Protocol for converting values to spans.

This protocol allows any type to be used as a span source. Built-in implementations are provided for:

• Pentiment.Span.Byte and Pentiment.Span.Position structs (identity)
• Tuples in common formats (see below)
• Ranges for byte spans

Tuple Formats

The following tuple formats are supported:

• {start, length} - Byte offset span (2-tuple of integers)
• {line, column} - Single-point position span (when both are positive)
• {start_line, start_col, end_line, end_col} - Position range (4-tuple)

Note: {start, length} and {line, column} are ambiguous for 2-tuples. By default, 2-tuples are interpreted as byte spans. Use Pentiment.Span.position/2 explicitly for line/column positions, or implement this protocol for your own types.

Custom Implementations

You can implement this protocol for your own types:

defimpl Pentiment.Spannable, for: MyApp.Token do
  def to_span(%MyApp.Token{line: l, col: c, length: len}) do
    Pentiment.Span.position(l, c, l, c + len)
  end
end