writer.go

	if idx, ok := w.localsIdx[obj]; w.Bool(ok) {
		w.Len(idx)
		return
	}

	idx, ok := w.closureVarsIdx[obj]
	if !ok {
		if w.closureVarsIdx == nil {
			w.closureVarsIdx = make(map[*types2.Var]int)
		}
		idx = len(w.closureVars)
		w.closureVars = append(w.closureVars, posVar{pos, obj})
		w.closureVarsIdx[obj] = idx
	}
	w.Len(idx)
}

func (w *writer) openScope(pos syntax.Pos) {
	w.Sync(pkgbits.SyncOpenScope)
	w.pos(pos)
}

func (w *writer) closeScope(pos syntax.Pos) {
	w.Sync(pkgbits.SyncCloseScope)
	w.pos(pos)
	w.closeAnotherScope()
}

func (w *writer) closeAnotherScope() {
	w.Sync(pkgbits.SyncCloseAnotherScope)
}

// @@@ Statements

// stmt writes the given statement into the function body bitstream.
func (w *writer) stmt(stmt syntax.Stmt) {
	var stmts []syntax.Stmt
	if stmt != nil {
		stmts = []syntax.Stmt{stmt}
	}
	w.stmts(stmts)
}

func (w *writer) stmts(stmts []syntax.Stmt) {
	w.Sync(pkgbits.SyncStmts)
	for _, stmt := range stmts {
		w.stmt1(stmt)
	}
	w.Code(stmtEnd)
	w.Sync(pkgbits.SyncStmtsEnd)
}

func (w *writer) stmt1(stmt syntax.Stmt) {
	switch stmt := stmt.(type) {
	default:
		w.p.unexpected("statement", stmt)

	case nil, *syntax.EmptyStmt:
		return

	case *syntax.AssignStmt:
		switch {
		case stmt.Rhs == nil:
			w.Code(stmtIncDec)
			w.op(binOps[stmt.Op])
			w.expr(stmt.Lhs)
			w.pos(stmt)

		case stmt.Op != 0 && stmt.Op != syntax.Def:
			w.Code(stmtAssignOp)
			w.op(binOps[stmt.Op])
			w.expr(stmt.Lhs)
			w.pos(stmt)
			w.expr(stmt.Rhs)

		default:
			w.Code(stmtAssign)
			w.pos(stmt)
			w.assignList(stmt.Lhs)
			w.exprList(stmt.Rhs)
		}

	case *syntax.BlockStmt:
		w.Code(stmtBlock)
		w.blockStmt(stmt)

	case *syntax.BranchStmt:
		w.Code(stmtBranch)
		w.pos(stmt)
		w.op(branchOps[stmt.Tok])
		w.optLabel(stmt.Label)

	case *syntax.CallStmt:
		w.Code(stmtCall)
		w.pos(stmt)
		w.op(callOps[stmt.Tok])
		w.expr(stmt.Call)

	case *syntax.DeclStmt:
		for _, decl := range stmt.DeclList {
			w.declStmt(decl)
		}

	case *syntax.ExprStmt:
		w.Code(stmtExpr)
		w.expr(stmt.X)

	case *syntax.ForStmt:
		w.Code(stmtFor)
		w.forStmt(stmt)

	case *syntax.IfStmt:
		w.Code(stmtIf)
		w.ifStmt(stmt)

	case *syntax.LabeledStmt:
		w.Code(stmtLabel)
		w.pos(stmt)
		w.label(stmt.Label)
		w.stmt1(stmt.Stmt)

	case *syntax.ReturnStmt:
		w.Code(stmtReturn)
		w.pos(stmt)
		w.exprList(stmt.Results)

	case *syntax.SelectStmt:
		w.Code(stmtSelect)
		w.selectStmt(stmt)

	case *syntax.SendStmt:
		w.Code(stmtSend)
		w.pos(stmt)
		w.expr(stmt.Chan)
		w.expr(stmt.Value)

	case *syntax.SwitchStmt:
		w.Code(stmtSwitch)
		w.switchStmt(stmt)
	}
}

func (w *writer) assignList(expr syntax.Expr) {
	exprs := unpackListExpr(expr)
	w.Len(len(exprs))

	for _, expr := range exprs {
		w.assign(expr)
	}
}

func (w *writer) assign(expr syntax.Expr) {
	expr = unparen(expr)

	if name, ok := expr.(*syntax.Name); ok {
		if name.Value == "_" {
			w.Code(assignBlank)
			return
		}

		if obj, ok := w.p.info.Defs[name]; ok {
			obj := obj.(*types2.Var)

			w.Code(assignDef)
			w.pos(obj)
			w.localIdent(obj)
			w.typ(obj.Type())

