How do you obtain the instantiated CXXRecordDecl of a templated class in Clang?

For example, I have a class:

template<typename T>
class Foo {
public:
    T getBar();

private:
    T bar_;
};

It is instantiated with:

using FooBarT = Foo<Bar>;

How do I get the CXXRecordDecl with resolved fields and methods for Foo<bar>?

I tried:

const auto *typeAliasDecl = llvm::dyn_cast<clang::TypeAliasDecl>(decl);
typeAliasDecl->getUnderlyingType()->getAsCXXRecordDecl()->dump();

The output I get is:

ClassTemplateSpecializationDecl 0x0000000 class Foo
`-TemplateArgument type 'Bar'

However, I want the CXXRecordDecl with the fields and methods too so I can iterate through them. I've also tried:

for (const auto *contextDecl: typeAliasDecl->getUnderlyingType()->getUnqualifiedDesugaredType()->getAsCXXRecordDecl()->getDeclContext()->decls()) {
    const auto *classTemplateDecl = llvm::dyn_cast<clang::ClassTemplateDecl>(contextDecl);
    classTemplateDecl->dump();
}

The output:

ClassTemplateDecl Foo
|-TemplateTypeParmDecl 0x0000000 referenced typename depth 0 index 0 T
|-CXXRecordDecl class Foo definition
| ... 
| |-FieldDecl 0x0000000 referenced bar_ 'T'
|-ClassTemplateSpecializationDecl 0x0000000 class Foo
  `-TemplateArgument type 'Bar'

As you can see the CXXRecordDecl class Foo definition has access to the FieldDecl, but doesn't know about the type instantiation of bar_, while the ClassTemplateSpecializationDecl does.

I want the CXXRecordDecl with the instantiated type for FieldDecl bar_