SemanticModel is unable to infer type of a 'var' pattern variable

[AlekseyTs]

        [Fact]
        public void FailureToInferTypeOfAVarPatternVariable()
        {
            var source =
@"
class Program
{
    public static void Main(string[] args)
    {
    }

    public static void Test(int val)
    {
        if (val is var o1) 
        {
            System.Console.WriteLine(o1);
        }
    }
}
";
            var compilation = CreateCompilationWithMscorlib45(source, options: TestOptions.DebugExe);
            compilation.VerifyDiagnostics(
                );
            var tree = compilation.SyntaxTrees[0];

            var model1 = compilation.GetSemanticModel(tree);

            var declaration = tree.GetRoot().DescendantNodes().OfType<IsPatternExpressionSyntax>().Single();
            var o1 = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(id => id.Identifier.ValueText == "o1").Single();

            var typeInfo1 = model1.GetTypeInfo(declaration);
            Assert.Equal(SymbolKind.NamedType, typeInfo1.Type.Kind);
            Assert.Equal("System.Boolean", typeInfo1.Type.ToTestDisplayString());

            typeInfo1 = model1.GetTypeInfo(o1);
            Assert.Equal(SymbolKind.NamedType, typeInfo1.Type.Kind);
            Assert.Equal("System.Int32", typeInfo1.Type.ToTestDisplayString());


            var model2 = compilation.GetSemanticModel(tree);

            var typeInfo2 = model2.GetTypeInfo(o1);
            Assert.Equal(SymbolKind.NamedType, typeInfo2.Type.Kind);
            Assert.Equal("System.Int32", typeInfo2.Type.ToTestDisplayString());
        }

The following assert

            Assert.Equal(SymbolKind.NamedType, typeInfo2.Type.Kind);

fails

Test 'Microsoft.CodeAnalysis.CSharp.UnitTests.PatternMatchingTests.FailureToInferTypeOfAVarPatternVariable' failed: Assert.Equal() Failure
Expected: NamedType
Actual:   ErrorType

[gafter]

The relevant (missing) code is this:

        protected virtual TypeSymbol InferTypeOfVarVariable(DiagnosticBag diagnostics)
        {
            // TODO: this method must be overridden for pattern variables to bind the
            // expression or statement that is the nearest enclosing to the pattern variable's
            // declaration. That will cause the type of the pattern variable to be set as a side-effect.
            return _type;
        }