internal/abi: clean up type of Kind and Type.Kind_

Currently, Type.Kind_ is a uint8, Kind is a uint, and some of the
abi.Kind consts are not of type Kind. Clean this all up by making Kind
a uint8, then making Type.Kind a Kind, and finally making all Kind
consts actually have type Kind. This has some ripple effect, but I
think all of the changes are improvements.

Change-Id: If39be74699c2cdb52bf0ad7092d392bc8fb68d15
Reviewed-on: https://go-review.googlesource.com/c/go/+/575579
Auto-Submit: Austin Clements <austin@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/cmd/link/internal/ld/data.go

@@ -1346,7 +1346,7 @@ func (p *GCProg) AddSym(s loader.Sym) {
 	}
 
 	sval := ldr.SymValue(s)
-	if decodetypeUsegcprog(p.ctxt.Arch, typData) == 0 {
+	if !decodetypeUsegcprog(p.ctxt.Arch, typData) {
 		// Copy pointers from mask into program.
 		mask := decodetypeGcmask(p.ctxt, typ)
 		for i := int64(0); i < nptr; i++ {

src/cmd/link/internal/ld/deadcode.go

@@ -512,7 +512,7 @@ func (d *deadcodePass) decodeIfaceMethod(ldr *loader.Loader, arch *sys.Arch, sym
 	if p == nil {
 		panic(fmt.Sprintf("missing symbol %q", ldr.SymName(symIdx)))
 	}
-	if abi.Kind(decodetypeKind(arch, p)&abi.KindMask) != abi.Interface {
+	if decodetypeKind(arch, p) != abi.Interface {
 		panic(fmt.Sprintf("symbol %q is not an interface", ldr.SymName(symIdx)))
 	}
 	relocs := ldr.Relocs(symIdx)
@@ -533,7 +533,7 @@ func (d *deadcodePass) decodetypeMethods(ldr *loader.Loader, arch *sys.Arch, sym
 		panic(fmt.Sprintf("no methods on %q", ldr.SymName(symIdx)))
 	}
 	off := commonsize(arch) // reflect.rtype
-	switch abi.Kind(decodetypeKind(arch, p) & abi.KindMask) {
+	switch decodetypeKind(arch, p) {
 	case abi.Struct: // reflect.structType
 		off += 4 * arch.PtrSize
 	case abi.Pointer: // reflect.ptrType

src/cmd/link/internal/ld/decodesym.go

@@ -37,13 +37,13 @@ func structfieldSize(arch *sys.Arch) int { return abi.StructFieldSize(arch.PtrSi
 func uncommonSize(arch *sys.Arch) int    { return int(abi.UncommonSize()) }           // runtime.uncommontype
 
 // Type.commonType.kind
-func decodetypeKind(arch *sys.Arch, p []byte) uint8 {
-	return p[2*arch.PtrSize+7] & abi.KindMask //  0x13 / 0x1f
+func decodetypeKind(arch *sys.Arch, p []byte) abi.Kind {
+	return abi.Kind(p[2*arch.PtrSize+7]) & abi.KindMask //  0x13 / 0x1f
 }
 
 // Type.commonType.kind
-func decodetypeUsegcprog(arch *sys.Arch, p []byte) uint8 {
-	return p[2*arch.PtrSize+7] & abi.KindGCProg //  0x13 / 0x1f
+func decodetypeUsegcprog(arch *sys.Arch, p []byte) bool {
+	return abi.Kind(p[2*arch.PtrSize+7])&abi.KindGCProg != 0 //  0x13 / 0x1f
 }
 
 // Type.commonType.size

src/cmd/link/internal/ld/dwarf.go

@@ -542,7 +542,7 @@ func (d *dwctxt) newtype(gotype loader.Sym) *dwarf.DWDie {
 	bytesize := decodetypeSize(d.arch, tdata)
 
 	var die, typedefdie *dwarf.DWDie
-	switch abi.Kind(kind) {
+	switch kind {
 	case abi.Bool:
 		die = d.newdie(&dwtypes, dwarf.DW_ABRV_BASETYPE, name)
 		newattr(die, dwarf.DW_AT_encoding, dwarf.DW_CLS_CONSTANT, dwarf.DW_ATE_boolean, 0)

src/internal/abi/type.go

@@ -72,9 +72,9 @@ const (
 
 const (
 	// TODO (khr, drchase) why aren't these in TFlag?  Investigate, fix if possible.
-	KindDirectIface = 1 << 5
-	KindGCProg      = 1 << 6 // Type.gc points to GC program
-	KindMask        = (1 << 5) - 1
+	KindDirectIface Kind = 1 << 5
+	KindGCProg      Kind = 1 << 6 // Type.gc points to GC program
+	KindMask        Kind = (1 << 5) - 1
 )
 
 // TFlag is used by a Type to signal what extra type information is
@@ -166,7 +166,7 @@ var kindNames = []string{
 	UnsafePointer: "unsafe.Pointer",
 }
 
-func (t *Type) Kind() Kind { return Kind(t.Kind_ & KindMask) }
+func (t *Type) Kind() Kind { return t.Kind_ & KindMask }
 
 func (t *Type) HasName() bool {
 	return t.TFlag&TFlagNamed != 0

src/internal/reflectlite/type.go

@@ -661,5 +661,5 @@ func toType(t *abi.Type) Type {
 
 // ifaceIndir reports whether t is stored indirectly in an interface value.
 func ifaceIndir(t *abi.Type) bool {
-	return t.Kind_&abi.KindDirectIface == 0
+	return abi.Kind(t.Kind_)&abi.KindDirectIface == 0
 }