Fix a few AND operator parser bugs and regressions (#17113)

dotnet · May 15, 2024 · 3f7772a · 3f7772a
1 parent bd24c88
commit 3f7772a
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diff --git a/docs/release-notes/.FSharp.Compiler.Service/8.0.400.md b/docs/release-notes/.FSharp.Compiler.Service/8.0.400.md
@@ -12,6 +12,7 @@
 * Fix calling an overridden virtual static method via the interface ([PR #17013](https://github.com/dotnet/fsharp/pull/17013))
 * Fix state machines compilation, when big decision trees are involved, by removing code split when resumable code is detected ([PR #17076](https://github.com/dotnet/fsharp/pull/17076))
 * Fix for exponential runtime in CE builders when using nested implicit yields [PR #17096](https://github.com/dotnet/fsharp/pull/17096)
+* Fix several AND operator parser bugs and regressions ([Issue #16447](https://github.com/dotnet/fsharp/issues/16447), [Issue #17134](https://github.com/dotnet/fsharp/issues/17134), [Issue #16309](https://github.com/dotnet/fsharp/issues/16309), [PR #17113](https://github.com/dotnet/fsharp/pull/17113))
 
 ### Added
 

diff --git a/src/Compiler/pars.fsy b/src/Compiler/pars.fsy
@@ -2558,6 +2558,10 @@ opt_explicitValTyparDecls:
   |
       { SynValTyparDecls(None, true) }
 
+hashConstraint:
+  | HASH atomType
+     { SynType.HashConstraint($2, lhs parseState) }
+
 /* Any tokens in this grammar must be added to the lex filter rule 'peekAdjacentTypars' */
 /* See the F# specification "Lexical analysis of type applications and type parameter definitions" */
 opt_typeConstraints:
@@ -2579,20 +2583,20 @@ typeConstraints:
 /* Any tokens in this grammar must be added to the lex filter rule 'peekAdjacentTypars' */
 /* See the F# specification "Lexical analysis of type applications and type parameter definitions" */
 intersectionConstraints:
-  | intersectionConstraints AMP atomType %prec prec_no_more_attr_bindings // todo precedence
+  | intersectionConstraints AMP hashConstraint %prec prec_no_more_attr_bindings
       { let constraints, mAmpersands = $1
+        ($3 :: constraints), (rhs parseState 2 :: mAmpersands) }
 
-        match $3 with
-        | SynType.HashConstraint _ -> ()
-        | ty -> errorR(Error(FSComp.SR.parsConstraintIntersectionSyntaxUsedWithNonFlexibleType(), ty.Range))
-
+  | intersectionConstraints AMP atomType %prec prec_no_more_attr_bindings
+      { let constraints, mAmpersands = $1
+        errorR(Error(FSComp.SR.parsConstraintIntersectionSyntaxUsedWithNonFlexibleType(), $3.Range))
         ($3 :: constraints), (rhs parseState 2 :: mAmpersands) }
 
-  | atomType
-      { match $1 with
-        | SynType.HashConstraint _ -> ()
-        | ty -> errorR(Error(FSComp.SR.parsConstraintIntersectionSyntaxUsedWithNonFlexibleType(), ty.Range))
+  | hashConstraint
+      { [ $1 ], [] }
 
+  | atomType
+      { errorR(Error(FSComp.SR.parsConstraintIntersectionSyntaxUsedWithNonFlexibleType(), $1.Range))
         [ $1 ], [] }
 
 /* Any tokens in this grammar must be added to the lex filter rule 'peekAdjacentTypars' */
@@ -5993,11 +5997,11 @@ tupleOrQuotTypeElements:
       { [ SynTupleTypeSegment.Type $1 ] }
 
 intersectionType:
-  | typar AMP intersectionConstraints %prec prec_no_more_attr_bindings // todo precedence
+  | typar AMP intersectionConstraints %prec prec_no_more_attr_bindings
     { let constraints, mAmpersands = $3
       SynType.Intersection(Some $1, List.rev constraints, lhs parseState, { AmpersandRanges = rhs parseState 2 :: List.rev mAmpersands }) }
 
