go.tools/go/types: track init cycles through closures

R=adonovan
CC=golang-dev
https://golang.org/cl/21790044

go/types/expr.go

@@ -969,8 +969,11 @@ func (check *checker) exprInternal(x *operand, e ast.Expr, hint Type) exprKind {
 		if sig, ok := check.typ(e.Type, nil, false).(*Signature); ok {
 			x.mode = value
 			x.typ = sig
-			// TODO(gri) provide correct *declInfo here
-			check.later(nil, nil, sig, e.Body)
+			// Anonymous functions are considered part of the
+			// init expression/func declaration which contains
+			// them: use the current package-level declaration
+			// info.
+			check.later(nil, check.decl, sig, e.Body)
 		} else {
 			check.invalidAST(e.Pos(), "invalid function literal %s", e)
 			goto Error

go/types/stdlib_test.go

@@ -124,7 +124,7 @@ func TestStdtest(t *testing.T) {
 
 func TestStdfixed(t *testing.T) {
 	testTestDir(t, filepath.Join(runtime.GOROOT(), "test", "fixedbugs"),
-		"bug223.go", "bug413.go", "bug459.go", // TODO(gri) complete initialization checks
+		"bug459.go",                           // TODO(gri) complete initialization checks
 		"bug248.go", "bug302.go", "bug369.go", // complex test instructions - ignore
 		"issue3924.go", // incorrect test - see issue 6671
 		"issue4847.go", // TODO(gri) initialization cycle error not found

go/types/testdata/init0.src

@@ -44,3 +44,15 @@ var x6, x7 /* ERROR initialization cycle */ = f2()
 var x8 = x7
 func f2() (int, int) { return f3() + f3(), 0 }
 func f3() int { return x8 }
+
+// cycles via closures
+var x9 /* ERROR initialization cycle */ = func() int { return x9 }()
+
+var x10 /* ERROR initialization cycle */ = f4()
+
+func f4() int {
+	_ = func() {
+		_ = x10
+	}
+	return 0
+}