Upstep Go dependencies (#340)

* Upstep Go dependencies

* tiny linter fix

* Tidy

18 files changed, 986 insertions, 199 deletions

diff --git a/vendor/golang.org/x/tools/go/gcexportdata/gcexportdata.go b/vendor/golang.org/x/tools/go/gcexportdata/gcexportdata.go
index fc8beea5d..cec819d64 100644
--- a/vendor/golang.org/x/tools/go/gcexportdata/gcexportdata.go
+++ b/vendor/golang.org/x/tools/go/gcexportdata/gcexportdata.go
@@ -50,11 +50,24 @@ func Find(importPath, srcDir string) (filename, path string) {
 // additional trailing data beyond the end of the export data.
 func NewReader(r io.Reader) (io.Reader, error) {
 	buf := bufio.NewReader(r)
-	_, err := gcimporter.FindExportData(buf)
-	// If we ever switch to a zip-like archive format with the ToC
-	// at the end, we can return the correct portion of export data,
-	// but for now we must return the entire rest of the file.
-	return buf, err
+	_, size, err := gcimporter.FindExportData(buf)
+	if err != nil {
+		return nil, err
+	}
+
+	if size >= 0 {
+		// We were given an archive and found the __.PKGDEF in it.
+		// This tells us the size of the export data, and we don't
+		// need to return the entire file.
+		return &io.LimitedReader{
+			R: buf,
+			N: size,
+		}, nil
+	} else {
+		// We were given an object file. As such, we don't know how large
+		// the export data is and must return the entire file.
+		return buf, nil
+	}
 }
 
 // Read reads export data from in, decodes it, and returns type
diff --git a/vendor/golang.org/x/tools/go/internal/gcimporter/bexport.go b/vendor/golang.org/x/tools/go/internal/gcimporter/bexport.go
index 072005af8..0a3cdb9a3 100644
--- a/vendor/golang.org/x/tools/go/internal/gcimporter/bexport.go
+++ b/vendor/golang.org/x/tools/go/internal/gcimporter/bexport.go
@@ -34,9 +34,6 @@ import (
 // (suspected) format errors, and whenever a change is made to the format.
 const debugFormat = false // default: false
 
-// If trace is set, debugging output is printed to std out.
-const trace = false // default: false
-
 // Current export format version. Increase with each format change.
 // Note: The latest binary (non-indexed) export format is at version 6.
 //       This exporter is still at level 4, but it doesn't matter since
diff --git a/vendor/golang.org/x/tools/go/internal/gcimporter/bimport.go b/vendor/golang.org/x/tools/go/internal/gcimporter/bimport.go
index b02312000..b85de0147 100644
--- a/vendor/golang.org/x/tools/go/internal/gcimporter/bimport.go
+++ b/vendor/golang.org/x/tools/go/internal/gcimporter/bimport.go
@@ -74,9 +74,10 @@ func BImportData(fset *token.FileSet, imports map[string]*types.Package, data []
 		pathList:   []string{""}, // empty string is mapped to 0
 		fake: fakeFileSet{
 			fset:  fset,
-			files: make(map[string]*token.File),
+			files: make(map[string]*fileInfo),
 		},
 	}
+	defer p.fake.setLines() // set lines for files in fset
 
 	// read version info
 	var versionstr string
@@ -338,37 +339,49 @@ func (p *importer) pos() token.Pos {
 // Synthesize a token.Pos
 type fakeFileSet struct {
 	fset  *token.FileSet
-	files map[string]*token.File
+	files map[string]*fileInfo
 }
 
+type fileInfo struct {
+	file     *token.File
+	lastline int
+}
+
+const maxlines = 64 * 1024
+
 func (s *fakeFileSet) pos(file string, line, column int) token.Pos {
 	// TODO(mdempsky): Make use of column.
 
-	// Since we don't know the set of needed file positions, we
-	// reserve maxlines positions per file.
-	const maxlines = 64 * 1024
+	// Since we don't know the set of needed file positions, we reserve maxlines
+	// positions per file. We delay calling token.File.SetLines until all
+	// positions have been calculated (by way of fakeFileSet.setLines), so that
+	// we can avoid setting unnecessary lines. See also golang/go#46586.
 	f := s.files[file]
 	if f == nil {
-		f = s.fset.AddFile(file, -1, maxlines)
+		f = &fileInfo{file: s.fset.AddFile(file, -1, maxlines)}
 		s.files[file] = f
-		// Allocate the fake linebreak indices on first use.
-		// TODO(adonovan): opt: save ~512KB using a more complex scheme?
-		fakeLinesOnce.Do(func() {
-			fakeLines = make([]int, maxlines)
-			for i := range fakeLines {
-				fakeLines[i] = i
-			}
-		})
-		f.SetLines(fakeLines)
 	}
-
 	if line > maxlines {
 		line = 1
 	}
+	if line > f.lastline {
+		f.lastline = line
+	}
 
-	// Treat the file as if it contained only newlines
-	// and column=1: use the line number as the offset.
-	return f.Pos(line - 1)
+	// Return a fake position assuming that f.file consists only of newlines.
+	return token.Pos(f.file.Base() + line - 1)
+}
+
+func (s *fakeFileSet) setLines() {
+	fakeLinesOnce.Do(func() {
+		fakeLines = make([]int, maxlines)
+		for i := range fakeLines {
+			fakeLines[i] = i
+		}
+	})
+	for _, f := range s.files {
+		f.file.SetLines(fakeLines[:f.lastline])
+	}
 }
 
 var (
diff --git a/vendor/golang.org/x/tools/go/internal/gcimporter/exportdata.go b/vendor/golang.org/x/tools/go/internal/gcimporter/exportdata.go
index f33dc5613..f6437feb1 100644
--- a/vendor/golang.org/x/tools/go/internal/gcimporter/exportdata.go
+++ b/vendor/golang.org/x/tools/go/internal/gcimporter/exportdata.go
@@ -16,7 +16,7 @@ import (
 	"strings"
 )
 
-func readGopackHeader(r *bufio.Reader) (name string, size int, err error) {
+func readGopackHeader(r *bufio.Reader) (name string, size int64, err error) {
 	// See $GOROOT/include/ar.h.
 	hdr := make([]byte, 16+12+6+6+8+10+2)
 	_, err = io.ReadFull(r, hdr)
@@ -28,7 +28,8 @@ func readGopackHeader(r *bufio.Reader) (name string, size int, err error) {
 		fmt.Printf("header: %s", hdr)
 	}
 	s := strings.TrimSpace(string(hdr[16+12+6+6+8:][:10]))
-	size, err = strconv.Atoi(s)
+	length, err := strconv.Atoi(s)
+	size = int64(length)
 	if err != nil || hdr[len(hdr)-2] != '`' || hdr[len(hdr)-1] != '\n' {
 		err = fmt.Errorf("invalid archive header")
 		return
@@ -42,8 +43,8 @@ func readGopackHeader(r *bufio.Reader) (name string, size int, err error) {
 // file by reading from it. The reader must be positioned at the
 // start of the file before calling this function. The hdr result
 // is the string before the export data, either "$$" or "$$B".
-//
-func FindExportData(r *bufio.Reader) (hdr string, err error) {
+// The size result is the length of the export data in bytes, or -1 if not known.
+func FindExportData(r *bufio.Reader) (hdr string, size int64, err error) {
 	// Read first line to make sure this is an object file.
 	line, err := r.ReadSlice('\n')
 	if err != nil {
@@ -54,7 +55,7 @@ func FindExportData(r *bufio.Reader) (hdr string, err error) {
 	if string(line) == "!<arch>\n" {
 		// Archive file. Scan to __.PKGDEF.
 		var name string
-		if name, _, err = readGopackHeader(r); err != nil {
+		if name, size, err = readGopackHeader(r); err != nil {
 			return
 		}
 
@@ -70,6 +71,7 @@ func FindExportData(r *bufio.Reader) (hdr string, err error) {
 			err = fmt.Errorf("can't find export data (%v)", err)
 			return
 		}
+		size -= int64(len(line))
 	}
 
 	// Now at __.PKGDEF in archive or still at beginning of file.
@@ -86,8 +88,12 @@ func FindExportData(r *bufio.Reader) (hdr string, err error) {
 			err = fmt.Errorf("can't find export data (%v)", err)
 			return
 		}
+		size -= int64(len(line))
 	}
 	hdr = string(line)
+	if size < 0 {
+		size = -1
+	}
 
 	return
 }
diff --git a/vendor/golang.org/x/tools/go/internal/gcimporter/gcimporter.go b/vendor/golang.org/x/tools/go/internal/gcimporter/gcimporter.go
index e8cba6b23..3ab66830d 100644
--- a/vendor/golang.org/x/tools/go/internal/gcimporter/gcimporter.go
+++ b/vendor/golang.org/x/tools/go/internal/gcimporter/gcimporter.go
@@ -29,8 +29,14 @@ import (
 	"text/scanner"
 )
 
