Merge pull request #1767 from kentcb/Issue1766

Treat System.Void as the absence of a type.

Fixes #1766.

src/Workspaces/Core/Portable/Editing/SyntaxGenerator.cs

@@ -132,7 +132,7 @@ public SyntaxNode MethodDeclaration(IMethodSymbol method, IEnumerable<SyntaxNode
             var decl = MethodDeclaration(
                 method.Name,
                 parameters: method.Parameters.Select(p => ParameterDeclaration(p)),
-                returnType: TypeExpression(method.ReturnType),
+                returnType: method.ReturnType.IsSystemVoid() ? null : TypeExpression(method.ReturnType),
                 accessibility: method.DeclaredAccessibility,
                 modifiers: DeclarationModifiers.From(method),
                 statements: statements);

src/Workspaces/VisualBasicTest/CodeGeneration/SyntaxGeneratorTests.vb

@@ -697,6 +697,22 @@ End Function</x>.Value)
 End Sub</x>.Value)
         End Sub
 
+        <Fact>
+        Public Sub MethodDeclarationCanRoundTrip()
+            Dim tree = VisualBasicSyntaxTree.ParseText(
+<x>
+Public Sub Test()
+End Sub</x>.Value)
+            Dim compilation = VisualBasicCompilation.Create("AssemblyName", syntaxTrees:={tree})
+            Dim model = compilation.GetSemanticModel(tree)
+            Dim node = tree.GetRoot().DescendantNodes().First()
+            Dim symbol = CType(model.GetDeclaredSymbol(node), IMethodSymbol)
+            VerifySyntax(Of MethodBlockSyntax)(
+                _g.MethodDeclaration(symbol),
+<x>Public Sub Test()
+End Sub</x>.Value)
+        End Sub
+
         <Fact>
         Public Sub TestPropertyDeclarations()
             VerifySyntax(Of PropertyStatementSyntax)(