[dev.typeparams] cmd/compile/internal/types2: (TypeParam) SetBound -> SetConstraint

This matches the accessor named Constraint, and any documentation we have so far.
Use iface instead of Bound internally to types2; keep Bound because of two external
uses but mark it as deprecated. Adjust clients.

Change-Id: Id1a2c2f28259a16082e875eee0534d46cf157336
Reviewed-on: https://go-review.googlesource.com/c/go/+/338196
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

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

@@ -384,7 +384,7 @@ func (r *importReader) obj(name string) {
 		id := ident{r.currPkg.Name(), name}
 		r.p.tparamIndex[id] = t
 
-		t.SetBound(r.typ())
+		t.SetConstraint(r.typ())
 
 	case 'V':
 		typ := r.typ()

src/cmd/compile/internal/noder/reader2.go

@@ -485,7 +485,7 @@ func (r *reader2) typeParamNames() []*types2.TypeName {
 	}
 
 	for i, bound := range r.dict.bounds {
-		r.dict.tparams[i].SetBound(r.p.typIdx(bound, r.dict))
+		r.dict.tparams[i].SetConstraint(r.p.typIdx(bound, r.dict))
 	}
 
 	return names

src/cmd/compile/internal/types2/builtins.go

@@ -817,7 +817,7 @@ func (check *Checker) applyTypeFunc(f func(Type) Type, x Type) Type {
 		// type and collect possible result types at the same time.
 		var rtypes []Type
 		var tildes []bool
-		if !tp.Bound().is(func(typ Type, tilde bool) bool {
+		if !tp.iface().is(func(typ Type, tilde bool) bool {
 			if r := f(typ); r != nil {
 				rtypes = append(rtypes, r)
 				tildes = append(tildes, tilde)

src/cmd/compile/internal/types2/call.go

@@ -479,7 +479,7 @@ func (check *Checker) selector(x *operand, e *syntax.SelectorExpr) {
 			var why string
 			if tpar := asTypeParam(x.typ); tpar != nil {
 				// Type parameter bounds don't specify fields, so don't mention "field".
-				if tname := tpar.Bound().obj; tname != nil {
+				if tname := tpar.iface().obj; tname != nil {
 					why = check.sprintf("interface %s has no method %s", tname.name, sel)
 				} else {
 					why = check.sprintf("type bound for %s has no method %s", x.typ, sel)

src/cmd/compile/internal/types2/instantiate.go

@@ -160,7 +160,7 @@ func (check *Checker) verify(pos syntax.Pos, tparams []*TypeName, targs []Type,
 // A suitable error is reported if the result is false.
 // TODO(gri) This should be a method of interfaces or type sets.
 func (check *Checker) satisfies(pos syntax.Pos, targ Type, tpar *TypeParam, smap *substMap) bool {
-	iface := tpar.Bound()
+	iface := tpar.iface()
 	if iface.Empty() {
 		return true // no type bound
 	}
@@ -174,7 +174,7 @@ func (check *Checker) satisfies(pos syntax.Pos, targ Type, tpar *TypeParam, smap
 	// if iface is comparable, targ must be comparable
 	// TODO(gri) the error messages needs to be better, here
 	if iface.IsComparable() && !Comparable(targ) {
-		if tpar := asTypeParam(targ); tpar != nil && tpar.Bound().typeSet().IsTop() {
+		if tpar := asTypeParam(targ); tpar != nil && tpar.iface().typeSet().IsTop() {
 			check.softErrorf(pos, "%s has no constraints", targ)
 			return false
 		}
@@ -219,7 +219,7 @@ func (check *Checker) satisfies(pos syntax.Pos, targ Type, tpar *TypeParam, smap
 	// If targ is itself a type parameter, each of its possible types, but at least one, must be in the
 	// list of iface types (i.e., the targ type list must be a non-empty subset of the iface types).
 	if targ := asTypeParam(targ); targ != nil {
-		targBound := targ.Bound()
+		targBound := targ.iface()
 		if targBound.typeSet().types == nil {
 			check.softErrorf(pos, "%s does not satisfy %s (%s has no type constraints)", targ, tpar.bound, targ)
 			return false

src/cmd/compile/internal/types2/lookup.go

@@ -186,7 +186,7 @@ func lookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (o
 				}
 
 			case *TypeParam:
-				if i, m := t.Bound().typeSet().LookupMethod(pkg, name); m != nil {
+				if i, m := t.iface().typeSet().LookupMethod(pkg, name); m != nil {
 					assert(m.typ != nil)
 					index = concat(e.index, i)
 					if obj != nil || e.multiples {

src/cmd/compile/internal/types2/predicates.go

@@ -113,7 +113,7 @@ func comparable(T Type, seen map[Type]bool) bool {
 	case *Array:
 		return comparable(t.elem, seen)
 	case *TypeParam:
-		return t.Bound().IsComparable()
+		return t.iface().IsComparable()
 	}
 	return false
 }

src/cmd/compile/internal/types2/type.go

@@ -56,7 +56,7 @@ func optype(typ Type) Type {
 		// for a type parameter list of the form:
 		// (type T interface { type T }).
 		// See also issue #39680.
-		if a := t.Bound().typeSet().types; a != nil {
+		if a := t.iface().typeSet().types; a != nil {
 			// If we have a union with a single entry, ignore
 			// any tilde because under(~t) == under(t).
 			if u, _ := a.(*Union); u != nil && u.NumTerms() == 1 {

src/cmd/compile/internal/types2/typeparam.go

@@ -72,21 +72,27 @@ func (t *TypeParam) Constraint() Type {
 	return t.bound
 }
 
-// Bound returns the underlying type of the type parameter's
-// constraint.
-// Deprecated for external use. Use Constraint instead.
-func (t *TypeParam) Bound() *Interface {
+// SetConstraint sets the type constraint for t.
+func (t *TypeParam) SetConstraint(bound Type) {
+	if bound == nil {
+		panic("types2.TypeParam.SetConstraint: bound must not be nil")
+	}
+	t.bound = bound
+}
+
+// iface returns the constraint interface of t.
+func (t *TypeParam) iface() *Interface {
 	if iface, _ := under(t.Constraint()).(*Interface); iface != nil {
 		return iface
 	}
 	return &emptyInterface
 }
 
-func (t *TypeParam) SetBound(bound Type) {
-	if bound == nil {
-		panic("types2.TypeParam.SetBound: bound must not be nil")
-	}
-	t.bound = bound
+// Bound returns the constraint interface of t.
+// Deprecated. Only here for the compiler.
+// TODO(gri) remove in favor of uses of Constraint.
+func (t *TypeParam) Bound() *Interface {
+	return t.iface()
 }
 
 func (t *TypeParam) Underlying() Type { return t }
@@ -132,5 +138,5 @@ func bindTParams(list []*TypeName) *TypeParams {
 // Implementation
 
 func (t *TypeParam) underIs(f func(Type) bool) bool {
-	return t.Bound().typeSet().underIs(f)
+	return t.iface().typeSet().underIs(f)
 }