[dev.regabi] cmd/compile: split out package noder [generated]

[git-generate]
cd src/cmd/compile/internal/gc

rf '
	mv ArhdrSize HeaderSize
	mv arsize ReadHeader
	mv formathdr FormatHeader
	mv HeaderSize ReadHeader FormatHeader archive.go
	mv archive.go cmd/internal/archive

	mv makePos main.go

	mv checkDotImports CheckDotImports
	mv parseFiles ParseFiles

	mv Pragma pragmas
	mv PragmaEmbed pragmaEmbed
	mv PragmaPos pragmaPos
	mv FuncPragmas funcPragmas
	mv TypePragmas typePragmas

	mv fakeRecv noder.funcLit renameinitgen renameinit oldname varEmbed noder.go
	mv isDriveLetter islocalname findpkg myheight importfile \
		reservedimports isbadimport \
		pkgnotused \
		mkpackage clearImports \
		CheckDotImports dotImports importDot \
		importName \
		import.go

	mv noder _noder
	mv import.go lex.go lex_test.go noder.go cmd/compile/internal/noder
'
cd ../noder
rf '
	mv _noder noder
'

Change-Id: Iac2b856f7b86143c666d818e4b7c5b261cf387d5
Reviewed-on: https://go-review.googlesource.com/c/go/+/279473
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 1938 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/noder/noder.go b/src/cmd/compile/internal/noder/noder.go
new file mode 100644
index 0000000000..a684673c8f
--- /dev/null
+++ b/src/cmd/compile/internal/noder/noder.go
@@ -0,0 +1,1938 @@
+// Copyright 2016 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 noder
+
+import (
+	"fmt"
+	"go/constant"
+	"go/token"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strconv"
+	"strings"
+	"unicode"
+	"unicode/utf8"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/syntax"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/internal/objabi"
+	"cmd/internal/src"
+)
+
+// ParseFiles concurrently parses files into *syntax.File structures.
+// Each declaration in every *syntax.File is converted to a syntax tree
+// and its root represented by *Node is appended to Target.Decls.
+// Returns the total count of parsed lines.
+func ParseFiles(filenames []string) uint {
+	noders := make([]*noder, 0, len(filenames))
+	// Limit the number of simultaneously open files.
+	sem := make(chan struct{}, runtime.GOMAXPROCS(0)+10)
+
+	for _, filename := range filenames {
+		p := &noder{
+			basemap:     make(map[*syntax.PosBase]*src.PosBase),
+			err:         make(chan syntax.Error),
+			trackScopes: base.Flag.Dwarf,
+		}
+		noders = append(noders, p)
+
+		go func(filename string) {
+			sem <- struct{}{}
+			defer func() { <-sem }()
+			defer close(p.err)
+			base := syntax.NewFileBase(filename)
+
+			f, err := os.Open(filename)
+			if err != nil {
+				p.error(syntax.Error{Msg: err.Error()})
+				return
+			}
+			defer f.Close()
+
+			p.file, _ = syntax.Parse(base, f, p.error, p.pragma, syntax.CheckBranches) // errors are tracked via p.error
+		}(filename)
+	}
+
+	var lines uint
+	for _, p := range noders {
+		for e := range p.err {
+			p.errorAt(e.Pos, "%s", e.Msg)
+		}
+
+		p.node()
+		lines += p.file.Lines
+		p.file = nil // release memory
+
+		if base.SyntaxErrors() != 0 {
+			base.ErrorExit()
+		}
+		// Always run testdclstack here, even when debug_dclstack is not set, as a sanity measure.
+		types.CheckDclstack()
+	}
+
+	for _, p := range noders {
+		p.processPragmas()
+	}
+
+	types.LocalPkg.Height = myheight
+
+	return lines
+}
+
+// makeSrcPosBase translates from a *syntax.PosBase to a *src.PosBase.
+func (p *noder) makeSrcPosBase(b0 *syntax.PosBase) *src.PosBase {
+	// fast path: most likely PosBase hasn't changed
+	if p.basecache.last == b0 {
+		return p.basecache.base
+	}
+
+	b1, ok := p.basemap[b0]
+	if !ok {
+		fn := b0.Filename()
+		if b0.IsFileBase() {
+			b1 = src.NewFileBase(fn, absFilename(fn))
+		} else {
+			// line directive base
+			p0 := b0.Pos()
+			p0b := p0.Base()
+			if p0b == b0 {
+				panic("infinite recursion in makeSrcPosBase")
+			}
+			p1 := src.MakePos(p.makeSrcPosBase(p0b), p0.Line(), p0.Col())
+			b1 = src.NewLinePragmaBase(p1, fn, fileh(fn), b0.Line(), b0.Col())
+		}
+		p.basemap[b0] = b1
+	}
+
+	// update cache
+	p.basecache.last = b0
+	p.basecache.base = b1
+
+	return b1
+}
+
+func (p *noder) makeXPos(pos syntax.Pos) (_ src.XPos) {
+	return base.Ctxt.PosTable.XPos(src.MakePos(p.makeSrcPosBase(pos.Base()), pos.Line(), pos.Col()))
+}
+
+func (p *noder) errorAt(pos syntax.Pos, format string, args ...interface{}) {
+	base.ErrorfAt(p.makeXPos(pos), format, args...)
+}
+
+// TODO(gri) Can we eliminate fileh in favor of absFilename?
+func fileh(name string) string {
+	return objabi.AbsFile("", name, base.Flag.TrimPath)
+}
+
+func absFilename(name string) string {
+	return objabi.AbsFile(base.Ctxt.Pathname, name, base.Flag.TrimPath)
+}
+
+// noder transforms package syntax's AST into a Node tree.
+type noder struct {
+	basemap   map[*syntax.PosBase]*src.PosBase
+	basecache struct {
+		last *syntax.PosBase
+		base *src.PosBase
+	}
+
+	file           *syntax.File
+	linknames      []linkname
+	pragcgobuf     [][]string
+	err            chan syntax.Error
+	scope          ir.ScopeID
+	importedUnsafe bool
+	importedEmbed  bool
+
+	// scopeVars is a stack tracking the number of variables declared in the
+	// current function at the moment each open scope was opened.
+	trackScopes bool
+	scopeVars   []int
+
+	lastCloseScopePos syntax.Pos
+}
+
+func (p *noder) funcBody(fn *ir.Func, block *syntax.BlockStmt) {
+	oldScope := p.scope
+	p.scope = 0
+	typecheck.StartFuncBody(fn)
+
+	if block != nil {
+		body := p.stmts(block.List)
+		if body == nil {
+			body = []ir.Node{ir.NewBlockStmt(base.Pos, nil)}
+		}
+		fn.Body.Set(body)
+
+		base.Pos = p.makeXPos(block.Rbrace)
+		fn.Endlineno = base.Pos
+	}
+
+	typecheck.FinishFuncBody()
+	p.scope = oldScope
+}
+
+func (p *noder) openScope(pos syntax.Pos) {
+	types.Markdcl()
+
+	if p.trackScopes {
+		ir.CurFunc.Parents = append(ir.CurFunc.Parents, p.scope)
+		p.scopeVars = append(p.scopeVars, len(ir.CurFunc.Dcl))
+		p.scope = ir.ScopeID(len(ir.CurFunc.Parents))
+
+		p.markScope(pos)
+	}
+}
+
+func (p *noder) closeScope(pos syntax.Pos) {
+	p.lastCloseScopePos = pos
+	types.Popdcl()
+
+	if p.trackScopes {
+		scopeVars := p.scopeVars[len(p.scopeVars)-1]
+		p.scopeVars = p.scopeVars[:len(p.scopeVars)-1]
+		if scopeVars == len(ir.CurFunc.Dcl) {
+			// no variables were declared in this scope, so we can retract it.
+
+			if int(p.scope) != len(ir.CurFunc.Parents) {
+				base.Fatalf("scope tracking inconsistency, no variables declared but scopes were not retracted")
+			}
+
+			p.scope = ir.CurFunc.Parents[p.scope-1]
+			ir.CurFunc.Parents = ir.CurFunc.Parents[:len(ir.CurFunc.Parents)-1]
+
+			nmarks := len(ir.CurFunc.Marks)
+			ir.CurFunc.Marks[nmarks-1].Scope = p.scope
+			prevScope := ir.ScopeID(0)
+			if nmarks >= 2 {
+				prevScope = ir.CurFunc.Marks[nmarks-2].Scope
+			}
+			if ir.CurFunc.Marks[nmarks-1].Scope == prevScope {
+				ir.CurFunc.Marks = ir.CurFunc.Marks[:nmarks-1]
+			}
+			return
+		}
+
+		p.scope = ir.CurFunc.Parents[p.scope-1]
+
+		p.markScope(pos)
+	}
+}
+
+func (p *noder) markScope(pos syntax.Pos) {
+	xpos := p.makeXPos(pos)
+	if i := len(ir.CurFunc.Marks); i > 0 && ir.CurFunc.Marks[i-1].Pos == xpos {
+		ir.CurFunc.Marks[i-1].Scope = p.scope
+	} else {
+		ir.CurFunc.Marks = append(ir.CurFunc.Marks, ir.Mark{Pos: xpos, Scope: p.scope})
+	}
+}
+
+// closeAnotherScope is like closeScope, but it reuses the same mark
+// position as the last closeScope call. This is useful for "for" and
+// "if" statements, as their implicit blocks always end at the same
+// position as an explicit block.
