reflect: fix method type string

By picking up a spurious tFlagExtraStar, the method type was printing
as unc instead of func.

Updates #15673

Change-Id: I0c2c189b99bdd4caeb393693be7520b8e3f342bf
Reviewed-on: https://go-review.googlesource.com/23103Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/reflect/all_test.go

@@ -5782,3 +5782,24 @@ func TestMethodPkgPathReadable(t *testing.T) {
 		t.Errorf(`PkgPath=%q, want "reflect"`, m.PkgPath)
 	}
 }
+
+func TestTypeStrings(t *testing.T) {
+	type stringTest struct {
+		typ  Type
+		want string
+	}
+	stringTests := []stringTest{
+		{TypeOf(func(int) {}), "func(int)"},
+		{FuncOf([]Type{TypeOf(int(0))}, nil, false), "func(int)"},
+		{TypeOf(XM{}), "reflect_test.XM"},
+		{TypeOf(new(XM)), "*reflect_test.XM"},
+		{TypeOf(new(XM).String), "func() string"},
+		{TypeOf(new(XM)).Method(0).Type, "func(*reflect_test.XM) string"},
+	}
+
+	for i, test := range stringTests {
+		if got, want := test.typ.String(), test.want; got != want {
+			t.Errorf("type %d String()=%q, want %q", i, got, want)
+		}
+	}
+}

src/reflect/type.go

@@ -1985,6 +1985,7 @@ func FuncOf(in, out []Type, variadic bool) Type {
 	if len(args) > 50 {
 		panic("reflect.FuncOf does not support more than 50 arguments")
 	}
+	ft.tflag = 0
 	ft.hash = hash
 	ft.inCount = uint16(len(in))
 	ft.outCount = uint16(len(out))