[dev.typeparams] cmd/compile: introduce IsTypeParam() helper

better than Kind() == types.TTYPEPARAM

Change-Id: I4f35a177cd0cda3be615a92b7b2af1b5a60a3bbc
Reviewed-on: https://go-review.googlesource.com/c/go/+/325410
Trust: Keith Randall <khr@golang.org>
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>

src/cmd/compile/internal/noder/helpers.go

@@ -63,7 +63,7 @@ func FixValue(typ *types.Type, val constant.Value) constant.Value {
 	if !typ.IsUntyped() {
 		val = typecheck.DefaultLit(ir.NewBasicLit(src.NoXPos, val), typ).Val()
 	}
-	if typ.Kind() != types.TTYPEPARAM {
+	if !typ.IsTypeParam() {
 		ir.AssertValidTypeForConst(typ, val)
 	}
 	return val

src/cmd/compile/internal/typecheck/iexport.go

@@ -522,7 +522,7 @@ func (p *iexporter) doDecl(n *ir.Name) {
 		}
 
 	case ir.OTYPE:
-		if n.Type().Kind() == types.TTYPEPARAM && n.Type().Underlying() == n.Type() {
+		if n.Type().IsTypeParam() && n.Type().Underlying() == n.Type() {
 			// Even though it has local scope, a typeparam requires a
 			// declaration via its package and unique name, because it
 			// may be referenced within its type bound during its own
@@ -898,7 +898,7 @@ func (w *exportWriter) doTyp(t *types.Type) {
 	// The 't.Underlying() == t' check is to confirm this is a base typeparam
 	// type, rather than a defined type with typeparam underlying type, like:
 	// type orderedAbs[T any] T
-	if t.Kind() == types.TTYPEPARAM && t.Underlying() == t {
+	if t.IsTypeParam() && t.Underlying() == t {
 		assert(base.Flag.G > 0)
 		if s.Pkg == types.BuiltinPkg || s.Pkg == ir.Pkgs.Unsafe {
 			base.Fatalf("builtin type missing from typIndex: %v", t)
@@ -1042,7 +1042,7 @@ func (w *exportWriter) typeList(ts []*types.Type) {
 func (w *exportWriter) tparamList(fs []*types.Field) {
 	w.uint64(uint64(len(fs)))
 	for _, f := range fs {
-		if f.Type.Kind() != types.TTYPEPARAM {
+		if !f.Type.IsTypeParam() {
 			base.Fatalf("unexpected non-typeparam")
 		}
 		w.typ(f.Type)
@@ -1095,7 +1095,7 @@ func (w *exportWriter) value(typ *types.Type, v constant.Value) {
 	var kind constant.Kind
 	var valType *types.Type
 
-	if typ.Kind() == types.TTYPEPARAM {
+	if typ.IsTypeParam() {
 		// A constant will have a TYPEPARAM type if it appears in a place
 		// where it must match that typeparam type (e.g. in a binary
 		// operation with a variable of that typeparam type). If so, then

src/cmd/compile/internal/typecheck/iimport.go

@@ -415,7 +415,7 @@ func (p *importReader) value(typ *types.Type) constant.Value {
 	var kind constant.Kind
 	var valType *types.Type
 
-	if typ.Kind() == types.TTYPEPARAM {
+	if typ.IsTypeParam() {
 		// If a constant had a typeparam type, then we wrote out its
 		// actual constant kind as well.
 		kind = constant.Kind(p.int64())

src/cmd/compile/internal/typecheck/subr.go

@@ -984,7 +984,7 @@ func (ts *Tsubster) Typ(t *types.Type) *types.Type {
 		return t
 	}
 
-	if t.Kind() == types.TTYPEPARAM {
+	if t.IsTypeParam() {
 		for i, tp := range ts.Tparams {
 			if tp == t {
 				return ts.Targs[i]

src/cmd/compile/internal/types/type.go

@@ -1487,6 +1487,10 @@ func (t *Type) IsUnion() bool {
 	return t.kind == TUNION
 }
 
+func (t *Type) IsTypeParam() bool {
+	return t.kind == TTYPEPARAM
+}
+
 // IsEmptyInterface reports whether t is an empty interface type.
 func (t *Type) IsEmptyInterface() bool {
 	return t.IsInterface() && t.AllMethods().Len() == 0