-// debugging/development support
-const debug = false
+const (
+	// Enable debug during development: it adds some additional checks, and
+	// prevents errors from being recovered.
+	debug = false
+
+	// If trace is set, debugging output is printed to std out.
+	trace = false
+)
 
 var pkgExts = [...]string{".a", ".o"}
 
@@ -179,7 +185,7 @@ func Import(packages map[string]*types.Package, path, srcDir string, lookup func
 
 	var hdr string
 	buf := bufio.NewReader(rc)
-	if hdr, err = FindExportData(buf); err != nil {
+	if hdr, _, err = FindExportData(buf); err != nil {
 		return
 	}
 
diff --git a/vendor/golang.org/x/tools/go/internal/gcimporter/iexport.go b/vendor/golang.org/x/tools/go/internal/gcimporter/iexport.go
index be8b7459a..b4d51f352 100644
--- a/vendor/golang.org/x/tools/go/internal/gcimporter/iexport.go
+++ b/vendor/golang.org/x/tools/go/internal/gcimporter/iexport.go
@@ -11,6 +11,7 @@ package gcimporter
 import (
 	"bytes"
 	"encoding/binary"
+	"fmt"
 	"go/ast"
 	"go/constant"
 	"go/token"
@@ -19,6 +20,7 @@ import (
 	"math/big"
 	"reflect"
 	"sort"
+	"strings"
 
 	"golang.org/x/tools/internal/typeparams"
 )
@@ -33,15 +35,15 @@ const bundleVersion = 0
 // The package path of the top-level package will not be recorded,
 // so that calls to IImportData can override with a provided package path.
 func IExportData(out io.Writer, fset *token.FileSet, pkg *types.Package) error {
-	return iexportCommon(out, fset, false, []*types.Package{pkg})
+	return iexportCommon(out, fset, false, iexportVersion, []*types.Package{pkg})
 }
 
 // IExportBundle writes an indexed export bundle for pkgs to out.
 func IExportBundle(out io.Writer, fset *token.FileSet, pkgs []*types.Package) error {
-	return iexportCommon(out, fset, true, pkgs)
+	return iexportCommon(out, fset, true, iexportVersion, pkgs)
 }
 
-func iexportCommon(out io.Writer, fset *token.FileSet, bundle bool, pkgs []*types.Package) (err error) {
+func iexportCommon(out io.Writer, fset *token.FileSet, bundle bool, version int, pkgs []*types.Package) (err error) {
 	if !debug {
 		defer func() {
 			if e := recover(); e != nil {
@@ -57,9 +59,11 @@ func iexportCommon(out io.Writer, fset *token.FileSet, bundle bool, pkgs []*type
 
 	p := iexporter{
 		fset:        fset,
+		version:     version,
 		allPkgs:     map[*types.Package]bool{},
 		stringIndex: map[string]uint64{},
 		declIndex:   map[types.Object]uint64{},
+		tparamNames: map[types.Object]string{},
 		typIndex:    map[types.Type]uint64{},
 	}
 	if !bundle {
@@ -119,7 +123,7 @@ func iexportCommon(out io.Writer, fset *token.FileSet, bundle bool, pkgs []*type
 	if bundle {
 		hdr.uint64(bundleVersion)
 	}
-	hdr.uint64(iexportVersion)
+	hdr.uint64(uint64(p.version))
 	hdr.uint64(uint64(p.strings.Len()))
 	hdr.uint64(dataLen)
 
@@ -136,8 +140,12 @@ func iexportCommon(out io.Writer, fset *token.FileSet, bundle bool, pkgs []*type
 // non-compiler tools and includes a complete package description
 // (i.e., name and height).
 func (w *exportWriter) writeIndex(index map[types.Object]uint64) {
+	type pkgObj struct {
+		obj  types.Object
+		name string // qualified name; differs from obj.Name for type params
+	}
 	// Build a map from packages to objects from that package.
-	pkgObjs := map[*types.Package][]types.Object{}
+	pkgObjs := map[*types.Package][]pkgObj{}
 
 	// For the main index, make sure to include every package that
 	// we reference, even if we're not exporting (or reexporting)
@@ -150,7 +158,8 @@ func (w *exportWriter) writeIndex(index map[types.Object]uint64) {
 	}
 
 	for obj := range index {
-		pkgObjs[obj.Pkg()] = append(pkgObjs[obj.Pkg()], obj)
+		name := w.p.indexName(obj)
+		pkgObjs[obj.Pkg()] = append(pkgObjs[obj.Pkg()], pkgObj{obj, name})
 	}
 
 	var pkgs []*types.Package
@@ -158,7 +167,7 @@ func (w *exportWriter) writeIndex(index map[types.Object]uint64) {
 		pkgs = append(pkgs, pkg)
 
 		sort.Slice(objs, func(i, j int) bool {
-			return indexName(objs[i]) < indexName(objs[j])
+			return objs[i].name < objs[j].name
 		})
 	}
 
@@ -175,29 +184,26 @@ func (w *exportWriter) writeIndex(index map[types.Object]uint64) {
 		objs := pkgObjs[pkg]
 		w.uint64(uint64(len(objs)))
 		for _, obj := range objs {
-			w.string(indexName(obj))
-			w.uint64(index[obj])
+			w.string(obj.name)
+			w.uint64(index[obj.obj])
 		}
 	}
 }
 
 // indexName returns the 'indexed' name of an object. It differs from
-// obj.Name() only for type parameter names, where we include the subscripted
-// type parameter ID.
-//
-// TODO(rfindley): remove this once we no longer need subscripts.
-func indexName(obj types.Object) (res string) {
-	if _, ok := obj.(*types.TypeName); ok {
-		if tparam, ok := obj.Type().(*typeparams.TypeParam); ok {
-			return types.TypeString(tparam, func(*types.Package) string { return "" })
-		}
+// obj.Name() only for type parameter names, where the name is qualified by
+// owner.
+func (p *iexporter) indexName(obj types.Object) (res string) {
+	if name := p.tparamNames[obj]; name != "" {
+		return name
 	}
 	return obj.Name()
 }
 
 type iexporter struct {
-	fset *token.FileSet
-	out  *bytes.Buffer
+	fset    *token.FileSet
+	out     *bytes.Buffer
+	version int
 
 	localpkg *types.Package
 
@@ -211,9 +217,21 @@ type iexporter struct {
 	strings     intWriter
 	stringIndex map[string]uint64
 
-	data0     intWriter
-	declIndex map[types.Object]uint64
-	typIndex  map[types.Type]uint64
+	data0       intWriter
+	declIndex   map[types.Object]uint64
+	tparamNames map[types.Object]string // typeparam->qualified name
+	typIndex    map[types.Type]uint64
+
+	indent int // for tracing support
+}
+
+func (p *iexporter) trace(format string, args ...interface{}) {
+	if !trace {
+		// Call sites should also be guarded, but having this check here allows
+		// easily enabling/disabling debug trace statements.
+		return
+	}
+	fmt.Printf(strings.Repeat("..", p.indent)+format+"\n", args...)
 }
 
 // stringOff returns the offset of s within the string section.
@@ -239,7 +257,7 @@ func (p *iexporter) pushDecl(obj types.Object) {
 		return
 	}
 
-	p.declIndex[obj] = ^uint64(0) // mark n present in work queue
+	p.declIndex[obj] = ^uint64(0) // mark obj present in work queue
 	p.declTodo.pushTail(obj)
 }
 
@@ -262,6 +280,14 @@ func (w *exportWriter) exportPath(pkg *types.Package) string {
 }
 
 func (p *iexporter) doDecl(obj types.Object) {
+	if trace {
+		p.trace("exporting decl %v (%T)", obj, obj)
+		p.indent++
+		defer func() {
+			p.indent--
+			p.trace("=> %s", obj)
+		}()
+	}
 	w := p.newWriter()
 	w.setPkg(obj.Pkg(), false)
 
@@ -291,7 +317,7 @@ func (p *iexporter) doDecl(obj types.Object) {
 		// other places in the signature and function that they
 		// are used.
 		if tparams := typeparams.ForSignature(sig); tparams.Len() > 0 {
-			w.tparamList(tparams, obj.Pkg())
+			w.tparamList(obj, tparams, obj.Pkg())
 		}
 		w.signature(sig)
 
@@ -306,7 +332,15 @@ func (p *iexporter) doDecl(obj types.Object) {
 		if tparam, ok := t.(*typeparams.TypeParam); ok {
 			w.tag('P')
 			w.pos(obj.Pos())
-			w.typ(tparam.Constraint(), obj.Pkg())
+			constraint := tparam.Constraint()
+			if p.version >= iexportVersionGo1_18 {
+				implicit := false
+				if iface, _ := constraint.(*types.Interface); iface != nil {
+					implicit = typeparams.IsImplicit(iface)
+				}
+				w.bool(implicit)
+			}
+			w.typ(constraint, obj.Pkg())
 			break
 		}
 
