writer.go

		w.stmts(block.List)
		w.pos(block.Rbrace)
	}

	return w.Flush(), w.closureVars
}

func (w *writer) funcargs(sig *types2.Signature) {
	do := func(params *types2.Tuple, result bool) {
		for i := 0; i < params.Len(); i++ {
			w.funcarg(params.At(i), result)
		}
	}

	if recv := sig.Recv(); recv != nil {
		w.funcarg(recv, false)
	}
	do(sig.Params(), false)
	do(sig.Results(), true)
}

func (w *writer) funcarg(param *types2.Var, result bool) {
	if param.Name() != "" || result {
		w.addLocal(param)
	}
}

// addLocal records the declaration of a new local variable.
func (w *writer) addLocal(obj *types2.Var) {
	w.Sync(pkgbits.SyncAddLocal)
	idx := len(w.localsIdx)
	if w.p.SyncMarkers() {
		w.Int(idx)
	}
	if w.localsIdx == nil {
		w.localsIdx = make(map[*types2.Var]int)
	}
	w.localsIdx[obj] = idx
}

// useLocal writes a reference to the given local or free variable
// into the bitstream.
func (w *writer) useLocal(pos syntax.Pos, obj *types2.Var) {
	w.Sync(pkgbits.SyncUseObjLocal)

	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)

			var typ types2.Type
			if stmt.Op != syntax.Shl && stmt.Op != syntax.Shr {
				typ = w.p.typeOf(stmt.Lhs)
			}
			w.implicitConvExpr(stmt, typ, stmt.Rhs)

		default:
			w.assignStmt(stmt, stmt.Lhs, 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)

		resultTypes := w.sig.Results()
		dstType := func(i int) types2.Type {
			return resultTypes.At(i).Type()
		}
		w.multiExpr(stmt, dstType, unpackListExpr(stmt.Results))

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

	case *syntax.SendStmt:
		chanType := types2.CoreType(w.p.typeOf(stmt.Chan)).(*types2.Chan)

		w.Code(stmtSend)
		w.pos(stmt)
		w.expr(stmt.Chan)
		w.implicitConvExpr(stmt, chanType.Elem(), 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.assignStmt(decl, namesAsExpr(decl.NameList), decl.Values)
	}
}

// assignStmt writes out an assignment for "lhs = rhs".
func (w *writer) assignStmt(pos poser, lhs0, rhs0 syntax.Expr) {
	lhs := unpackListExpr(lhs0)
	rhs := unpackListExpr(rhs0)

	w.Code(stmtAssign)
	w.pos(pos)

	// As if w.assignList(lhs0).
	w.Len(len(lhs))
	for _, expr := range lhs {
		w.assign(expr)
	}

	dstType := func(i int) types2.Type {
		dst := lhs[i]

		// Finding dstType is somewhat involved, because for VarDecl
		// statements, the Names are only added to the info.{Defs,Uses}
		// maps, not to info.Types.
		if name, ok := unparen(dst).(*syntax.Name); ok {
			if name.Value == "_" {
				return nil // ok: no implicit conversion
			} else if def, ok := w.p.info.Defs[name].(*types2.Var); ok {
				return def.Type()
			} else if use, ok := w.p.info.Uses[name].(*types2.Var); ok {
				return use.Type()
			} else {
				w.p.fatalf(dst, "cannot find type of destination object: %v", dst)
			}
		}

		return w.p.typeOf(dst)
	}

	w.multiExpr(pos, dstType, rhs)
}

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)

		xtyp := w.p.typeOf(rang.X)
		if _, isMap := types2.CoreType(xtyp).(*types2.Map); isMap {
			w.rtype(xtyp)
		}
		{
			lhs := unpackListExpr(rang.Lhs)
			assign := func(i int, src types2.Type) {
				if i >= len(lhs) {
					return
				}
				dst := unparen(lhs[i])
				if name, ok := dst.(*syntax.Name); ok && name.Value == "_" {
					return
				}

				var dstType types2.Type
				if rang.Def {
					// For `:=` assignments, the LHS names only appear in Defs,
					// not Types (as used by typeOf).
					dstType = w.p.info.Defs[dst.(*syntax.Name)].(*types2.Var).Type()
				} else {
					dstType = w.p.typeOf(dst)
				}

				w.convRTTI(src, dstType)
			}

			keyType, valueType := w.p.rangeTypes(rang.X)
			assign(0, keyType)
			assign(1, valueType)
		}

