cmd/compile: allow embed into any byte slice type

Fixes #47735

Change-Id: Ia21ea9a67f36a3edfef1b299ae4f3b00c306cd68
Reviewed-on: https://go-review.googlesource.com/c/go/+/342851
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Alexander Rakoczy <alex@golang.org>

src/cmd/compile/internal/staticdata/embed.go

@@ -73,7 +73,7 @@ func embedKind(typ *types.Type) int {
 	if typ.Kind() == types.TSTRING {
 		return embedString
 	}
-	if typ.Sym() == nil && typ.IsSlice() && typ.Elem().Kind() == types.TUINT8 {
+	if typ.IsSlice() && typ.Elem().Kind() == types.TUINT8 {
 		return embedBytes
 	}
 	return embedUnknown

src/embed/internal/embedtest/embed_test.go

@@ -129,3 +129,43 @@ func TestUninitialized(t *testing.T) {
 		t.Errorf("in uninitialized embed.FS, . is not a directory")
 	}
 }
+
+var (
+	//go:embed "testdata/hello.txt"
+	helloT []T
+	//go:embed "testdata/hello.txt"
+	helloUint8 []uint8
+	//go:embed "testdata/hello.txt"
+	helloEUint8 []EmbedUint8
+	//go:embed "testdata/hello.txt"
+	helloBytes EmbedBytes
+	//go:embed "testdata/hello.txt"
+	helloString EmbedString
+)
+
+type T byte
+type EmbedUint8 uint8
+type EmbedBytes []byte
+type EmbedString string
+
+// golang.org/issue/47735
+func TestAliases(t *testing.T) {
+	all := testDirAll
+	want, e := all.ReadFile("testdata/hello.txt")
+	if e != nil {
+		t.Fatal("ReadFile:", e)
+	}
+	check := func(g interface{}) {
+		got := reflect.ValueOf(g)
+		for i := 0; i < got.Len(); i++ {
+			if byte(got.Index(i).Uint()) != want[i] {
+				t.Fatalf("got %v want %v", got.Bytes(), want)
+			}
+		}
+	}
+	check(helloT)
+	check(helloUint8)
+	check(helloEUint8)
+	check(helloBytes)
+	check(helloString)
+}