[Git][ghc/ghc][master] 2 commits: Fix panic in multiline string with unterminated gap (#25530)

[Marge Bot (@marge-bot)]

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC


Commits:
a8ceccf3 by Brandon Chinn at 2024-12-09T16:25:43-05:00
Fix panic in multiline string with unterminated gap (#25530)

- - - - -
9e464ad0 by Brandon Chinn at 2024-12-09T16:25:43-05:00
Add test case for unterminated multiline string

- - - - -


6 changed files:

- compiler/GHC/Parser/Lexer.x
- + testsuite/tests/parser/should_fail/MultilineStringsUnterminated.hs
- + testsuite/tests/parser/should_fail/MultilineStringsUnterminated.stderr
- + testsuite/tests/parser/should_fail/T25530.hs
- + testsuite/tests/parser/should_fail/T25530.stderr
- testsuite/tests/parser/should_fail/all.T


Changes:

=====================================
compiler/GHC/Parser/Lexer.x
=====================================
@@ -2204,14 +2204,15 @@ tok_string_multi startSpan startBuf _len _buf2 = do
       case alexScan i0 string_multi_content of
         AlexToken i1 len _
           | Just i2 <- lexDelim i1 -> pure (i1, i2)
-          | -- is the next token a tab character?
-            -- need this explicitly because there's a global rule matching $tab
-            Just ('\t', _) <- alexGetChar' i1 -> setInput i1 >> lexError LexError
-          | isEOF i1  -> checkSmartQuotes >> lexError LexError
-          | len == 0  -> panic $ "parsing multiline string got into infinite loop at: " ++ show i0
+          | isEOF i1 -> checkSmartQuotes >> setInput i1 >> lexError LexError
+          -- is the next token a tab character?
+          -- need this explicitly because there's a global rule matching $tab
+          | Just ('\t', _) <- alexGetChar' i1 -> setInput i1 >> lexError LexError
+          -- Can happen if no patterns match, e.g. an unterminated gap
+          | len == 0  -> setInput i1 >> lexError LexError
           | otherwise -> goContent i1
         AlexSkip i1 _ -> goContent i1
-        _ -> lexError LexError
+        _ -> setInput i0 >> lexError LexError
 
     lexDelim =
       let go 0 i = Just i


=====================================
testsuite/tests/parser/should_fail/MultilineStringsUnterminated.hs
=====================================
@@ -0,0 +1,9 @@
+{-# LANGUAGE MultilineStrings #-}
+
+x :: String
+x =
+  """
+  test
+
+y :: Int
+y = 0


=====================================
testsuite/tests/parser/should_fail/MultilineStringsUnterminated.stderr
=====================================
@@ -0,0 +1,3 @@
+MultilineStringsUnterminated.hs:10:1: error: [GHC-21231]
+    lexical error at end of input
+


=====================================
testsuite/tests/parser/should_fail/T25530.hs
=====================================
@@ -0,0 +1,9 @@
+{-# LANGUAGE MultilineStrings #-}
+
+foo =
+  """
+  a\
+  b
+  """
+
+main = print foo


=====================================
testsuite/tests/parser/should_fail/T25530.stderr
=====================================
@@ -0,0 +1,2 @@
+T25530.hs:5:4: error: [GHC-21231] lexical error at character '\\'
+


=====================================
testsuite/tests/parser/should_fail/all.T
=====================================
@@ -231,9 +231,13 @@ test('T17879a', normal, compile_fail, [''])
 test('T17879b', normal, compile_fail, [''])
 test('Or1', normal, compile_fail, [''])
 test('OrPatInExprErr', normal, compile_fail, [''])
+
+# Multiline Strings
 test('MultilineStringsError', [normalise_whitespace_fun(lambda s: s)], compile_fail, [''])
 test('MultilineStringsSmartQuotes', normal, compile_fail, [''])
 test('MultilineStringsInnerTab', normal, compile_fail, [''])
+test('MultilineStringsUnterminated', normal, compile_fail, [''])
 test('T25258a', normal, compile_fail, [''])
 test('T25258b', normal, compile_fail, [''])
 test('T25258c', normal, compile_fail, [''])
+test('T25530', normal, compile_fail, [''])



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/b519c06b889139f7e24f1e84d2e30461cc6cf4a5...9e464ad01f5f60f774504fcaf8d0c30bdd291159

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/b519c06b889139f7e24f1e84d2e30461cc6cf4a5...9e464ad01f5f60f774504fcaf8d0c30bdd291159
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