Fix for empty quasi-quotations

Author: sheaf

CHANGELOG.md

@@ -8,6 +8,7 @@
 - Add `meta.embedded.block.{quasi-quoter}` scope to quasi-quotations.
 - Ensure highlighting of unicode forall syntax matches that of alphabetic forall syntax
   ([#175](https://github.com/JustusAdam/language-haskell/issues/175)).
+- Fix highlighting of empty quasi-quotations such as `[i||]`.
 
 ## 3.3.0 - 25.06.2020
 

syntaxes/haskell.YAML-tmLanguage

@@ -1721,7 +1721,7 @@ repository:
           (?x)
             (\[)
             (e|d|p)?
-            (\|\|?)
+            (\|(?:\|(?!\]))?)
         beginCaptures:
           '1': {name: keyword.operator.quasi-quotation.begin.haskell}
           '2': {name: entity.name.quasi-quoter.haskell}
@@ -1736,7 +1736,7 @@ repository:
           (?x)
             (\[)
             (t)
-            (\|\|?)
+            (\|(?:\|(?!\]))?)
         beginCaptures:
           '1': {name: keyword.operator.quasi-quotation.begin.haskell}
           '2': {name: entity.name.quasi-quoter.haskell}
@@ -1754,7 +1754,7 @@ repository:
             (?!'\|')                                             # Don't parse ['|'...] as a quasi quotation
             ((?:[\p{Lu}\p{Lt}][\p{Ll}_\p{Lu}\p{Lt}\p{Nd}']*\.)*) # Optional qualifier
             ((?:[^\s\p{S}\p{P}]|['_])*)                          # Quasi-quoter
-            (\|\|?)
+            (\|(?:\|(?!\]))?)
         beginCaptures:
           '1': {name: keyword.operator.quasi-quotation.begin.haskell}
           '2': {name: keyword.operator.prefix.double-dollar.haskell}

test/tickets/T0023.hs

@@ -0,0 +1,13 @@
+-- SYNTAX TEST "source.haskell" "Empty quasi-quote"
+
+instance Show NixIndexException where
+  show (NixEnvFail errCode _ _) = [i||]
+--                                ^ ^ keyword.operator.quasi-quotation.begin.haskell
+--                                 ^ entity.name.quasi-quoter.haskell
+--                                   ^^ keyword.operator.quasi-quotation.end.haskell
+  show ParseNixEnvResError = "Failed to parse the output of nix-env"
+-- <------------------------------------------------------------------ - meta.quasi-quotation.haskell
+
+type S = String
+
+-- <--------------- -meta.quasi-quotation.haskell