			// TODO(mdempsky): Minimize locals index size by deferring
			// this until the variables actually come into scope.
			w.addLocal(obj)
			return
		}
	}

	w.Code(assignExpr)
	w.expr(expr)
}

func (w *writer) declStmt(decl syntax.Decl) {
	switch decl := decl.(type) {
	default:
		w.p.unexpected("declaration", decl)

	case *syntax.ConstDecl, *syntax.TypeDecl:

	case *syntax.VarDecl:
		w.Code(stmtAssign)
		w.pos(decl)
		w.assignList(namesAsExpr(decl.NameList))
		w.exprList(decl.Values)
	}
}

func (w *writer) blockStmt(stmt *syntax.BlockStmt) {
	w.Sync(pkgbits.SyncBlockStmt)
	w.openScope(stmt.Pos())
	w.stmts(stmt.List)
	w.closeScope(stmt.Rbrace)
}

func (w *writer) forStmt(stmt *syntax.ForStmt) {
	w.Sync(pkgbits.SyncForStmt)
	w.openScope(stmt.Pos())

	if rang, ok := stmt.Init.(*syntax.RangeClause); w.Bool(ok) {
		w.pos(rang)
		w.assignList(rang.Lhs)
		w.expr(rang.X)
	} else {
		w.pos(stmt)
		w.stmt(stmt.Init)
		w.optExpr(stmt.Cond)
		w.stmt(stmt.Post)
	}

	w.blockStmt(stmt.Body)
	w.closeAnotherScope()
}

func (w *writer) ifStmt(stmt *syntax.IfStmt) {
	w.Sync(pkgbits.SyncIfStmt)
	w.openScope(stmt.Pos())
	w.pos(stmt)
	w.stmt(stmt.Init)
	w.expr(stmt.Cond)
	w.blockStmt(stmt.Then)
	w.stmt(stmt.Else)
	w.closeAnotherScope()
}

func (w *writer) selectStmt(stmt *syntax.SelectStmt) {
	w.Sync(pkgbits.SyncSelectStmt)

	w.pos(stmt)
	w.Len(len(stmt.Body))
	for i, clause := range stmt.Body {
		if i > 0 {
			w.closeScope(clause.Pos())
		}
		w.openScope(clause.Pos())

		w.pos(clause)
		w.stmt(clause.Comm)
		w.stmts(clause.Body)
	}
	if len(stmt.Body) > 0 {
		w.closeScope(stmt.Rbrace)
	}
}

func (w *writer) switchStmt(stmt *syntax.SwitchStmt) {
	w.Sync(pkgbits.SyncSwitchStmt)

	w.openScope(stmt.Pos())
	w.pos(stmt)
	w.stmt(stmt.Init)

	var iface types2.Type
	if guard, ok := stmt.Tag.(*syntax.TypeSwitchGuard); w.Bool(ok) {
		tv, ok := w.p.info.Types[guard.X]
		assert(ok && tv.IsValue())
		iface = tv.Type

		w.pos(guard)
		if tag := guard.Lhs; w.Bool(tag != nil) {
			w.pos(tag)
			w.String(tag.Value)
		}
		w.expr(guard.X)
	} else {
		w.optExpr(stmt.Tag)
	}

	w.Len(len(stmt.Body))
	for i, clause := range stmt.Body {
		if i > 0 {
			w.closeScope(clause.Pos())
		}
		w.openScope(clause.Pos())

		w.pos(clause)