@@ -331,7 +365,7 @@ func (p *iexporter) doDecl(obj types.Object) {
 		w.pos(obj.Pos())
 
 		if typeparams.ForNamed(named).Len() > 0 {
-			w.tparamList(typeparams.ForNamed(named), obj.Pkg())
+			w.tparamList(obj, typeparams.ForNamed(named), obj.Pkg())
 		}
 
 		underlying := obj.Type().Underlying()
@@ -348,6 +382,15 @@ func (p *iexporter) doDecl(obj types.Object) {
 			w.pos(m.Pos())
 			w.string(m.Name())
 			sig, _ := m.Type().(*types.Signature)
+
+			// Receiver type parameters are type arguments of the receiver type, so
+			// their name must be qualified before exporting recv.
+			rparams := typeparams.RecvTypeParams(sig)
+			for i := 0; i < rparams.Len(); i++ {
+				rparam := rparams.At(i)
+				name := obj.Name() + "." + m.Name() + "." + rparam.Obj().Name()
+				w.p.tparamNames[rparam.Obj()] = name
+			}
 			w.param(sig.Recv())
 			w.signature(sig)
 		}
@@ -364,7 +407,7 @@ func (w *exportWriter) tag(tag byte) {
 }
 
 func (w *exportWriter) pos(pos token.Pos) {
-	if iexportVersion >= iexportVersionPosCol {
+	if w.p.version >= iexportVersionPosCol {
 		w.posV1(pos)
 	} else {
 		w.posV0(pos)
@@ -447,9 +490,11 @@ func (w *exportWriter) pkg(pkg *types.Package) {
 }
 
 func (w *exportWriter) qualifiedIdent(obj types.Object) {
+	name := w.p.indexName(obj)
+
 	// Ensure any referenced declarations are written out too.
 	w.p.pushDecl(obj)
-	w.string(indexName(obj))
+	w.string(name)
 	w.pkg(obj.Pkg())
 }
 
@@ -483,6 +528,14 @@ func (w *exportWriter) startType(k itag) {
 }
 
 func (w *exportWriter) doTyp(t types.Type, pkg *types.Package) {
+	if trace {
+		w.p.trace("exporting type %s (%T)", t, t)
+		w.p.indent++
+		defer func() {
+			w.p.indent--
+			w.p.trace("=> %s", t)
+		}()
+	}
 	switch t := t.(type) {
 	case *types.Named:
 		if targs := typeparams.NamedTypeArgs(t); targs.Len() > 0 {
@@ -619,10 +672,14 @@ func (w *exportWriter) typeList(ts *typeparams.TypeList, pkg *types.Package) {
 	}
 }
 
-func (w *exportWriter) tparamList(list *typeparams.TypeParamList, pkg *types.Package) {
+func (w *exportWriter) tparamList(owner types.Object, list *typeparams.TypeParamList, pkg *types.Package) {
 	ll := uint64(list.Len())
 	w.uint64(ll)
 	for i := 0; i < list.Len(); i++ {
+		tparam := list.At(i)
+		// Qualify the type parameter name before exporting its type.
+		name := owner.Name() + "." + tparam.Obj().Name()
+		w.p.tparamNames[tparam.Obj()] = name
 		w.typ(list.At(i), pkg)
 	}
 }
@@ -643,6 +700,9 @@ func (w *exportWriter) param(obj types.Object) {
 
 func (w *exportWriter) value(typ types.Type, v constant.Value) {
 	w.typ(typ, nil)
+	if w.p.version >= iexportVersionGo1_18 {
+		w.int64(int64(v.Kind()))
+	}
 
 	switch b := typ.Underlying().(*types.Basic); b.Info() & types.IsConstType {
 	case types.IsBoolean:
@@ -832,7 +892,7 @@ func (w *exportWriter) localIdent(obj types.Object) {
 		return
 	}
 
-	name := indexName(obj)
+	name := obj.Name()
 	if name == "_" {
 		w.string("_")
 		return
diff --git a/vendor/golang.org/x/tools/go/internal/gcimporter/iimport.go b/vendor/golang.org/x/tools/go/internal/gcimporter/iimport.go
index 1fcc87e58..cdb332cd1 100644
--- a/vendor/golang.org/x/tools/go/internal/gcimporter/iimport.go
+++ b/vendor/golang.org/x/tools/go/internal/gcimporter/iimport.go
@@ -18,6 +18,7 @@ import (
 	"go/types"
 	"io"
 	"sort"
+	"strings"
 
 	"golang.org/x/tools/internal/typeparams"
 )
@@ -44,13 +45,20 @@ func (r *intReader) uint64() uint64 {
 }
 
 // Keep this in sync with constants in iexport.go.
+//
+// Temporarily, the x/tools importer accepts generic code at both version 1 and
+// 2. However, version 2 contains some breaking changes on top of version 1:
+//   - the 'implicit' bit is added to exported constraints
+//   - a 'kind' byte is added to constant values (not yet done)
+//
+// Once we've completed the bump to version 2 in the standard library, we'll
+// remove support for generics here at version 1.
 const (
 	iexportVersionGo1_11 = 0
 	iexportVersionPosCol = 1
+	iexportVersionGo1_18 = 2
 	// TODO: before release, change this back to 2.
 	iexportVersionGenerics = iexportVersionPosCol
-
-	iexportVersionCurrent = iexportVersionGenerics
 )
 
 type ident struct {
@@ -123,9 +131,9 @@ func iimportCommon(fset *token.FileSet, imports map[string]*types.Package, data
 
 	version = int64(r.uint64())
 	switch version {
-	case /* iexportVersionGenerics, */ iexportVersionPosCol, iexportVersionGo1_11:
+	case iexportVersionGo1_18, iexportVersionPosCol, iexportVersionGo1_11:
 	default:
-		if version > iexportVersionGenerics {
+		if version > iexportVersionGo1_18 {
 			errorf("unstable iexport format version %d, just rebuild compiler and std library", version)
 		} else {
 			errorf("unknown iexport format version %d", version)
@@ -141,9 +149,8 @@ func iimportCommon(fset *token.FileSet, imports map[string]*types.Package, data
 	r.Seek(sLen+dLen, io.SeekCurrent)
 
 	p := iimporter{
-		exportVersion: version,
-		ipath:         path,
-		version:       int(version),
+		version: int(version),
+		ipath:   path,
 
 		stringData:  stringData,
 		stringCache: make(map[uint64]string),
@@ -153,14 +160,15 @@ func iimportCommon(fset *token.FileSet, imports map[string]*types.Package, data
 		pkgIndex: make(map[*types.Package]map[string]uint64),
 		typCache: make(map[uint64]types.Type),
 		// Separate map for typeparams, keyed by their package and unique
-		// name (name with subscript).
+		// name.
 		tparamIndex: make(map[ident]types.Type),
 
 		fake: fakeFileSet{
 			fset:  fset,
-			files: make(map[string]*token.File),
+			files: make(map[string]*fileInfo),
 		},
 	}
+	defer p.fake.setLines() // set lines for files in fset
 
 	for i, pt := range predeclared() {
 		p.typCache[uint64(i)] = pt
@@ -246,9 +254,8 @@ func iimportCommon(fset *token.FileSet, imports map[string]*types.Package, data
 }
 
 type iimporter struct {
-	exportVersion int64
-	ipath         string
-	version       int
+	version int
+	ipath   string
 
 	stringData  []byte
 	stringCache map[uint64]string
@@ -261,9 +268,28 @@ type iimporter struct {
 
 	fake          fakeFileSet
 	interfaceList []*types.Interface
+
+	indent int // for tracing support
+}
+
+func (p *iimporter) trace(format string, args ...interface{}) {
+	if !trace {
+		// Call sites should also be guarded, but having this check here allows
+		// easily enabling/disabling debug trace statements.
+		return
+	}
+	fmt.Printf(strings.Repeat("..", p.indent)+format+"\n", args...)
 }
 
 func (p *iimporter) doDecl(pkg *types.Package, name string) {
+	if debug {
+		p.trace("import decl %s", name)
+		p.indent++
+		defer func() {
+			p.indent--
+			p.trace("=> %s", name)
+		}()
+	}
 	// See if we've already imported this declaration.
 	if obj := pkg.Scope().Lookup(name); obj != nil {
 		return
@@ -305,7 +331,7 @@ func (p *iimporter) pkgAt(off uint64) *types.Package {
 }
 
 func (p *iimporter) typAt(off uint64, base *types.Named) types.Type {
-	if t, ok := p.typCache[off]; ok && (base == nil || !isInterface(t)) {
+	if t, ok := p.typCache[off]; ok && canReuse(base, t) {
 		return t
 	}
 
@@ -317,12 +343,30 @@ func (p *iimporter) typAt(off uint64, base *types.Named) types.Type {
 	r.declReader.Reset(p.declData[off-predeclReserved:])
 	t := r.doType(base)
 
