dartdoc no longer shows actual locations, but the toString of some object, in warning output

[jcollins-g]

In the example below, Operator operator [].location should be the actual location. Presumably this was introduced in the location changes in #2034, but I am sure I would have noticed that...

warning: unresolved doc reference [index], from dart-ffi.Int16Pointer.[]: Operator operator [].location

[jcollins-g]

I erroneously deleted some braces in a last second style change. Fixed in #2043.