Commit 89d80921 authored by Ryan Scott's avatar Ryan Scott

Fix embarrassing infinite loop in pprParendType

Summary:
`pprParendType` was missing an explicit case for
`EqualityT`, which caused it to fall through to a catch-all case
that invokes `ppr`. But `ppr` itself does not have a case for a
partial application of `EqualityT`, so //it// falls back to
`pprParendType`, resulting in an infinite loop!

The fix is simple: add a case for `EqualityT` in `pprParendType`.
While I was in the neighborhood, I removed the catch-call case in
`pprParendType` to make this sort of mistake less likely to happen
in the future.

Test Plan: make test TEST=T15985

Reviewers: bgamari, monoidal, simonpj

Reviewed By: monoidal, simonpj

Subscribers: rwbarton, carter

GHC Trac Issues: #15985

Differential Revision: https://phabricator.haskell.org/D5403
parent 2e6cc3d0
......@@ -739,7 +739,9 @@ pprParendType tuple | (TupleT n, args) <- split tuple
, length args == n
= parens (commaSep args)
pprParendType (ImplicitParamT n t)= text ('?':n) <+> text "::" <+> ppr t
pprParendType other = parens (ppr other)
pprParendType EqualityT = text "(~)"
pprParendType t@(ForallT {}) = parens (ppr t)
pprParendType t@(AppT {}) = parens (ppr t)
pprUInfixT :: Type -> Doc
pprUInfixT (UInfixT x n y) = pprUInfixT x <+> pprName' Infix n <+> pprUInfixT y
......
{-# LANGUAGE TemplateHaskell #-}
module T15985 where
import Language.Haskell.TH
foo :: String
foo = $(stringE (pprint EqualityT))
......@@ -451,3 +451,4 @@ test('T15815', normal, multimod_compile,
test('T15845', normal, compile, ['-v0 -dsuppress-uniques'])
test('T15437', expect_broken(15437), multimod_compile,
['T15437', '-v0 ' + config.ghc_th_way_flags])
test('T15985', normal, compile, [''])
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