Go version 1.5

Summary

We've run into some behavior we didn't expect from go/types importing packages. If a package p has been imported (by some other package) and its source code is present but not installed (that is, there is no package archive such as $GOROOT/pkg/darwin_amd64/p.a) then Check returns an error saying it can't find the package.

We're not sure if this is intended behavior, but we found it surprising.

cc @tessr

We've tried to produce a minimal test case:
https://github.com/kr/gotypesrepro

Steps to reproduce

1. git clone https://github.com/kr/gotypesrepro $GOPATH/src/p
2. cd $GOPATH/src/p
3. go run try.go # fails
4. go install p
5. go run try.go # now it works

Expected output

package testdata ("testdata")
package testdata ("testdata")

Actual output

testdata/import.go:3:8: could not import p (can't find import: p)
package testdata ("testdata")