[Copilot]

Query precompilation drops implicit conversions when reconstructing conditional branches and binary operands. This causes valid C# projections with nullable results—and equality comparisons requiring user-defined conversions—to fail during expression-tree construction.

• Translation

  • Apply conversions using Roslyn’s semantic ConvertedType before constructing conditional and binary nodes.
  • Preserve compiler-style reference equality and existing is/as handling.

• Coverage

  • Cover nullable lifting in either branch, explicit-cast controls, numeric conversions, and custom-type equality/inequality.
  • Add a shared precompiled-query regression covering generation, generated-code compilation, and execution.

Nullable constructor arguments no longer require an explicit cast on the non-null branch:

new GenerationMetric(
    state,
    count,
    hasCompleted ? durations.Average() : null)

• Fixes Query precompiler fails to lift a double branch in a target-typed nullable conditional #39304

[github-actions]

Agent harness evaluation deferred

This PR affects: query-pipeline. Automatic evaluation is deferred because this PR is currently marked as draft. Once it is ready for review, the usual author authorization rules apply. A contributor with write access can comment /eval or /eval component-name, or run the workflow manually for pull request #39313.

[Copilot]

🔵 Needs a closer look

Binary conversion handling affects multiple operators, and Roslyn and provider regression tests were not executed during this review.

No open issues 🎉

What changed in this PR

Fixes query precompilation failures by preserving implicit conversions when reconstructing expression trees.

Changes:

• Applies semantic conversions to conditional branches and binary operands while preserving reference equality and is/as handling.
• Adds conversion-focused unit tests and a shared precompiled-query regression with SQL Server assertions.
• Documents the conversion requirement in query-pipeline guidance.

File	Description
test/​EFCore.SqlServer.FunctionalTests/​Query/​AdHocPrecompiledQuerySqlServerTest.cs	Adds SQL baseline for the regression.
test/​EFCore.Relational.Specification.Tests/​Query/​AdHocPrecompiledQueryRelationalTestBase.cs	Adds shared generation, compilation, and execution coverage.
test/​EFCore.Design.Tests/​Query/​CSharpToLinqTranslatorTest.cs	Tests nullable, numeric, and user-defined conversions.
src/​EFCore.Design/​Query/​Internal/​CSharpToLinqTranslator.cs	Preserves semantic operand and branch conversions.
.agents/​skills/​query-pipeline/​SKILL.md	Documents expression reconstruction requirements.

_{Review effort: Balanced}

[Copilot]

🟡 Changes recommended

Conversion reconstruction can select an explicit operator instead of the source’s implicit conversion, changing query results.

1 open issue

• Preserve Roslyn's selected user-defined conversion in precompiled queries · New

_{Review effort: Balanced}

[github-code-quality]

Code coverage overview

Languages: C#

C# / code-coverage

main 4317e84	copilot/fix-query-pr... 44a37a2	+/-
76%	76%	0%

View coverage of the 10 most impacted files.

File	main 4317e84	copilot/fix-query-pr... 44a37a2	+/-
src/EFCore.Desi...nqTranslator.cs	84%	84%	0%
src/EFCore.Abst...erExtensions.cs	100%	100%	0%
src/EFCore.Anal...icSuppressor.cs	96%	96%	0%
src/EFCore.Desi...CSharpHelper.cs	96%	96%	0%
src/EFCore.Desi...seOperations.cs	91%	91%	0%
src/EFCore.Desi...xtOperations.cs	57%	57%	0%
src/EFCore.Desi...ySafetyRules.cs	94%	94%	0%
src/EFCore.Rela...osticsLogger.cs	98%	99%	+1%
src/EFCore.Rela...CommandCache.cs	98%	100%	+2%
src/Microsoft.D...nnectionPool.cs	97%	100%	+3%

ℹ️ Calculations represent line coverage. Results may change as calculations are updated.

---

_{Updated October 22, 2026 01:33 UTC}

[Copilot]

🟡 Changes recommended

Operator lookup ambiguity and incorrect nullable-lifting detection still cause valid C# queries to fail during precompilation.

2 open issues

• Match conversion operator return type during lookup · New
• Avoid nullable lifting for boxing-based user-defined conversions · New

1 resolved since last review

• Preserve Roslyn's selected user-defined conversion in precompiled queries

_{Review effort: Balanced}

[Copilot]

🔵 Needs a closer look

Compiler-sensitive conversion and nullable-lifting behavior needs regression-suite confirmation against the pinned SDK before approval.

No open issues 🎉

2 resolved since last review

• Avoid nullable lifting for boxing-based user-defined conversions
• Match conversion operator return type during lookup

_{Review effort: Balanced}