+func (p *noder) closeAnotherScope() {
+	p.closeScope(p.lastCloseScopePos)
+}
+
+// linkname records a //go:linkname directive.
+type linkname struct {
+	pos    syntax.Pos
+	local  string
+	remote string
+}
+
+func (p *noder) node() {
+	types.Block = 1
+	p.importedUnsafe = false
+	p.importedEmbed = false
+
+	p.setlineno(p.file.PkgName)
+	mkpackage(p.file.PkgName.Value)
+
+	if pragma, ok := p.file.Pragma.(*pragmas); ok {
+		pragma.Flag &^= ir.GoBuildPragma
+		p.checkUnused(pragma)
+	}
+
+	typecheck.Target.Decls = append(typecheck.Target.Decls, p.decls(p.file.DeclList)...)
+
+	base.Pos = src.NoXPos
+	clearImports()
+}
+
+func (p *noder) processPragmas() {
+	for _, l := range p.linknames {
+		if !p.importedUnsafe {
+			p.errorAt(l.pos, "//go:linkname only allowed in Go files that import \"unsafe\"")
+			continue
+		}
+		n := ir.AsNode(typecheck.Lookup(l.local).Def)
+		if n == nil || n.Op() != ir.ONAME {
+			// TODO(mdempsky): Change to p.errorAt before Go 1.17 release.
+			// base.WarnfAt(p.makeXPos(l.pos), "//go:linkname must refer to declared function or variable (will be an error in Go 1.17)")
+			continue
+		}
+		if n.Sym().Linkname != "" {
+			p.errorAt(l.pos, "duplicate //go:linkname for %s", l.local)
+			continue
+		}
+		n.Sym().Linkname = l.remote
+	}
+	typecheck.Target.CgoPragmas = append(typecheck.Target.CgoPragmas, p.pragcgobuf...)
+}
+
+func (p *noder) decls(decls []syntax.Decl) (l []ir.Node) {
+	var cs constState
+
+	for _, decl := range decls {
+		p.setlineno(decl)
+		switch decl := decl.(type) {
+		case *syntax.ImportDecl:
+			p.importDecl(decl)
+
+		case *syntax.VarDecl:
+			l = append(l, p.varDecl(decl)...)
+
+		case *syntax.ConstDecl:
+			l = append(l, p.constDecl(decl, &cs)...)
+
+		case *syntax.TypeDecl:
+			l = append(l, p.typeDecl(decl))
+
+		case *syntax.FuncDecl:
+			l = append(l, p.funcDecl(decl))
+
+		default:
+			panic("unhandled Decl")
+		}
+	}
+
+	return
+}
+
+func (p *noder) importDecl(imp *syntax.ImportDecl) {
+	if imp.Path.Bad {
+		return // avoid follow-on errors if there was a syntax error
+	}
+
+	if pragma, ok := imp.Pragma.(*pragmas); ok {
+		p.checkUnused(pragma)
+	}
+
+	ipkg := importfile(p.basicLit(imp.Path))
+	if ipkg == nil {
+		if base.Errors() == 0 {
+			base.Fatalf("phase error in import")
+		}
+		return
+	}
+
+	if ipkg == ir.Pkgs.Unsafe {
+		p.importedUnsafe = true
+	}
+	if ipkg.Path == "embed" {
+		p.importedEmbed = true
+	}
+
+	if !ipkg.Direct {
+		typecheck.Target.Imports = append(typecheck.Target.Imports, ipkg)
+	}
+	ipkg.Direct = true
+
+	var my *types.Sym
+	if imp.LocalPkgName != nil {
+		my = p.name(imp.LocalPkgName)
+	} else {
+		my = typecheck.Lookup(ipkg.Name)
+	}
+
+	pack := ir.NewPkgName(p.pos(imp), my, ipkg)
+
+	switch my.Name {
+	case ".":
+		importDot(pack)
+		return
+	case "init":
+		base.ErrorfAt(pack.Pos(), "cannot import package as init - init must be a func")
+		return
+	case "_":
+		return
+	}
+	if my.Def != nil {
+		typecheck.Redeclared(pack.Pos(), my, "as imported package name")
+	}
+	my.Def = pack
+	my.Lastlineno = pack.Pos()
+	my.Block = 1 // at top level
+}
+
+func (p *noder) varDecl(decl *syntax.VarDecl) []ir.Node {
+	names := p.declNames(ir.ONAME, decl.NameList)
+	typ := p.typeExprOrNil(decl.Type)
+
+	var exprs []ir.Node
+	if decl.Values != nil {
+		exprs = p.exprList(decl.Values)
+	}
+
+	if pragma, ok := decl.Pragma.(*pragmas); ok {
+		if len(pragma.Embeds) > 0 {
+			if !p.importedEmbed {
+				// This check can't be done when building the list pragma.Embeds
+				// because that list is created before the noder starts walking over the file,
+				// so at that point it hasn't seen the imports.
+				// We're left to check now, just before applying the //go:embed lines.
+				for _, e := range pragma.Embeds {
+					p.errorAt(e.Pos, "//go:embed only allowed in Go files that import \"embed\"")
+				}
+			} else {
+				exprs = varEmbed(p, names, typ, exprs, pragma.Embeds)
+			}
+			pragma.Embeds = nil
+		}
+		p.checkUnused(pragma)
+	}
+
+	p.setlineno(decl)
+	return typecheck.DeclVars(names, typ, exprs)
+}
+
+// constState tracks state between constant specifiers within a
+// declaration group. This state is kept separate from noder so nested
+// constant declarations are handled correctly (e.g., issue 15550).
+type constState struct {
+	group  *syntax.Group
+	typ    ir.Ntype
+	values []ir.Node
+	iota   int64
+}
+
+func (p *noder) constDecl(decl *syntax.ConstDecl, cs *constState) []ir.Node {
+	if decl.Group == nil || decl.Group != cs.group {
+		*cs = constState{
+			group: decl.Group,
+		}
+	}
+
+	if pragma, ok := decl.Pragma.(*pragmas); ok {
+		p.checkUnused(pragma)
+	}
+
+	names := p.declNames(ir.OLITERAL, decl.NameList)
+	typ := p.typeExprOrNil(decl.Type)
+
+	var values []ir.Node
+	if decl.Values != nil {
+		values = p.exprList(decl.Values)
+		cs.typ, cs.values = typ, values
+	} else {
+		if typ != nil {
+			base.Errorf("const declaration cannot have type without expression")
+		}
+		typ, values = cs.typ, cs.values
+	}
+
+	nn := make([]ir.Node, 0, len(names))
+	for i, n := range names {
+		if i >= len(values) {
+			base.Errorf("missing value in const declaration")
+			break
+		}
+		v := values[i]
+		if decl.Values == nil {
+			v = ir.DeepCopy(n.Pos(), v)
+		}
+		typecheck.Declare(n, typecheck.DeclContext)
+
+		n.Ntype = typ
+		n.Defn = v
+		n.SetIota(cs.iota)
+
+		nn = append(nn, ir.NewDecl(p.pos(decl), ir.ODCLCONST, n))
+	}
+
+	if len(values) > len(names) {
+		base.Errorf("extra expression in const declaration")
+	}
+
+	cs.iota++
+
+	return nn
+}
+
+func (p *noder) typeDecl(decl *syntax.TypeDecl) ir.Node {
+	n := p.declName(ir.OTYPE, decl.Name)
+	typecheck.Declare(n, typecheck.DeclContext)
+
+	// decl.Type may be nil but in that case we got a syntax error during parsing
+	typ := p.typeExprOrNil(decl.Type)
+
+	n.Ntype = typ
+	n.SetAlias(decl.Alias)
+	if pragma, ok := decl.Pragma.(*pragmas); ok {
+		if !decl.Alias {
+			n.SetPragma(pragma.Flag & typePragmas)
+			pragma.Flag &^= typePragmas
+		}
+		p.checkUnused(pragma)
+	}
+
+	nod := ir.NewDecl(p.pos(decl), ir.ODCLTYPE, n)
+	if n.Alias() && !types.AllowsGoVersion(types.LocalPkg, 1, 9) {
+		base.ErrorfAt(nod.Pos(), "type aliases only supported as of -lang=go1.9")
+	}
+	return nod
+}
+
+func (p *noder) declNames(op ir.Op, names []*syntax.Name) []*ir.Name {
+	nodes := make([]*ir.Name, 0, len(names))
+	for _, name := range names {
+		nodes = append(nodes, p.declName(op, name))
+	}
+	return nodes
+}
+
+func (p *noder) declName(op ir.Op, name *syntax.Name) *ir.Name {
+	return ir.NewDeclNameAt(p.pos(name), op, p.name(name))
+}
+
+func (p *noder) funcDecl(fun *syntax.FuncDecl) ir.Node {
+	name := p.name(fun.Name)
+	t := p.signature(fun.Recv, fun.Type)
+	f := ir.NewFunc(p.pos(fun))
+
+	if fun.Recv == nil {
+		if name.Name == "init" {
+			name = renameinit()
+			if len(t.Params) > 0 || len(t.Results) > 0 {
+				base.ErrorfAt(f.Pos(), "func init must have no arguments and no return values")
+			}
+			typecheck.Target.Inits = append(typecheck.Target.Inits, f)
+		}
+
+		if types.LocalPkg.Name == "main" && name.Name == "main" {
+			if len(t.Params) > 0 || len(t.Results) > 0 {
+				base.ErrorfAt(f.Pos(), "func main must have no arguments and no return values")
+			}
+		}
+	} else {
+		f.Shortname = name
+		name = ir.BlankNode.Sym() // filled in by typecheckfunc
+	}
+
+	f.Nname = ir.NewFuncNameAt(p.pos(fun.Name), name, f)
+	f.Nname.Defn = f
+	f.Nname.Ntype = t
+
+	if pragma, ok := fun.Pragma.(*pragmas); ok {
+		f.Pragma = pragma.Flag & funcPragmas
+		if pragma.Flag&ir.Systemstack != 0 && pragma.Flag&ir.Nosplit != 0 {
+			base.ErrorfAt(f.Pos(), "go:nosplit and go:systemstack cannot be combined")
+		}
+		pragma.Flag &^= funcPragmas
+		p.checkUnused(pragma)
+	}
+
+	if fun.Recv == nil {
+		typecheck.Declare(f.Nname, ir.PFUNC)
+	}
+
+	p.funcBody(f, fun.Body)
+
+	if fun.Body != nil {
+		if f.Pragma&ir.Noescape != 0 {
+			base.ErrorfAt(f.Pos(), "can only use //go:noescape with external func implementations")
+		}
+	} else {
+		if base.Flag.Complete || strings.HasPrefix(ir.FuncName(f), "init.") {
+			// Linknamed functions are allowed to have no body. Hopefully
+			// the linkname target has a body. See issue 23311.