	} else {
		w.pos(stmt)
		w.stmt(stmt.Init)
		w.optExpr(stmt.Cond)
		w.stmt(stmt.Post)
	}

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

// rangeTypes returns the types of values produced by ranging over
// expr.
func (pw *pkgWriter) rangeTypes(expr syntax.Expr) (key, value types2.Type) {
	typ := pw.typeOf(expr)
	switch typ := types2.CoreType(typ).(type) {
	case *types2.Pointer: // must be pointer to array
		return types2.Typ[types2.Int], types2.CoreType(typ.Elem()).(*types2.Array).Elem()
	case *types2.Array:
		return types2.Typ[types2.Int], typ.Elem()
	case *types2.Slice:
		return types2.Typ[types2.Int], typ.Elem()
	case *types2.Basic:
		if typ.Info()&types2.IsString != 0 {
			return types2.Typ[types2.Int], runeTypeName.Type()
		}
	case *types2.Map:
		return typ.Key(), typ.Elem()
	case *types2.Chan:
		return typ.Elem(), nil
	}
	pw.fatalf(expr, "unexpected range type: %v", typ)
	panic("unreachable")
}

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, tagType types2.Type
	if guard, ok := stmt.Tag.(*syntax.TypeSwitchGuard); w.Bool(ok) {
		iface = w.p.typeOf(guard.X)

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

		if tag != nil {
			tagType = w.p.typeOf(tag)
		} else {
			tagType = types2.Typ[types2.Bool]
		}

		// Walk is going to emit comparisons between the tag value and
		// each case expression, and we want these comparisons to always
		// have the same type. If there are any case values that can't be
		// converted to the tag value's type, then convert everything to
		// `any` instead.
	Outer:
		for _, clause := range stmt.Body {
			for _, cas := range unpackListExpr(clause.Cases) {
				if casType := w.p.typeOf(cas); !types2.AssignableTo(casType, tagType) {
					tagType = types2.NewInterfaceType(nil, nil)
					break Outer
				}
			}
		}

		if w.Bool(tag != nil) {
			w.implicitConvExpr(tag, tagType, 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)

		cases := unpackListExpr(clause.Cases)
		if iface != nil {
			w.Len(len(cases))
			for _, cas := range cases {
				if w.Bool(isNil(w.p.info, cas)) {
					continue
				}
				w.exprType(iface, cas)
			}
		} else {
			// As if w.exprList(clause.Cases),
			// but with implicit conversions to tagType.

			w.Sync(pkgbits.SyncExprList)
			w.Sync(pkgbits.SyncExprs)
			w.Len(len(cases))
			for _, cas := range cases {
				w.implicitConvExpr(cas, tagType, cas)
			}
		}

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

		if tv.Value != nil {
			w.Code(exprConst)
			w.pos(expr)
			typ := idealType(tv)
			assert(typ != nil)
			w.typ(typ)
			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 _, isNil := obj.(*types2.Nil); isNil {
			w.Code(exprNil)
			w.pos(expr)
			w.typ(tv.Type)
			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) {
			tv, ok := w.p.info.Types[expr.X]
			assert(ok)
			assert(tv.IsType())

			typInfo := w.p.typIdx(tv.Type, w.dict)
			if w.Bool(typInfo.derived) {
				methodInfo := w.p.selectorIdx(sel.Obj())
				idx := w.dict.methodExprIdx(typInfo, methodInfo)
				w.Len(idx)
				break
			}

			w.typInfo(typInfo)
		} else {
			w.expr(expr.X)
		}
		w.pos(expr)
		w.selector(sel.Obj())

	case *syntax.IndexExpr:
		_ = w.p.typeOf(expr.Index) // ensure this is an index expression, not an instantiation

		xtyp := w.p.typeOf(expr.X)

		var keyType types2.Type
		if mapType, ok := types2.CoreType(xtyp).(*types2.Map); ok {
			keyType = mapType.Key()
		}

		w.Code(exprIndex)
		w.expr(expr.X)
		w.pos(expr)
		w.implicitConvExpr(expr, keyType, expr.Index)
		if keyType != nil {
			w.rtype(xtyp)
		}

