case err := <-c:
		if err == nil {
			t.Error("error expected")
		} else if err != io.ErrNoProgress {
			t.Error("unexpected error:", err)
		}
	case <-time.After(time.Second):
		t.Error("test timed out (endless loop in ReadByte?)")
	}
}

// A StringReader delivers its data one string segment at a time via Read.
type StringReader struct {
	data []string
	step int
}

	T := pkg.Scope().Lookup("T").Type().(*Named)
	if n := T.TypeParams().Len(); n != 1 {
		t.Fatalf("expected 1 type parameter; found %d", n)
	}

	// instantiation should succeed (no endless recursion)
	// even with a nil *Checker
	res, err := Instantiate(nil, T, []Type{Typ[Int]}, false)
	if err != nil {
		t.Fatal(err)
	}

	// instantiated type should point to itself

	// This follows the structure of function identical in identity.go
	// with two exceptions.
	// 1. Symbols are compared more carefully because a <,=,> result is desired.
	// 2. Maps are treated specially to avoid endless recursion -- maps
	//    contain an internal data type not expressible in Go source code.
	if t == x {
		return CMPeq
	}
	if t == nil {
		return CMPlt
	}
	if x == nil {
		return CMPgt