+			isLinknamed := false
+			for _, n := range p.linknames {
+				if ir.FuncName(f) == n.local {
+					isLinknamed = true
+					break
+				}
+			}
+			if !isLinknamed {
+				base.ErrorfAt(f.Pos(), "missing function body")
+			}
+		}
+	}
+
+	return f
+}
+
+func (p *noder) signature(recv *syntax.Field, typ *syntax.FuncType) *ir.FuncType {
+	var rcvr *ir.Field
+	if recv != nil {
+		rcvr = p.param(recv, false, false)
+	}
+	return ir.NewFuncType(p.pos(typ), rcvr,
+		p.params(typ.ParamList, true),
+		p.params(typ.ResultList, false))
+}
+
+func (p *noder) params(params []*syntax.Field, dddOk bool) []*ir.Field {
+	nodes := make([]*ir.Field, 0, len(params))
+	for i, param := range params {
+		p.setlineno(param)
+		nodes = append(nodes, p.param(param, dddOk, i+1 == len(params)))
+	}
+	return nodes
+}
+
+func (p *noder) param(param *syntax.Field, dddOk, final bool) *ir.Field {
+	var name *types.Sym
+	if param.Name != nil {
+		name = p.name(param.Name)
+	}
+
+	typ := p.typeExpr(param.Type)
+	n := ir.NewField(p.pos(param), name, typ, nil)
+
+	// rewrite ...T parameter
+	if typ, ok := typ.(*ir.SliceType); ok && typ.DDD {
+		if !dddOk {
+			// We mark these as syntax errors to get automatic elimination
+			// of multiple such errors per line (see ErrorfAt in subr.go).
+			base.Errorf("syntax error: cannot use ... in receiver or result parameter list")
+		} else if !final {
+			if param.Name == nil {
+				base.Errorf("syntax error: cannot use ... with non-final parameter")
+			} else {
+				p.errorAt(param.Name.Pos(), "syntax error: cannot use ... with non-final parameter %s", param.Name.Value)
+			}
+		}
+		typ.DDD = false
+		n.IsDDD = true
+	}
+
+	return n
+}
+
+func (p *noder) exprList(expr syntax.Expr) []ir.Node {
+	if list, ok := expr.(*syntax.ListExpr); ok {
+		return p.exprs(list.ElemList)
+	}
+	return []ir.Node{p.expr(expr)}
+}
+
+func (p *noder) exprs(exprs []syntax.Expr) []ir.Node {
+	nodes := make([]ir.Node, 0, len(exprs))
+	for _, expr := range exprs {
+		nodes = append(nodes, p.expr(expr))
+	}
+	return nodes
+}
+
+func (p *noder) expr(expr syntax.Expr) ir.Node {
+	p.setlineno(expr)
+	switch expr := expr.(type) {
+	case nil, *syntax.BadExpr:
+		return nil
+	case *syntax.Name:
+		return p.mkname(expr)
+	case *syntax.BasicLit:
+		n := ir.NewLiteral(p.basicLit(expr))
+		if expr.Kind == syntax.RuneLit {
+			n.SetType(types.UntypedRune)
+		}
+		n.SetDiag(expr.Bad) // avoid follow-on errors if there was a syntax error
+		return n
+	case *syntax.CompositeLit:
+		n := ir.NewCompLitExpr(p.pos(expr), ir.OCOMPLIT, nil, nil)
+		if expr.Type != nil {
+			n.Ntype = ir.Node(p.expr(expr.Type)).(ir.Ntype)
+		}
+		l := p.exprs(expr.ElemList)
+		for i, e := range l {
+			l[i] = p.wrapname(expr.ElemList[i], e)
+		}
+		n.List.Set(l)
+		base.Pos = p.makeXPos(expr.Rbrace)
+		return n
+	case *syntax.KeyValueExpr:
+		// use position of expr.Key rather than of expr (which has position of ':')
+		return ir.NewKeyExpr(p.pos(expr.Key), p.expr(expr.Key), p.wrapname(expr.Value, p.expr(expr.Value)))
+	case *syntax.FuncLit:
+		return p.funcLit(expr)
+	case *syntax.ParenExpr:
+		return ir.NewParenExpr(p.pos(expr), p.expr(expr.X))
+	case *syntax.SelectorExpr:
+		// parser.new_dotname
+		obj := p.expr(expr.X)
+		if obj.Op() == ir.OPACK {
+			pack := obj.(*ir.PkgName)
+			pack.Used = true
+			return importName(pack.Pkg.Lookup(expr.Sel.Value))
+		}
+		n := ir.NewSelectorExpr(base.Pos, ir.OXDOT, obj, p.name(expr.Sel))
+		n.SetPos(p.pos(expr)) // lineno may have been changed by p.expr(expr.X)
+		return n
+	case *syntax.IndexExpr:
+		return ir.NewIndexExpr(p.pos(expr), p.expr(expr.X), p.expr(expr.Index))
+	case *syntax.SliceExpr:
+		op := ir.OSLICE
+		if expr.Full {
+			op = ir.OSLICE3
+		}
+		n := ir.NewSliceExpr(p.pos(expr), op, p.expr(expr.X))
+		var index [3]ir.Node
+		for i, x := range &expr.Index {
+			if x != nil {
+				index[i] = p.expr(x)
+			}
+		}
+		n.SetSliceBounds(index[0], index[1], index[2])
+		return n
+	case *syntax.AssertExpr:
+		return ir.NewTypeAssertExpr(p.pos(expr), p.expr(expr.X), p.typeExpr(expr.Type).(ir.Ntype))
+	case *syntax.Operation:
+		if expr.Op == syntax.Add && expr.Y != nil {
+			return p.sum(expr)
+		}
+		x := p.expr(expr.X)
+		if expr.Y == nil {
+			pos, op := p.pos(expr), p.unOp(expr.Op)
+			switch op {
+			case ir.OADDR:
+				return typecheck.NodAddrAt(pos, x)
+			case ir.ODEREF:
+				return ir.NewStarExpr(pos, x)
+			}
+			return ir.NewUnaryExpr(pos, op, x)
+		}
+
+		pos, op, y := p.pos(expr), p.binOp(expr.Op), p.expr(expr.Y)
+		switch op {
+		case ir.OANDAND, ir.OOROR:
+			return ir.NewLogicalExpr(pos, op, x, y)
+		}
+		return ir.NewBinaryExpr(pos, op, x, y)
+	case *syntax.CallExpr:
+		n := ir.NewCallExpr(p.pos(expr), ir.OCALL, p.expr(expr.Fun), nil)
+		n.Args.Set(p.exprs(expr.ArgList))
+		n.IsDDD = expr.HasDots
+		return n
+
+	case *syntax.ArrayType:
+		var len ir.Node
+		if expr.Len != nil {
+			len = p.expr(expr.Len)
+		}
+		return ir.NewArrayType(p.pos(expr), len, p.typeExpr(expr.Elem))
+	case *syntax.SliceType:
+		return ir.NewSliceType(p.pos(expr), p.typeExpr(expr.Elem))
+	case *syntax.DotsType:
+		t := ir.NewSliceType(p.pos(expr), p.typeExpr(expr.Elem))
+		t.DDD = true
+		return t
+	case *syntax.StructType:
+		return p.structType(expr)
+	case *syntax.InterfaceType:
+		return p.interfaceType(expr)
+	case *syntax.FuncType:
+		return p.signature(nil, expr)
+	case *syntax.MapType:
+		return ir.NewMapType(p.pos(expr),
+			p.typeExpr(expr.Key), p.typeExpr(expr.Value))
+	case *syntax.ChanType:
+		return ir.NewChanType(p.pos(expr),
+			p.typeExpr(expr.Elem), p.chanDir(expr.Dir))
+
+	case *syntax.TypeSwitchGuard:
+		var tag *ir.Ident
+		if expr.Lhs != nil {
+			tag = ir.NewIdent(p.pos(expr.Lhs), p.name(expr.Lhs))
+			if ir.IsBlank(tag) {
+				base.Errorf("invalid variable name %v in type switch", tag)
+			}
+		}
+		return ir.NewTypeSwitchGuard(p.pos(expr), tag, p.expr(expr.X))
+	}
+	panic("unhandled Expr")
+}
+
+// sum efficiently handles very large summation expressions (such as
+// in issue #16394). In particular, it avoids left recursion and
+// collapses string literals.
