Avoid an InvalidCastException while calculating LocalSyntaxOffset within...

Avoid an InvalidCastException while calculating LocalSyntaxOffset within synthetic lambda. (changeset 1352239)

Src/Compilers/VisualBasic/Portable/Lowering/LambdaRewriter/SynthesizedLambdaMethod.vb

@@ -238,17 +238,13 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
             Return False
         End Function
 
-        Friend Shadows Function GetSyntax() As LambdaExpressionSyntax
-            Return DirectCast(Me.Syntax, LambdaExpressionSyntax)
-        End Function
-
         Friend Overrides Function CalculateLocalSyntaxOffset(localPosition As Integer, localTree As SyntaxTree) As Integer
-            Dim syntax = Me.GetSyntax()
+            Dim syntax = TryCast(Me.Syntax, LambdaExpressionSyntax)
 
             ' Assign -1 offset to all variables that are associated with the header.
             ' We can't assign >=0 since user-defined variables defined in the first statement of the body have 0
             ' and user-defined variables need to have a unique syntax offset.
-            If localPosition = syntax.Begin.SpanStart Then
+            If syntax Is Nothing OrElse localPosition = syntax.Begin.SpanStart Then
                 Return -1
             End If
 

Src/Compilers/VisualBasic/Test/Semantic/Semantics/QueryExpressions.vb

@@ -10816,6 +10816,27 @@ End Module
             CreateCompilationWithMscorlibAndVBRuntimeAndReferences(compilationDef, additionalRefs:={SystemCoreRef}, options:=TestOptions.ReleaseDll).AssertNoDiagnostics()
 
         End Sub
+
+        <Fact, WorkItem(1042011)>
+        Public Sub LambdaWithClosureInQueryExpressionAndPDB()
+            Dim compilationDef =
+<compilation name="QueryExpressions">
+    <file name="a.vb">
+Imports System.Linq
+
+Module Module1
+
+    Sub Main()
+        Dim x = From y In {1} Select Function() y
+    End Sub
+
+End Module
+    </file>
+</compilation>
+
+            CompileAndVerify(compilationDef, options:=TestOptions.DebugExe)
+        End Sub
+
     End Class
 
 End Namespace