Fuse maps and tuples for printing

[gldubc]

For printing types (tuples and maps), we do a general pass that fuses elements that differ by one element or less.

Example:
{:ok, integer()} or {:ok, float()} is shown as {:ok, float() or integer()}
%{..., a: float()} or %{..., a: integer()}is shown as %{..., a: float() or integer()}

and

:error or
  ({%Decimal{coef: :inf, exp: integer(), sign: integer()}, binary()} or
    {%Decimal{coef: :NaN, exp: integer(), sign: integer()}, binary()} or
    {%Decimal{coef: integer(), exp: integer(), sign: integer()}, term()} or
    {%Decimal{coef: :inf, exp: integer(), sign: integer()} or
        %Decimal{coef: :NaN, exp: integer(), sign: integer()} or
        %Decimal{coef: integer(), exp: integer(), sign: integer()}, term()})

is shown as

:error or
 ({%Decimal{coef: integer() or (:NaN or :inf), exp: integer(), sign: integer()}, term()} or
    {%Decimal{coef: :NaN or :inf, exp: integer(), sign: integer()}, binary()})
)

[ericmj]

Can we remove the parenthesis in integer() or (:NaN or :inf) by building the or AST with the operator's natural associativity?

[gldubc]

Not very easily, here the parenthesis appears because the AST for singleton atoms is built separately (before) the AST of all types is built

elixir/lib/elixir/lib/module/types/descr.ex

Line 392 in a947e32

unions -> unions |> Enum.sort() |> Enum.reduce(&{:or, [], [&2, &1]})

Those won't appear when printing for instance three singletons :NaN or :inf or :foo

[josevalim]

@gldubc we can probably do it by swapping the order we build the union. I will take a look at if before or after I merge. :)

[josevalim]

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