The gccgo compiler would fail this test. The fix for gccgo is
https://golang.org/cl/
116960043 .
LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/
118000043
--- /dev/null
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+var p2 = Printf // ERROR "undefined"
--- /dev/null
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+import . "fmt"
+
+var p1 = Print
--- /dev/null
+// errorcheckdir
+
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// The gccgo compiler had a bug: if one file in a package did a dot
+// import, then an earlier file in the package would incorrectly
+// resolve to the imported names rather than reporting undefined
+// errors.
+
+package ignored