-	if base == nil || !isInterface(t) {
+	if canReuse(base, t) {
 		p.typCache[off] = t
 	}
 	return t
 }
 
+// canReuse reports whether the type rhs on the RHS of the declaration for def
+// may be re-used.
+//
+// Specifically, if def is non-nil and rhs is an interface type with methods, it
+// may not be re-used because we have a convention of setting the receiver type
+// for interface methods to def.
+func canReuse(def *types.Named, rhs types.Type) bool {
+	if def == nil {
+		return true
+	}
+	iface, _ := rhs.(*types.Interface)
+	if iface == nil {
+		return true
+	}
+	// Don't use iface.Empty() here as iface may not be complete.
+	return iface.NumEmbeddeds() == 0 && iface.NumExplicitMethods() == 0
+}
+
 type importReader struct {
 	p          *iimporter
 	declReader bytes.Reader
@@ -352,8 +396,7 @@ func (r *importReader) obj(name string) {
 		if tag == 'G' {
 			tparams = r.tparamList()
 		}
-		sig := r.signature(nil)
-		typeparams.SetForSignature(sig, tparams)
+		sig := r.signature(nil, nil, tparams)
 		r.declare(types.NewFunc(pos, r.currPkg, name, sig))
 
 	case 'T', 'U':
@@ -377,23 +420,21 @@ func (r *importReader) obj(name string) {
 				mpos := r.pos()
 				mname := r.ident()
 				recv := r.param()
-				msig := r.signature(recv)
 
 				// If the receiver has any targs, set those as the
 				// rparams of the method (since those are the
 				// typeparams being used in the method sig/body).
-				targs := typeparams.NamedTypeArgs(baseType(msig.Recv().Type()))
+				base := baseType(recv.Type())
+				assert(base != nil)
+				targs := typeparams.NamedTypeArgs(base)
+				var rparams []*typeparams.TypeParam
 				if targs.Len() > 0 {
-					rparams := make([]*typeparams.TypeParam, targs.Len())
+					rparams = make([]*typeparams.TypeParam, targs.Len())
 					for i := range rparams {
-						// TODO(rfindley): this is less tolerant than the standard library
-						// go/internal/gcimporter, which calls under(...) and is tolerant
-						// of nil rparams. Bring them in sync by making the standard
-						// library importer stricter.
 						rparams[i] = targs.At(i).(*typeparams.TypeParam)
 					}
-					typeparams.SetRecvTypeParams(msig, rparams)
 				}
+				msig := r.signature(recv, rparams, nil)
 
 				named.AddMethod(types.NewFunc(mpos, r.currPkg, mname, msig))
 			}
@@ -403,25 +444,35 @@ func (r *importReader) obj(name string) {
 		// We need to "declare" a typeparam in order to have a name that
 		// can be referenced recursively (if needed) in the type param's
 		// bound.
-		if r.p.exportVersion < iexportVersionGenerics {
+		if r.p.version < iexportVersionGenerics {
 			errorf("unexpected type param type")
 		}
-		name0, sub := parseSubscript(name)
+		// Remove the "path" from the type param name that makes it unique
+		ix := strings.LastIndex(name, ".")
+		if ix < 0 {
+			errorf("missing path for type param")
+		}
+		name0 := name[ix+1:]
 		tn := types.NewTypeName(pos, r.currPkg, name0, nil)
 		t := typeparams.NewTypeParam(tn, nil)
-		if sub == 0 {
-			errorf("name %q missing subscript", name)
-		}
-
-		// TODO(rfindley): can we use a different, stable ID?
-		// t.SetId(sub)
 
 		// To handle recursive references to the typeparam within its
 		// bound, save the partial type in tparamIndex before reading the bounds.
 		id := ident{r.currPkg.Name(), name}
 		r.p.tparamIndex[id] = t
-
-		typeparams.SetTypeParamConstraint(t, r.typ())
+		var implicit bool
+		if r.p.version >= iexportVersionGo1_18 {
+			implicit = r.bool()
+		}
+		constraint := r.typ()
+		if implicit {
+			iface, _ := constraint.(*types.Interface)
+			if iface == nil {
+				errorf("non-interface constraint marked implicit")
+			}
+			typeparams.MarkImplicit(iface)
+		}
+		typeparams.SetTypeParamConstraint(t, constraint)
 
 	case 'V':
 		typ := r.typ()
@@ -439,6 +490,10 @@ func (r *importReader) declare(obj types.Object) {
 
 func (r *importReader) value() (typ types.Type, val constant.Value) {
 	typ = r.typ()
+	if r.p.version >= iexportVersionGo1_18 {
+		// TODO: add support for using the kind.
+		_ = constant.Kind(r.int64())
+	}
 
 	switch b := typ.Underlying().(*types.Basic); b.Info() & types.IsConstType {
 	case types.IsBoolean:
@@ -581,7 +636,7 @@ func (r *importReader) qualifiedIdent() (*types.Package, string) {
 }
 
 func (r *importReader) pos() token.Pos {
-	if r.p.exportVersion >= iexportVersionPosCol {
+	if r.p.version >= iexportVersionPosCol {
 		r.posv1()
 	} else {
 		r.posv0()
@@ -629,8 +684,17 @@ func isInterface(t types.Type) bool {
 func (r *importReader) pkg() *types.Package { return r.p.pkgAt(r.uint64()) }
 func (r *importReader) string() string      { return r.p.stringAt(r.uint64()) }
 
-func (r *importReader) doType(base *types.Named) types.Type {
-	switch k := r.kind(); k {
+func (r *importReader) doType(base *types.Named) (res types.Type) {
+	k := r.kind()
+	if debug {
+		r.p.trace("importing type %d (base: %s)", k, base)
+		r.p.indent++
+		defer func() {
+			r.p.indent--
+			r.p.trace("=> %s", res)
+		}()
+	}
+	switch k {
 	default:
 		errorf("unexpected kind tag in %q: %v", r.p.ipath, k)
 		return nil
@@ -653,7 +717,7 @@ func (r *importReader) doType(base *types.Named) types.Type {
 		return types.NewMap(r.typ(), r.typ())
 	case signatureType:
 		r.currPkg = r.pkg()
-		return r.signature(nil)
+		return r.signature(nil, nil, nil)
 
 	case structType:
 		r.currPkg = r.pkg()
@@ -693,7 +757,7 @@ func (r *importReader) doType(base *types.Named) types.Type {
 				recv = types.NewVar(token.NoPos, r.currPkg, "", base)
 			}
 
-			msig := r.signature(recv)
+			msig := r.signature(recv, nil, nil)
 			methods[i] = types.NewFunc(mpos, r.currPkg, mname, msig)
 		}
 
@@ -702,7 +766,7 @@ func (r *importReader) doType(base *types.Named) types.Type {
 		return typ
 
 	case typeParamType:
-		if r.p.exportVersion < iexportVersionGenerics {
+		if r.p.version < iexportVersionGenerics {
 			errorf("unexpected type param type")
 		}
 		pkg, name := r.qualifiedIdent()
@@ -716,7 +780,7 @@ func (r *importReader) doType(base *types.Named) types.Type {
 		return r.p.tparamIndex[id]
 
 	case instanceType:
-		if r.p.exportVersion < iexportVersionGenerics {
+		if r.p.version < iexportVersionGenerics {
 			errorf("unexpected instantiation type")
 		}
 		// pos does not matter for instances: they are positioned on the original
@@ -735,7 +799,7 @@ func (r *importReader) doType(base *types.Named) types.Type {
 		return t
 
 	case unionType:
-		if r.p.exportVersion < iexportVersionGenerics {
+		if r.p.version < iexportVersionGenerics {
 			errorf("unexpected instantiation type")
 		}
 		terms := make([]*typeparams.Term, r.uint64())
@@ -750,11 +814,11 @@ func (r *importReader) kind() itag {
 	return itag(r.uint64())
 }
 