+func (p *noder) sum(x syntax.Expr) ir.Node {
+	// While we need to handle long sums with asymptotic
+	// efficiency, the vast majority of sums are very small: ~95%
+	// have only 2 or 3 operands, and ~99% of string literals are
+	// never concatenated.
+
+	adds := make([]*syntax.Operation, 0, 2)
+	for {
+		add, ok := x.(*syntax.Operation)
+		if !ok || add.Op != syntax.Add || add.Y == nil {
+			break
+		}
+		adds = append(adds, add)
+		x = add.X
+	}
+
+	// nstr is the current rightmost string literal in the
+	// summation (if any), and chunks holds its accumulated
+	// substrings.
+	//
+	// Consider the expression x + "a" + "b" + "c" + y. When we
+	// reach the string literal "a", we assign nstr to point to
+	// its corresponding Node and initialize chunks to {"a"}.
+	// Visiting the subsequent string literals "b" and "c", we
+	// simply append their values to chunks. Finally, when we
+	// reach the non-constant operand y, we'll join chunks to form
+	// "abc" and reassign the "a" string literal's value.
+	//
+	// N.B., we need to be careful about named string constants
+	// (indicated by Sym != nil) because 1) we can't modify their
+	// value, as doing so would affect other uses of the string
+	// constant, and 2) they may have types, which we need to
+	// handle correctly. For now, we avoid these problems by
+	// treating named string constants the same as non-constant
+	// operands.
+	var nstr ir.Node
+	chunks := make([]string, 0, 1)
+
+	n := p.expr(x)
+	if ir.IsConst(n, constant.String) && n.Sym() == nil {
+		nstr = n
+		chunks = append(chunks, ir.StringVal(nstr))
+	}
+
+	for i := len(adds) - 1; i >= 0; i-- {
+		add := adds[i]
+
+		r := p.expr(add.Y)
+		if ir.IsConst(r, constant.String) && r.Sym() == nil {
+			if nstr != nil {
+				// Collapse r into nstr instead of adding to n.
+				chunks = append(chunks, ir.StringVal(r))
+				continue
+			}
+
+			nstr = r
+			chunks = append(chunks, ir.StringVal(nstr))
+		} else {
+			if len(chunks) > 1 {
+				nstr.SetVal(constant.MakeString(strings.Join(chunks, "")))
+			}
+			nstr = nil
+			chunks = chunks[:0]
+		}
+		n = ir.NewBinaryExpr(p.pos(add), ir.OADD, n, r)
+	}
+	if len(chunks) > 1 {
+		nstr.SetVal(constant.MakeString(strings.Join(chunks, "")))
+	}
+
+	return n
+}
+
+func (p *noder) typeExpr(typ syntax.Expr) ir.Ntype {
+	// TODO(mdempsky): Be stricter? typecheck should handle errors anyway.
+	n := p.expr(typ)
+	if n == nil {
+		return nil
+	}
+	if _, ok := n.(ir.Ntype); !ok {
+		ir.Dump("NOT NTYPE", n)
+	}
+	return n.(ir.Ntype)
+}
+
+func (p *noder) typeExprOrNil(typ syntax.Expr) ir.Ntype {
+	if typ != nil {
+		return p.typeExpr(typ)
+	}
+	return nil
+}
+
+func (p *noder) chanDir(dir syntax.ChanDir) types.ChanDir {
+	switch dir {
+	case 0:
+		return types.Cboth
+	case syntax.SendOnly:
+		return types.Csend
+	case syntax.RecvOnly:
+		return types.Crecv
+	}
+	panic("unhandled ChanDir")
+}
+
+func (p *noder) structType(expr *syntax.StructType) ir.Node {
+	l := make([]*ir.Field, 0, len(expr.FieldList))
+	for i, field := range expr.FieldList {
+		p.setlineno(field)
+		var n *ir.Field
+		if field.Name == nil {
+			n = p.embedded(field.Type)
+		} else {
+			n = ir.NewField(p.pos(field), p.name(field.Name), p.typeExpr(field.Type), nil)
+		}
+		if i < len(expr.TagList) && expr.TagList[i] != nil {
+			n.Note = constant.StringVal(p.basicLit(expr.TagList[i]))
+		}
+		l = append(l, n)
+	}
+
+	p.setlineno(expr)
+	return ir.NewStructType(p.pos(expr), l)
+}
+
+func (p *noder) interfaceType(expr *syntax.InterfaceType) ir.Node {
+	l := make([]*ir.Field, 0, len(expr.MethodList))
+	for _, method := range expr.MethodList {
+		p.setlineno(method)
+		var n *ir.Field
+		if method.Name == nil {
+			n = ir.NewField(p.pos(method), nil, importName(p.packname(method.Type)).(ir.Ntype), nil)
+		} else {
+			mname := p.name(method.Name)
+			if mname.IsBlank() {
+				base.Errorf("methods must have a unique non-blank name")
+				continue
+			}
+			sig := p.typeExpr(method.Type).(*ir.FuncType)
+			sig.Recv = fakeRecv()
+			n = ir.NewField(p.pos(method), mname, sig, nil)
+		}
+		l = append(l, n)
+	}
+
+	return ir.NewInterfaceType(p.pos(expr), l)
+}
+
+func (p *noder) packname(expr syntax.Expr) *types.Sym {
+	switch expr := expr.(type) {
+	case *syntax.Name:
+		name := p.name(expr)
+		if n := oldname(name); n.Name() != nil && n.Name().PkgName != nil {
+			n.Name().PkgName.Used = true
+		}
+		return name
+	case *syntax.SelectorExpr:
+		name := p.name(expr.X.(*syntax.Name))
+		def := ir.AsNode(name.Def)
+		if def == nil {
+			base.Errorf("undefined: %v", name)
+			return name
+		}
+		var pkg *types.Pkg
+		if def.Op() != ir.OPACK {
+			base.Errorf("%v is not a package", name)
+			pkg = types.LocalPkg
+		} else {
+			def := def.(*ir.PkgName)
+			def.Used = true
+			pkg = def.Pkg
+		}
+		return pkg.Lookup(expr.Sel.Value)
+	}
+	panic(fmt.Sprintf("unexpected packname: %#v", expr))
+}
+
+func (p *noder) embedded(typ syntax.Expr) *ir.Field {
+	op, isStar := typ.(*syntax.Operation)
+	if isStar {
+		if op.Op != syntax.Mul || op.Y != nil {
+			panic("unexpected Operation")
+		}
+		typ = op.X
+	}
+
+	sym := p.packname(typ)
+	n := ir.NewField(p.pos(typ), typecheck.Lookup(sym.Name), importName(sym).(ir.Ntype), nil)
+	n.Embedded = true
+
+	if isStar {
+		n.Ntype = ir.NewStarExpr(p.pos(op), n.Ntype)
+	}
+	return n
+}
+
+func (p *noder) stmts(stmts []syntax.Stmt) []ir.Node {
+	return p.stmtsFall(stmts, false)
+}
+
+func (p *noder) stmtsFall(stmts []syntax.Stmt, fallOK bool) []ir.Node {
+	var nodes []ir.Node
+	for i, stmt := range stmts {
+		s := p.stmtFall(stmt, fallOK && i+1 == len(stmts))
+		if s == nil {
+		} else if s.Op() == ir.OBLOCK && len(s.(*ir.BlockStmt).List) > 0 {
+			// Inline non-empty block.
