go/types: remove 1.18 APIs that have been replaced

Remove the Interface.IsConstraint, Signature.SetTypeParams, and
Signature.SetRecvTypeParams methods, as they have been replaced and
usage removed from x/tools.

Change-Id: I8786c3cf34e96ab5211cd8e7e6348e9ee792b843
Reviewed-on: https://go-review.googlesource.com/c/go/+/353570
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

src/go/types/call.go

@@ -112,7 +112,7 @@ func (check *Checker) callExpr(x *operand, call *ast.CallExpr) exprKind {
 					break
 				}
 				if t := asInterface(T); t != nil {
-					if t.IsConstraint() {
+					if !t.IsMethodSet() {
 						check.errorf(call, _Todo, "cannot use interface %s in conversion (contains type list or is comparable)", T)
 						break
 					}

src/go/types/decl.go

@@ -586,7 +586,7 @@ func (check *Checker) isImportedConstraint(typ Type) bool {
 		return false
 	}
 	u, _ := named.under().(*Interface)
-	return u != nil && u.IsConstraint()
+	return u != nil && !u.IsMethodSet()
 }
 
 func (check *Checker) typeDecl(obj *TypeName, tdecl *ast.TypeSpec, def *Named) {

src/go/types/interface.go

@@ -106,12 +106,7 @@ func (t *Interface) IsComparable() bool { return t.typeSet().IsComparable() }
 
 // IsMethodSet reports whether the interface t is fully described by its method
 // set.
-func (t *Interface) IsMethodSet() bool { return !t.typeSet().IsConstraint() }
+func (t *Interface) IsMethodSet() bool { return t.typeSet().IsMethodSet() }
-
-// IsConstraint reports whether interface t is not just a method set.
-//
-// TODO(rfindley): remove this method.
-func (t *Interface) IsConstraint() bool { return t.typeSet().IsConstraint() }
 
 // Complete computes the interface's type set. It must be called by users of
 // NewInterfaceType and NewInterface after the interface's embedded types are

src/go/types/signature.go

@@ -82,15 +82,9 @@ func (s *Signature) Recv() *Var { return s.recv }
 // TypeParams returns the type parameters of signature s, or nil.
 func (s *Signature) TypeParams() *TypeParamList { return s.tparams }
 
-// SetTypeParams sets the type parameters of signature s.
-func (s *Signature) SetTypeParams(tparams []*TypeParam) { s.tparams = bindTParams(tparams) }
-
 // RecvTypeParams returns the receiver type parameters of signature s, or nil.
 func (s *Signature) RecvTypeParams() *TypeParamList { return s.rparams }
 
-// SetRecvTypeParams sets the receiver type params of signature s.
-func (s *Signature) SetRecvTypeParams(rparams []*TypeParam) { s.rparams = bindTParams(rparams) }
-
 // Params returns the parameters of signature s, or nil.
 func (s *Signature) Params() *Tuple { return s.params }
 

src/go/types/typeset.go

@@ -28,8 +28,8 @@ func (s *_TypeSet) IsEmpty() bool { return s.terms.isEmpty() }
 // IsAll reports whether type set s is the set of all types (corresponding to the empty interface).
 func (s *_TypeSet) IsAll() bool { return !s.comparable && len(s.methods) == 0 && s.terms.isAll() }
 
-// IsConstraint reports whether type set s is not just a set of methods.
+// IsMethodSet reports whether the interface t is fully described by its method set.
-func (s *_TypeSet) IsConstraint() bool { return s.comparable || !s.terms.isAll() }
+func (s *_TypeSet) IsMethodSet() bool { return !s.comparable && s.terms.isAll() }
 
 // IsComparable reports whether each type in the set is comparable.
 func (s *_TypeSet) IsComparable() bool {

src/go/types/typexpr.go

@@ -139,7 +139,7 @@ func (check *Checker) varType(e ast.Expr) Type {
 	check.later(func() {
 		if t := asInterface(typ); t != nil {
 			tset := computeInterfaceTypeSet(check, e.Pos(), t) // TODO(gri) is this the correct position?
-			if tset.IsConstraint() {
+			if !tset.IsMethodSet() {
 				if tset.comparable {
 					check.softErrorf(e, _Todo, "interface is (or embeds) comparable")
 				} else {