Lexer: turn some fatal errors into non-fatal ones

The following previously fatal lexer errors are now non-fatal:

  * errors about enabling `LambdaCase`
  * errors about enabling `NumericUnderscores`
  * errors about having valid characters in primitive strings

See #16270

3 files changed, 18 insertions, 3 deletions

diff --git a/testsuite/tests/parser/should_fail/ParserNoLambdaCase.stderr b/testsuite/tests/parser/should_fail/ParserNoLambdaCase.stderr
index 24d5cfc168..601262c360 100644
--- a/testsuite/tests/parser/should_fail/ParserNoLambdaCase.stderr
+++ b/testsuite/tests/parser/should_fail/ParserNoLambdaCase.stderr
@@ -1,2 +1,2 @@
 ParserNoLambdaCase.hs:3:6:
-    Illegal lambda-case (use -XLambdaCase)
+    Illegal lambda-case (use LambdaCase)
diff --git a/testsuite/tests/parser/should_fail/T16270.hs b/testsuite/tests/parser/should_fail/T16270.hs
index 0c5166d402..0147f9776a 100644
--- a/testsuite/tests/parser/should_fail/T16270.hs
+++ b/testsuite/tests/parser/should_fail/T16270.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE NoTraditionalRecordSyntax, NoDoAndIfThenElse, NoMultiWayIf #-}
+{-# LANGUAGE NoTraditionalRecordSyntax, NoDoAndIfThenElse, NoMultiWayIf, NoLambdaCase, NoNumericUnderscores, MagicHash #-}
 {-# OPTIONS -Werror=missing-space-after-bang #-}
 
 module T16270 where
@@ -29,6 +29,13 @@ multiWayIf !i = (a, b)
     b = if | i -> False
            | otherwise -> True
 
+w = \case _ : _ -> True
+          _     -> False
+
+n = 123_456
+
+s = "hello ωorld"#   -- note the omega
+
 -- a fatal error.
 k = let
 
diff --git a/testsuite/tests/parser/should_fail/T16270.stderr b/testsuite/tests/parser/should_fail/T16270.stderr
index 7eccd9516e..f4e90e40fc 100644
--- a/testsuite/tests/parser/should_fail/T16270.stderr
+++ b/testsuite/tests/parser/should_fail/T16270.stderr
@@ -57,5 +57,13 @@ T16270.hs:27:9: error:
 T16270.hs:29:9: error:
     Multi-way if-expressions need MultiWayIf turned on
 
-T16270.hs:36:1: error:
+T16270.hs:32:6: Illegal lambda-case (use LambdaCase)
+
+T16270.hs:35:5:
+    Use NumericUnderscores to allow underscores in integer literals
+
+T16270.hs:37:5:
+    primitive string literal must contain only characters <= '/xFF'
+
+T16270.hs:43:1: error:
     parse error (possibly incorrect indentation or mismatched brackets)