-  | atomType AMP intersectionConstraints %prec prec_no_more_attr_bindings // todo precedence
+  | hashConstraint AMP intersectionConstraints %prec prec_no_more_attr_bindings
     { let constraints, mAmpersands = $3
       SynType.Intersection(None, $1 :: List.rev constraints, lhs parseState, { AmpersandRanges = rhs parseState 2 :: List.rev mAmpersands }) }
 
@@ -6213,8 +6217,8 @@ atomTypeOrAnonRecdType:
 /* Any tokens in this grammar must be added to the lex filter rule 'peekAdjacentTypars' */
 /* See the F# specification "Lexical analysis of type applications and type parameter definitions" */
 atomType:
-  | HASH atomType
-     { SynType.HashConstraint($2, lhs parseState) }
+  | hashConstraint
+     { $1 }
 
   | appTypeConPower %prec prec_atomtyp_path
      { $1 }

diff --git a/tests/FSharp.Compiler.ComponentTests/Conformance/PatternMatching/And/And.fs b/tests/FSharp.Compiler.ComponentTests/Conformance/PatternMatching/And/And.fs
@@ -34,6 +34,13 @@ module And =
         |> typecheck
         |> shouldSucceed
 
+    [<Theory; Directory(__SOURCE_DIRECTORY__, Includes=[|"andPattern04.fs"|])>]
+    let ``And - andPattern04_fs`` compilation =
+        compilation
+        |> asFs
+        |> typecheck
+        |> shouldSucceed
+
     // This test was automatically generated (moved from FSharpQA suite - Conformance/PatternMatching/And)
     [<Theory; Directory(__SOURCE_DIRECTORY__, Includes=[|"E_IdentBoundTwice.fs"|])>]
     let ``And - E_IdentBoundTwice_fs - --test:ErrorRanges`` compilation =

diff --git a/tests/FSharp.Compiler.ComponentTests/Conformance/PatternMatching/And/andPattern04.fs b/tests/FSharp.Compiler.ComponentTests/Conformance/PatternMatching/And/andPattern04.fs
@@ -0,0 +1,21 @@
+// #Conformance #PatternMatching #PatternMatchingGuards 
+
+open System
+
+let x: Result<unit, exn> = Error (NullReferenceException())
+
+match x with
+| Error (_: exn & :? NullReferenceException) -> printfn "NullRef"
+| _ -> ()
+
+match x with
+| Error (_: exn & (:? NullReferenceException)) -> printfn "NullRef"
+| _ -> ()
+
+match x with
+| Error ((_: exn) & :? NullReferenceException) -> printfn "NullRef"
+| _ -> ()
+
+match x with
+| Error ((_: exn) & (:? NullReferenceException)) -> printfn "NullRef"
+| _ -> ()
diff --git a/tests/FSharp.Compiler.ComponentTests/Conformance/PatternMatching/Named/Named.fs b/tests/FSharp.Compiler.ComponentTests/Conformance/PatternMatching/Named/Named.fs
@@ -87,7 +87,31 @@ module Named =
         |> withOptions ["--test:ErrorRanges"]
         |> typecheck
         |> shouldSucceed
+
+    [<Theory; Directory(__SOURCE_DIRECTORY__, Includes=[|"activePatterns09.fs"|])>]
+    let ``Named - activePatterns09_fs`` compilation =
+        compilation
+        |> asFs
+        |> typecheck
+        |> shouldSucceed
 
