Description Stephan Herrmann 2021-08-15 12:55:22 EDT

From bug 575397:

When parsing smth like
	if (true) {
		Thread.|
		someMethod();
	}
the completion scanner currently recognizes a dubious LocalDeclaration from 
    Thread.<emptyId> someMethod

This prematurely determines "Thread.<emptyId>" as a QualifiedTypeReference.

While bug 575397 resolves this for one kind of statement, we should find a general solution to steer the parser into a more likely AST.


Adding the following method in Scanner would allow us to recognize the part "the subsequent code can be interpreted as a legal statement":

public boolean isAtStatementStart() {
	VanguardParser vp = getVanguardParser();
	return vp.parse(Goal.BlockStatementoptGoal) == VanguardParser.SUCCESS;
}

We could use some additional routine for recognizing what's left of the cursor.

Finally, I'm thinking of synthesizing one or more tokens to allow reducing the part up until the completionIdentifier. Perhaps some speculative insertion could allow us to check if that would be accepted as a statement by the parser.

All this must bear in mind, that the prefix can legally be any name, resolving to variable or type.

In a quick-n-dirty experiment I had some success even by just scheduling a ';' right after the (empty) completion identifier (using Scanner.unget()), which suffices to separate both statements. It even helps to recover an enclosing if statement (see the example from bug 575397).