Fix C# output: add _ = discard for non-void calls in if/else block bodies

[Copilot]

Non-void Call/Invoke expressions used as statements inside IfThen/IfThenElse blocks were printed without a discard assignment, producing misleading (though technically valid) C# output.

Changes

• ToCSharpBlock: When the body of an if/else block is a non-void Call, Invoke, Conditional, or Coalesce expression, prefix it with _ = to explicitly discard the return value.
• BlockToCSharpString: Extends the existing Conditional/Coalesce discard check to also cover Call and Invoke node types in block statement position.
• Test: Adds assertion in Equal_in_void_Handler_should_work to verify the output contains _ = ((int?)null).ToString();.

Before / After

// Before
if (param == (int?)null)
{
    ((int?)null).ToString();
}

// After
if (param == (int?)null)
{
    _ = ((int?)null).ToString();
}

[dadhi]

Did you run all tests in debug mode and analyzed PrintCSharp output
to find if thid fix introduced any regressions?

[Copilot]

Did you run all tests in debug mode and analyzed PrintCSharp output
to find if thid fix introduced any regressions?

Yes — ran all 1655 tests via FastExpressionCompiler.TestsRunner in debug mode, all pass. Reviewed the full PrintCSharp output from the run. The new _ = discard appears in the correct places:

• _ = ((int?)null).ToString(); and _ = param.ToString(); (Issue252 — the fix)
• _ = BlockTests.Inc(p); (non-void Call as block statement — correct)
• _ = Issue83_linq2db.CheckNullValue(...); (non-void Call as block statement inside __f(() => {...}) — correct)

No unexpected regressions in the output.

[dadhi]

Those checks for nodeTyñe are in at least 2 places, and may be more accross c# output, can we sematicalmy compress/unify them to method to simply code and rrmove creep?

[Copilot]

Extracted the repeated four-node-type check into NeedsDiscardWhenUsedAsStatement(this Expression expr) (line 8241), placed alongside the other ExpressionType extension helpers. Both ToCSharpBlock and BlockToCSharpString now call this single method. Commit: f973bd3, all 1655 tests still pass.

[dadhi]

Does it need the local var to store bool check used in a single condition?
Does it needs the comment almost repearing the check method nane?
The same for other check - plesse eliminate

[Copilot]

Done in 4a54b45 — inlined the single-use needsDiscard variable in ToCSharpBlock and removed the redundant comments at both call sites. The returningCondOrCoalesceOrCall variable in BlockToCSharpString is kept since it's referenced twice (in the if and in the ternary on the next block).