lint: don't store facts of dependencies in cache

We currently have no way of making use of these facts when loading
from export data, so don't waste time and disk space on the data.

lint/runner.go

@@ -85,9 +85,8 @@ func (ids analyzerIDs) get(a *analysis.Analyzer) int {
 }
 
 type Fact struct {
-	PkgPath string
-	ObjPath string
-	Fact    analysis.Fact
+	Path string
+	Fact analysis.Fact
 }
 
 type newFact struct {
@@ -358,22 +357,23 @@ func (r *Runner) runAnalysisUser(pass *analysis.Pass, ac *analysisAction) (inter
 
 		// Persist facts to cache
 		var facts []Fact
-		// TODO(dh): also store package facts of dependencies
 		for _, fact := range ac.newFacts {
 			if fact.obj == nil {
-				facts = append(facts, Fact{fact.obj.Pkg().Path(), "", fact.fact})
+				facts = append(facts, Fact{"", fact.fact})
 			} else {
 				panic("unexpected object fact")
 			}
 		}
 		for obj, afacts := range ac.pkg.facts[ac.analyzerID] {
-			pkgpath := obj.Pkg().Path()
+			if obj.Pkg() != ac.pkg.Package.Types {
+				continue
+			}
 			path, err := objectpath.For(obj)
 			if err != nil {
 				continue
 			}
 			for _, fact := range afacts {
-				facts = append(facts, Fact{pkgpath, string(path), fact})
+				facts = append(facts, Fact{string(path), fact})
 			}
 		}
 
@@ -576,19 +576,12 @@ func (r *Runner) loadPkg(pkg *Package, analyzers []*analysis.Analyzer) error {
 			}
 
 			for _, f := range facts {
-				if pkg.PkgPath != f.PkgPath {
-					// TODO(dh): for now we load all packages in the
-					// dependency graph and don't utilize the fact
-					// that a package contains all the facts of its
-					// dependencies.
-					continue
-				}
-				if f.ObjPath == "" {
+				if f.Path == "" {
 					// This is a package fact
 					pkg.pkgFacts[r.analyzerIDs.get(a)] = append(pkg.pkgFacts[r.analyzerIDs.get(a)], f.Fact)
 					continue
 				}
-				obj, err := objectpath.Object(pkg.Types, objectpath.Path(f.ObjPath))
+				obj, err := objectpath.Object(pkg.Types, objectpath.Path(f.Path))
 				if err != nil {
 					// Be lenient about these errors. For example, when
 					// analysing io/ioutil from source, we may get a fact