+    [<Theory; Directory(__SOURCE_DIRECTORY__, Includes=[|"activePatterns10.fs"|])>]
+    let ``Named - activePatterns10_fs`` compilation =
+        compilation
+        |> asFs
+        |> typecheck
+        |> shouldFail
+        |> withDiagnostics [
+            (Warning 25, Line 6, Col 5, Line 6, Col 26, "Incomplete pattern matches on this expression.")
+            (Warning 25, Line 7, Col 5, Line 7, Col 28, "Incomplete pattern matches on this expression.")
+            (Warning 25, Line 8, Col 5, Line 8, Col 28, "Incomplete pattern matches on this expression.")
+            (Warning 25, Line 9, Col 5, Line 9, Col 30, "Incomplete pattern matches on this expression.")
+            (Warning 25, Line 13, Col 5, Line 13, Col 22, "Incomplete pattern matches on this expression. For example, the value '``some-other-subtype``' may indicate a case not covered by the pattern(s).")
+            (Warning 25, Line 14, Col 5, Line 14, Col 24, "Incomplete pattern matches on this expression. For example, the value '``some-other-subtype``' may indicate a case not covered by the pattern(s).")
+            (Warning 25, Line 15, Col 5, Line 15, Col 24, "Incomplete pattern matches on this expression. For example, the value '``some-other-subtype``' may indicate a case not covered by the pattern(s).")
+            (Warning 25, Line 16, Col 5, Line 16, Col 26, "Incomplete pattern matches on this expression. For example, the value '``some-other-subtype``' may indicate a case not covered by the pattern(s).")
+        ]
+
     // This test was automatically generated (moved from FSharpQA suite - Conformance/PatternMatching/Named)
     [<Theory; Directory(__SOURCE_DIRECTORY__, Includes=[|"ActivePatternUnconstrained01.fs"|])>]
     let ``Named - ActivePatternUnconstrained01_fs - --test:ErrorRanges`` compilation =