-func (r *importReader) signature(recv *types.Var) *types.Signature {
+func (r *importReader) signature(recv *types.Var, rparams []*typeparams.TypeParam, tparams []*typeparams.TypeParam) *types.Signature {
 	params := r.paramList()
 	results := r.paramList()
 	variadic := params.Len() > 0 && r.bool()
-	return types.NewSignature(recv, params, results, variadic)
+	return typeparams.NewSignatureType(recv, rparams, tparams, params, results, variadic)
 }
 
 func (r *importReader) tparamList() []*typeparams.TypeParam {
@@ -823,23 +887,3 @@ func baseType(typ types.Type) *types.Named {
 	n, _ := typ.(*types.Named)
 	return n
 }
-
-func parseSubscript(name string) (string, uint64) {
-	// Extract the subscript value from the type param name. We export
-	// and import the subscript value, so that all type params have
-	// unique names.
-	sub := uint64(0)
-	startsub := -1
-	for i, r := range name {
-		if '₀' <= r && r < '₀'+10 {
-			if startsub == -1 {
-				startsub = i
-			}
-			sub = sub*10 + uint64(r-'₀')
-		}
-	}
-	if startsub >= 0 {
-		name = name[:startsub]
-	}
-	return name, sub
-}
diff --git a/vendor/golang.org/x/tools/go/internal/gcimporter/support_go117.go b/vendor/golang.org/x/tools/go/internal/gcimporter/support_go117.go
index 817a147ef..d892273ef 100644
--- a/vendor/golang.org/x/tools/go/internal/gcimporter/support_go117.go
+++ b/vendor/golang.org/x/tools/go/internal/gcimporter/support_go117.go
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !typeparams || !go1.18
-// +build !typeparams !go1.18
+//go:build !go1.18
+// +build !go1.18
 
 package gcimporter
 
diff --git a/vendor/golang.org/x/tools/go/internal/gcimporter/support_go118.go b/vendor/golang.org/x/tools/go/internal/gcimporter/support_go118.go
index e6b81fc50..a99384323 100644
--- a/vendor/golang.org/x/tools/go/internal/gcimporter/support_go118.go
+++ b/vendor/golang.org/x/tools/go/internal/gcimporter/support_go118.go
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build typeparams && go1.18
-// +build typeparams,go1.18
+//go:build go1.18
+// +build go1.18
 
 package gcimporter
 
@@ -16,5 +16,8 @@ func additionalPredeclared() []types.Type {
 	return []types.Type{
 		// comparable
 		types.Universe.Lookup("comparable").Type(),
+
+		// any
+		types.Universe.Lookup("any").Type(),
 	}
 }
diff --git a/vendor/golang.org/x/tools/go/packages/packages.go b/vendor/golang.org/x/tools/go/packages/packages.go
index 8a1a2d681..d545b1375 100644
--- a/vendor/golang.org/x/tools/go/packages/packages.go
+++ b/vendor/golang.org/x/tools/go/packages/packages.go
@@ -26,6 +26,7 @@ import (
 	"golang.org/x/tools/go/gcexportdata"
 	"golang.org/x/tools/internal/gocommand"
 	"golang.org/x/tools/internal/packagesinternal"
+	"golang.org/x/tools/internal/typeparams"
 	"golang.org/x/tools/internal/typesinternal"
 )
 
@@ -910,6 +911,7 @@ func (ld *loader) loadPackage(lpkg *loaderPackage) {
 		Scopes:     make(map[ast.Node]*types.Scope),
 		Selections: make(map[*ast.SelectorExpr]*types.Selection),
 	}
+	typeparams.InitInstanceInfo(lpkg.TypesInfo)
 	lpkg.TypesSizes = ld.sizes
 
 	importer := importerFunc(func(path string) (*types.Package, error) {
diff --git a/vendor/golang.org/x/tools/internal/typeparams/common.go b/vendor/golang.org/x/tools/internal/typeparams/common.go
index 9fc6b4beb..961d036fd 100644
--- a/vendor/golang.org/x/tools/internal/typeparams/common.go
+++ b/vendor/golang.org/x/tools/internal/typeparams/common.go
@@ -13,6 +13,7 @@ package typeparams
 import (
 	"go/ast"
 	"go/token"
+	"go/types"
 )
 
 // A IndexExprData holds data from both ast.IndexExpr and the new
@@ -23,3 +24,9 @@ type IndexExprData struct {
 	Indices []ast.Expr // index expressions
 	Rbrack  token.Pos  // position of "]"
 }
+
+// IsTypeParam reports whether t is a type parameter.
+func IsTypeParam(t types.Type) bool {
+	_, ok := t.(*TypeParam)
+	return ok
+}
diff --git a/vendor/golang.org/x/tools/internal/typeparams/enabled_go117.go b/vendor/golang.org/x/tools/internal/typeparams/enabled_go117.go
index 72d010e51..18212390e 100644
--- a/vendor/golang.org/x/tools/internal/typeparams/enabled_go117.go
+++ b/vendor/golang.org/x/tools/internal/typeparams/enabled_go117.go
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !typeparams || !go1.18
-// +build !typeparams !go1.18
+//go:build !go1.18
+// +build !go1.18
 
 package typeparams
 
diff --git a/vendor/golang.org/x/tools/internal/typeparams/enabled_go118.go b/vendor/golang.org/x/tools/internal/typeparams/enabled_go118.go
index 642fc8ee2..d67148823 100644
--- a/vendor/golang.org/x/tools/internal/typeparams/enabled_go118.go
+++ b/vendor/golang.org/x/tools/internal/typeparams/enabled_go118.go
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build typeparams && go1.18
-// +build typeparams,go1.18
+//go:build go1.18
+// +build go1.18
 
