Reads a value from an existing TOML reader, populating an existing CLR instance when supported.
public virtual object? ReadInto(TomlReader reader, object? existingValue)
The TOML reader positioned at the value to read.
The existing CLR value to populate, if any.
The return value is the effective deserialized value for the caller to use. Implementations can return the
original populated instance or a replacement value. Returning the effective value is required for populate
scenarios involving structs and nullable value types, where a modified copy must be reassigned by the caller.
The default implementation ignores existingValue and falls back to
ReadAsObject(TomlReader), which preserves replace semantics for metadata that does not support
in-place population.