		if iface != nil {
			cases := unpackListExpr(clause.Cases)
			w.Len(len(cases))
			for _, cas := range cases {
				w.exprType(iface, cas, true)
			}
		} else {
			w.exprList(clause.Cases)
		}

		if obj, ok := w.p.info.Implicits[clause]; ok {
			// TODO(mdempsky): These pos details are quirkish, but also
			// necessary so the variable's position is correct for DWARF
			// scope assignment later. It would probably be better for us to
			// instead just set the variable's DWARF scoping info earlier so
			// we can give it the correct position information.
			pos := clause.Pos()
			if typs := unpackListExpr(clause.Cases); len(typs) != 0 {
				pos = typeExprEndPos(typs[len(typs)-1])
			}
			w.pos(pos)

			obj := obj.(*types2.Var)
			w.typ(obj.Type())
			w.addLocal(obj)
		}

		w.stmts(clause.Body)
	}
	if len(stmt.Body) > 0 {
		w.closeScope(stmt.Rbrace)
	}

	w.closeScope(stmt.Rbrace)
}

func (w *writer) label(label *syntax.Name) {
	w.Sync(pkgbits.SyncLabel)

	// TODO(mdempsky): Replace label strings with dense indices.
	w.String(label.Value)
}

func (w *writer) optLabel(label *syntax.Name) {
	w.Sync(pkgbits.SyncOptLabel)
	if w.Bool(label != nil) {
		w.label(label)
	}
}

// @@@ Expressions

// expr writes the given expression into the function body bitstream.
func (w *writer) expr(expr syntax.Expr) {
	base.Assertf(expr != nil, "missing expression")

	expr = unparen(expr) // skip parens; unneeded after typecheck

	obj, inst := lookupObj(w.p.info, expr)
	targs := inst.TypeArgs

	if tv, ok := w.p.info.Types[expr]; ok {
		// TODO(mdempsky): Be more judicious about which types are marked as "needed".
		if inst.Type != nil {
			w.needType(inst.Type)
		} else {
			w.needType(tv.Type)
		}

		if tv.IsType() {
			w.p.fatalf(expr, "unexpected type expression %v", syntax.String(expr))
		}

		if tv.Value != nil {
			w.Code(exprConst)
			w.pos(expr)
			w.typ(tv.Type)
			w.Value(tv.Value)

			// TODO(mdempsky): These details are only important for backend
			// diagnostics. Explore writing them out separately.
			w.op(constExprOp(expr))
			w.String(syntax.String(expr))
			return
		}
	}

	if obj != nil {
		if isGlobal(obj) {
			w.Code(exprGlobal)
			w.obj(obj, targs)
			return
		}

		obj := obj.(*types2.Var)
		assert(!obj.IsField())
		assert(targs.Len() == 0)

		w.Code(exprLocal)
		w.useLocal(expr.Pos(), obj)
		return
	}

	switch expr := expr.(type) {
	default:
		w.p.unexpected("expression", expr)

	case *syntax.CompositeLit:
		w.Code(exprCompLit)
		w.compLit(expr)

	case *syntax.FuncLit:
		w.Code(exprFuncLit)
		w.funcLit(expr)

	case *syntax.SelectorExpr:
		sel, ok := w.p.info.Selections[expr]
		assert(ok)

		w.Code(exprSelector)
		if w.Bool(sel.Kind() == types2.MethodExpr) {
			w.exprType(nil, expr.X, false)
		} else {
			w.expr(expr.X)
		}
		w.pos(expr)
		w.selector(sel.Obj())

	case *syntax.IndexExpr:
		tv, ok := w.p.info.Types[expr.Index]
		assert(ok && tv.IsValue())

		w.Code(exprIndex)
		w.expr(expr.X)
		w.pos(expr)
		w.expr(expr.Index)

	case *syntax.SliceExpr:
		w.Code(exprSlice)
		w.expr(expr.X)
		w.pos(expr)
		for _, n := range &expr.Index {
			w.optExpr(n)
		}

	case *syntax.AssertExpr:
		tv, ok := w.p.info.Types[expr.X]
		assert(ok && tv.IsValue())