 package typeparams
 
diff --git a/vendor/golang.org/x/tools/internal/typeparams/normalize.go b/vendor/golang.org/x/tools/internal/typeparams/normalize.go
new file mode 100644
index 000000000..090f142a5
--- /dev/null
+++ b/vendor/golang.org/x/tools/internal/typeparams/normalize.go
@@ -0,0 +1,216 @@
+// 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
+
+import (
+	"errors"
+	"fmt"
+	"go/types"
+	"os"
+	"strings"
+)
+
+//go:generate go run copytermlist.go
+
+const debug = false
+
+var ErrEmptyTypeSet = errors.New("empty type set")
+
+// StructuralTerms returns a slice of terms representing the normalized
+// structural type restrictions of a type parameter, if any.
+//
+// Structural type restrictions of a type parameter are created via
+// non-interface types embedded in its constraint interface (directly, or via a
+// chain of interface embeddings). For example, in the declaration
+//  type T[P interface{~int; m()}] int
+// the structural restriction of the type parameter P is ~int.
+//
+// With interface embedding and unions, the specification of structural type
+// restrictions may be arbitrarily complex. For example, consider the
+// following:
+//
+//  type A interface{ ~string|~[]byte }
+//
+//  type B interface{ int|string }
+//
+//  type C interface { ~string|~int }
+//
+//  type T[P interface{ A|B; C }] int
+//
+// In this example, the structural type restriction of P is ~string|int: A|B
+// expands to ~string|~[]byte|int|string, which reduces to ~string|~[]byte|int,
+// which when intersected with C (~string|~int) yields ~string|int.
+//
+// StructuralTerms computes these expansions and reductions, producing a
+// "normalized" form of the embeddings. A structural restriction is normalized
+// if it is a single union containing no interface terms, and is minimal in the
+// sense that removing any term changes the set of types satisfying the
+// constraint. It is left as a proof for the reader that, modulo sorting, there
+// is exactly one such normalized form.
+//
+// Because the minimal representation always takes this form, StructuralTerms
+// returns a slice of tilde terms corresponding to the terms of the union in
+// the normalized structural restriction. An error is returned if the
+// constraint interface is invalid, exceeds complexity bounds, or has an empty
+// type set. In the latter case, StructuralTerms returns ErrEmptyTypeSet.
+//
+// StructuralTerms makes no guarantees about the order of terms, except that it
+// is deterministic.
+func StructuralTerms(tparam *TypeParam) ([]*Term, error) {
+	constraint := tparam.Constraint()
+	if constraint == nil {
+		return nil, fmt.Errorf("%s has nil constraint", tparam)
+	}
+	iface, _ := constraint.Underlying().(*types.Interface)
+	if iface == nil {
+		return nil, fmt.Errorf("constraint is %T, not *types.Interface", constraint.Underlying())
+	}
+	return InterfaceTermSet(iface)
+}
+
+// InterfaceTermSet computes the normalized terms for a constraint interface,
+// returning an error if the term set cannot be computed or is empty. In the
+// latter case, the error will be ErrEmptyTypeSet.
+//
+// See the documentation of StructuralTerms for more information on
+// normalization.
+func InterfaceTermSet(iface *types.Interface) ([]*Term, error) {
+	return computeTermSet(iface)
+}
+
+// UnionTermSet computes the normalized terms for a union, returning an error
+// if the term set cannot be computed or is empty. In the latter case, the
+// error will be ErrEmptyTypeSet.
+//
+// See the documentation of StructuralTerms for more information on
+// normalization.
+func UnionTermSet(union *Union) ([]*Term, error) {
+	return computeTermSet(union)
+}
+
+func computeTermSet(typ types.Type) ([]*Term, error) {
+	tset, err := computeTermSetInternal(typ, make(map[types.Type]*termSet), 0)
+	if err != nil {
+		return nil, err
+	}
+	if tset.terms.isEmpty() {
+		return nil, ErrEmptyTypeSet
+	}
+	if tset.terms.isAll() {
+		return nil, nil
+	}
+	var terms []*Term
+	for _, term := range tset.terms {
+		terms = append(terms, NewTerm(term.tilde, term.typ))
+	}
+	return terms, nil
+}
+
+// A termSet holds the normalized set of terms for a given type.
+//
+// The name termSet is intentionally distinct from 'type set': a type set is
+// all types that implement a type (and includes method restrictions), whereas
+// a term set just represents the structural restrictions on a type.
+type termSet struct {
+	complete bool
+	terms    termlist
+}
+
+func indentf(depth int, format string, args ...interface{}) {
+	fmt.Fprintf(os.Stderr, strings.Repeat(".", depth)+format+"\n", args...)
+}
+
+func computeTermSetInternal(t types.Type, seen map[types.Type]*termSet, depth int) (res *termSet, err error) {
+	if t == nil {
+		panic("nil type")
+	}
+
+	if debug {
+		indentf(depth, "%s", t.String())
+		defer func() {
+			if err != nil {
+				indentf(depth, "=> %s", err)
+			} else {
+				indentf(depth, "=> %s", res.terms.String())
+			}
+		}()
+	}
+
+	const maxTermCount = 100
+	if tset, ok := seen[t]; ok {
+		if !tset.complete {
+			return nil, fmt.Errorf("cycle detected in the declaration of %s", t)
+		}
+		return tset, nil
+	}
+
+	// Mark the current type as seen to avoid infinite recursion.
+	tset := new(termSet)
+	defer func() {
+		tset.complete = true
+	}()
+	seen[t] = tset
+
+	switch u := t.Underlying().(type) {
+	case *types.Interface:
+		// The term set of an interface is the intersection of the term sets of its
+		// embedded types.
+		tset.terms = allTermlist
+		for i := 0; i < u.NumEmbeddeds(); i++ {
+			embedded := u.EmbeddedType(i)
+			if _, ok := embedded.Underlying().(*TypeParam); ok {
+				return nil, fmt.Errorf("invalid embedded type %T", embedded)
+			}
+			tset2, err := computeTermSetInternal(embedded, seen, depth+1)
+			if err != nil {
+				return nil, err
+			}
+			tset.terms = tset.terms.intersect(tset2.terms)
+		}
+	case *Union:
+		// The term set of a union is the union of term sets of its terms.
+		tset.terms = nil
+		for i := 0; i < u.Len(); i++ {
+			t := u.Term(i)
+			var terms termlist
+			switch t.Type().Underlying().(type) {
+			case *types.Interface:
+				tset2, err := computeTermSetInternal(t.Type(), seen, depth+1)
+				if err != nil {
+					return nil, err
+				}
+				terms = tset2.terms
+			case *TypeParam, *Union:
+				// A stand-alone type parameter or union is not permitted as union
+				// term.
+				return nil, fmt.Errorf("invalid union term %T", t)
+			default:
+				if t.Type() == types.Typ[types.Invalid] {
+					continue
+				}
+				terms = termlist{{t.Tilde(), t.Type()}}
+			}
+			tset.terms = tset.terms.union(terms)
+			if len(tset.terms) > maxTermCount {
+				return nil, fmt.Errorf("exceeded max term count %d", maxTermCount)
+			}
+		}
+	case *TypeParam:
+		panic("unreachable")
+	default:
+		// For all other types, the term set is just a single non-tilde term
+		// holding the type itself.
+		if u != types.Typ[types.Invalid] {
+			tset.terms = termlist{{false, t}}
+		}
+	}
+	return tset, nil
+}
+
+// under is a facade for the go/types internal function of the same name. It is
+// used by typeterm.go.
+func under(t types.Type) types.Type {
+	return t.Underlying()
+}
diff --git a/vendor/golang.org/x/tools/internal/typeparams/termlist.go b/vendor/golang.org/x/tools/internal/typeparams/termlist.go
new file mode 100644
index 000000000..10857d504
--- /dev/null
+++ b/vendor/golang.org/x/tools/internal/typeparams/termlist.go
@@ -0,0 +1,172 @@
+// 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.
+
+// Code generated by copytermlist.go DO NOT EDIT.
+
+package typeparams
+
+import (
+	"bytes"
+	"go/types"
+)
+
+// A termlist represents the type set represented by the union
+// t1 ∪ y2 ∪ ... tn of the type sets of the terms t1 to tn.
+// A termlist is in normal form if all terms are disjoint.
+// termlist operations don't require the operands to be in
+// normal form.
+type termlist []*term
+
+// allTermlist represents the set of all types.
+// It is in normal form.
+var allTermlist = termlist{new(term)}
+
+// String prints the termlist exactly (without normalization).
+func (xl termlist) String() string {
+	if len(xl) == 0 {
+		return "∅"
+	}
+	var buf bytes.Buffer
+	for i, x := range xl {
+		if i > 0 {
+			buf.WriteString(" ∪ ")
+		}
+		buf.WriteString(x.String())
+	}
+	return buf.String()
+}
+
+// isEmpty reports whether the termlist xl represents the empty set of types.
+func (xl termlist) isEmpty() bool {
+	// If there's a non-nil term, the entire list is not empty.
+	// If the termlist is in normal form, this requires at most
+	// one iteration.
+	for _, x := range xl {
+		if x != nil {
+			return false
+		}
+	}
+	return true
+}
+
+// isAll reports whether the termlist xl represents the set of all types.
+func (xl termlist) isAll() bool {
+	// If there's a 𝓤 term, the entire list is 𝓤.
+	// If the termlist is in normal form, this requires at most
+	// one iteration.
+	for _, x := range xl {
+		if x != nil && x.typ == nil {
+			return true
+		}
+	}
+	return false
+}
+
+// norm returns the normal form of xl.
+func (xl termlist) norm() termlist {
+	// Quadratic algorithm, but good enough for now.
+	// TODO(gri) fix asymptotic performance
+	used := make([]bool, len(xl))
+	var rl termlist
+	for i, xi := range xl {
+		if xi == nil || used[i] {
+			continue
+		}
+		for j := i + 1; j < len(xl); j++ {
+			xj := xl[j]
+			if xj == nil || used[j] {
+				continue
+			}
+			if u1, u2 := xi.union(xj); u2 == nil {
+				// If we encounter a 𝓤 term, the entire list is 𝓤.
+				// Exit early.
+				// (Note that this is not just an optimization;
+				// if we continue, we may end up with a 𝓤 term
+				// and other terms and the result would not be
+				// in normal form.)
+				if u1.typ == nil {
+					return allTermlist
+				}
+				xi = u1
+				used[j] = true // xj is now unioned into xi - ignore it in future iterations
+			}
+		}
+		rl = append(rl, xi)
+	}
+	return rl
+}
+
+// If the type set represented by xl is specified by a single (non-𝓤) term,
+// structuralType returns that type. Otherwise it returns nil.
+func (xl termlist) structuralType() types.Type {
+	if nl := xl.norm(); len(nl) == 1 {
+		return nl[0].typ // if nl.isAll() then typ is nil, which is ok
+	}
+	return nil
+}
+
+// union returns the union xl ∪ yl.
+func (xl termlist) union(yl termlist) termlist {
+	return append(xl, yl...).norm()
+}
+
+// intersect returns the intersection xl ∩ yl.
+func (xl termlist) intersect(yl termlist) termlist {
+	if xl.isEmpty() || yl.isEmpty() {
+		return nil
+	}
+
+	// Quadratic algorithm, but good enough for now.
+	// TODO(gri) fix asymptotic performance
+	var rl termlist
+	for _, x := range xl {
+		for _, y := range yl {
+			if r := x.intersect(y); r != nil {
+				rl = append(rl, r)
+			}
+		}
+	}
+	return rl.norm()
+}
+
+// equal reports whether xl and yl represent the same type set.
+func (xl termlist) equal(yl termlist) bool {
+	// TODO(gri) this should be more efficient
+	return xl.subsetOf(yl) && yl.subsetOf(xl)
+}
+
+// includes reports whether t ∈ xl.
+func (xl termlist) includes(t types.Type) bool {
+	for _, x := range xl {
+		if x.includes(t) {
+			return true
+		}
+	}
+	return false
+}
+
+// supersetOf reports whether y ⊆ xl.
+func (xl termlist) supersetOf(y *term) bool {
+	for _, x := range xl {
+		if y.subsetOf(x) {
+			return true
+		}
+	}
+	return false
+}
+
+// subsetOf reports whether xl ⊆ yl.
+func (xl termlist) subsetOf(yl termlist) bool {
+	if yl.isEmpty() {
+		return xl.isEmpty()
+	}
+
+	// each term x of xl must be a subset of yl
+	for _, x := range xl {
+		if !yl.supersetOf(x) {
+			return false // x is not a subset yl
+		}
+	}
+	return true
+}
diff --git a/vendor/golang.org/x/tools/internal/typeparams/typeparams_go117.go b/vendor/golang.org/x/tools/internal/typeparams/typeparams_go117.go
index 12817af85..e509daf7b 100644
--- a/vendor/golang.org/x/tools/internal/typeparams/typeparams_go117.go
+++ b/vendor/golang.org/x/tools/internal/typeparams/typeparams_go117.go
@@ -2,13 +2,14 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !typeparams || !go1.18
-// +build !typeparams !go1.18
+//go:build !go1.18
+// +build !go1.18
 
 package typeparams
 
 import (
 	"go/ast"
+	"go/token"
 	"go/types"
 )
 
