Fix an internal warning while typechecking (#761)

* Fix an internal warning while typechecking

The current typechecking code logs:

```
WARNING: Pin #infer methods are deprecated. Use #typify or #probe
instead.
```

Move the infer() call to typify(), as we know are interested in
validating the declared type exists, not the inferred one.

* Fix logic to account for class/module aliases

lib/solargraph/type_checker.rb

@@ -126,11 +126,16 @@ def method_return_type_problems_for pin
     # @return [Boolean]
     def resolved_constant? pin
       return true if pin.typify(api_map).defined?
-      api_map.get_constants('', *pin.closure.gates)
-        .select { |p| p.name == pin.return_type.namespace }
-        .any? { |p| p.infer(api_map).defined? }
+      constant_pins = api_map.get_constants('', *pin.closure.gates)
+               .select { |p| p.name == pin.return_type.namespace }
+      return true if constant_pins.find { |p| p.typify(api_map).defined? }
+      # will need to probe when a constant name is assigned to a
+      # class/module (alias)
+      return true if constant_pins.find { |p| p.probe(api_map).defined? }
+      false
     end
 
+    # @param pin [Pin::Base]
     def virtual_pin? pin
       pin.location && source_map.source.comment_at?(pin.location.range.ending)
     end