		w.Code(exprAssert)
		w.expr(expr.X)
		w.pos(expr)
		w.exprType(tv.Type, expr.Type, false)

	case *syntax.Operation:
		if expr.Y == nil {
			w.Code(exprUnaryOp)
			w.op(unOps[expr.Op])
			w.pos(expr)
			w.expr(expr.X)
			break
		}

		w.Code(exprBinaryOp)
		w.op(binOps[expr.Op])
		w.expr(expr.X)
		w.pos(expr)
		w.expr(expr.Y)

	case *syntax.CallExpr:
		tv, ok := w.p.info.Types[expr.Fun]
		assert(ok)
		if tv.IsType() {
			assert(len(expr.ArgList) == 1)
			assert(!expr.HasDots)

			w.Code(exprConvert)
			w.typ(tv.Type)
			w.pos(expr)
			w.expr(expr.ArgList[0])
			break
		}

		if name, ok := unparen(expr.Fun).(*syntax.Name); ok && tv.IsBuiltin() {
			switch name.Value {
			case "make":
				assert(len(expr.ArgList) >= 1)
				assert(!expr.HasDots)

				w.Code(exprMake)
				w.pos(expr)
				w.exprType(nil, expr.ArgList[0], false)
				w.exprs(expr.ArgList[1:])
				return

			case "new":
				assert(len(expr.ArgList) == 1)
				assert(!expr.HasDots)

				w.Code(exprNew)
				w.pos(expr)
				w.exprType(nil, expr.ArgList[0], false)
				return
			}
		}

		writeFunExpr := func() {
			if selector, ok := unparen(expr.Fun).(*syntax.SelectorExpr); ok {
				if sel, ok := w.p.info.Selections[selector]; ok && sel.Kind() == types2.MethodVal {
					w.expr(selector.X)
					w.Bool(true) // method call
					w.pos(selector)
					w.selector(sel.Obj())
					return
				}
			}

			w.expr(expr.Fun)
			w.Bool(false) // not a method call (i.e., normal function call)
		}

		w.Code(exprCall)
		writeFunExpr()
		w.pos(expr)
		if w.Bool(len(expr.ArgList) == 1 && isMultiValueExpr(w.p.info, expr.ArgList[0])) {
			// f(g()) call
			assert(!expr.HasDots)
			w.expr(expr.ArgList[0])
		} else {
			w.exprs(expr.ArgList)
			w.Bool(expr.HasDots)
		}
	}
}

func (w *writer) optExpr(expr syntax.Expr) {
	if w.Bool(expr != nil) {
		w.expr(expr)
	}
}

func (w *writer) compLit(lit *syntax.CompositeLit) {
	tv, ok := w.p.info.Types[lit]
	assert(ok)

	w.Sync(pkgbits.SyncCompLit)
	w.pos(lit)
	w.typ(tv.Type)

	typ := tv.Type
	if ptr, ok := types2.CoreType(typ).(*types2.Pointer); ok {
		typ = ptr.Elem()
	}
	str, isStruct := types2.CoreType(typ).(*types2.Struct)

	w.Len(len(lit.ElemList))
	for i, elem := range lit.ElemList {
		if isStruct {
			if kv, ok := elem.(*syntax.KeyValueExpr); ok {
				// use position of expr.Key rather than of elem (which has position of ':')
				w.pos(kv.Key)
				w.Len(fieldIndex(w.p.info, str, kv.Key.(*syntax.Name)))
				elem = kv.Value
			} else {
				w.pos(elem)
				w.Len(i)
			}
		} else {
			if kv, ok := elem.(*syntax.KeyValueExpr); w.Bool(ok) {
				// use position of expr.Key rather than of elem (which has position of ':')
				w.pos(kv.Key)
				w.expr(kv.Key)
				elem = kv.Value
			}
		}
		w.pos(elem)
		w.expr(elem)
	}
}

func (w *writer) funcLit(expr *syntax.FuncLit) {
	tv, ok := w.p.info.Types[expr]
	assert(ok)
	sig := tv.Type.(*types2.Signature)

	body, closureVars := w.p.bodyIdx(sig, expr.Body, w.dict)

