#16183: GHC HEAD regression: -ddump-splices incorrectly parenthesizes HsKindSig applications -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.8.1 Component: Template Haskell | Version: 8.7 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Debugging | Unknown/Multiple information is incorrect | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Description changed by RyanGlScott: Old description:

When you compile this file with GHC 8.6.3 and HEAD:

{{{#!hs {-# LANGUAGE KindSignatures #-} {-# LANGUAGE TemplateHaskell #-} {-# OPTIONS_GHC -ddump-splices #-} module Bug where

import Data.Kind

type F = $([t| (Maybe :: Type -> Type) Int |]) }}}

You get two different results:

{{{ $ /opt/ghc/8.6.3/bin/ghc -fforce-recomp Bug.hs [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) Bug.hs:8:12-45: Splicing type [t| (Maybe :: Type -> Type) Int |] ======> (Maybe :: Type -> Type) Int

$ ~/Software/ghc4/inplace/bin/ghc-stage2 -fforce-recomp Bug.hs [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) Bug.hs:8:12-45: Splicing type [t| (Maybe :: Type -> Type) Int |] ======> Maybe :: Type -> Type Int }}}

Notice how in the GHC HEAD output, GHC forgets to put parentheses around `Maybe :: Type -> Type`, leading to the utterly nonsensical type `Maybe :: Type -> Type Int`.

The commit that introduced this regression is [https://gitlab.haskell.org/ghc/ghc/commit/ae2c9b40f5b6bf272251d1f4107c60003f... ae2c9b40f5b6bf272251d1f4107c60003f541b62].

New description: When you compile this file with GHC 8.6.3 and HEAD: {{{#!hs {-# LANGUAGE KindSignatures #-} {-# LANGUAGE TemplateHaskell #-} {-# OPTIONS_GHC -ddump-splices #-} module Bug where import Data.Kind type F = $([t| (Maybe :: Type -> Type) Int |]) }}} You get two different results: {{{ $ /opt/ghc/8.6.3/bin/ghc -fforce-recomp Bug.hs [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) Bug.hs:8:12-45: Splicing type [t| (Maybe :: Type -> Type) Int |] ======> (Maybe :: Type -> Type) Int $ ~/Software/ghc4/inplace/bin/ghc-stage2 -fforce-recomp Bug.hs [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) Bug.hs:8:12-45: Splicing type [t| (Maybe :: Type -> Type) Int |] ======> Maybe :: Type -> Type Int }}} Notice how in the GHC HEAD output, GHC forgets to put parentheses around `Maybe :: Type -> Type`, leading to the utterly nonsensical type `Maybe :: Type -> Type Int`. The commit that introduced this regression is [https://gitlab.haskell.org/ghc/ghc/commit/bace26aadaafa4064e78f9ed088c1e2217... bace26aadaafa4064e78f9ed088c1e2217221acc]. -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16183#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#16183: GHC HEAD regression: -ddump-splices incorrectly parenthesizes HsKindSig applications -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.8.1 Component: Template Haskell | Version: 8.7 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Debugging | Unknown/Multiple information is incorrect | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): So are type family equations: {{{#!hs {-# LANGUAGE TemplateHaskell #-} {-# LANGUAGE TypeFamilies #-} {-# OPTIONS_GHC -ddump-splices #-} module Bug where import Data.Kind $([d| type family F a where F (a :: Type) = Int |]) }}} {{{ $ ~/Software/ghc4/inplace/bin/ghc-stage2 --interactive Bug.hs GHCi, version 8.7.20190114: https://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug.hs, interpreted ) Bug.hs:(8,3)-(9,30): Splicing declarations [d| type family F_a1B4 a_a1B5 where F_a1B4 (a_a1B6 :: Type) = Int |] ======> type family F_a4tB a_a4tC where F_a4tB a_a4tD :: Type = Int }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16183#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#16183: GHC HEAD regression: -ddump-splices incorrectly parenthesizes HsKindSig applications -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: merge Priority: normal | Milestone: 8.8.1 Component: Template Haskell | Version: 8.7 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Debugging | Unknown/Multiple information is incorrect | Test Case: th/T16183 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | https://gitlab.haskell.org/ghc/ghc/merge_requests/121 -------------------------------------+------------------------------------- Changes (by RyanGlScott): * status: patch => merge * testcase: => th/T16183 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16183#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler