Preserve nullable typing for ignored null-conditional access in coalesce expressions

[Copilot]

NullConditionalRewriteSupport.Ignore currently strips ?. to direct member access, which breaks ?? when the left side was originally nullable (e.g. Price?.Amount ?? 0m becoming Price.Amount ?? 0m). This causes invalid generated code (decimal ?? decimal).

• Generator fix: typed rewrite for ?? left operand

  • Updated ExpressionSyntaxRewriter null-conditional ignore path to detect when a conditional access is the left operand of a coalesce.
  • If the original converted type is Nullable<T> and the rewritten member/index access is T, the generator now emits an explicit cast to Nullable<T>.

• Scope control

  • The nullable cast is applied only in coalesce-left contexts to avoid changing existing ignore semantics in non-coalesce expressions.

• Regression coverage

  • Added NullConditionalNullCoalesceTypeConversion_WithIgnoreSupport in NullableTests.
  • Added corresponding snapshot to assert nullable cast emission in generated expression code.

// source
[Projectable(AllowBlockBody = true, NullConditionalRewriteSupport = NullConditionalRewriteSupport.Ignore)]
public decimal GetCost() => Price?.Amount ?? 0m;

// generated (relevant part)
return (global::Product @this) => (decimal? )(@this.Price.Amount) ?? 0m;

[Copilot]

Pull request overview

This PR updates the generator’s null-conditional ignore rewrite so nullable value typing is preserved for simple ?? left operands, preventing invalid generated expressions like decimal ?? decimal.

Changes:

• Adds nullable cast emission when an ignored conditional access feeds directly into a coalesce expression.
• Adds a regression generator test and verified snapshot for Price?.Amount ?? 0m.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/EntityFrameworkCore.Projectables.Generator/SyntaxRewriters/ExpressionSyntaxRewriter.NullConditionalRewrite.cs	Adds coalesce-left detection and nullable cast generation for ignored null-conditional access.
tests/EntityFrameworkCore.Projectables.Generator.Tests/NullableTests.cs	Adds regression coverage for ignored null-conditional access with ??.
tests/EntityFrameworkCore.Projectables.Generator.Tests/NullableTests.NullConditionalNullCoalesceTypeConversion_WithIgnoreSupport.verified.txt	Adds the expected generated expression snapshot.