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

	case *syntax.AssertExpr:
		iface := w.p.typeOf(expr.X)

		w.Code(exprAssert)
		w.expr(expr.X)
		w.pos(expr)
		w.exprType(iface, expr.Type)
		w.rtype(iface)

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

		var commonType types2.Type
		switch expr.Op {
		case syntax.Shl, syntax.Shr:
			// ok: operands are allowed to have different types
		default:
			xtyp := w.p.typeOf(expr.X)
			ytyp := w.p.typeOf(expr.Y)
			switch {
			case types2.AssignableTo(xtyp, ytyp):
				commonType = ytyp
			case types2.AssignableTo(ytyp, xtyp):
				commonType = xtyp
			default:
				w.p.fatalf(expr, "failed to find common type between %v and %v", xtyp, ytyp)
			}
		}

		w.Code(exprBinaryOp)
		w.op(binOps[expr.Op])
		w.implicitConvExpr(expr, commonType, expr.X)
		w.pos(expr)
		w.implicitConvExpr(expr, commonType, 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.Bool(false) // explicit
			w.typ(tv.Type)
			w.pos(expr)
			w.convRTTI(w.p.typeOf(expr.ArgList[0]), tv.Type)
			w.Bool(isTypeParam(tv.Type))
			w.expr(expr.ArgList[0])
			break
		}

		var rtype types2.Type
		if tv.IsBuiltin() {
			switch obj, _ := lookupObj(w.p.info, expr.Fun); obj.Name() {
			case "make":
				assert(len(expr.ArgList) >= 1)
				assert(!expr.HasDots)

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

				typ := w.p.typeOf(expr)
				switch coreType := types2.CoreType(typ).(type) {
				default:
					w.p.fatalf(expr, "unexpected core type: %v", coreType)
				case *types2.Chan:
					w.rtype(typ)
				case *types2.Map:
					w.rtype(typ)
				case *types2.Slice:
					w.rtype(sliceElem(typ))
				}

				return

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

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

			case "append":
				rtype = sliceElem(w.p.typeOf(expr))
			case "copy":
				typ := w.p.typeOf(expr.ArgList[0])
				if tuple, ok := typ.(*types2.Tuple); ok { // "copy(g())"
					typ = tuple.At(0).Type()
				}
				rtype = sliceElem(typ)
			case "delete":
				typ := w.p.typeOf(expr.ArgList[0])
				if tuple, ok := typ.(*types2.Tuple); ok { // "delete(g())"
					typ = tuple.At(0).Type()
				}
				rtype = typ
			case "Slice":
				rtype = sliceElem(w.p.typeOf(expr))
			}
		}

		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)
		}

		sigType := types2.CoreType(tv.Type).(*types2.Signature)
		paramTypes := sigType.Params()

		w.Code(exprCall)
		writeFunExpr()
		w.pos(expr)

		paramType := func(i int) types2.Type {
			if sigType.Variadic() && !expr.HasDots && i >= paramTypes.Len()-1 {
				return paramTypes.At(paramTypes.Len() - 1).Type().(*types2.Slice).Elem()
			}
			return paramTypes.At(i).Type()
		}

		w.multiExpr(expr, paramType, expr.ArgList)
		w.Bool(expr.HasDots)
		if rtype != nil {
			w.rtype(rtype)
		}
	}
}

func sliceElem(typ types2.Type) types2.Type {
	return types2.CoreType(typ).(*types2.Slice).Elem()
}

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

// multiExpr writes a sequence of expressions, where the i'th value is
// implicitly converted to dstType(i). It also handles when exprs is a
// single, multi-valued expression (e.g., the multi-valued argument in
// an f(g()) call, or the RHS operand in a comma-ok assignment).
func (w *writer) multiExpr(pos poser, dstType func(int) types2.Type, exprs []syntax.Expr) {
	w.Sync(pkgbits.SyncMultiExpr)

	if len(exprs) == 1 {
		expr := exprs[0]
		if tuple, ok := w.p.typeOf(expr).(*types2.Tuple); ok {
			assert(tuple.Len() > 1)
			w.Bool(true) // N:1 assignment
			w.pos(pos)
			w.expr(expr)

