go/types: fix incorrect InitOrder in packages created from multiple calls to (*Checker).Files.

The InitOrder needs to be reset.

+ Test.

This bug manifested itself in duplicate HTML in the godoc -analysis view,
e.g. "f((x)" or "funcfunc f()"

LGTM=gri
R=gri
CC=golang-codereviews
https://golang.org/cl/107660044

go/types/api_test.go

@@ -479,14 +479,16 @@ func TestInitOrderInfo(t *testing.T) {
 func TestFiles(t *testing.T) {
 	var sources = []string{
 		"package p; type T struct{}; func (T) m1() {}",
-		"package p; func (T) m2() {}; var _ interface{ m1(); m2() } = T{}",
-		"package p; func (T) m3() {}; var _ interface{ m1(); m2(); m3() } = T{}",
+		"package p; func (T) m2() {}; var x interface{ m1(); m2() } = T{}",
+		"package p; func (T) m3() {}; var y interface{ m1(); m2(); m3() } = T{}",
+		"package p",
 	}
 
 	var conf Config
 	fset := token.NewFileSet()
 	pkg := NewPackage("p", "p")
-	check := NewChecker(&conf, fset, pkg, nil)
+	var info Info
+	check := NewChecker(&conf, fset, pkg, &info)
 
 	for i, src := range sources {
 		filename := fmt.Sprintf("sources%d", i)
@@ -498,6 +500,17 @@ func TestFiles(t *testing.T) {
 			t.Error(err)
 		}
 	}
+
+	// check InitOrder is [x y]
+	var vars []string
+	for _, init := range info.InitOrder {
+		for _, v := range init.Lhs {
+			vars = append(vars, v.Name())
+		}
+	}
+	if got, want := fmt.Sprint(vars), "[x y]"; got != want {
+		t.Errorf("InitOrder == %s, want %s", got, want)
+	}
 }
 
 func TestSelection(t *testing.T) {

go/types/initorder.go

@@ -11,6 +11,10 @@ import (
 
 // initOrder computes the Info.InitOrder for package variables.
 func (check *Checker) initOrder() {
+	// An InitOrder may already have been computed if a package is
+	// built from several calls to (*Checker).Files.  Clear it.
+	check.Info.InitOrder = check.Info.InitOrder[:0]
+
 	// compute the object dependency graph and
 	// initialize a priority queue with the list
 	// of graph nodes