From a911d9008d1f732040244007778232b02ebb2b84 Mon Sep 17 00:00:00 2001
From: Rebecca Stambler <rstambler@golang.org>
Date: Sun, 24 Nov 2019 13:04:54 -0500
Subject: [PATCH] internal/lsp: only search for references in reverse
 dependencies

Updates golang/go#35597

Change-Id: I78e83ad0ee1ae3c59a7452c467b3abd34587a845
Reviewed-on: https://go-review.googlesource.com/c/tools/+/208657
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Cottrell <iancottrell@google.com>
---
 internal/lsp/cache/snapshot.go    |  2 +-
 internal/lsp/source/references.go | 22 +++++++++++++++++-----
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/internal/lsp/cache/snapshot.go b/internal/lsp/cache/snapshot.go
index 17d15d3015f..4ae68bb4e1e 100644
--- a/internal/lsp/cache/snapshot.go
+++ b/internal/lsp/cache/snapshot.go
@@ -94,7 +94,7 @@ func (s *snapshot) PackageHandles(ctx context.Context, f source.File) ([]source.
 		cphs = results
 	}
 	if len(cphs) == 0 {
-		return nil, errors.Errorf("no CheckPackageHandles for %s", f)
+		return nil, errors.Errorf("no CheckPackageHandles for %s", f.URI())
 	}
 	return cphs, nil
 }
diff --git a/internal/lsp/source/references.go b/internal/lsp/source/references.go
index 921a7564450..88ecf113c6d 100644
--- a/internal/lsp/source/references.go
+++ b/internal/lsp/source/references.go
@@ -10,6 +10,8 @@ import (
 	"go/types"
 
 	"golang.org/x/tools/go/types/objectpath"
+	"golang.org/x/tools/internal/lsp/telemetry"
+	"golang.org/x/tools/internal/telemetry/log"
 	"golang.org/x/tools/internal/telemetry/trace"
 	errors "golang.org/x/xerrors"
 )
@@ -73,12 +75,22 @@ func (i *IdentifierInfo) References(ctx context.Context) ([]*ReferenceInfo, erro
 	var searchpkgs []Package
 	if i.Declaration.obj.Exported() {
 		// Only search all packages if the identifier is exported.
-		// TODO(matloob): This only needs to look into reverse-dependencies.
-		// Avoid checking types of other packages.
-		searchpkgs = i.Snapshot.KnownPackages(ctx)
-	} else {
-		searchpkgs = []Package{i.pkg}
+		for _, id := range i.Snapshot.GetReverseDependencies(i.pkg.ID()) {
+			cph, err := i.Snapshot.PackageHandle(ctx, id)
+			if err != nil {
+				log.Error(ctx, "References: no CheckPackageHandle", err, telemetry.Package.Of(id))
+				continue
+			}
+			pkg, err := cph.Check(ctx)
+			if err != nil {
+				log.Error(ctx, "References: no Package", err, telemetry.Package.Of(id))
+				continue
+			}
+			searchpkgs = append(searchpkgs, pkg)
+		}
 	}
+	// Add the package in which the identifier is declared.
+	searchpkgs = append(searchpkgs, i.pkg)
 	for _, pkg := range searchpkgs {
 		for ident, obj := range pkg.GetTypesInfo().Uses {
 			if obj == nil || !(sameObj(obj, i.Declaration.obj)) {