@@ -30,6 +31,34 @@ func GetIndexExprData(n ast.Node) *IndexExprData {
 	return nil
 }
 
+// PackIndexExpr returns an *ast.IndexExpr with the given index.
+// Calling PackIndexExpr with len(indices) != 1 will panic.
+func PackIndexExpr(x ast.Expr, lbrack token.Pos, indices []ast.Expr, rbrack token.Pos) ast.Expr {
+	switch len(indices) {
+	case 0:
+		panic("empty indices")
+	case 1:
+		return &ast.IndexExpr{
+			X:      x,
+			Lbrack: lbrack,
+			Index:  indices[0],
+			Rbrack: rbrack,
+		}
+	default:
+		panic("cannot pack multiple indices at this go version")
+	}
+}
+
+// IndexListExpr is a placeholder type, as type parameters are not supported at
+// this Go version. Its methods panic on use.
+type IndexListExpr struct {
+	ast.Expr
+	X       ast.Expr   // expression
+	Lbrack  token.Pos  // position of "["
+	Indices []ast.Expr // index expressions
+	Rbrack  token.Pos  // position of "]"
+}
+
 // ForTypeSpec returns an empty field list, as type parameters on not supported
 // at this Go version.
 func ForTypeSpec(*ast.TypeSpec) *ast.FieldList {
@@ -46,6 +75,7 @@ func ForFuncType(*ast.FuncType) *ast.FieldList {
 // this Go version. Its methods panic on use.
 type TypeParam struct{ types.Type }
 
+func (*TypeParam) Index() int             { unsupported(); return 0 }
 func (*TypeParam) Constraint() types.Type { unsupported(); return nil }
 func (*TypeParam) Obj() *types.TypeName   { unsupported(); return nil }
 
@@ -72,42 +102,46 @@ func SetTypeParamConstraint(tparam *TypeParam, constraint types.Type) {
 	unsupported()
 }
 
+// NewSignatureType calls types.NewSignature, panicking if recvTypeParams or
+// typeParams is non-empty.
+func NewSignatureType(recv *types.Var, recvTypeParams, typeParams []*TypeParam, params, results *types.Tuple, variadic bool) *types.Signature {
+	if len(recvTypeParams) != 0 || len(typeParams) != 0 {
+		panic("signatures cannot have type parameters at this Go version")
+	}
+	return types.NewSignature(recv, params, results, variadic)
+}
+
 // ForSignature returns an empty slice.
 func ForSignature(*types.Signature) *TypeParamList {
 	return nil
 }
 
-// SetForSignature panics if tparams is non-empty.
-func SetForSignature(_ *types.Signature, tparams []*TypeParam) {
-	if len(tparams) > 0 {
-		unsupported()
-	}
-}
-
 // RecvTypeParams returns a nil slice.
 func RecvTypeParams(sig *types.Signature) *TypeParamList {
 	return nil
 }
 
-// SetRecvTypeParams panics if rparams is non-empty.
-func SetRecvTypeParams(sig *types.Signature, rparams []*TypeParam) {
-	if len(rparams) > 0 {
-		unsupported()
-	}
-}
-
 // IsComparable returns false, as no interfaces are type-restricted at this Go
 // version.
 func IsComparable(*types.Interface) bool {
 	return false
 }
 
-// IsConstraint returns false, as no interfaces are type-restricted at this Go
+// IsMethodSet returns true, as no interfaces are type-restricted at this Go
 // version.
-func IsConstraint(*types.Interface) bool {
+func IsMethodSet(*types.Interface) bool {
+	return true
+}
+
+// IsImplicit returns false, as no interfaces are implicit at this Go version.
+func IsImplicit(*types.Interface) bool {
 	return false
 }
 
+// MarkImplicit does nothing, because this Go version does not have implicit
+// interfaces.
+func MarkImplicit(*types.Interface) {}
+
 // ForNamed returns an empty type parameter list, as type parameters are not
 // supported at this Go version.
 func ForNamed(*types.Named) *TypeParamList {
@@ -131,19 +165,25 @@ func NamedTypeOrigin(named *types.Named) types.Type {
 	return named
 }
 
-// Term is a placeholder type, as type parameters are not supported at this Go
-// version. Its methods panic on use.
-type Term struct{}
+// Term holds information about a structural type restriction.
+type Term struct {
+	tilde bool
+	typ   types.Type
+}
 
-func (*Term) Tilde() bool            { unsupported(); return false }
-func (*Term) Type() types.Type       { unsupported(); return nil }
-func (*Term) String() string         { unsupported(); return "" }
-func (*Term) Underlying() types.Type { unsupported(); return nil }
+func (m *Term) Tilde() bool      { return m.tilde }
+func (m *Term) Type() types.Type { return m.typ }
+func (m *Term) String() string {
+	pre := ""
+	if m.tilde {
+		pre = "~"
+	}
+	return pre + m.typ.String()
+}
 
 // NewTerm is unsupported at this Go version, and panics.
 func NewTerm(tilde bool, typ types.Type) *Term {
-	unsupported()
-	return nil
+	return &Term{tilde, typ}
 }
 
 // Union is a placeholder type, as type parameters are not supported at this Go
@@ -162,16 +202,23 @@ func NewUnion(terms []*Term) *Union {
 // InitInstanceInfo is a noop at this Go version.
 func InitInstanceInfo(*types.Info) {}
 
-// GetInstance returns nothing, as type parameters are not supported at this Go
-// version.
-func GetInstance(*types.Info, *ast.Ident) (*TypeList, types.Type) { return nil, nil }
+// Instance is a placeholder type, as type parameters are not supported at this
+// Go version.
+type Instance struct {
+	TypeArgs *TypeList
+	Type     types.Type
+}
+
+// GetInstances returns a nil map, as type parameters are not supported at this
+// Go version.
+func GetInstances(info *types.Info) map[*ast.Ident]Instance { return nil }
 
-// Environment is a placeholder type, as type parameters are not supported at
+// Context is a placeholder type, as type parameters are not supported at
 // this Go version.
-type Environment struct{}
+type Context struct{}
 
 // Instantiate is unsupported on this Go version, and panics.
-func Instantiate(env *Environment, typ types.Type, targs []types.Type, validate bool) (types.Type, error) {
+func Instantiate(ctxt *Context, typ types.Type, targs []types.Type, validate bool) (types.Type, error) {
 	unsupported()
 	return nil, nil
 }
diff --git a/vendor/golang.org/x/tools/internal/typeparams/typeparams_go118.go b/vendor/golang.org/x/tools/internal/typeparams/typeparams_go118.go
index 8ab17b777..e45896fb0 100644
--- a/vendor/golang.org/x/tools/internal/typeparams/typeparams_go118.go
+++ b/vendor/golang.org/x/tools/internal/typeparams/typeparams_go118.go
@@ -2,13 +2,14 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build typeparams && go1.18
-// +build typeparams,go1.18
+//go:build go1.18
+// +build go1.18
 
 package typeparams
 
 import (
 	"go/ast"
+	"go/token"
 	"go/types"
 )
 
@@ -21,6 +22,7 @@ import (
 //
 // For nodes that don't represent index expressions, GetIndexExprData returns
 // nil.
+// TODO(rfindley): remove this function in favor of using the alias below.
 func GetIndexExprData(n ast.Node) *IndexExprData {
 	switch e := n.(type) {
 	case *ast.IndexExpr:
@@ -36,6 +38,33 @@ func GetIndexExprData(n ast.Node) *IndexExprData {
 	return nil
 }
 
+// PackIndexExpr returns an *ast.IndexExpr or *ast.IndexListExpr, depending on
+// the cardinality of indices. Calling PackIndexExpr with len(indices) == 0
+// will panic.
+func PackIndexExpr(x ast.Expr, lbrack token.Pos, indices []ast.Expr, rbrack token.Pos) ast.Expr {
+	switch len(indices) {
+	case 0:
+		panic("empty indices")
+	case 1:
+		return &ast.IndexExpr{
+			X:      x,
+			Lbrack: lbrack,
+			Index:  indices[0],
+			Rbrack: rbrack,
+		}
+	default:
+		return &ast.IndexListExpr{
+			X:       x,
+			Lbrack:  lbrack,
+			Indices: indices,
+			Rbrack:  rbrack,
+		}
+	}
+}
+
+// IndexListExpr is an alias for ast.IndexListExpr.
+type IndexListExpr = ast.IndexListExpr
+
 // ForTypeSpec returns n.TypeParams.
 func ForTypeSpec(n *ast.TypeSpec) *ast.FieldList {
 	if n == nil {
@@ -71,34 +100,39 @@ func SetTypeParamConstraint(tparam *TypeParam, constraint types.Type) {
 	tparam.SetConstraint(constraint)
 }
 
