TableCell admits Para but not Span Block elements about panflute HOT 3 CLOSED

data Inline
    = Str String            -- ^ Text (string)
    | Emph [Inline]         -- ^ Emphasized text (list of inlines)
    | Strong [Inline]       -- ^ Strongly emphasized text (list of inlines)
    | Strikeout [Inline]    -- ^ Strikeout text (list of inlines)
    | Superscript [Inline]  -- ^ Superscripted text (list of inlines)
    | Subscript [Inline]    -- ^ Subscripted text (list of inlines)
    | SmallCaps [Inline]    -- ^ Small caps text (list of inlines)
    | Quoted QuoteType [Inline] -- ^ Quoted text (list of inlines)
    | Cite [Citation]  [Inline] -- ^ Citation (list of inlines)
    | Code Attr String      -- ^ Inline code (literal)
    | Space                 -- ^ Inter-word space
    | SoftBreak             -- ^ Soft line break
    | LineBreak             -- ^ Hard line break
    | Math MathType String  -- ^ TeX math (literal)
    | RawInline Format String -- ^ Raw inline
    | Link Attr [Inline] Target  -- ^ Hyperlink: alt text (list of inlines), target
    | Image Attr [Inline] Target -- ^ Image:  alt text (list of inlines), target
    | Note [Block]          -- ^ Footnote or endnote
    | Span Attr [Inline]    -- ^ Generic inline container with attributes

data Block
    = Plain [Inline]        -- ^ Plain text, not a paragraph
    | Para [Inline]         -- ^ Paragraph
    | LineBlock [[Inline]]  -- ^ Multiple non-breaking lines
    | CodeBlock Attr String -- ^ Code block (literal) with attributes
    | RawBlock Format String -- ^ Raw block
    | BlockQuote [Block]    -- ^ Block quote (list of blocks)
    | OrderedList ListAttributes [[Block]] -- ^ Ordered list (attributes
                            -- and a list of items, each a list of blocks)
    | BulletList [[Block]]  -- ^ Bullet list (list of items, each
                            -- a list of blocks)
    | DefinitionList [([Inline],[[Block]])]  -- ^ Definition list
                            -- Each list item is a pair consisting of a
                            -- term (a list of inlines) and one or more
                            -- definitions (each a list of blocks)
    | Header Int Attr [Inline] -- ^ Header - level (integer) and text (inlines)
    | HorizontalRule        -- ^ Horizontal rule
    | Table [Inline] [Alignment] [Double] [TableCell] [[TableCell]]  -- ^ Table,
                            -- with caption, column alignments (required),
                            -- relative column widths (0 = default),
                            -- column headers (each a list of blocks), and
                            -- rows (each a list of lists of blocks)
    | Div Attr [Block]      -- ^ Generic block container with attributes
    | Null                  -- ^ Nothing