diff --git a/tests/FSharp.Compiler.ComponentTests/Conformance/PatternMatching/Named/activePatterns09.fs b/tests/FSharp.Compiler.ComponentTests/Conformance/PatternMatching/Named/activePatterns09.fs
@@ -0,0 +1,18 @@
+// #Conformance #PatternMatching #ActivePatterns 
+#light
+
+// Verify AND on active patterns with exceptions
+
+let (_ : exn & Failure _ | _) = exn ()
+let ((_ : exn) & (Failure _) | (_)) = exn ()
+let (_ : exn & (Failure _) | _) = exn ()
+let ((_ : exn) & Failure _ | (_)) = exn ()
+
+exception MyExn
+
+let (_ : exn & MyExn | _) = exn ()
+let ((_ : exn) & (MyExn) | (_)) = exn ()
+let (_ : exn & (MyExn) | _) = exn ()
+let ((_ : exn) & MyExn | (_)) = exn ()
+
+exit 0
diff --git a/tests/FSharp.Compiler.ComponentTests/Conformance/PatternMatching/Named/activePatterns10.fs b/tests/FSharp.Compiler.ComponentTests/Conformance/PatternMatching/Named/activePatterns10.fs
@@ -0,0 +1,18 @@
+// #Conformance #PatternMatching #ActivePatterns 
+#light
+
+// Verify AND on incomplete active patterns with exceptions
+
+let (_ : exn & Failure _) = exn ()
+let ((_ : exn) & Failure _) = exn ()
+let (_ : exn & (Failure _)) = exn ()
+let ((_ : exn) & (Failure _)) = exn ()
+
+exception MyExn
+
+let (_ : exn & MyExn) = exn ()
+let ((_ : exn) & MyExn) = exn ()
+let (_ : exn & (MyExn)) = exn ()
+let ((_ : exn) & (MyExn)) = exn ()
+
+exit 0
diff --git a/tests/FSharp.Compiler.ComponentTests/Language/ConstraintIntersectionTests.fs b/tests/FSharp.Compiler.ComponentTests/Language/ConstraintIntersectionTests.fs
@@ -84,4 +84,18 @@ let y (f: #seq<int> & System.IDisposable) = ()
     |> withDiagnostics [
         Error 3572, Line 2, Col 25, Line 2, Col 43, "Constraint intersection syntax may only be used with flexible types, e.g. '#IDisposable & #ISomeInterface'."
         Error 3572, Line 4, Col 23, Line 4, Col 41, "Constraint intersection syntax may only be used with flexible types, e.g. '#IDisposable & #ISomeInterface'."
-    ]
+    ]
+
+// bug 16309
+[<Fact>]
+let ``Constraint intersection handles invalid types``() =
+    FSharp """
+let f (x: 't when 't :> ABRAKADABRAA & #seq<int>) = ()
+    """
+    |> withLangVersion80
+    |> typecheck
+    |> shouldFail
+    |> withDiagnostics [
+        Error 0010, Line 2, Col 40, Line 2, Col 41, "Unexpected symbol # in pattern"
+        Error 0583, Line 2, Col 7, Line 2, Col 8, "Unmatched '('"
+    ]
diff --git a/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 01.fs b/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 01.fs
@@ -0,0 +1 @@
+let (_ : exn & Failure _) = exn ()
diff --git a/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 01.fs.bsl b/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 01.fs.bsl
@@ -0,0 +1,34 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/OperatorName/ActivePatternAnd 01.fs", false,
+      QualifiedNameOfFile ActivePatternAnd 01, [], [],
+      [SynModuleOrNamespace
+         ([ActivePatternAnd 01], false, AnonModule,
+          [Let
+             (false,
+              [SynBinding
+                 (None, Normal, false, false, [],
+                  PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector),
+                  SynValData
+                    (None, SynValInfo ([], SynArgInfo ([], false, None)), None),
+                  Paren
+                    (Ands
+                       ([Typed
+                           (Wild (1,5--1,6),
+                            LongIdent (SynLongIdent ([exn], [], [None])),
+                            (1,5--1,12));
+                         LongIdent
+                           (SynLongIdent ([Failure], [], [None]), None, None,
+                            Pats [Wild (1,23--1,24)], None, (1,15--1,24))],
+                        (1,5--1,24)), (1,4--1,25)), None,
+                  App
+                    (NonAtomic, false, Ident exn, Const (Unit, (1,32--1,34)),
+                     (1,28--1,34)), (1,4--1,25), Yes (1,0--1,34),
+                  { LeadingKeyword = Let (1,0--1,3)
+                    InlineKeyword = None
+                    EqualsRange = Some (1,26--1,27) })], (1,0--1,34))],
+          PreXmlDocEmpty, [], None, (1,0--1,34), { LeadingKeyword = None })],
+      (true, true), { ConditionalDirectives = []
+                      CodeComments = [] }, set []))
+
+(1,0)-(1,34) parse warning The declarations in this file will be placed in an implicit module 'ActivePatternAnd 01' based on the file name 'ActivePatternAnd 01.fs'. However this is not a valid F# identifier, so the contents will not be accessible from other files. Consider renaming the file or adding a 'module' or 'namespace' declaration at the top of the file.
diff --git a/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 02.fs b/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 02.fs