	w.Sync(pkgbits.SyncFuncLit)
	w.pos(expr)
	w.signature(sig)

	w.Len(len(closureVars))
	for _, cv := range closureVars {
		w.pos(cv.pos)
		w.useLocal(cv.pos, cv.var_)
	}

	w.Reloc(pkgbits.RelocBody, body)
}

type posVar struct {
	pos  syntax.Pos
	var_ *types2.Var
}

func (w *writer) exprList(expr syntax.Expr) {
	w.Sync(pkgbits.SyncExprList)
	w.exprs(unpackListExpr(expr))
}

func (w *writer) exprs(exprs []syntax.Expr) {
	w.Sync(pkgbits.SyncExprs)
	w.Len(len(exprs))
	for _, expr := range exprs {
		w.expr(expr)
	}
}

func (w *writer) exprType(iface types2.Type, typ syntax.Expr, nilOK bool) {
	base.Assertf(iface == nil || isInterface(iface), "%v must be nil or an interface type", iface)

	tv, ok := w.p.info.Types[typ]
	assert(ok)

	w.Sync(pkgbits.SyncExprType)

	if nilOK && w.Bool(tv.IsNil()) {
		return
	}

	assert(tv.IsType())
	info := w.p.typIdx(tv.Type, w.dict)

	w.pos(typ)

	if w.Bool(info.derived && iface != nil && !iface.Underlying().(*types2.Interface).Empty()) {
		ifaceInfo := w.p.typIdx(iface, w.dict)

		idx := -1
		for i, itab := range w.dict.itabs {
			if itab.typIdx == info.idx && itab.iface == ifaceInfo {
				idx = i
			}
		}
		if idx < 0 {
			idx = len(w.dict.itabs)
			w.dict.itabs = append(w.dict.itabs, itabInfo{typIdx: info.idx, iface: ifaceInfo})
		}
		w.Len(idx)
		return
	}

	w.typInfo(info)
}

// isInterface reports whether typ is known to be an interface type.
// If typ is a type parameter, then isInterface reports an internal
// compiler error instead.
func isInterface(typ types2.Type) bool {
	if _, ok := typ.(*types2.TypeParam); ok {
		// typ is a type parameter and may be instantiated as either a
		// concrete or interface type, so the writer can't depend on
		// knowing this.
		base.Fatalf("%v is a type parameter", typ)
	}

	_, ok := typ.Underlying().(*types2.Interface)
	return ok
}

// op writes an Op into the bitstream.
func (w *writer) op(op ir.Op) {
	// TODO(mdempsky): Remove in favor of explicit codes? Would make
	// export data more stable against internal refactorings, but low
	// priority at the moment.
	assert(op != 0)
	w.Sync(pkgbits.SyncOp)
	w.Len(int(op))
}

func (w *writer) needType(typ types2.Type) {
	// Decompose tuple into component element types.
	if typ, ok := typ.(*types2.Tuple); ok {
		for i := 0; i < typ.Len(); i++ {
			w.needType(typ.At(i).Type())
		}
		return
	}

	if info := w.p.typIdx(typ, w.dict); info.derived {
		w.dict.derived[info.idx].needed = true
	}
}

// @@@ Package initialization

// Caution: This code is still clumsy, because toolstash -cmp is
// particularly sensitive to it.

type typeDeclGen struct {
	*syntax.TypeDecl
	gen int

	// Implicit type parameters in scope at this type declaration.
	implicits []*types2.TypeName
}

type fileImports struct {
	importedEmbed, importedUnsafe bool
}

// declCollector is a visitor type that collects compiler-needed
// information about declarations that types2 doesn't track.
//
// Notably, it maps declared types and functions back to their
// declaration statement, keeps track of implicit type parameters, and
// assigns unique type "generation" numbers to local defined types.
type declCollector struct {
	pw         *pkgWriter
	typegen    *int
	file       *fileImports
	withinFunc bool
	implicits  []*types2.TypeName
}

func (c *declCollector) withTParams(obj types2.Object) *declCollector {
	tparams := objTypeParams(obj)
	n := tparams.Len()
	if n == 0 {
		return c
	}

