oracle: support "referrers" query on package declaration

Added test.

Change-Id: Id7d061b0f74959166b5631a3fde8da4000ffb8d2
Reviewed-on: https://go-review.googlesource.com/9326
Reviewed-by: David Crawshaw <crawshaw@golang.org>

oracle/definition.go

@@ -46,7 +46,9 @@ func definition(q *Query) error {
 
 	obj := qpos.info.ObjectOf(id)
 	if obj == nil {
-		// Happens for y in "switch y := x.(type)", but I think that's all.
+		// Happens for y in "switch y := x.(type)",
+		// and the package declaration,
+		// but I think that's all.
 		return fmt.Errorf("no object for identifier")
 	}
 

oracle/referrers.go

@@ -18,9 +18,6 @@ import (
 	"golang.org/x/tools/refactor/importgraph"
 )
 
-// TODO(adonovan): use golang.org/x/tools/refactor/importgraph to choose
-// the scope automatically.
-
 // Referrers reports all identifiers that resolve to the same object
 // as the queried identifier, within any package in the analysis scope.
 func referrers(q *Query) error {
@@ -57,20 +54,26 @@ func referrers(q *Query) error {
 
 		obj = qpos.info.ObjectOf(id)
 		if obj == nil {
-			// Happens for y in "switch y := x.(type)", but I think that's all.
-			return fmt.Errorf("no object for identifier")
+			// Happens for y in "switch y := x.(type)",
+			// the package declaration,
+			// and unresolved identifiers.
+			if _, ok := qpos.path[1].(*ast.File); ok { // package decl?
+				pkg := qpos.info.Pkg
+				obj = types.NewPkgName(id.Pos(), pkg, pkg.Name(), pkg)
+			} else {
+				return fmt.Errorf("no object for identifier: %T", qpos.path[1])
+			}
+		}
+
+		if pass2 {
+			break
 		}
 
 		// If the identifier is exported, we must load all packages that
 		// depend transitively upon the package that defines it.
-		//
-		// TODO(adonovan): we should do this for PkgName objects
-		// too, even though they're lowercase.
-		//
-		// TODO(adonovan): opt: skip this step if obj.Pkg() is a test or
-		// main package.
-		if pass2 || !obj.Exported() {
-			break
+		// Treat PkgNames as exported, even though they're lowercase.
+		if _, isPkg := obj.(*types.PkgName); !(isPkg || obj.Exported()) {
+			break // not exported
 		}
 
 		// Scan the workspace and build the import graph.

oracle/testdata/src/referrers-json/main.golden

@@ -22,10 +22,10 @@
 			"testdata/src/imports/main.go:22:9",
 			"testdata/src/referrers-json/main.go:15:8",
 			"testdata/src/referrers-json/main.go:16:8",
-			"testdata/src/referrers/ext_test.go:7:17",
+			"testdata/src/referrers/ext_test.go:10:17",
 			"testdata/src/referrers/int_test.go:7:17",
-			"testdata/src/referrers/main.go:15:8",
-			"testdata/src/referrers/main.go:16:8"
+			"testdata/src/referrers/main.go:17:8",
+			"testdata/src/referrers/main.go:18:8"
 		]
 	}
 }

oracle/testdata/src/referrers/ext_test.go

@@ -1,8 +1,12 @@
 package main_test
 
-import "lib"
+import (
+	"lib"
+	renamed "referrers" // package has name "main", path "referrers", local name "renamed"
+)
 
 func _() {
 	// This reference should be found by the ref-method query.
 	_ = (lib.Type).Method // ref from external test package
+	var _ renamed.T
 }

oracle/testdata/src/referrers/main.go

@@ -1,4 +1,4 @@
-package main
+package main // @referrers package-decl "main"
 
 // Tests of 'referrers' query.
 // See go.tools/oracle/oracle_test.go for explanation.
@@ -6,10 +6,12 @@ package main
 
 import "lib"
 
-type s struct { // @referrers ref-type " s "
+type s struct { // @referrers type " s "
 	f int
 }
 
+type T int
+
 func main() {
 	var v lib.Type = lib.Const // @referrers ref-package "lib"
 	_ = v.Method               // @referrers ref-method "Method"

oracle/testdata/src/referrers/main.golden

@@ -1,10 +1,16 @@
--------- @referrers ref-type --------
+-------- @referrers package-decl --------
+1 references to package main ("referrers")
+	var _ renamed.T
+
+-------- @referrers type --------
 2 references to type s struct{f int}
 	_ = s{}.f // @referrers ref-field "f"
 	var s2 s
 
 -------- @referrers ref-package --------
-2 references to package lib
+4 references to package lib
+	_ = (lib.Type).Method // ref from external test package
+	_ = (lib.Type).Method // ref from internal test package
 	var v lib.Type = lib.Const // @referrers ref-package "lib"
 	var v lib.Type = lib.Const // @referrers ref-package "lib"