@@ -0,0 +1 @@
+let ((_ : exn) & Failure _) = exn ()
diff --git a/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 02.fs.bsl b/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 02.fs.bsl
@@ -0,0 +1,35 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/OperatorName/ActivePatternAnd 02.fs", false,
+      QualifiedNameOfFile ActivePatternAnd 02, [], [],
+      [SynModuleOrNamespace
+         ([ActivePatternAnd 02], false, AnonModule,
+          [Let
+             (false,
+              [SynBinding
+                 (None, Normal, false, false, [],
+                  PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector),
+                  SynValData
+                    (None, SynValInfo ([], SynArgInfo ([], false, None)), None),
+                  Paren
+                    (Ands
+                       ([Paren
+                           (Typed
+                              (Wild (1,6--1,7),
+                               LongIdent (SynLongIdent ([exn], [], [None])),
+                               (1,6--1,13)), (1,5--1,14));
+                         LongIdent
+                           (SynLongIdent ([Failure], [], [None]), None, None,
+                            Pats [Wild (1,25--1,26)], None, (1,17--1,26))],
+                        (1,5--1,26)), (1,4--1,27)), None,
+                  App
+                    (NonAtomic, false, Ident exn, Const (Unit, (1,34--1,36)),
+                     (1,30--1,36)), (1,4--1,27), Yes (1,0--1,36),
+                  { LeadingKeyword = Let (1,0--1,3)
+                    InlineKeyword = None
+                    EqualsRange = Some (1,28--1,29) })], (1,0--1,36))],
+          PreXmlDocEmpty, [], None, (1,0--1,36), { LeadingKeyword = None })],
+      (true, true), { ConditionalDirectives = []
+                      CodeComments = [] }, set []))
+
+(1,0)-(1,36) parse warning The declarations in this file will be placed in an implicit module 'ActivePatternAnd 02' based on the file name 'ActivePatternAnd 02.fs'. However this is not a valid F# identifier, so the contents will not be accessible from other files. Consider renaming the file or adding a 'module' or 'namespace' declaration at the top of the file.
diff --git a/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 03.fs b/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 03.fs
@@ -0,0 +1 @@
+let (_ : exn & (Failure _)) = exn ()
diff --git a/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 03.fs.bsl b/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 03.fs.bsl
@@ -0,0 +1,35 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/OperatorName/ActivePatternAnd 03.fs", false,
+      QualifiedNameOfFile ActivePatternAnd 03, [], [],
+      [SynModuleOrNamespace
+         ([ActivePatternAnd 03], false, AnonModule,
+          [Let
+             (false,
+              [SynBinding
+                 (None, Normal, false, false, [],
+                  PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector),
+                  SynValData
+                    (None, SynValInfo ([], SynArgInfo ([], false, None)), None),
+                  Paren
+                    (Ands
+                       ([Typed
+                           (Wild (1,5--1,6),
+                            LongIdent (SynLongIdent ([exn], [], [None])),
+                            (1,5--1,12));
+                         Paren
+                           (LongIdent
+                              (SynLongIdent ([Failure], [], [None]), None, None,
+                               Pats [Wild (1,24--1,25)], None, (1,16--1,25)),
+                            (1,15--1,26))], (1,5--1,26)), (1,4--1,27)), None,
+                  App
+                    (NonAtomic, false, Ident exn, Const (Unit, (1,34--1,36)),
+                     (1,30--1,36)), (1,4--1,27), Yes (1,0--1,36),
+                  { LeadingKeyword = Let (1,0--1,3)
+                    InlineKeyword = None
+                    EqualsRange = Some (1,28--1,29) })], (1,0--1,36))],
+          PreXmlDocEmpty, [], None, (1,0--1,36), { LeadingKeyword = None })],
+      (true, true), { ConditionalDirectives = []
+                      CodeComments = [] }, set []))
+
+(1,0)-(1,36) parse warning The declarations in this file will be placed in an implicit module 'ActivePatternAnd 03' based on the file name 'ActivePatternAnd 03.fs'. However this is not a valid F# identifier, so the contents will not be accessible from other files. Consider renaming the file or adding a 'module' or 'namespace' declaration at the top of the file.
diff --git a/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 04.fs b/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 04.fs
@@ -0,0 +1 @@
+let ((_ : exn) & (Failure _)) = exn ()
diff --git a/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 04.fs.bsl b/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 04.fs.bsl
@@ -0,0 +1,36 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/OperatorName/ActivePatternAnd 04.fs", false,
+      QualifiedNameOfFile ActivePatternAnd 04, [], [],
+      [SynModuleOrNamespace
+         ([ActivePatternAnd 04], false, AnonModule,
+          [Let
+             (false,
+              [SynBinding
+                 (None, Normal, false, false, [],
+                  PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector),
+                  SynValData
+                    (None, SynValInfo ([], SynArgInfo ([], false, None)), None),
+                  Paren
+                    (Ands
+                       ([Paren
+                           (Typed
+                              (Wild (1,6--1,7),
+                               LongIdent (SynLongIdent ([exn], [], [None])),
+                               (1,6--1,13)), (1,5--1,14));
+                         Paren
+                           (LongIdent
+                              (SynLongIdent ([Failure], [], [None]), None, None,
+                               Pats [Wild (1,26--1,27)], None, (1,18--1,27)),
+                            (1,17--1,28))], (1,5--1,28)), (1,4--1,29)), None,
+                  App
+                    (NonAtomic, false, Ident exn, Const (Unit, (1,36--1,38)),
+                     (1,32--1,38)), (1,4--1,29), Yes (1,0--1,38),
+                  { LeadingKeyword = Let (1,0--1,3)
+                    InlineKeyword = None
+                    EqualsRange = Some (1,30--1,31) })], (1,0--1,38))],
+          PreXmlDocEmpty, [], None, (1,0--1,38), { LeadingKeyword = None })],
+      (true, true), { ConditionalDirectives = []
+                      CodeComments = [] }, set []))
+
+(1,0)-(1,38) parse warning The declarations in this file will be placed in an implicit module 'ActivePatternAnd 04' based on the file name 'ActivePatternAnd 04.fs'. However this is not a valid F# identifier, so the contents will not be accessible from other files. Consider renaming the file or adding a 'module' or 'namespace' declaration at the top of the file.
diff --git a/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 05.fs b/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 05.fs
@@ -0,0 +1 @@
+let (_ : exn & Failure _ | _) = exn ()
diff --git a/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 05.fs.bsl b/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 05.fs.bsl
@@ -0,0 +1,36 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/OperatorName/ActivePatternAnd 05.fs", false,
+      QualifiedNameOfFile ActivePatternAnd 05, [], [],
+      [SynModuleOrNamespace
+         ([ActivePatternAnd 05], false, AnonModule,
+          [Let
+             (false,
+              [SynBinding
+                 (None, Normal, false, false, [],
+                  PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector),
+                  SynValData
+                    (None, SynValInfo ([], SynArgInfo ([], false, None)), None),
+                  Paren
+                    (Or
+                       (Ands
+                          ([Typed
+                              (Wild (1,5--1,6),
+                               LongIdent (SynLongIdent ([exn], [], [None])),
+                               (1,5--1,12));
+                            LongIdent
+                              (SynLongIdent ([Failure], [], [None]), None, None,
+                               Pats [Wild (1,23--1,24)], None, (1,15--1,24))],
+                           (1,5--1,24)), Wild (1,27--1,28), (1,5--1,28),
+                        { BarRange = (1,25--1,26) }), (1,4--1,29)), None,
+                  App
+                    (NonAtomic, false, Ident exn, Const (Unit, (1,36--1,38)),
+                     (1,32--1,38)), (1,4--1,29), Yes (1,0--1,38),
+                  { LeadingKeyword = Let (1,0--1,3)
+                    InlineKeyword = None
+                    EqualsRange = Some (1,30--1,31) })], (1,0--1,38))],
+          PreXmlDocEmpty, [], None, (1,0--1,38), { LeadingKeyword = None })],
+      (true, true), { ConditionalDirectives = []
+                      CodeComments = [] }, set []))
+
+(1,0)-(1,38) parse warning The declarations in this file will be placed in an implicit module 'ActivePatternAnd 05' based on the file name 'ActivePatternAnd 05.fs'. However this is not a valid F# identifier, so the contents will not be accessible from other files. Consider renaming the file or adding a 'module' or 'namespace' declaration at the top of the file.
diff --git a/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 06.fs b/tests/service/data/SyntaxTree/OperatorName/ActivePatternAnd 06.fs
@@ -0,0 +1 @@
+let ((_ : exn) & (Failure _) | (_)) = exn ()