Description

When the first part of a namespace of a bound type exists under the Microsoft namespace an error will occur

using Microsoft.Extensions.Configuration;
var c = new ConfigurationBuilder().Build();
c.Get<Foo.Bar.BType>();

namespace Microsoft.Foo
{
    internal class AType {}
}

namespace Foo.Bar
{
    internal class BType {}
}

C:\scratch\namespaceConflict\Microsoft.Extensions.Configuration.Binder.SourceGeneration\Microsoft.Extensions.Configuration.Binder.SourceGeneration.ConfigurationBindingGenerator\BindingExtensions.g.cs(22,15): error CS0234: The type or namespace name 'Bar' does not exist in the namespace 'Microsoft.Foo' (are you missing an assembly reference?) [C:\scratch\namespaceConflict\namespaceConflict.csproj]

This is happening because the generator places using statements in a namespace Microsoft.Extensions.Configuration.Binder.SourceGeneration and this will cause the compiler to first search in containing namespaces at every level before considering the global namespace for usings placed in that namespace.

Hit this when porting eShopOnContainers.

Reproduction Steps

Build
namespaceConflict.zip

Expected behavior

Builds without issue

Actual behavior

Compilation error.

Regression?

No

Known Workarounds

Alias the reference that has the conflicting namespace, change namespace names, etc.

Configuration

No response

Other information

No response