debug/macho: make Type implements fmt.(Go)Stringer interfaces

Fixes #21436

Change-Id: I56f43e2852696c28edbcc772a54125a9a9c32497
Reviewed-on: https://go-review.googlesource.com/55262Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/debug/macho/file_test.go

@@ -217,3 +217,12 @@ func TestRelocTypeString(t *testing.T) {
 		t.Errorf("got %v, want %v", X86_64_RELOC_BRANCH.GoString(), "macho.X86_64_RELOC_BRANCH")
 	}
 }
+
+func TestTypeString(t *testing.T) {
+	if TypeExec.String() != "Exec" {
+		t.Errorf("got %v, want %v", TypeExec.String(), "Exec")
+	}
+	if TypeExec.GoString() != "macho.Exec" {
+		t.Errorf("got %v, want %v", TypeExec.GoString(), "macho.Exec")
+	}
+}

src/debug/macho/macho.go

@@ -41,6 +41,16 @@ const (
 	TypeBundle Type = 8
 )
 
+var typeStrings = []intName{
+	{uint32(TypeObj), "Obj"},
+	{uint32(TypeExec), "Exec"},
+	{uint32(TypeDylib), "Dylib"},
+	{uint32(TypeBundle), "Bundle"},
+}
+
+func (t Type) String() string   { return stringName(uint32(t), typeStrings, false) }
+func (t Type) GoString() string { return stringName(uint32(t), typeStrings, true) }
+
 // A Cpu is a Mach-O cpu type.
 type Cpu uint32