imports: fix renamed sibling imports more

This is the fix I should have made in CL 153440. What I get for being in
a rush.

Fixes golang/go#29180

Change-Id: I7ee3e26173b86c70574b9710f84094e46db27a37
Reviewed-on: https://go-review.googlesource.com/c/153859
Run-TryBot: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Cottrell <iancottrell@google.com>

imports/fix.go

@@ -200,7 +200,12 @@ func (p *pass) findMissingImport(pkg string, syms map[string]bool) *importInfo {
 		if !ok {
 			continue
 		}
-		if candidate.name != pkg && pkgInfo.name != pkg {
+		// If the candidate import has a name, it must match pkg.
+		if candidate.name != "" && candidate.name != pkg {
+			continue
+		}
+		// Otherwise, the real name of the package must match.
+		if candidate.name == "" && pkgInfo.name != pkg {
 			continue
 		}
 

imports/fix_test.go

@@ -1966,6 +1966,34 @@ func LogSomethingElse() {
 	}.processTest(t, "foo.com", "p/needs_import.go", nil, nil, want)
 }
 
+// Tests #29180: a sibling import of the right package with the wrong name is used.
+func TestSiblingImport_Misnamed(t *testing.T) {
+	const sibling = `package main
+import renamed "fmt"
+var _ = renamed.Printf
+`
+	const input = `package pkg
+var _ = fmt.Printf
+`
+	const want = `package pkg
+
+import "fmt"
+
+var _ = fmt.Printf
+`
+
+	testConfig{
+		module: packagestest.Module{
+			Name: "foo.com",
+			Files: fm{
+				"pkg/main.go": sibling,
+				"pkg/uses.go": input,
+			},
+		},
+	}.processTest(t, "foo.com", "pkg/uses.go", nil, nil, want)
+
+}
+
 func TestPkgIsCandidate(t *testing.T) {
 	tests := []struct {
 		name     string