Increase the simplifier tick limit on GHC 8.0

This is a crude but effective workaround for #50. I have opened #51 as a
reminder to investigate this more carefully and come up with a more robust fix.

Resolves #50.

CHANGELOG.md

@@ -1,3 +1,7 @@
+### next [????.??.??]
+* Work around a GHC 8.0–specific issue in which GHC's simplifier ticks would
+  become exhausted, causing compilation to fail.
+
 ### 3.9.4 [2021.12.26]
 * Allow the test suite to build with `text-2.0.*` and
   `transformers-compat-0.7.1`.

src/TextShow/Data/Complex.hs

@@ -1,5 +1,10 @@
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE TemplateHaskell #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
+#if __GLASGOW_HASKELL__ == 800
+-- See Note [Increased simpl-tick-factor on old GHCs]
+{-# OPTIONS_GHC -fsimpl-tick-factor=200 #-}
+#endif
 
 {-|
 Module:      TextShow.Data.Ratio
@@ -30,3 +35,22 @@ instance TextShow a => TextShow (Complex a) where
 
 -- | /Since: 2/
 $(deriveTextShow1 ''Complex)
+
+{-
+Note [Increased simpl-tick-factor on old GHCs]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Compiling certain text-show modules with optimizations on old versions of GHC
+(particularly 8.0 and 8.2) will trigger "Simplifier ticks exhausted" panics.
+To make things worse, this sometimes depends on whether a certain version of
+the text library is being used. There are two possible ways to work around
+this issue:
+
+1. Figure out which uses of the INLINE pragma in text-show are responsible
+   and remove them.
+2. Just increase the tick limit.
+
+Since executing on (1) will require a lot of effort to fix an issue that only
+happens on old versions of GHC, I've opted for the simple solution of (2) for
+now. Issue #51 is a reminder to revisit this choice.
+-}

src/TextShow/GHC/Stats.hs

@@ -4,6 +4,10 @@
 {-# LANGUAGE TemplateHaskell #-}
 {-# OPTIONS_GHC -fno-warn-deprecations #-}
 {-# OPTIONS_GHC -fno-warn-orphans      #-}
+# if __GLASGOW_HASKELL__ == 800
+-- See Note [Increased simpl-tick-factor on old GHCs] in TextShow.Data.Complex
+{-# OPTIONS_GHC -fsimpl-tick-factor=200 #-}
+# endif
 #endif
 
 {-|

tests/Instances/GHC/RTS/Flags.hs

@@ -8,12 +8,8 @@
 {-# LANGUAGE TypeSynonymInstances #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 # if __GLASGOW_HASKELL__ == 802
--- For whatever reason, compiling this module with optimizations on GHC 8.2.2
--- triggers a "Simplifier ticks exhausted" panic, and increasing the tick limit
--- doesn't seem to help. Moreover, 8.2.2 is the /only/ GHC version I have seen
--- this happen on. Life is short, so I'm just going to work around this by
--- disabling optimizations on 8.2.2 only.
-{-# OPTIONS_GHC -O0               #-}
+-- See Note [Increased simpl-tick-factor on old GHCs] in TextShow.Data.Complex
+{-# OPTIONS_GHC -fsimpl-tick-factor=200 #-}
 # endif
 #endif