Add WriteTo method to DelimitedSyntaxList<T>, IsPresent property, and WriteDelimitedList overloads to SyntaxWriter

[Copilot]

The pattern of manually iterating a DelimitedSyntaxList — null-checking OpenToken, looping with separator interleaving, writing CloseToken — was duplicated across the runtime and in code emitted by the generator.

Changes

• DelimitedSyntaxList<T> — New WriteTo(SyntaxWriter, string openLeadingTrivia, Action<T, SyntaxWriter, string> writeElement) method. No-ops when the list is not present; otherwise writes open/elements/separators/close with correct spacing. New IsPresent property (=> OpenToken.HasValue) that indicates whether the list has delimiters in the source, replacing direct OpenToken == null checks throughout.

• SyntaxWriter — New WriteDelimitedList overloads for each concrete list type used in the codebase: DelimitedSyntaxList<SyntaxToken>, DelimitedSyntaxList<NamedAttributeSyntax>, and DelimitedSyntaxList<BlockArgumentSyntax>. Each overload delegates to DelimitedSyntaxList<T>.WriteTo with the appropriate element-writing logic, so callers never need to supply a lambda.

• GenericOperationBodySyntax — Replaced three manual iteration blocks (OperandList, SuccessorList, Attributes) with writer.WriteDelimitedList(...) calls.

• BlockSyntax — Replaced manual Arguments iteration (and now-redundant OpenToken != null guard) with a writer.WriteDelimitedList(...) call.

• DialectSourceEmitter — GenerateDelimitedNamedAttributeWriteTo / GenerateDelimitedTokenWriteTo now emit a single writer.WriteDelimitedList(...) call instead of a multi-line if/for block.

Usage

// Before
if (Arguments.OpenToken != null)
{
    writer.WriteToken(Arguments.OpenToken.Value, string.Empty);
    for (var i = 0; i < Arguments.Count; i++)
    {
        if (i > 0)
            writer.WriteToken(Arguments.SeparatorTokens[i - 1], string.Empty);
        Arguments[i].WriteTo(writer, i > 0 ? " " : string.Empty);
    }
    writer.WriteToken(Arguments.CloseToken!.Value, string.Empty);
}

// After
writer.WriteDelimitedList(Arguments, string.Empty);

// Checking presence
if (Arguments.IsPresent) { ... }

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[jonathanvdc]

Looks great. Can you add overloaded methods to SyntaxWriter for every type of DelimitedSyntaxList that may need to be written? Then have callers invoke those overloads. The idea is to spare callers from having to directly invoke DelimitedSyntaxList.WriteTo with a lambda, creating cleaner code.

[Copilot]

Looks great. Can you add overloaded methods to SyntaxWriter for every type of DelimitedSyntaxList that may need to be written? Then have callers invoke those overloads. The idea is to spare callers fr...

Done in 03703ff. Added three WriteDelimitedList overloads to SyntaxWriter — one each for DelimitedSyntaxList<SyntaxToken>, DelimitedSyntaxList<NamedAttributeSyntax>, and DelimitedSyntaxList<BlockArgumentSyntax>. All callers in GenericOperationBodySyntax, BlockSyntax, and the generated code from DialectSourceEmitter now use these overloads directly, with no lambdas at the call site.

[jonathanvdc]

Nice work. Also add a property to DelimitedSyntaxList that tells us whether the list exists or not (i.e., whether the opening token is null). Use that property instead of directly checking if the opening token is null. Give it an appropriate name.

[Copilot]

Nice work. Also add a property to DelimitedSyntaxList that tells us whether the list exists or not (i.e., whether the opening token is null). Use that property instead of directly checking if the open...

Done in 298bdb8. Added IsPresent => OpenToken.HasValue to DelimitedSyntaxList<T>, updated WriteTo to check !IsPresent instead of OpenToken == null, and updated the test to assert IsPresent == false for an absent list.

[jonathanvdc]

Great work!