+			// Empty blocks must be preserved for checkreturn.
+			nodes = append(nodes, s.(*ir.BlockStmt).List...)
+		} else {
+			nodes = append(nodes, s)
+		}
+	}
+	return nodes
+}
+
+func (p *noder) stmt(stmt syntax.Stmt) ir.Node {
+	return p.stmtFall(stmt, false)
+}
+
+func (p *noder) stmtFall(stmt syntax.Stmt, fallOK bool) ir.Node {
+	p.setlineno(stmt)
+	switch stmt := stmt.(type) {
+	case *syntax.EmptyStmt:
+		return nil
+	case *syntax.LabeledStmt:
+		return p.labeledStmt(stmt, fallOK)
+	case *syntax.BlockStmt:
+		l := p.blockStmt(stmt)
+		if len(l) == 0 {
+			// TODO(mdempsky): Line number?
+			return ir.NewBlockStmt(base.Pos, nil)
+		}
+		return ir.NewBlockStmt(src.NoXPos, l)
+	case *syntax.ExprStmt:
+		return p.wrapname(stmt, p.expr(stmt.X))
+	case *syntax.SendStmt:
+		return ir.NewSendStmt(p.pos(stmt), p.expr(stmt.Chan), p.expr(stmt.Value))
+	case *syntax.DeclStmt:
+		return ir.NewBlockStmt(src.NoXPos, p.decls(stmt.DeclList))
+	case *syntax.AssignStmt:
+		if stmt.Op != 0 && stmt.Op != syntax.Def {
+			n := ir.NewAssignOpStmt(p.pos(stmt), p.binOp(stmt.Op), p.expr(stmt.Lhs), p.expr(stmt.Rhs))
+			n.IncDec = stmt.Rhs == syntax.ImplicitOne
+			return n
+		}
+
+		rhs := p.exprList(stmt.Rhs)
+		if list, ok := stmt.Lhs.(*syntax.ListExpr); ok && len(list.ElemList) != 1 || len(rhs) != 1 {
+			n := ir.NewAssignListStmt(p.pos(stmt), ir.OAS2, nil, nil)
+			n.Def = stmt.Op == syntax.Def
+			n.Lhs.Set(p.assignList(stmt.Lhs, n, n.Def))
+			n.Rhs.Set(rhs)
+			return n
+		}
+
+		n := ir.NewAssignStmt(p.pos(stmt), nil, nil)
+		n.Def = stmt.Op == syntax.Def
+		n.X = p.assignList(stmt.Lhs, n, n.Def)[0]
+		n.Y = rhs[0]
+		return n
+
+	case *syntax.BranchStmt:
+		var op ir.Op
+		switch stmt.Tok {
+		case syntax.Break:
+			op = ir.OBREAK
+		case syntax.Continue:
+			op = ir.OCONTINUE
+		case syntax.Fallthrough:
+			if !fallOK {
+				base.Errorf("fallthrough statement out of place")
+			}
+			op = ir.OFALL
+		case syntax.Goto:
+			op = ir.OGOTO
+		default:
+			panic("unhandled BranchStmt")
+		}
+		var sym *types.Sym
+		if stmt.Label != nil {
+			sym = p.name(stmt.Label)
+		}
+		return ir.NewBranchStmt(p.pos(stmt), op, sym)
+	case *syntax.CallStmt:
+		var op ir.Op
+		switch stmt.Tok {
+		case syntax.Defer:
+			op = ir.ODEFER
+		case syntax.Go:
+			op = ir.OGO
+		default:
+			panic("unhandled CallStmt")
+		}
+		return ir.NewGoDeferStmt(p.pos(stmt), op, p.expr(stmt.Call))
+	case *syntax.ReturnStmt:
+		var results []ir.Node
+		if stmt.Results != nil {
+			results = p.exprList(stmt.Results)
+		}
+		n := ir.NewReturnStmt(p.pos(stmt), nil)
+		n.Results.Set(results)
+		if len(n.Results) == 0 && ir.CurFunc != nil {
+			for _, ln := range ir.CurFunc.Dcl {
+				if ln.Class_ == ir.PPARAM {
+					continue
+				}
+				if ln.Class_ != ir.PPARAMOUT {
+					break
+				}
+				if ln.Sym().Def != ln {
+					base.Errorf("%s is shadowed during return", ln.Sym().Name)
+				}
+			}
+		}
+		return n
+	case *syntax.IfStmt:
+		return p.ifStmt(stmt)
+	case *syntax.ForStmt:
+		return p.forStmt(stmt)
+	case *syntax.SwitchStmt:
+		return p.switchStmt(stmt)
+	case *syntax.SelectStmt:
+		return p.selectStmt(stmt)
+	}
+	panic("unhandled Stmt")
+}
+
+func (p *noder) assignList(expr syntax.Expr, defn ir.Node, colas bool) []ir.Node {
+	if !colas {
+		return p.exprList(expr)
+	}
+
+	var exprs []syntax.Expr
+	if list, ok := expr.(*syntax.ListExpr); ok {
+		exprs = list.ElemList
+	} else {
+		exprs = []syntax.Expr{expr}
+	}
+
+	res := make([]ir.Node, len(exprs))
+	seen := make(map[*types.Sym]bool, len(exprs))
+
+	newOrErr := false
+	for i, expr := range exprs {
+		p.setlineno(expr)
+		res[i] = ir.BlankNode
+
+		name, ok := expr.(*syntax.Name)
+		if !ok {
+			p.errorAt(expr.Pos(), "non-name %v on left side of :=", p.expr(expr))
+			newOrErr = true
+			continue
+		}
+
+		sym := p.name(name)
+		if sym.IsBlank() {
+			continue
+		}
+
+		if seen[sym] {
+			p.errorAt(expr.Pos(), "%v repeated on left side of :=", sym)
+			newOrErr = true
+			continue
+		}
+		seen[sym] = true
+
+		if sym.Block == types.Block {
+			res[i] = oldname(sym)
+			continue
+		}
+
+		newOrErr = true
+		n := typecheck.NewName(sym)
+		typecheck.Declare(n, typecheck.DeclContext)
+		n.Defn = defn
+		defn.PtrInit().Append(ir.NewDecl(base.Pos, ir.ODCL, n))
+		res[i] = n
+	}
+
+	if !newOrErr {
+		base.ErrorfAt(defn.Pos(), "no new variables on left side of :=")
+	}
+	return res
+}
+
+func (p *noder) blockStmt(stmt *syntax.BlockStmt) []ir.Node {
+	p.openScope(stmt.Pos())
+	nodes := p.stmts(stmt.List)
+	p.closeScope(stmt.Rbrace)
+	return nodes
+}
+
+func (p *noder) ifStmt(stmt *syntax.IfStmt) ir.Node {
+	p.openScope(stmt.Pos())
+	n := ir.NewIfStmt(p.pos(stmt), nil, nil, nil)
+	if stmt.Init != nil {
+		*n.PtrInit() = []ir.Node{p.stmt(stmt.Init)}
+	}
+	if stmt.Cond != nil {
+		n.Cond = p.expr(stmt.Cond)
+	}
+	n.Body.Set(p.blockStmt(stmt.Then))
+	if stmt.Else != nil {
+		e := p.stmt(stmt.Else)
+		if e.Op() == ir.OBLOCK {
+			e := e.(*ir.BlockStmt)
+			n.Else.Set(e.List)
+		} else {
+			n.Else = []ir.Node{e}
+		}
+	}
+	p.closeAnotherScope()
+	return n
+}
+
+func (p *noder) forStmt(stmt *syntax.ForStmt) ir.Node {
+	p.openScope(stmt.Pos())
+	if r, ok := stmt.Init.(*syntax.RangeClause); ok {
+		if stmt.Cond != nil || stmt.Post != nil {
+			panic("unexpected RangeClause")
+		}
+
+		n := ir.NewRangeStmt(p.pos(r), nil, p.expr(r.X), nil)
+		if r.Lhs != nil {
+			n.Def = r.Def
+			n.Vars.Set(p.assignList(r.Lhs, n, n.Def))
+		}
+		n.Body.Set(p.blockStmt(stmt.Body))
+		p.closeAnotherScope()
+		return n
+	}
+
+	n := ir.NewForStmt(p.pos(stmt), nil, nil, nil, nil)
+	if stmt.Init != nil {
+		*n.PtrInit() = []ir.Node{p.stmt(stmt.Init)}
+	}
+	if stmt.Cond != nil {
+		n.Cond = p.expr(stmt.Cond)
+	}
+	if stmt.Post != nil {
+		n.Post = p.stmt(stmt.Post)
+	}
+	n.Body.Set(p.blockStmt(stmt.Body))
+	p.closeAnotherScope()
+	return n
+}
+
+func (p *noder) switchStmt(stmt *syntax.SwitchStmt) ir.Node {
+	p.openScope(stmt.Pos())
+	n := ir.NewSwitchStmt(p.pos(stmt), nil, nil)
+	if stmt.Init != nil {
+		*n.PtrInit() = []ir.Node{p.stmt(stmt.Init)}
+	}
+	if stmt.Tag != nil {
+		n.Tag = p.expr(stmt.Tag)
+	}
+
+	var tswitch *ir.TypeSwitchGuard
+	if l := n.Tag; l != nil && l.Op() == ir.OTYPESW {
+		tswitch = l.(*ir.TypeSwitchGuard)
+	}
+	n.Cases.Set(p.caseClauses(stmt.Body, tswitch, stmt.Rbrace))
+
+	p.closeScope(stmt.Rbrace)
+	return n
+}
+
+func (p *noder) caseClauses(clauses []*syntax.CaseClause, tswitch *ir.TypeSwitchGuard, rbrace syntax.Pos) []ir.Node {
+	nodes := make([]ir.Node, 0, len(clauses))
+	for i, clause := range clauses {
+		p.setlineno(clause)
+		if i > 0 {
+			p.closeScope(clause.Pos())
+		}
+		p.openScope(clause.Pos())
+
+		n := ir.NewCaseStmt(p.pos(clause), nil, nil)
+		if clause.Cases != nil {
+			n.List.Set(p.exprList(clause.Cases))
+		}
+		if tswitch != nil && tswitch.Tag != nil {
+			nn := typecheck.NewName(tswitch.Tag.Sym())
+			typecheck.Declare(nn, typecheck.DeclContext)
+			n.Vars = []ir.Node{nn}
+			// keep track of the instances for reporting unused
+			nn.Defn = tswitch
+		}
+
+		// Trim trailing empty statements. We omit them from
+		// the Node AST anyway, and it's easier to identify
+		// out-of-place fallthrough statements without them.