+// NewSignatureType calls types.NewSignatureType.
+func NewSignatureType(recv *types.Var, recvTypeParams, typeParams []*TypeParam, params, results *types.Tuple, variadic bool) *types.Signature {
+	return types.NewSignatureType(recv, recvTypeParams, typeParams, params, results, variadic)
+}
+
 // ForSignature returns sig.TypeParams()
 func ForSignature(sig *types.Signature) *TypeParamList {
 	return sig.TypeParams()
 }
 
-// SetForSignature calls sig.SetTypeParams(tparams)
-func SetForSignature(sig *types.Signature, tparams []*TypeParam) {
-	sig.SetTypeParams(tparams)
-}
-
 // RecvTypeParams returns sig.RecvTypeParams().
 func RecvTypeParams(sig *types.Signature) *TypeParamList {
 	return sig.RecvTypeParams()
 }
 
-// SetRecvTypeParams calls sig.SetRecvTypeParams(rparams).
-func SetRecvTypeParams(sig *types.Signature, rparams []*TypeParam) {
-	sig.SetRecvTypeParams(rparams)
-}
-
 // IsComparable calls iface.IsComparable().
 func IsComparable(iface *types.Interface) bool {
 	return iface.IsComparable()
 }
 
-// IsConstraint calls iface.IsConstraint().
-func IsConstraint(iface *types.Interface) bool {
-	return iface.IsConstraint()
+// IsMethodSet calls iface.IsMethodSet().
+func IsMethodSet(iface *types.Interface) bool {
+	return iface.IsMethodSet()
+}
+
+// IsImplicit calls iface.IsImplicit().
+func IsImplicit(iface *types.Interface) bool {
+	return iface.IsImplicit()
+}
+
+// MarkImplicit calls iface.MarkImplicit().
+func MarkImplicit(iface *types.Interface) {
+	iface.MarkImplicit()
 }
 
 // ForNamed extracts the (possibly empty) type parameter object list from
@@ -145,21 +179,18 @@ func InitInstanceInfo(info *types.Info) {
 	info.Instances = make(map[*ast.Ident]types.Instance)
 }
 
-// GetInstance extracts information about the instantiation occurring at the
-// identifier id. id should be the identifier denoting a parameterized type or
-// function in an instantiation expression or function call.
-func GetInstance(info *types.Info, id *ast.Ident) (*TypeList, types.Type) {
-	if info.Instances != nil {
-		inf := info.Instances[id]
-		return inf.TypeArgs, inf.Type
-	}
-	return nil, nil
+// Instance is an alias for types.Instance.
+type Instance = types.Instance
+
+// GetInstances returns info.Instances.
+func GetInstances(info *types.Info) map[*ast.Ident]Instance {
+	return info.Instances
 }
 
-// Environment is an alias for types.Environment.
-type Environment = types.Environment
+// Context is an alias for types.Context.
+type Context = types.Context
 
 // Instantiate calls types.Instantiate.
-func Instantiate(env *Environment, typ types.Type, targs []types.Type, validate bool) (types.Type, error) {
-	return types.Instantiate(env, typ, targs, validate)
+func Instantiate(ctxt *Context, typ types.Type, targs []types.Type, validate bool) (types.Type, error) {
+	return types.Instantiate(ctxt, typ, targs, validate)
 }
diff --git a/vendor/golang.org/x/tools/internal/typeparams/typeterm.go b/vendor/golang.org/x/tools/internal/typeparams/typeterm.go
new file mode 100644
index 000000000..7ddee28d9
--- /dev/null
+++ b/vendor/golang.org/x/tools/internal/typeparams/typeterm.go
@@ -0,0 +1,170 @@
+// 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.
+
+// Code generated by copytermlist.go DO NOT EDIT.
+
+package typeparams
+
+import "go/types"
+
+// A term describes elementary type sets:
+//
+//   ∅:  (*term)(nil)     == ∅                      // set of no types (empty set)
+//   𝓤:  &term{}          == 𝓤                      // set of all types (𝓤niverse)
+//   T:  &term{false, T}  == {T}                    // set of type T
+//  ~t:  &term{true, t}   == {t' | under(t') == t}  // set of types with underlying type t
+//
+type term struct {
+	tilde bool // valid if typ != nil
+	typ   types.Type
+}
+
+func (x *term) String() string {
+	switch {
+	case x == nil:
+		return "∅"
+	case x.typ == nil:
+		return "𝓤"
+	case x.tilde:
+		return "~" + x.typ.String()
+	default:
+		return x.typ.String()
+	}
+}
+
+// equal reports whether x and y represent the same type set.
+func (x *term) equal(y *term) bool {
+	// easy cases
+	switch {
+	case x == nil || y == nil:
+		return x == y
+	case x.typ == nil || y.typ == nil:
+		return x.typ == y.typ
+	}
+	// ∅ ⊂ x, y ⊂ 𝓤
+
+	return x.tilde == y.tilde && types.Identical(x.typ, y.typ)
+}
+
+// union returns the union x ∪ y: zero, one, or two non-nil terms.
+func (x *term) union(y *term) (_, _ *term) {
+	// easy cases
+	switch {
+	case x == nil && y == nil:
+		return nil, nil // ∅ ∪ ∅ == ∅
+	case x == nil:
+		return y, nil // ∅ ∪ y == y
+	case y == nil:
+		return x, nil // x ∪ ∅ == x
+	case x.typ == nil:
+		return x, nil // 𝓤 ∪ y == 𝓤
+	case y.typ == nil:
+		return y, nil // x ∪ 𝓤 == 𝓤
+	}
+	// ∅ ⊂ x, y ⊂ 𝓤
+
+	if x.disjoint(y) {
+		return x, y // x ∪ y == (x, y) if x ∩ y == ∅
+	}
+	// x.typ == y.typ
+
+	// ~t ∪ ~t == ~t
+	// ~t ∪  T == ~t
+	//  T ∪ ~t == ~t
+	//  T ∪  T ==  T
+	if x.tilde || !y.tilde {
+		return x, nil
+	}
+	return y, nil
+}
+
+// intersect returns the intersection x ∩ y.
+func (x *term) intersect(y *term) *term {
+	// easy cases
+	switch {
+	case x == nil || y == nil:
+		return nil // ∅ ∩ y == ∅ and ∩ ∅ == ∅
+	case x.typ == nil:
+		return y // 𝓤 ∩ y == y
+	case y.typ == nil:
+		return x // x ∩ 𝓤 == x
+	}
+	// ∅ ⊂ x, y ⊂ 𝓤
+
+	if x.disjoint(y) {
+		return nil // x ∩ y == ∅ if x ∩ y == ∅
+	}
+	// x.typ == y.typ
+
+	// ~t ∩ ~t == ~t
+	// ~t ∩  T ==  T
+	//  T ∩ ~t ==  T
+	//  T ∩  T ==  T
+	if !x.tilde || y.tilde {
+		return x
+	}
+	return y
+}
+
+// includes reports whether t ∈ x.
+func (x *term) includes(t types.Type) bool {
+	// easy cases
+	switch {
+	case x == nil:
+		return false // t ∈ ∅ == false
+	case x.typ == nil:
+		return true // t ∈ 𝓤 == true
+	}
+	// ∅ ⊂ x ⊂ 𝓤
+
+	u := t
+	if x.tilde {
+		u = under(u)
+	}
+	return types.Identical(x.typ, u)
+}
+
+// subsetOf reports whether x ⊆ y.
+func (x *term) subsetOf(y *term) bool {
+	// easy cases
+	switch {
+	case x == nil:
+		return true // ∅ ⊆ y == true
+	case y == nil:
+		return false // x ⊆ ∅ == false since x != ∅
+	case y.typ == nil:
+		return true // x ⊆ 𝓤 == true
+	case x.typ == nil:
+		return false // 𝓤 ⊆ y == false since y != 𝓤
+	}
+	// ∅ ⊂ x, y ⊂ 𝓤
+
+	if x.disjoint(y) {
+		return false // x ⊆ y == false if x ∩ y == ∅
+	}
+	// x.typ == y.typ
+
+	// ~t ⊆ ~t == true
+	// ~t ⊆ T == false
+	//  T ⊆ ~t == true
+	//  T ⊆  T == true
+	return !x.tilde || y.tilde
+}
+
+// disjoint reports whether x ∩ y == ∅.
+// x.typ and y.typ must not be nil.
+func (x *term) disjoint(y *term) bool {
+	if debug && (x.typ == nil || y.typ == nil) {
+		panic("invalid argument(s)")
+	}
+	ux := x.typ
+	if y.tilde {
+		ux = under(ux)
+	}
+	uy := y.typ
+	if x.tilde {
+		uy = under(uy)
+	}
+	return !types.Identical(ux, uy)
+}