diff --git a/doc.go b/doc.go
new file mode 100644
index 0000000..5583947
--- /dev/null
+++ b/doc.go
@@ -0,0 +1,11 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package typeparams provides functions to work indirectly with type parameter
+// data stored in go/ast and go/types objects, while these API are guarded by a
+// build constraint.
+//
+// This package exists to make it easier for tools to work with generic code,
+// while also compiling against older Go versions.
+package typeparams
diff --git a/notypeparams.go b/notypeparams.go
new file mode 100644
index 0000000..3a0abc7
--- /dev/null
+++ b/notypeparams.go
@@ -0,0 +1,90 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !typeparams || !go1.17
+// +build !typeparams !go1.17
+
+package typeparams
+
+import (
+	"go/ast"
+	"go/types"
+)
+
+// NOTE: doc comments must be kept in sync with typeparams.go.
+
+// Enabled reports whether type parameters are enabled in the current build
+// environment.
+const Enabled = false
+
+// UnpackIndex extracts all index expressions from e. For non-generic code this
+// is always one expression: e.Index, but may be more than one expression for
+// generic type instantiation.
+func UnpackIndex(e *ast.IndexExpr) []ast.Expr {
+	return []ast.Expr{e.Index}
+}
+
+// IsListExpr reports whether n is an *ast.ListExpr, which is a new node type
+// introduced to hold type arguments for generic type instantiation.
+func IsListExpr(n ast.Node) bool {
+	return false
+}
+
+// ForTypeDecl extracts the (possibly nil) type parameter node list from n.
+func ForTypeDecl(*ast.TypeSpec) *ast.FieldList {
+	return nil
+}
+
+// ForFuncDecl extracts the (possibly nil) type parameter node list from n.
+func ForFuncDecl(*ast.FuncDecl) *ast.FieldList {
+	return nil
+}
+
+// ForSignature extracts the (possibly empty) type parameter object list from
+// sig.
+func ForSignature(*types.Signature) []*types.TypeName {
+	return nil
+}
+
+// HasTypeSet reports if iface has a type set.
+func HasTypeSet(*types.Interface) bool {
+	return false
+}
+
+// IsComparable reports if iface is the comparable interface.
+func IsComparable(*types.Interface) bool {
+	return false
+}
+
+// IsConstraint reports whether iface may only be used as a type parameter
+// constraint (i.e. has a type set or is the comparable interface).
+func IsConstraint(*types.Interface) bool {
+	return false
+}
+
+// ForNamed extracts the (possibly empty) type parameter object list from
+// named.
+func ForNamed(*types.Named) []*types.TypeName {
+	return nil
+}
+
+// NamedTArgs extracts the (possibly empty) type argument list from named.
+func NamedTArgs(*types.Named) []types.Type {
+	return nil
+}
+
+// InitInferred initializes info to record inferred type information.
+func InitInferred(*types.Info) {
+}
+
+// GetInferred extracts inferred type information from info for e.
+//
+// The expression e may have an inferred type if it is an *ast.IndexExpr
+// representing partial instantiation of a generic function type for which type
+// arguments have been inferred using constraint type inference, or if it is an
+// *ast.CallExpr for which type type arguments have be inferred using both
+// constraint type inference and function argument inference.
+func GetInferred(*types.Info, ast.Expr) ([]types.Type, *types.Signature) {
+	return nil, nil
+}
diff --git a/typeparams.go b/typeparams.go
new file mode 100644
index 0000000..624ce37
--- /dev/null
+++ b/typeparams.go
@@ -0,0 +1,105 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build typeparams && go1.17
+// +build typeparams,go1.17
+
+package typeparams
+
+import (
+	"go/ast"
+	"go/types"
+)
+
+// NOTE: doc comments must be kept in sync with notypeparams.go.
+
+// Enabled reports whether type parameters are enabled in the current build
+// environment.
+const Enabled = true
+
+// UnpackIndex extracts all index expressions from e. For non-generic code this
+// is always one expression: e.Index, but may be more than one expression for
+// generic type instantiation.
+func UnpackIndex(e *ast.IndexExpr) []ast.Expr {
+	if x, _ := e.Index.(*ast.ListExpr); x != nil {
+		return x.ElemList
+	}
+	if e.Index != nil {
+		return []ast.Expr{e.Index}
+	}
+	return nil
+}
+
+// IsListExpr reports whether n is an *ast.ListExpr, which is a new node type
+// introduced to hold type arguments for generic type instantiation.
+func IsListExpr(n ast.Node) bool {
+	_, ok := n.(*ast.ListExpr)
+	return ok
+}
+
+// ForTypeDecl extracts the (possibly nil) type parameter node list from n.
+func ForTypeDecl(n *ast.TypeSpec) *ast.FieldList {
+	return n.TParams
+}
+
+// ForFuncDecl extracts the (possibly nil) type parameter node list from n.
+func ForFuncDecl(n *ast.FuncDecl) *ast.FieldList {
+	if n.Type != nil {
+		return n.Type.TParams
+	}
+	return nil
+}
+
+// ForSignature extracts the (possibly empty) type parameter object list from
+// sig.
+func ForSignature(sig *types.Signature) []*types.TypeName {
+	return sig.TParams()
+}
+
+// HasTypeSet reports if iface has a type set.
+func HasTypeSet(iface *types.Interface) bool {
+	return iface.HasTypeList()
+}
+
+// IsComparable reports if iface is the comparable interface.
+func IsComparable(iface *types.Interface) bool {
+	return iface.IsComparable()
+}
+
+// IsConstraint reports whether iface may only be used as a type parameter
+// constraint (i.e. has a type set or is the comparable interface).
+func IsConstraint(iface *types.Interface) bool {
+	return iface.IsConstraint()
+}
+
+// ForNamed extracts the (possibly empty) type parameter object list from
+// named.
+func ForNamed(named *types.Named) []*types.TypeName {
+	return named.TParams()
+}
+
+// NamedTArgs extracts the (possibly empty) type argument list from named.
+func NamedTArgs(named *types.Named) []types.Type {
+	return named.TArgs()
+}
+
+// InitInferred initializes info to record inferred type information.
+func InitInferred(info *types.Info) {
+	info.Inferred = make(map[ast.Expr]types.Inferred)
+}
+
+// GetInferred extracts inferred type information from info for e.
+//
+// The expression e may have an inferred type if it is an *ast.IndexExpr
+// representing partial instantiation of a generic function type for which type
+// arguments have been inferred using constraint type inference, or if it is an
+// *ast.CallExpr for which type type arguments have be inferred using both
+// constraint type inference and function argument inference.
+func GetInferred(info *types.Info, e ast.Expr) ([]types.Type, *types.Signature) {
+	if info.Inferred == nil {
+		return nil, nil
+	}
+	inf := info.Inferred[e]
+	return inf.Targs, inf.Sig
+}