Add support for inner type completions on partially-qualified expressions w/o supporting import

[eric-milles]

In Java editor, code assist for Map.Ent| results in a proposal for java.util.Map.Entry and application of the proposal adds an import or qualifier (depending on Content Assist preferences). Groovy editor is missing proposals for partially-qualified names like Map.Ent when the supporting type name is not imported (i.e. Map is a bad example for Groovy since java.util is default imported).

[eric-milles]

Constructor completion is missing necessary qualifier segments. "new Outer.Inn|" shows proposal that is missing "Outer" and completes to "new pack.Inner()" or "import pack.Inner; new Inner()". Type completion followed by typing () followed by method context proposals from within the parens is an available workaround.

[eric-milles]

NOTE: Groovy and Java seem to be indexed differently because org.eclipse.jdt.internal.core.SearchableEnvironment.findConstructorDeclarations(char[], boolean, ISearchRequestor, IProgressMonitor) is finding inner type constructors for Groovy but not Java. This should be understood so that Groovy can provide consistent behavior.

[mauromol]

Hi Eric,
please note that when trying to verify this fix with 3.0.0.xx-201802122322-e47, I face an inconsistency which I think has its root cause in #411. I'll try to explain.
If I type: Map. => (pause) => Ent and then look at the list of suggestions (which opens automatically in this case, because I have Java | Editor | Content Assist | Enable Auto Activation option checked), Map.Entry is not available.
If, instead, I start from: Map.Ent (being the suggestion list closed) and hit Ctrl+Space, Map.Entry is completed correctly (being the only applicable suggestion, so no list is needed).

[eric-milles]

Can you open a separate issu for that? Starting from "Map.|" there may need to be parser recovery to produce a ClassExpression in the AST so that content assist works propery.