+		body := clause.Body
+		for len(body) > 0 {
+			if _, ok := body[len(body)-1].(*syntax.EmptyStmt); !ok {
+				break
+			}
+			body = body[:len(body)-1]
+		}
+
+		n.Body.Set(p.stmtsFall(body, true))
+		if l := len(n.Body); l > 0 && n.Body[l-1].Op() == ir.OFALL {
+			if tswitch != nil {
+				base.Errorf("cannot fallthrough in type switch")
+			}
+			if i+1 == len(clauses) {
+				base.Errorf("cannot fallthrough final case in switch")
+			}
+		}
+
+		nodes = append(nodes, n)
+	}
+	if len(clauses) > 0 {
+		p.closeScope(rbrace)
+	}
+	return nodes
+}
+
+func (p *noder) selectStmt(stmt *syntax.SelectStmt) ir.Node {
+	n := ir.NewSelectStmt(p.pos(stmt), nil)
+	n.Cases.Set(p.commClauses(stmt.Body, stmt.Rbrace))
+	return n
+}
+
+func (p *noder) commClauses(clauses []*syntax.CommClause, rbrace syntax.Pos) []ir.Node {
+	nodes := make([]ir.Node, 0, len(clauses))
+	for i, clause := range clauses {
+		p.setlineno(clause)
+		if i > 0 {
+			p.closeScope(clause.Pos())
+		}
+		p.openScope(clause.Pos())
+
+		n := ir.NewCaseStmt(p.pos(clause), nil, nil)
+		if clause.Comm != nil {
+			n.List = []ir.Node{p.stmt(clause.Comm)}
+		}
+		n.Body.Set(p.stmts(clause.Body))
+		nodes = append(nodes, n)
+	}
+	if len(clauses) > 0 {
+		p.closeScope(rbrace)
+	}
+	return nodes
+}
+
+func (p *noder) labeledStmt(label *syntax.LabeledStmt, fallOK bool) ir.Node {
+	sym := p.name(label.Label)
+	lhs := ir.NewLabelStmt(p.pos(label), sym)
+
+	var ls ir.Node
+	if label.Stmt != nil { // TODO(mdempsky): Should always be present.
+		ls = p.stmtFall(label.Stmt, fallOK)
+		// Attach label directly to control statement too.
+		if ls != nil {
+			switch ls.Op() {
+			case ir.OFOR:
+				ls := ls.(*ir.ForStmt)
+				ls.Label = sym
+			case ir.ORANGE:
+				ls := ls.(*ir.RangeStmt)
+				ls.Label = sym
+			case ir.OSWITCH:
+				ls := ls.(*ir.SwitchStmt)
+				ls.Label = sym
+			case ir.OSELECT:
+				ls := ls.(*ir.SelectStmt)
+				ls.Label = sym
+			}
+		}
+	}
+
+	l := []ir.Node{lhs}
+	if ls != nil {
+		if ls.Op() == ir.OBLOCK {
+			ls := ls.(*ir.BlockStmt)
+			l = append(l, ls.List...)
+		} else {
+			l = append(l, ls)
+		}
+	}
+	return ir.NewBlockStmt(src.NoXPos, l)
+}
+
+var unOps = [...]ir.Op{
+	syntax.Recv: ir.ORECV,
+	syntax.Mul:  ir.ODEREF,
+	syntax.And:  ir.OADDR,
+
+	syntax.Not: ir.ONOT,
+	syntax.Xor: ir.OBITNOT,
+	syntax.Add: ir.OPLUS,
+	syntax.Sub: ir.ONEG,
+}
+
+func (p *noder) unOp(op syntax.Operator) ir.Op {
+	if uint64(op) >= uint64(len(unOps)) || unOps[op] == 0 {
+		panic("invalid Operator")
+	}
+	return unOps[op]
+}
+
+var binOps = [...]ir.Op{
+	syntax.OrOr:   ir.OOROR,
+	syntax.AndAnd: ir.OANDAND,
+
+	syntax.Eql: ir.OEQ,
+	syntax.Neq: ir.ONE,
+	syntax.Lss: ir.OLT,
+	syntax.Leq: ir.OLE,
+	syntax.Gtr: ir.OGT,
+	syntax.Geq: ir.OGE,
+
+	syntax.Add: ir.OADD,
+	syntax.Sub: ir.OSUB,
+	syntax.Or:  ir.OOR,
+	syntax.Xor: ir.OXOR,
+
+	syntax.Mul:    ir.OMUL,
+	syntax.Div:    ir.ODIV,
+	syntax.Rem:    ir.OMOD,
+	syntax.And:    ir.OAND,
+	syntax.AndNot: ir.OANDNOT,
+	syntax.Shl:    ir.OLSH,
+	syntax.Shr:    ir.ORSH,
+}
+
+func (p *noder) binOp(op syntax.Operator) ir.Op {
+	if uint64(op) >= uint64(len(binOps)) || binOps[op] == 0 {
+		panic("invalid Operator")
+	}
+	return binOps[op]
+}
+
+// checkLangCompat reports an error if the representation of a numeric
+// literal is not compatible with the current language version.
+func checkLangCompat(lit *syntax.BasicLit) {
+	s := lit.Value
+	if len(s) <= 2 || types.AllowsGoVersion(types.LocalPkg, 1, 13) {
+		return
+	}
+	// len(s) > 2
+	if strings.Contains(s, "_") {
+		base.ErrorfVers("go1.13", "underscores in numeric literals")
+		return
+	}
+	if s[0] != '0' {
+		return
+	}
+	radix := s[1]
+	if radix == 'b' || radix == 'B' {
+		base.ErrorfVers("go1.13", "binary literals")
+		return
+	}
+	if radix == 'o' || radix == 'O' {
+		base.ErrorfVers("go1.13", "0o/0O-style octal literals")
+		return
+	}
+	if lit.Kind != syntax.IntLit && (radix == 'x' || radix == 'X') {
+		base.ErrorfVers("go1.13", "hexadecimal floating-point literals")
+	}
+}
+
+func (p *noder) basicLit(lit *syntax.BasicLit) constant.Value {
+	// We don't use the errors of the conversion routines to determine
+	// if a literal string is valid because the conversion routines may
+	// accept a wider syntax than the language permits. Rely on lit.Bad
+	// instead.
+	if lit.Bad {
+		return constant.MakeUnknown()
+	}
+
+	switch lit.Kind {
+	case syntax.IntLit, syntax.FloatLit, syntax.ImagLit:
+		checkLangCompat(lit)
+	}
+
+	v := constant.MakeFromLiteral(lit.Value, tokenForLitKind[lit.Kind], 0)
+	if v.Kind() == constant.Unknown {
+		// TODO(mdempsky): Better error message?
+		p.errorAt(lit.Pos(), "malformed constant: %s", lit.Value)
+	}
+
+	// go/constant uses big.Rat by default, which is more precise, but
+	// causes toolstash -cmp and some tests to fail. For now, convert
+	// to big.Float to match cmd/compile's historical precision.
