"Variable declaration can be inlined" even when used by multiple cases in a switch

[zspitz]

I have code like the following:

Dictionary<string, (int start, int length)> pathSpans;
var ret = x.o switch {
    Expression expr => expr.ToString(TextualTree, out pathSpans, "C#"),
    MemberBinding mbind => mbind.ToString(TextualTree, out pathSpans, "C#"),
    ElementInit init => init.ToString(TextualTree, out pathSpans, "C#"),
    SwitchCase switchCase => switchCase.ToString(TextualTree, out pathSpans, "C#"),
    CatchBlock catchBlock => catchBlock.ToString(TextualTree, out pathSpans, "C#"),
    LabelTarget labelTarget => labelTarget.ToString(TextualTree, out pathSpans, "C#"),
    _ => throw new InvalidOperationException(),
};

The analyzer recommends inlining the variable in the first case of the switch:

var ret = x.o switch {
    Expression expr => expr.ToString(TextualTree, out var pathSpans, "C#"),
...

but if I do that, the variable isn't available to the other cases in the switch.

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• ID: 5fce4950-f4e0-2383-264a-166a6a35b38f
• Version Independent ID: 3557b307-e917-b4a2-dec5-1bfdf70654c1
• Content: IDE0018: Inline variable declaration - .NET
• Content Source: docs/fundamentals/code-analysis/style-rules/ide0018.md
• Product: dotnet-fundamentals
• GitHub Login: @gewarren
• Microsoft Alias: gewarren

[BillWagner]

Thanks for writing this @zspitz

If you accept that recommendation, you'd need to add the var declaration in the other switch arms as well:

Dictionary<string, (int start, int length)> pathSpans;
var ret = x.o switch {
    Expression expr => expr.ToString(TextualTree, out var pathSpans, "C#"),
    MemberBinding mbind => mbind.ToString(TextualTree, out var pathSpans, "C#"),
    ElementInit init => init.ToString(TextualTree, out var pathSpans, "C#"),
    SwitchCase switchCase => switchCase.ToString(TextualTree, out var pathSpans, "C#"),
    CatchBlock catchBlock => catchBlock.ToString(TextualTree, out var pathSpans, "C#"),
    LabelTarget labelTarget => labelTarget.ToString(TextualTree, out var pathSpans, "C#"),
    _ => throw new InvalidOperationException(),
};

I'll close this as an answered question.