strLitNodeAsString

fn strLitNodeAsString(astgen: *AstGen, node: Ast.Node.Index) !IndexSlice {
    const tree = astgen.tree;

    const start, const end = tree.nodeData(node).token_and_token;

    const gpa = astgen.gpa;
    const string_bytes = &astgen.string_bytes;
    const str_index = string_bytes.items.len;

    // First line: do not append a newline.
    var tok_i = start;
    {
        const slice = tree.tokenSlice(tok_i);
        const line_bytes = slice[2..];
        try string_bytes.appendSlice(gpa, line_bytes);
        tok_i += 1;
    }
    // Following lines: each line prepends a newline.
    while (tok_i <= end) : (tok_i += 1) {
        const slice = tree.tokenSlice(tok_i);
        const line_bytes = slice[2..];
        try string_bytes.ensureUnusedCapacity(gpa, line_bytes.len + 1);
        string_bytes.appendAssumeCapacity('\n');
        string_bytes.appendSliceAssumeCapacity(line_bytes);
    }
    const len = string_bytes.items.len - str_index;
    try string_bytes.append(gpa, 0);
    return IndexSlice{
        .index = @fromBackingInt(@intCast(str_index)),
        .len = @intCast(len),
    };
}