Opened 3 years ago

Closed 3 years ago

Last modified 23 months ago

#10325 closed bug (fixed)

Clearify status of ImpredicativeTypes Extension

Reported by: j80JjBjVNRMajmA Owned by:
Priority: normal Milestone: 8.0.1
Component: Documentation Version: 7.10.1
Keywords: Cc:
Operating System: Unknown/Multiple Architecture: Unknown/Multiple
Type of failure: None/Unknown Test Case:
Blocked By: Blocking:
Related Tickets: #9618, #10281 Differential Rev(s):
Wiki Page:

Description

There seem to be many statements about this extension and its problems floating around in the internet. But a user of GHC will first fall into a possibly large number of traps and problems before he finds them.

I think it would help, if the GHC manual https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/other-type-extensions.html#impredicative-polymorphism and the compiler warned about this extension (instead of suggesting it!).

Change History (4)

comment:1 Changed 3 years ago by rwbarton

I agree with j80JjBjVNRMajmA, and see also #9618. Meanwhile #10281 is in part about expanding the documentation of ImpredicativeTypes slightly.

comment:2 Changed 3 years ago by Simon Peyton Jones <simonpj@…>

In c715166f9860635d84e4beaa76bf4e23ab764342/ghc:

Improve error reporting for impredicative types

Don't suggest -XImpredicativeTypes; and document its flakiness
Fixes Trac #10325

comment:3 Changed 3 years ago by simonpj

Resolution: fixed
Status: newclosed

Done! Thanks.

comment:4 Changed 23 months ago by thomie

Milestone: 8.0.1
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