/Bugs/7333/Tests7333.cs, affected generator snapshots, tests/TUnit.TestProject/Bugs/_7333/ClassMethodDataSourceInferenceTests.cs, _7161/ClassDataForMethodRowInstantiationTests.cs, and tests/TUnit.Engine.Tests/Issue7333Tests.cs / Issue7208Tests.cs. Reconcile runtime regressions introduced by the prerequisite rather than duplicating them.
Reuse preserved branch issue-7333-class-method-source, head df168fa58f32f0ef591b731330cf2407b4922fc9.

Acceptance criteria

Deliver Source-gen: generic test class does not infer its type arguments from a class-level [MethodDataSource]; reflection does #7333 own/external class-source inference and uninferable-source diagnostics, preserving constructor selection, method-row matching, explicit generic instantiations, constraints, factories, arrays, null and empty row semantics covered by the branch fixtures.
Consume the sibling runtime support after it merges; do not bring its implementation into this PR.
Retain the null-collection regression requested in Codex finding fix(generator): infer generic class types from class MethodDataSource rows #7422 (comment) when enabling inferred class rows.
Run full generator snapshot tests and targeted fixtures in both modes, review verified snapshots, run PublicAPI checks where applicable, and publish/execute Native AOT fixtures. Leave Engine.Tests to CI.
For the cached-constructor invariant, ensure malformed metadata cannot silently drop all tests; explain or test the invariant. Nonblocking class-row-plan/caching/expression-emission refactoring remains tracked in Share class-row type inference between the source generator, analyzer and reflection #7377.

Split because #7422 reached 21 automated review rounds with a new blocking parity finding. Parent #7333 remains open until both parts deliver its acceptance criteria.

Triaged against origin/main at 87d2a30. The inference changes and ConfigureInferredSource runtime support from closed, unmerged #7422 are still absent. Both sibling issues remain necessary; #7425 covers diagnostics but does not deliver class-source inference. Removed the redundant blocked label; the native blocked_by dependency on #7445 remains authoritative.

Additional row-partition parity case found while fixing #7518's method-provider retention. A declared interface constructor source plus a concrete method source produces an extra inferred class test in generated discovery. Reflection only runs the explicitly requested interface instantiation.

[GenerateGenericTest(typeof(IComparable))]
[MethodDataSource(nameof(ConstructorRows))]
public class C<T>(T value)
{
    public static IEnumerable<IComparable> ConstructorRows() => [42];
    public static IEnumerable<int> MethodRows() => [43];
    [Test, MethodDataSource(nameof(MethodRows))]
    public void Test(T argument) { }
}

SDK 10.0.403, net10.0, macOS arm64. At #7518 head 4a5e436, generated discovery emits C (passing) and C (missing method arguments); reflection emits only the passing C. The provider-retention fix repairs C, but the extra generated C remains. The same difference occurs with a DataSourceGeneratorAttribute method provider. Expected: both modes run the same closed instantiations.

Reproduce with the ExplicitCompatibleMethodRows and ExplicitCompatibleTypedMethodRows fixtures added to tests/TUnit.TestProject/Bugs/_7490/Tests.cs in #7518: run net10.0 with --treenode-filter '//TUnit.TestProject.Bugs._7490/ExplicitCompatibleMethodRows/*', then add --reflection. Please cover these declared-source/explicit-type combinations in this issue's class-source inference and partition work.

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Infer generic class types from class MethodDataSource rows using shared runtime support #7446

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Infer generic class types from class MethodDataSource rows using shared runtime support #7446

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thomhurst commented on Nov 3, 2026

thomhurst commented on Nov 4, 2026

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