+	// TODO(mdempsky): Remove.
+	if v.Kind() == constant.Float {
+		v = constant.Make(ir.BigFloat(v))
+	}
+
+	return v
+}
+
+var tokenForLitKind = [...]token.Token{
+	syntax.IntLit:    token.INT,
+	syntax.RuneLit:   token.CHAR,
+	syntax.FloatLit:  token.FLOAT,
+	syntax.ImagLit:   token.IMAG,
+	syntax.StringLit: token.STRING,
+}
+
+func (p *noder) name(name *syntax.Name) *types.Sym {
+	return typecheck.Lookup(name.Value)
+}
+
+func (p *noder) mkname(name *syntax.Name) ir.Node {
+	// TODO(mdempsky): Set line number?
+	return mkname(p.name(name))
+}
+
+func (p *noder) wrapname(n syntax.Node, x ir.Node) ir.Node {
+	// These nodes do not carry line numbers.
+	// Introduce a wrapper node to give them the correct line.
+	switch x.Op() {
+	case ir.OTYPE, ir.OLITERAL:
+		if x.Sym() == nil {
+			break
+		}
+		fallthrough
+	case ir.ONAME, ir.ONONAME, ir.OPACK:
+		p := ir.NewParenExpr(p.pos(n), x)
+		p.SetImplicit(true)
+		return p
+	}
+	return x
+}
+
+func (p *noder) pos(n syntax.Node) src.XPos {
+	// TODO(gri): orig.Pos() should always be known - fix package syntax
+	xpos := base.Pos
+	if pos := n.Pos(); pos.IsKnown() {
+		xpos = p.makeXPos(pos)
+	}
+	return xpos
+}
+
+func (p *noder) setlineno(n syntax.Node) {
+	if n != nil {
+		base.Pos = p.pos(n)
+	}
+}
+
+// error is called concurrently if files are parsed concurrently.
+func (p *noder) error(err error) {
+	p.err <- err.(syntax.Error)
+}
+
+// pragmas that are allowed in the std lib, but don't have
+// a syntax.Pragma value (see lex.go) associated with them.
+var allowedStdPragmas = map[string]bool{
+	"go:cgo_export_static":  true,
+	"go:cgo_export_dynamic": true,
+	"go:cgo_import_static":  true,
+	"go:cgo_import_dynamic": true,
+	"go:cgo_ldflag":         true,
+	"go:cgo_dynamic_linker": true,
+	"go:embed":              true,
+	"go:generate":           true,
+}
+
+// *pragmas is the value stored in a syntax.pragmas during parsing.
+type pragmas struct {
+	Flag   ir.PragmaFlag // collected bits
+	Pos    []pragmaPos   // position of each individual flag
+	Embeds []pragmaEmbed
+}
+
+type pragmaPos struct {
+	Flag ir.PragmaFlag
+	Pos  syntax.Pos
+}
+
+type pragmaEmbed struct {
+	Pos      syntax.Pos
+	Patterns []string
+}
+
+func (p *noder) checkUnused(pragma *pragmas) {
+	for _, pos := range pragma.Pos {
+		if pos.Flag&pragma.Flag != 0 {
+			p.errorAt(pos.Pos, "misplaced compiler directive")
+		}
+	}
+	if len(pragma.Embeds) > 0 {
+		for _, e := range pragma.Embeds {
+			p.errorAt(e.Pos, "misplaced go:embed directive")
+		}
+	}
+}
+
+func (p *noder) checkUnusedDuringParse(pragma *pragmas) {
+	for _, pos := range pragma.Pos {
+		if pos.Flag&pragma.Flag != 0 {
+			p.error(syntax.Error{Pos: pos.Pos, Msg: "misplaced compiler directive"})
+		}
+	}
+	if len(pragma.Embeds) > 0 {
+		for _, e := range pragma.Embeds {
+			p.error(syntax.Error{Pos: e.Pos, Msg: "misplaced go:embed directive"})
+		}
+	}
+}
+
+// pragma is called concurrently if files are parsed concurrently.
+func (p *noder) pragma(pos syntax.Pos, blankLine bool, text string, old syntax.Pragma) syntax.Pragma {
+	pragma, _ := old.(*pragmas)
+	if pragma == nil {
+		pragma = new(pragmas)
+	}
+
+	if text == "" {
+		// unused pragma; only called with old != nil.
+		p.checkUnusedDuringParse(pragma)
+		return nil
+	}
+
+	if strings.HasPrefix(text, "line ") {
+		// line directives are handled by syntax package
+		panic("unreachable")
+	}
+
+	if !blankLine {
+		// directive must be on line by itself
+		p.error(syntax.Error{Pos: pos, Msg: "misplaced compiler directive"})
+		return pragma
+	}
+
+	switch {
+	case strings.HasPrefix(text, "go:linkname "):
+		f := strings.Fields(text)
+		if !(2 <= len(f) && len(f) <= 3) {
+			p.error(syntax.Error{Pos: pos, Msg: "usage: //go:linkname localname [linkname]"})
+			break
+		}
+		// The second argument is optional. If omitted, we use
+		// the default object symbol name for this and
+		// linkname only serves to mark this symbol as
+		// something that may be referenced via the object
+		// symbol name from another package.
+		var target string
+		if len(f) == 3 {
+			target = f[2]
+		} else if base.Ctxt.Pkgpath != "" {
+			// Use the default object symbol name if the
+			// user didn't provide one.
+			target = objabi.PathToPrefix(base.Ctxt.Pkgpath) + "." + f[1]
+		} else {
+			p.error(syntax.Error{Pos: pos, Msg: "//go:linkname requires linkname argument or -p compiler flag"})
+			break
+		}
+		p.linknames = append(p.linknames, linkname{pos, f[1], target})
+
+	case text == "go:embed", strings.HasPrefix(text, "go:embed "):
+		args, err := parseGoEmbed(text[len("go:embed"):])
+		if err != nil {
+			p.error(syntax.Error{Pos: pos, Msg: err.Error()})
+		}
+		if len(args) == 0 {
+			p.error(syntax.Error{Pos: pos, Msg: "usage: //go:embed pattern..."})
+			break
+		}
+		pragma.Embeds = append(pragma.Embeds, pragmaEmbed{pos, args})
+
+	case strings.HasPrefix(text, "go:cgo_import_dynamic "):
+		// This is permitted for general use because Solaris
+		// code relies on it in golang.org/x/sys/unix and others.
+		fields := pragmaFields(text)
+		if len(fields) >= 4 {
+			lib := strings.Trim(fields[3], `"`)
+			if lib != "" && !safeArg(lib) && !isCgoGeneratedFile(pos) {
+				p.error(syntax.Error{Pos: pos, Msg: fmt.Sprintf("invalid library name %q in cgo_import_dynamic directive", lib)})
+			}
+			p.pragcgo(pos, text)
+			pragma.Flag |= pragmaFlag("go:cgo_import_dynamic")
+			break
+		}
+		fallthrough
+	case strings.HasPrefix(text, "go:cgo_"):
+		// For security, we disallow //go:cgo_* directives other
+		// than cgo_import_dynamic outside cgo-generated files.
+		// Exception: they are allowed in the standard library, for runtime and syscall.
+		if !isCgoGeneratedFile(pos) && !base.Flag.Std {
+			p.error(syntax.Error{Pos: pos, Msg: fmt.Sprintf("//%s only allowed in cgo-generated code", text)})
+		}
+		p.pragcgo(pos, text)
+		fallthrough // because of //go:cgo_unsafe_args
+	default:
+		verb := text
+		if i := strings.Index(text, " "); i >= 0 {
+			verb = verb[:i]
+		}
+		flag := pragmaFlag(verb)
+		const runtimePragmas = ir.Systemstack | ir.Nowritebarrier | ir.Nowritebarrierrec | ir.Yeswritebarrierrec
+		if !base.Flag.CompilingRuntime && flag&runtimePragmas != 0 {
+			p.error(syntax.Error{Pos: pos, Msg: fmt.Sprintf("//%s only allowed in runtime", verb)})
+		}
+		if flag == 0 && !allowedStdPragmas[verb] && base.Flag.Std {
+			p.error(syntax.Error{Pos: pos, Msg: fmt.Sprintf("//%s is not allowed in the standard library", verb)})
+		}
+		pragma.Flag |= flag
+		pragma.Pos = append(pragma.Pos, pragmaPos{flag, pos})
+	}
+
+	return pragma
+}
+
+// isCgoGeneratedFile reports whether pos is in a file
+// generated by cgo, which is to say a file with name
+// beginning with "_cgo_". Such files are allowed to
+// contain cgo directives, and for security reasons
+// (primarily misuse of linker flags), other files are not.
+// See golang.org/issue/23672.
+func isCgoGeneratedFile(pos syntax.Pos) bool {
+	return strings.HasPrefix(filepath.Base(filepath.Clean(fileh(pos.Base().Filename()))), "_cgo_")
+}
+
+// safeArg reports whether arg is a "safe" command-line argument,
+// meaning that when it appears in a command-line, it probably
+// doesn't have some special meaning other than its own name.
