Fix struct complex type boxing in collection materialization

[roji]

When projecting a struct complex type alongside a collection navigation, CompensateForCollectionMaterialization added the value-type expression to _valuesArrayInitializers without boxing, causing NewArrayInit(typeof(object), ...) to throw:

InvalidOperationException: An expression of type 'Outer' cannot be used to initialize an array of type 'System.Object'

The fix boxes value types before adding to the object[] array, matching the existing pattern in the scalar projection path.

Fixes #37926

[Copilot]

Pull request overview

Fixes a regression in relational query shaper compilation where projecting a value-type (struct) complex property alongside a collection navigation could add an unboxed value-type expression into an object[] initializer, causing Expression.NewArrayInit to throw at runtime. Adds coverage to prevent recurrence across providers.

Changes:

• Box value-type expressions before adding them to the internal object[] value buffer used during collection materialization.
• Add a specification regression test reproducing the struct complex type + entity collection navigation projection scenario (#37926).
• Add provider-specific overrides/baselines (SQL Server) and a Cosmos override for the new test.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/EFCore.Relational/Query/RelationalShapedQueryCompilingExpressionVisitor.ShaperProcessingExpressionVisitor.cs	Boxes value-type parameters before storing them in _valuesArrayInitializers during collection materialization compensation.
test/EFCore.Specification.Tests/Query/Associations/ComplexProperties/ComplexPropertiesCollectionTestBase.cs	Adds regression test for projecting a struct complex property together with an entity collection navigation.
test/EFCore.SqlServer.FunctionalTests/Query/Associations/ComplexJson/ComplexJsonCollectionSqlServerTest.cs	Overrides the new test to assert the expected SQL baseline on SQL Server.
test/EFCore.Cosmos.FunctionalTests/Query/Associations/ComplexProperties/ComplexPropertiesCollectionCosmosTest.cs	Adds an override for the new test (currently implemented as a no-op completion).

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[Copilot]

Pull request overview

Fixes a regression in EF Core’s relational query materialization pipeline where projecting a struct complex type alongside a collection navigation could fail due to missing boxing when building an object[] used during collection materialization.

Changes:

• Box value-type projection expressions before adding them to the object[] initializer list used during collection materialization compensation.
• Add a new specification test covering struct complex type + entity collection navigation projection.
• Add provider-specific overrides: SQL Server SQL baseline assertion; Cosmos override asserting translation failure.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/EFCore.Relational/Query/RelationalShapedQueryCompilingExpressionVisitor.ShaperProcessingExpressionVisitor.cs	Boxes value types before storing them in the object[] used for collection materialization compensation.
test/EFCore.Specification.Tests/Query/Associations/ComplexProperties/ComplexPropertiesCollectionTestBase.cs	Adds regression test for projecting a struct complex property alongside an entity collection navigation.
test/EFCore.SqlServer.FunctionalTests/Query/Associations/ComplexJson/ComplexJsonCollectionSqlServerTest.cs	Overrides the new test and asserts the generated SQL baseline on SQL Server.
test/EFCore.Cosmos.FunctionalTests/Query/Associations/ComplexProperties/ComplexPropertiesCollectionCosmosTest.cs	Overrides the new test to assert translation failure (collection navigations across documents unsupported).

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