	copy := *c
	copy.implicits = copy.implicits[:len(copy.implicits):len(copy.implicits)]
	for i := 0; i < n; i++ {
		copy.implicits = append(copy.implicits, tparams.At(i).Obj())
	}
	return &copy
}

func (c *declCollector) Visit(n syntax.Node) syntax.Visitor {
	pw := c.pw

	switch n := n.(type) {
	case *syntax.File:
		pw.checkPragmas(n.Pragma, ir.GoBuildPragma, false)

	case *syntax.ImportDecl:
		pw.checkPragmas(n.Pragma, 0, false)

		switch pkgNameOf(pw.info, n).Imported().Path() {
		case "embed":
			c.file.importedEmbed = true
		case "unsafe":
			c.file.importedUnsafe = true
		}

	case *syntax.ConstDecl:
		pw.checkPragmas(n.Pragma, 0, false)

	case *syntax.FuncDecl:
		pw.checkPragmas(n.Pragma, funcPragmas, false)

		obj := pw.info.Defs[n.Name].(*types2.Func)
		pw.funDecls[obj] = n

		return c.withTParams(obj)

	case *syntax.TypeDecl:
		obj := pw.info.Defs[n.Name].(*types2.TypeName)
		d := typeDeclGen{TypeDecl: n, implicits: c.implicits}

		if n.Alias {
			pw.checkPragmas(n.Pragma, 0, false)
		} else {
			pw.checkPragmas(n.Pragma, typePragmas, false)

			// Assign a unique ID to function-scoped defined types.
			if c.withinFunc {
				*c.typegen++
				d.gen = *c.typegen
			}
		}

		pw.typDecls[obj] = d

		// TODO(mdempsky): Omit? Not strictly necessary; only matters for
		// type declarations within function literals within parameterized
		// type declarations, but types2 the function literals will be
		// constant folded away.
		return c.withTParams(obj)

	case *syntax.VarDecl:
		pw.checkPragmas(n.Pragma, 0, true)

		if p, ok := n.Pragma.(*pragmas); ok && len(p.Embeds) > 0 {
			if err := checkEmbed(n, c.file.importedEmbed, c.withinFunc); err != nil {
				pw.errorf(p.Embeds[0].Pos, "%s", err)
			}
		}

	case *syntax.BlockStmt:
		if !c.withinFunc {
			copy := *c
			copy.withinFunc = true
			return &copy
		}
	}

	return c
}

func (pw *pkgWriter) collectDecls(noders []*noder) {
	var typegen int
	for _, p := range noders {
		var file fileImports

		syntax.Walk(p.file, &declCollector{
			pw:      pw,
			typegen: &typegen,
			file:    &file,
		})

		pw.cgoPragmas = append(pw.cgoPragmas, p.pragcgobuf...)

		for _, l := range p.linknames {
			if !file.importedUnsafe {
				pw.errorf(l.pos, "//go:linkname only allowed in Go files that import \"unsafe\"")
				continue
			}

			switch obj := pw.curpkg.Scope().Lookup(l.local).(type) {
			case *types2.Func, *types2.Var:
				if _, ok := pw.linknames[obj]; !ok {
					pw.linknames[obj] = l.remote
				} else {
					pw.errorf(l.pos, "duplicate //go:linkname for %s", l.local)
				}

			default:
				pw.errorf(l.pos, "//go:linkname must refer to declared function or variable")
			}
		}
	}
}

func (pw *pkgWriter) checkPragmas(p syntax.Pragma, allowed ir.PragmaFlag, embedOK bool) {
	if p == nil {
		return
	}
	pragma := p.(*pragmas)

	for _, pos := range pragma.Pos {
		if pos.Flag&^allowed != 0 {
			pw.errorf(pos.Pos, "misplaced compiler directive")
		}
	}

	if !embedOK {
		for _, e := range pragma.Embeds {
			pw.errorf(e.Pos, "misplaced go:embed directive")
		}
	}
}

func (w *writer) pkgInit(noders []*noder) {
	w.Len(len(w.p.cgoPragmas))
	for _, cgoPragma := range w.p.cgoPragmas {
		w.Strings(cgoPragma)
	}

