Add PlainPanic for throwing exceptions without depending on pprint

This commit splits out a subset of GhcException which do not depend on
pretty printing (SDoc), as a new datatype called
PlainGhcException. These exceptions can be caught as GhcException,
because 'fromException' will convert them.

The motivation for this change is that that the Panic module
transitively depends on many modules, primarily due to pretty printing
code.  It's on the order of about 130 modules.  This large set of
dependencies has a few implications:

1. To avoid cycles / use of boot files, these dependencies cannot
throw GhcException.

2. There are some utility modules that use UnboxedTuples and also use
`panic`. This means that when loading GHC into GHCi, about 130
additional modules would need to be compiled instead of
interpreted. Splitting the non-pprint exception throwing into a new
module resolves this issue. See #13101

1 files changed, 1 insertions, 1 deletions

diff --git a/compiler/utils/StringBuffer.hs b/compiler/utils/StringBuffer.hs
index 64578bffde..98b8c19340 100644
--- a/compiler/utils/StringBuffer.hs
+++ b/compiler/utils/StringBuffer.hs
@@ -50,7 +50,7 @@ import GhcPrelude
 import Encoding
 import FastString
 import FastFunctions
-import Outputable
+import PlainPanic
 import Util
 
 import Data.Maybe