Type inference issue in the spring security/mockito project

The following is a simplified class [HttpSecurityConfigurationTests.java](https://github.com/spring-projects/spring-security/blob/main/config/src/test/java/org/springframework/security/config/annotation/web/configuration/HttpSecurityConfigurationTests.java) from the spring-security project:
```
public class TestClass {
public static void main(String[] args) {
@SuppressWarnings("unchecked")
ArgumentCaptor.AuthorizationManagerRequestMatcherRegistry> arg = ArgumentCaptor
.forClass(AuthorizeHttpRequestsConfigurer.AuthorizationManagerRequestMatcherRegistry.class);
System.out.println(arg);
}
}

class ArgumentCaptor {
@SuppressWarnings("unused")
private final Class clazz;

private ArgumentCaptor(Class clazz) {
this.clazz = clazz;
}

public static ArgumentCaptor forClass(Class clazz) {
return new ArgumentCaptor<>(clazz);
}
}

class AuthorizeHttpRequestsConfigurer {
public final class AuthorizationManagerRequestMatcherRegistry {
}
}
```

ECJ shows the following error:
```
Type mismatch: cannot convert from ArgumentCaptor to ArgumentCaptor.AuthorizationManagerRequestMatcherRegistry>
```
at line 4.
javac compiles and runs this class.

I am preparing a test and a potential PR.

Start with the simplified TestClass reproducer and compare ECJ's type-inference result with javac. Use config/src/test/java/org/springframework/security/config/annotation/web/configuration/HttpSecurityConfigurationTests.java as the real-world case, then add a regression test showing that the valid ArgumentCaptor assignment compiles without the reported mismatch.

Written by the indexing model from the issue text.