internal/lsp: support multi-dereferencing completion candidates

Now we keep a count of how many times to dereference a candidate. For
example:

    var foo ***int
    var _ int = f<> // Now we offer "***foo" instead of "*foo".

Change-Id: I14edc40aeec6884399eceb3dd3b4f85dc74a773c
Reviewed-on: https://go-review.googlesource.com/c/tools/+/218580
Run-TryBot: Muir Manders <muir@mnd.rs>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>

internal/lsp/source/completion.go

@@ -384,8 +384,9 @@ type candidate struct {
 	// makePointer is true if the candidate type name T should be made into *T.
 	makePointer bool
 
-	// dereference is true if the candidate obj should be made into *obj.
-	dereference bool
+	// dereference is a count of how many times to dereference the candidate obj.
+	// For example, dereference=2 turns "foo" into "**foo" when formatting.
+	dereference int
 
 	// imp is the import that needs to be added to this package in order
 	// for this candidate to be valid. nil if no import needed.
@@ -1804,9 +1805,10 @@ func (c *completer) matchingCandidate(cand *candidate, seen map[types.Type]struc
 			seen[cand.obj.Type()] = struct{}{}
 		}
 
-		if !saw && c.matchingCandidate(&candidate{obj: c.fakeObj(ptr.Elem())}, seen) {
+		fakeCandidate := candidate{obj: c.fakeObj(ptr.Elem())}
+		if !saw && c.matchingCandidate(&fakeCandidate, seen) {
 			// Mark the candidate so we know to prepend "*" when formatting.
-			cand.dereference = true
+			cand.dereference = 1 + fakeCandidate.dereference
 			return true
 		}
 	}

internal/lsp/source/completion_format.go

@@ -134,8 +134,10 @@ func (c *completer) item(cand candidate) (CompletionItem, error) {
 	var prefixOp string
 	if cand.takeAddress {
 		prefixOp = "&"
-	} else if cand.makePointer || cand.dereference {
+	} else if cand.makePointer {
 		prefixOp = "*"
+	} else if cand.dereference > 0 {
+		prefixOp = strings.Repeat("*", cand.dereference)
 	}
 
 	if prefixOp != "" {

internal/lsp/testdata/lsp/primarymod/address/address.go

@@ -37,6 +37,10 @@ func _() {
 
 	wantsVariadic() //@rank(")", addrCPtr, addrA),snippet(")", addrCPtr, "*c", "*c")
 
+	var d **int
+	**d           //@item(addrDPtr, "**d", "**int", "var")
+	var _ int = _ //@rank("_ //", addrDPtr, addrA),snippet("_ //", addrDPtr, "**d", "**d")
+
 	type namedPtr *int
 	var np namedPtr
 	*np           //@item(addrNamedPtr, "*np", "namedPtr", "var")

internal/lsp/testdata/lsp/summary.txt.golden

@@ -1,10 +1,10 @@
 -- summary --
 CompletionsCount = 227
-CompletionSnippetCount = 66
+CompletionSnippetCount = 67
 UnimportedCompletionsCount = 11
 DeepCompletionsCount = 5
 FuzzyCompletionsCount = 8
-RankedCompletionsCount = 84
+RankedCompletionsCount = 86
 CaseSensitiveCompletionsCount = 4
 DiagnosticsCount = 38
 FoldingRangesCount = 2