diff --git a/compiler/basicTypes/Lexeme.hs b/compiler/basicTypes/Lexeme.hs
index c5bda4dbdd36c63f81edac9666eb5e02d6f2f89d..a2409614d1f4cccc3e98a1340e0591d056f60b9a 100644
--- a/compiler/basicTypes/Lexeme.hs
+++ b/compiler/basicTypes/Lexeme.hs
@@ -28,6 +28,7 @@ module Lexeme (
) where
import FastString
+import Util ((<||>))
import Data.Char
import qualified Data.Set as Set
@@ -194,7 +195,8 @@ okConSymOcc str = all okSymChar str &&
-- but not worrying about case or clashing with reserved words?
okIdOcc :: String -> Bool
okIdOcc str
- = let hashes = dropWhile okIdChar str in
+ -- TODO. #10196. Only allow modifier letters in the suffix of an identifier.
+ = let hashes = dropWhile (okIdChar <||> okIdSuffixChar) str in
all (== '#') hashes -- -XMagicHash allows a suffix of hashes
-- of course, `all` says "True" to an empty list
@@ -210,6 +212,13 @@ okIdChar c = case generalCategory c of
OtherNumber -> True
_ -> c == '\'' || c == '_'
+-- | Is this character acceptable in the suffix of an identifier.
+-- See alexGetByte in Lexer.x
+okIdSuffixChar :: Char -> Bool
+okIdSuffixChar c = case generalCategory c of
+ ModifierLetter -> True -- See #10196
+ _ -> False
+
-- | Is this character acceptable in a symbol (after the first char)?
-- See alexGetByte in Lexer.x
okSymChar :: Char -> Bool
diff --git a/compiler/parser/Lexer.x b/compiler/parser/Lexer.x
index 432686e5af321dc5bd87107fd8088b45a634d2d1..7fbbd132fc25614177bb0e9a3176e2185ad50399 100644
--- a/compiler/parser/Lexer.x
+++ b/compiler/parser/Lexer.x
@@ -156,7 +156,10 @@ $graphic = [$small $large $symbol $digit $special $unigraphic \"\']
$binit = 0-1
$octit = 0-7
$hexit = [$decdigit A-F a-f]
-$idchar = [$small $large $digit \']
+
+$suffix = \x07 -- Trick Alex into handling Unicode. See alexGetByte.
+-- TODO #10196. Only allow modifier letters in the suffix of an identifier.
+$idchar = [$small $large $digit $suffix \']
$pragmachar = [$small $large $digit]
@@ -1835,6 +1838,7 @@ alexGetByte (AI loc s)
symbol = '\x04'
space = '\x05'
other_graphic = '\x06'
+ suffix = '\x07'
adj_c
| c <= '\x06' = non_graphic
@@ -1851,7 +1855,7 @@ alexGetByte (AI loc s)
UppercaseLetter -> upper
LowercaseLetter -> lower
TitlecaseLetter -> upper
- ModifierLetter -> other_graphic
+ ModifierLetter -> suffix -- see #10196
OtherLetter -> lower -- see #1103
NonSpacingMark -> other_graphic
SpacingCombiningMark -> other_graphic
diff --git a/compiler/utils/Util.hs b/compiler/utils/Util.hs
index aa3a19b64c2758a5d86b7e367a4b8390f20c6346..b2492f169fd553838e90b6b33cb0c4207b16146d 100644
--- a/compiler/utils/Util.hs
+++ b/compiler/utils/Util.hs
@@ -55,6 +55,7 @@ module Util (
isEqual, eqListBy, eqMaybeBy,
thenCmp, cmpList,
removeSpaces,
+ (<&&>), (<||>),
-- * Edit distance
fuzzyMatch, fuzzyLookup,
@@ -115,6 +116,10 @@ import Data.List hiding (group)
import FastTypes
#endif
+#if __GLASGOW_HASKELL__ < 709
+import Control.Applicative (Applicative)
+#endif
+import Control.Applicative ( liftA2 )
import Control.Monad ( liftM )
import System.IO.Error as IO ( isDoesNotExistError )
import System.Directory ( doesDirectoryExist, getModificationTime )
@@ -653,6 +658,15 @@ cmpList cmp (a:as) (b:bs)
removeSpaces :: String -> String
removeSpaces = dropWhileEndLE isSpace . dropWhile isSpace
+-- Boolean operators lifted to Applicative
+(<&&>) :: Applicative f => f Bool -> f Bool -> f Bool
+(<&&>) = liftA2 (&&)
+infixr 3 <&&> -- same as (&&)
+
+(<||>) :: Applicative f => f Bool -> f Bool -> f Bool
+(<||>) = liftA2 (||)
+infixr 2 <||> -- same as (||)
+
{-
************************************************************************
* *
diff --git a/testsuite/tests/parser/should_compile/T10196.hs b/testsuite/tests/parser/should_compile/T10196.hs
new file mode 100644
index 0000000000000000000000000000000000000000..f80911829b33ece1b476abbaa67d4487a3477cd3
--- /dev/null
+++ b/testsuite/tests/parser/should_compile/T10196.hs
@@ -0,0 +1,13 @@