	w.Sync(pkgbits.SyncDecls)
	for _, p := range noders {
		for _, decl := range p.file.DeclList {
			w.pkgDecl(decl)
		}
	}
	w.Code(declEnd)

	w.Sync(pkgbits.SyncEOF)
}

func (w *writer) pkgDecl(decl syntax.Decl) {
	switch decl := decl.(type) {
	default:
		w.p.unexpected("declaration", decl)

	case *syntax.ImportDecl:

	case *syntax.ConstDecl:
		w.Code(declOther)
		w.pkgObjs(decl.NameList...)

	case *syntax.FuncDecl:
		if decl.Name.Value == "_" {
			break // skip blank functions
		}

		obj := w.p.info.Defs[decl.Name].(*types2.Func)
		sig := obj.Type().(*types2.Signature)

		if sig.RecvTypeParams() != nil || sig.TypeParams() != nil {
			break // skip generic functions
		}

		if recv := sig.Recv(); recv != nil {
			w.Code(declMethod)
			w.typ(recvBase(recv))
			w.selector(obj)
			break
		}

		w.Code(declFunc)
		w.pkgObjs(decl.Name)

	case *syntax.TypeDecl:
		if len(decl.TParamList) != 0 {
			break // skip generic type decls
		}

		if decl.Name.Value == "_" {
			break // skip blank type decls
		}

		name := w.p.info.Defs[decl.Name].(*types2.TypeName)
		// Skip type declarations for interfaces that are only usable as
		// type parameter bounds.
		if iface, ok := name.Type().Underlying().(*types2.Interface); ok && !iface.IsMethodSet() {
			break
		}

		w.Code(declOther)
		w.pkgObjs(decl.Name)

	case *syntax.VarDecl:
		w.Code(declVar)
		w.pos(decl)
		w.pkgObjs(decl.NameList...)
		w.exprList(decl.Values)

		var embeds []pragmaEmbed
		if p, ok := decl.Pragma.(*pragmas); ok {
			embeds = p.Embeds
		}
		w.Len(len(embeds))
		for _, embed := range embeds {
			w.pos(embed.Pos)
			w.Strings(embed.Patterns)
		}
	}
}

func (w *writer) pkgObjs(names ...*syntax.Name) {
	w.Sync(pkgbits.SyncDeclNames)
	w.Len(len(names))

	for _, name := range names {
		obj, ok := w.p.info.Defs[name]
		assert(ok)

		w.Sync(pkgbits.SyncDeclName)
		w.obj(obj, nil)
	}
}

// @@@ Helpers

// isDefinedType reports whether obj is a defined type.
func isDefinedType(obj types2.Object) bool {
	if obj, ok := obj.(*types2.TypeName); ok {
		return !obj.IsAlias()
	}
	return false
}

// isGlobal reports whether obj was declared at package scope.
//
// Caveat: blank objects are not declared.
func isGlobal(obj types2.Object) bool {
	return obj.Parent() == obj.Pkg().Scope()
}

// lookupObj returns the object that expr refers to, if any. If expr
// is an explicit instantiation of a generic object, then the instance
// object is returned as well.
func lookupObj(info *types2.Info, expr syntax.Expr) (obj types2.Object, inst types2.Instance) {
	if index, ok := expr.(*syntax.IndexExpr); ok {
		args := unpackListExpr(index.Index)
		if len(args) == 1 {
			tv, ok := info.Types[args[0]]
			assert(ok)
			if tv.IsValue() {
				return // normal index expression
			}
		}

		expr = index.X
	}

	// Strip package qualifier, if present.
	if sel, ok := expr.(*syntax.SelectorExpr); ok {
		if !isPkgQual(info, sel) {
			return // normal selector expression
		}
		expr = sel.Sel
	}

	if name, ok := expr.(*syntax.Name); ok {
		obj = info.Uses[name]
		inst = info.Instances[name]
	}
	return
}

// isPkgQual reports whether the given selector expression is a
// package-qualified identifier.
func isPkgQual(info *types2.Info, sel *syntax.SelectorExpr) bool {