+// This is copied from SafeArg in cmd/go/internal/load/pkg.go.
+func safeArg(name string) bool {
+	if name == "" {
+		return false
+	}
+	c := name[0]
+	return '0' <= c && c <= '9' || 'A' <= c && c <= 'Z' || 'a' <= c && c <= 'z' || c == '.' || c == '_' || c == '/' || c >= utf8.RuneSelf
+}
+
+func mkname(sym *types.Sym) ir.Node {
+	n := oldname(sym)
+	if n.Name() != nil && n.Name().PkgName != nil {
+		n.Name().PkgName.Used = true
+	}
+	return n
+}
+
+// parseGoEmbed parses the text following "//go:embed" to extract the glob patterns.
+// It accepts unquoted space-separated patterns as well as double-quoted and back-quoted Go strings.
+// go/build/read.go also processes these strings and contains similar logic.
+func parseGoEmbed(args string) ([]string, error) {
+	var list []string
+	for args = strings.TrimSpace(args); args != ""; args = strings.TrimSpace(args) {
+		var path string
+	Switch:
+		switch args[0] {
+		default:
+			i := len(args)
+			for j, c := range args {
+				if unicode.IsSpace(c) {
+					i = j
+					break
+				}
+			}
+			path = args[:i]
+			args = args[i:]
+
+		case '`':
+			i := strings.Index(args[1:], "`")
+			if i < 0 {
+				return nil, fmt.Errorf("invalid quoted string in //go:embed: %s", args)
+			}
+			path = args[1 : 1+i]
+			args = args[1+i+1:]
+
+		case '"':
+			i := 1
+			for ; i < len(args); i++ {
+				if args[i] == '\\' {
+					i++
+					continue
+				}
+				if args[i] == '"' {
+					q, err := strconv.Unquote(args[:i+1])
+					if err != nil {
+						return nil, fmt.Errorf("invalid quoted string in //go:embed: %s", args[:i+1])
+					}
+					path = q
+					args = args[i+1:]
+					break Switch
+				}
+			}
+			if i >= len(args) {
+				return nil, fmt.Errorf("invalid quoted string in //go:embed: %s", args)
+			}
+		}
+
+		if args != "" {
+			r, _ := utf8.DecodeRuneInString(args)
+			if !unicode.IsSpace(r) {
+				return nil, fmt.Errorf("invalid quoted string in //go:embed: %s", args)
+			}
+		}
+		list = append(list, path)
+	}
+	return list, nil
+}
+
+func fakeRecv() *ir.Field {
+	return ir.NewField(base.Pos, nil, nil, types.FakeRecvType())
+}
+
+func (p *noder) funcLit(expr *syntax.FuncLit) ir.Node {
+	xtype := p.typeExpr(expr.Type)
+	ntype := p.typeExpr(expr.Type)
+
+	fn := ir.NewFunc(p.pos(expr))
+	fn.SetIsHiddenClosure(ir.CurFunc != nil)
+	fn.Nname = ir.NewFuncNameAt(p.pos(expr), ir.BlankNode.Sym(), fn) // filled in by typecheckclosure
+	fn.Nname.Ntype = xtype
+	fn.Nname.Defn = fn
+
+	clo := ir.NewClosureExpr(p.pos(expr), fn)
+	fn.ClosureType = ntype
+	fn.OClosure = clo
+
+	p.funcBody(fn, expr.Body)
+
+	// closure-specific variables are hanging off the
+	// ordinary ones in the symbol table; see oldname.
+	// unhook them.
+	// make the list of pointers for the closure call.
+	for _, v := range fn.ClosureVars {
+		// Unlink from v1; see comment in syntax.go type Param for these fields.
+		v1 := v.Defn
+		v1.Name().Innermost = v.Outer
+
+		// If the closure usage of v is not dense,
+		// we need to make it dense; now that we're out
+		// of the function in which v appeared,
+		// look up v.Sym in the enclosing function
+		// and keep it around for use in the compiled code.
+		//
+		// That is, suppose we just finished parsing the innermost
+		// closure f4 in this code:
+		//
+		//	func f() {
+		//		v := 1
+		//		func() { // f2
+		//			use(v)
+		//			func() { // f3
+		//				func() { // f4
+		//					use(v)
+		//				}()
+		//			}()
+		//		}()
+		//	}
+		//
+		// At this point v.Outer is f2's v; there is no f3's v.
+		// To construct the closure f4 from within f3,
+		// we need to use f3's v and in this case we need to create f3's v.
+		// We are now in the context of f3, so calling oldname(v.Sym)
+		// obtains f3's v, creating it if necessary (as it is in the example).
+		//
+		// capturevars will decide whether to use v directly or &v.
+		v.Outer = oldname(v.Sym()).(*ir.Name)
+	}
+
+	return clo
+}
+
+// A function named init is a special case.
+// It is called by the initialization before main is run.
+// To make it unique within a package and also uncallable,
+// the name, normally "pkg.init", is altered to "pkg.init.0".
+var renameinitgen int
+
+func renameinit() *types.Sym {
+	s := typecheck.LookupNum("init.", renameinitgen)
+	renameinitgen++
+	return s
+}
+
+// oldname returns the Node that declares symbol s in the current scope.
+// If no such Node currently exists, an ONONAME Node is returned instead.
+// Automatically creates a new closure variable if the referenced symbol was
+// declared in a different (containing) function.
+func oldname(s *types.Sym) ir.Node {
+	if s.Pkg != types.LocalPkg {
+		return ir.NewIdent(base.Pos, s)
+	}
+
+	n := ir.AsNode(s.Def)
+	if n == nil {
+		// Maybe a top-level declaration will come along later to
+		// define s. resolve will check s.Def again once all input
+		// source has been processed.
+		return ir.NewIdent(base.Pos, s)
+	}
+
+	if ir.CurFunc != nil && n.Op() == ir.ONAME && n.Name().Curfn != nil && n.Name().Curfn != ir.CurFunc {
+		// Inner func is referring to var in outer func.
+		//
+		// TODO(rsc): If there is an outer variable x and we
+		// are parsing x := 5 inside the closure, until we get to
+		// the := it looks like a reference to the outer x so we'll
+		// make x a closure variable unnecessarily.
+		n := n.(*ir.Name)
+		c := n.Name().Innermost
+		if c == nil || c.Curfn != ir.CurFunc {
+			// Do not have a closure var for the active closure yet; make one.
+			c = typecheck.NewName(s)
+			c.Class_ = ir.PAUTOHEAP
+			c.SetIsClosureVar(true)
+			c.SetIsDDD(n.IsDDD())
+			c.Defn = n
+
+			// Link into list of active closure variables.
+			// Popped from list in func funcLit.
+			c.Outer = n.Name().Innermost
+			n.Name().Innermost = c
+
+			ir.CurFunc.ClosureVars = append(ir.CurFunc.ClosureVars, c)
+		}
+
+		// return ref to closure var, not original
+		return c
+	}
+
+	return n
+}
+
+func varEmbed(p *noder, names []*ir.Name, typ ir.Ntype, exprs []ir.Node, embeds []pragmaEmbed) (newExprs []ir.Node) {
+	haveEmbed := false
+	for _, decl := range p.file.DeclList {
+		imp, ok := decl.(*syntax.ImportDecl)
+		if !ok {
+			// imports always come first
+			break
+		}
+		path, _ := strconv.Unquote(imp.Path.Value)
+		if path == "embed" {
+			haveEmbed = true
+			break
+		}
+	}
+
+	pos := embeds[0].Pos
+	if !haveEmbed {
+		p.errorAt(pos, "invalid go:embed: missing import \"embed\"")
+		return exprs
+	}
+	if base.Flag.Cfg.Embed.Patterns == nil {
+		p.errorAt(pos, "invalid go:embed: build system did not supply embed configuration")
+		return exprs
+	}
+	if len(names) > 1 {
+		p.errorAt(pos, "go:embed cannot apply to multiple vars")
+		return exprs
+	}
+	if len(exprs) > 0 {
+		p.errorAt(pos, "go:embed cannot apply to var with initializer")
+		return exprs
+	}
+	if typ == nil {
+		// Should not happen, since len(exprs) == 0 now.
+		p.errorAt(pos, "go:embed cannot apply to var without type")
+		return exprs
+	}
+	if typecheck.DeclContext != ir.PEXTERN {
+		p.errorAt(pos, "go:embed cannot apply to var inside func")
+		return exprs
+	}
+
+	v := names[0]
+	typecheck.Target.Embeds = append(typecheck.Target.Embeds, v)
+	v.Embed = new([]ir.Embed)
+	for _, e := range embeds {
+		*v.Embed = append(*v.Embed, ir.Embed{Pos: p.makeXPos(e.Pos), Patterns: e.Patterns})
+	}
+	return exprs
+}