+module T10196 where
+
+data X = Xᵦ | Xᵤ | Xᵩ | Xᵢ | Xᵪ | Xᵣ
+
+f :: Int
+f =
+ let xᵦ = 1
+ xᵤ = xᵦ
+ xᵩ = xᵤ
+ xᵢ = xᵩ
+ xᵪ = xᵢ
+ xᵣ = xᵪ
+ in xáµ£
diff --git a/testsuite/tests/parser/should_compile/all.T b/testsuite/tests/parser/should_compile/all.T
index 13acedf0141306c0320d9325fc71d1bed3a26224..0bff4085c7fc28e5c49426614cd319fe0a2755c1 100644
--- a/testsuite/tests/parser/should_compile/all.T
+++ b/testsuite/tests/parser/should_compile/all.T
@@ -98,3 +98,4 @@ test('T7118', normal, compile, [''])
test('T7776', normal, compile, [''])
test('RdrNoStaticPointers01', when(compiler_lt('ghc', '7.9'), skip), compile, [''])
test('T5682', normal, compile, [''])
+test('T10196', normal, compile, [''])
diff --git a/testsuite/tests/parser/should_fail/T10196Fail1.hs b/testsuite/tests/parser/should_fail/T10196Fail1.hs
new file mode 100644
index 0000000000000000000000000000000000000000..2f1c8f39ea3a1d90af448ece061de2689a6d198e
--- /dev/null
+++ b/testsuite/tests/parser/should_fail/T10196Fail1.hs
@@ -0,0 +1,4 @@
+module T10196Fail1 where
+
+-- Constructors are not allowed to start with a modifier letter.
+data Foo = ᵦfoo
diff --git a/testsuite/tests/parser/should_fail/T10196Fail1.stderr b/testsuite/tests/parser/should_fail/T10196Fail1.stderr
new file mode 100644
index 0000000000000000000000000000000000000000..3c4a173eefd4668d90543f9ef59838854e9a0c7b
--- /dev/null
+++ b/testsuite/tests/parser/should_fail/T10196Fail1.stderr
@@ -0,0 +1,2 @@
+
+T10196Fail1.hs:4:12: error: lexical error at character '\7526'
diff --git a/testsuite/tests/parser/should_fail/T10196Fail2.hs b/testsuite/tests/parser/should_fail/T10196Fail2.hs
new file mode 100644
index 0000000000000000000000000000000000000000..64b3cacd6210dccd2cb64e6989344a8aaadba850
--- /dev/null
+++ b/testsuite/tests/parser/should_fail/T10196Fail2.hs
@@ -0,0 +1,4 @@
+module T10196Fail2 where
+
+-- Variables are not allowed to start with a modifier letter.
+ᵦ = 1
diff --git a/testsuite/tests/parser/should_fail/T10196Fail2.stderr b/testsuite/tests/parser/should_fail/T10196Fail2.stderr
new file mode 100644
index 0000000000000000000000000000000000000000..abba8aa04c014a12ecd413c2dddcf68f2bd05b04
--- /dev/null
+++ b/testsuite/tests/parser/should_fail/T10196Fail2.stderr
@@ -0,0 +1,2 @@
+
+T10196Fail2.hs:4:1: error: lexical error at character '\7526'
diff --git a/testsuite/tests/parser/should_fail/T10196Fail3.hs b/testsuite/tests/parser/should_fail/T10196Fail3.hs
new file mode 100644
index 0000000000000000000000000000000000000000..09b80ddeff01ace2f2a76f78aaee8653917c67fb
--- /dev/null
+++ b/testsuite/tests/parser/should_fail/T10196Fail3.hs
@@ -0,0 +1,6 @@
+module T10196Fail3 where
+
+-- Modifier letters are not allowed in the middle of an identifier.
+-- And this should not be lexed as 2 separate identifiers either.
+xᵦx :: Int
+xᵦx = 1
diff --git a/testsuite/tests/parser/should_fail/T10196Fail3.stderr b/testsuite/tests/parser/should_fail/T10196Fail3.stderr
new file mode 100644
index 0000000000000000000000000000000000000000..64037440e23ad00a7a49e219b15dba36cb453091
--- /dev/null
+++ b/testsuite/tests/parser/should_fail/T10196Fail3.stderr
@@ -0,0 +1,2 @@
+
+T10196Fail3.hs:5:2: error: lexical error at character '/7526'
diff --git a/testsuite/tests/parser/should_fail/all.T b/testsuite/tests/parser/should_fail/all.T
index 7e286cf3f23b7d387fda723865a65d38a43f0fa9..26d576757a5a44ec9a66e43159141146a092eba6 100644
--- a/testsuite/tests/parser/should_fail/all.T
+++ b/testsuite/tests/parser/should_fail/all.T
@@ -86,3 +86,6 @@ test('ExportCommaComma', normal, compile_fail, [''])
test('T8430', literate, compile_fail, [''])
test('T8431', [timeout_multiplier(0.05)], compile_fail, ['-XAlternativeLayoutRule'])
test('T8506', normal, compile_fail, [''])
+test('T10196Fail1', normal, compile_fail, [''])
+test('T10196Fail2', normal, compile_fail, [''])
+test('T10196Fail3', expect_broken(10196), compile_fail, [''])