			w.Len(tuple.Len())
			for i := 0; i < tuple.Len(); i++ {
				src := tuple.At(i).Type()
				// TODO(mdempsky): Investigate not writing src here. I think
				// the reader should be able to infer it from expr anyway.
				w.typ(src)
				if dst := dstType(i); w.Bool(dst != nil && !types2.Identical(src, dst)) {
					if src == nil || dst == nil {
						w.p.fatalf(pos, "src is %v, dst is %v", src, dst)
					}
					if !types2.AssignableTo(src, dst) {
						w.p.fatalf(pos, "%v is not assignable to %v", src, dst)
					}
					w.typ(dst)
					w.convRTTI(src, dst)
				}
			}
			return
		}
	}

	w.Bool(false) // N:N assignment
	w.Len(len(exprs))
	for i, expr := range exprs {
		w.implicitConvExpr(pos, dstType(i), expr)
	}
}

// implicitConvExpr is like expr, but if dst is non-nil and different from
// expr's type, then an implicit conversion operation is inserted at
// pos.
func (w *writer) implicitConvExpr(pos poser, dst types2.Type, expr syntax.Expr) {
	src := w.p.typeOf(expr)
	if dst != nil && !types2.Identical(src, dst) {
		if !types2.AssignableTo(src, dst) {
			w.p.fatalf(pos, "%v is not assignable to %v", src, dst)
		}
		w.Code(exprConvert)
		w.Bool(true) // implicit
		w.typ(dst)
		w.pos(pos)
		w.convRTTI(src, dst)
		w.Bool(isTypeParam(dst))
		// fallthrough
	}
	w.expr(expr)
}

func (w *writer) compLit(lit *syntax.CompositeLit) {
	typ := w.p.typeOf(lit)

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

	if ptr, ok := types2.CoreType(typ).(*types2.Pointer); ok {
		typ = ptr.Elem()
	}
	var keyType, elemType types2.Type
	var structType *types2.Struct
	switch typ0 := typ; typ := types2.CoreType(typ).(type) {
	default:
		w.p.fatalf(lit, "unexpected composite literal type: %v", typ)
	case *types2.Array:
		elemType = typ.Elem()
	case *types2.Map:
		w.rtype(typ0)
		keyType, elemType = typ.Key(), typ.Elem()
	case *types2.Slice:
		elemType = typ.Elem()
	case *types2.Struct:
		structType = typ
	}

	w.Len(len(lit.ElemList))
	for i, elem := range lit.ElemList {
		elemType := elemType
		if structType != nil {
			if kv, ok := elem.(*syntax.KeyValueExpr); ok {
				// use position of expr.Key rather than of elem (which has position of ':')
				w.pos(kv.Key)
				i = fieldIndex(w.p.info, structType, kv.Key.(*syntax.Name))
				elem = kv.Value
			} else {
				w.pos(elem)
			}
			elemType = structType.Field(i).Type()
			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.implicitConvExpr(kv.Key, keyType, kv.Key)
				elem = kv.Value
			}
		}
		w.pos(elem)
		w.implicitConvExpr(elem, elemType, elem)
	}
}

func (w *writer) funcLit(expr *syntax.FuncLit) {
	sig := w.p.typeOf(expr).(*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)
	}
}

// rtype writes information so that the reader can construct an
// expression of type *runtime._type representing typ.
func (w *writer) rtype(typ types2.Type) {
	w.Sync(pkgbits.SyncRType)
	w.typNeeded(typ)
}

// typNeeded writes a reference to typ, and records that its
// *runtime._type is needed.
func (w *writer) typNeeded(typ types2.Type) {
	info := w.p.typIdx(typ, w.dict)
	w.typInfo(info)

	if info.derived {
		w.dict.derived[info.idx].needed = true
	}
}

// convRTTI writes information so that the reader can construct
// expressions for converting from src to dst.
func (w *writer) convRTTI(src, dst types2.Type) {
	w.Sync(pkgbits.SyncConvRTTI)
	w.typNeeded(src)
	w.typNeeded(dst)
}

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

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

	w.Sync(pkgbits.SyncExprType)
	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)
	if info.derived {
		w.dict.derived[info.idx].needed = true
	}