Only Class::Name#foo can become pending bp

[ko1]

Now method breakpoints accepts expr.name and expr#name.
And with any expr can become a pending method bp.
However, general expr in other context does not make sense,
so only ClassName style expressions can become pending bps.
They can be activated when the ClassName#foo is defined.

[ko1]

memo:

$ exe/rdbg  -n  target.rb
[1, 7] in target.rb
=>   1| binding.b do: 'b x.y.foo'
     2| binding.b do: 'b Foo::Bar.foo'
     3| binding.b do: 'b ::Foo::Bar.foo'
     4| binding.b do: 'b'
     5|
     6|
     7| __END__
=>#0    <main> at target.rb:1
(rdbg:binding.break) b x.y.foo
Not a constant name: "x.y"
[1, 7] in target.rb
     1| binding.b do: 'b x.y.foo'
=>   2| binding.b do: 'b Foo::Bar.foo'
     3| binding.b do: 'b ::Foo::Bar.foo'
     4| binding.b do: 'b'
     5|
     6|
     7| __END__
=>#0    <main> at target.rb:2
(rdbg:binding.break) b Foo::Bar.foo
Unknown constant name: "Foo"
#0  BP - Method (pending)  Foo::Bar.foo
[1, 7] in target.rb
     1| binding.b do: 'b x.y.foo'
     2| binding.b do: 'b Foo::Bar.foo'
=>   3| binding.b do: 'b ::Foo::Bar.foo'
     4| binding.b do: 'b'
     5|
     6|
     7| __END__
=>#0    <main> at target.rb:3
(rdbg:binding.break) b ::Foo::Bar.foo
Unknown constant name: "Foo"
#1  BP - Method (pending)  ::Foo::Bar.foo
[1, 7] in target.rb
     1| binding.b do: 'b x.y.foo'
     2| binding.b do: 'b Foo::Bar.foo'
     3| binding.b do: 'b ::Foo::Bar.foo'
=>   4| binding.b do: 'b'
     5|
     6|
     7| __END__
=>#0    <main> at target.rb:4
(rdbg:binding.break) b
#0  BP - Method (pending)  Foo::Bar.foo
#1  BP - Method (pending)  ::Foo::Bar.foo