#15294: Unused "foralls" prevent types from being Coercible -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Resolution: | Keywords: Roles Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Description changed by Iceland_jack: Old description:

Just a quick question, do these have the same representation?

{{{#!hs newtype A where A :: (Int -> Bool) -> A

newtype B where B :: (forall (a::Type). Int -> Bool) -> B }}}

I'm wondering because they aren't `Coercible`

{{{

...

:t coerce :: A -> B

<interactive>:1:1: error: • Couldn't match representation of type ‘forall a. Int -> Bool’ with that of ‘Int -> Bool’ arising from a use of ‘coerce’ • In the expression: coerce :: A -> B }}}

What about a new type `C`, that isn't `Coercible` to `B` either

{{{#!hs newtype C where C :: (forall k (a :: k). Int -> Bool) -> C }}}

Some is true when it's just the order of variables

{{{#!hs -- D is not Coercible to E, "can't match type ‘Bool’ with ‘Ordering’"

newtype D where D :: (forall (a::Bool) (b::Ordering). Int -> Bool) -> D

newtype E where E :: (forall (a::Ordering) (b::Bool). Int -> Bool) -> E }}}

My question is is this intended?

New description: Just a quick question, do these have the same representation? {{{#!hs newtype A where A :: (Int -> Bool) -> A newtype B where B :: (forall (a::Type). Int -> Bool) -> B }}} I'm wondering because they aren't `Coercible` {{{

:t coerce :: A -> B

<interactive>:1:1: error: • Couldn't match representation of type ‘forall a. Int -> Bool’ with that of ‘Int -> Bool’ arising from a use of ‘coerce’ • In the expression: coerce :: A -> B }}} `C` isn't `Coercible` to `B` either {{{#!hs newtype C where C :: (forall k (a :: k). Int -> Bool) -> C }}} Also {{{#!hs -- D is not Coercible to E, "can't match type ‘Bool’ with ‘Ordering’" newtype D where D :: (forall (a::Bool) (b::Ordering). Int -> Bool) -> D newtype E where E :: (forall (a::Ordering) (b::Bool). Int -> Bool) -> E }}} My question is is this intended? -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15294#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#15294: Unused "foralls" prevent types from being Coercible -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Resolution: wontfix | Keywords: Roles Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by Iceland_jack): * status: new => closed * resolution: => wontfix Comment: Ah yeah I see the difficulty, I wanted to make sure :) thanks for the response closing -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15294#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler