Bugfix:: Make bound values available to filter clause for try-with in seq{} (#17990)

Author: T-Gro

docs/release-notes/.FSharp.Compiler.Service/9.0.200.md

@@ -10,6 +10,7 @@
 * Fix nullness inference for member val and other OO scenarios  ([PR #17845](https://github.com/dotnet/fsharp/pull/17845))
 * Fix internal error when analyzing incomplete inherit member ([PR #17905](https://github.com/dotnet/fsharp/pull/17905))
 * Fix missing nullness warning in case of method resolution multiple candidates ([PR #17917](https://github.com/dotnet/fsharp/pull/17918))
+* Fix failure to use bound values in `when` clauses of `try-with` in `seq` expressions ([# 17990](https://github.com/dotnet/fsharp/pull/17990))
 
 ### Added
 

src/Compiler/Checking/Expressions/CheckSequenceExpressions.fs

@@ -340,7 +340,7 @@ let TcSequenceExpression (cenv: TcFileState) env tpenv comp (overallTy: OverallT
                         MatchClause(patR, condR, TTarget(vspecs, matchBody, None), patR.Range)
 
                     let filterClause =
-                        MatchClause(patR, condR, TTarget([], Expr.Const(Const.Int32 1, m, g.int_ty), None), patR.Range)
+                        MatchClause(patR, condR, TTarget(vspecs, Expr.Const(Const.Int32 1, m, g.int_ty), None), patR.Range)
 
                     (handlerClause, filterClause), tpenv)
 

tests/FSharp.Compiler.ComponentTests/Language/SequenceExpressions/SequenceExpressionTests.fs

@@ -335,6 +335,54 @@ if sum <> 110 then
     |> runCode
     |> shouldSucceed
 
+[<Fact>]
+let ``With clause in seq expression can bind specific exn type``() =
+
+    Fsx """
+open System
+let whatIsIt =
+    seq {
+        try
+            yield 1
+        with
+        | :? AggregateException as exc when (exc.InnerException :? OperationCanceledException) -> ()
+    }
+    |> Seq.head
+    """
+    |> compile
+    |> verifyIL [
+    """IL_0000:  ldarg.1
+       IL_0001:  isinst     [runtime]System.AggregateException
+       IL_0006:  stloc.0
+       IL_0007:  ldloc.0""";
+    
+    """IL_000a:  ldloc.0
+       IL_000b:  callvirt   instance class [runtime]System.Exception [runtime]System.Exception::get_InnerException()
+       IL_0010:  stloc.1
+       IL_0011:  ldloc.1
+       IL_0012:  isinst     [runtime]System.OperationCanceledException"""]
+
+[<Fact>]
+let ``With clause in seq expression can bind many exn subtypes``() =
+
+    Fsx """
+open System
+let whatIsIt =
+    seq {
+        try
+            yield (10/0)
+        with
+        | :? AggregateException as exc when (exc.InnerException :? OperationCanceledException) -> ()
+        | :? AggregateException as exagg when (exagg.InnerExceptions.GetHashCode()) = 15 -> yield (exagg.InnerExceptions.GetHashCode())
+        | :? AggregateException as exagg -> yield (exagg.InnerExceptions.GetHashCode())
+        | :? DivideByZeroException as exn when exn.Message = "abc" -> yield 0
+        | _ -> yield 1
+    }
+    |> Seq.head
+    """
+    |> runCode
+    |> shouldSucceed
+
 [<Theory>]
 [<InlineData("41","42","43")>]
 [<InlineData("()","42","43")>]