Completion for unimported types doesn't work

[snjeza]

Fixes #1502

[stephan-herrmann]

Found this only after commenting in #1502 - still a few answers to my questions there would help the reviewer :)

[akurtakov]

Are @snjeza 's answers on the issue good?

[jukzi]

@snjeza please resolve conflicts and update the commit message to reflect the change and and contain a reference to the bug

[snjeza]

@jukzi I have updated the PR.

[jukzi]

LGTM, and it usefull. i tested it. It could be improved, please:

package aaa;

import java.util.ArrayList;

public class X {
	void foo() {
		new ArrayList<>().add(null);
		new HashMap().cl|
		}
}

results in not compile-able completion:
new HashMap<K, V>().clear();

it would be better if it completes to diamond operator new HashMap<>().clear(); as K and V are not defined.

[snjeza]

results in not compile-able completion:
new HashMap<K, V>().clear();
it would be better if it completes to diamond operator new HashMap<>().clear(); as K and V are not defined.

This should be resolved in eclipse.jdt.ui - https://github.com/eclipse-jdt/eclipse.jdt.ui/blob/a4c1b5bc5dbb294e8c23b93296effeb1d5c2cae0/org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/text/java/JavaMethodCompletionProposal.java#L474

[rgrunber]

results in not compile-able completion:
new HashMap<K, V>().clear();
it would be better if it completes to diamond operator new HashMap<>().clear(); as K and V are not defined.

This should be resolved in eclipse.jdt.ui - https://github.com/eclipse-jdt/eclipse.jdt.ui/blob/a4c1b5bc5dbb294e8c23b93296effeb1d5c2cae0/org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/text/java/JavaMethodCompletionProposal.java#L474

Looks to still be an issue for me with this PR on latest master of jdt.core and latest jdt.ui.

[stephan-herrmann]

results in not compile-able completion:
new HashMap<K, V>().clear();
it would be better if it completes to diamond operator new HashMap<>().clear(); as K and V are not defined.

This should be resolved in eclipse.jdt.ui - https://github.com/eclipse-jdt/eclipse.jdt.ui/blob/a4c1b5bc5dbb294e8c23b93296effeb1d5c2cae0/org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/text/java/JavaMethodCompletionProposal.java#L474

Looks to still be an issue for me with this PR on latest master of jdt.core and latest jdt.ui.

I guess JavaMethodCompletionProposal is good, but perhaps somewhere in the implementation of canUseDiamon() this situation is handled wrongly. In particular InternalExtendedCompletionContext.canUseDiamond(String[], char[][]) from https://bugs.eclipse.org/578969 has a suspicious comment:

// If no LHS or return type expected, then we can safely use diamond

No LHS is actually the situation mentioned by @jukzi , and for this very reason a diamond is illegal.