================================================================================
Simplified:
`$d2'  ::  `{PrelBase.Eval (M a)}'
`$d2' =
    _/\_ `$x0' -> `PrelBase.void'
`$d1'  ::  `{PrelBase.Eval (L a)}'
`$d1' =
    _/\_ `$x0' -> `PrelBase.void'
`N'  ::  `L a'
`N' =
    _/\_ `$x0' -> `N' {_@_ `$x0'}
`C'  ::  `a -> Syn a -> L a'
`C' =
    _/\_ `$x0' -> \ `$x1'  ::  `$x0'
		    `$x1' `$x2'  ::  `Syn $x0'
			  `$x2' ->
	`C' {_@_ `$x0' `$x1' `$x2'}
Rec {
`idL'  ::  `L (Syn taBE) -> L (Syn taBE)'
`idL' =
    _/\_ `$x0' -> \ `$x1'  ::  `L (Syn $x0)'
		    `$x1' ->
	case `$x1' of {
	  `N' -> `N' {_@_ (`Syn' `$x0')};
	  `C' `$x2' `$x3' ->
	      let {
		`$x4'  ::  `L (Syn $x0)'
		`$x4' =
		    `idL' _@_ `$x0' `$x3'
	      } in  `C' {_@_ (`Syn' `$x0') `$x2' `$x4'};
	}
end Rec }
`A'  ::  `M a'
`A' =
    _/\_ `$x0' -> `A' {_@_ `$x0'}
`B'  ::  `a -> M a -> M a'
`B' =
    _/\_ `$x0' -> \ `$x1'  ::  `$x0'
		    `$x1' `$x2'  ::  `M $x0'
			  `$x2' ->
	`B' {_@_ `$x0' `$x1' `$x2'}
Rec {
`idM'  ::  `M (L (Syn taC4)) -> M (L (Syn taC4))'
`idM' =
    _/\_ `$x0' -> \ `$x1'  ::  `M (L (Syn $x0))'
		    `$x1' ->
	case `$x1' of {
	  `A' -> `A' {_@_ (`L' (`Syn' `$x0'))};
	  `B' `$x2' `$x3' ->
	      let {
		`$x4'  ::  `M (L (Syn $x0))'
		`$x4' =
		    `idM' _@_ `$x0' `$x3' } in
	      let {
		`$x5'  ::  `L (Syn $x0)'
		`$x5' =
		    `idL' _@_ `$x0' `$x2'
	      } in  `B' {_@_ (`L' (`Syn' `$x0')) `$x5' `$x4'};
	}
end Rec }