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planner.go
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planner.go
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// Copyright 2018 The OPA Authors. All rights reserved.
// Use of this source code is governed by an Apache2
// license that can be found in the LICENSE file.
// Package planner contains a query planner for Rego queries.
package planner
import (
"errors"
"fmt"
"sort"
"github.com/open-policy-agent/opa/ast"
"github.com/open-policy-agent/opa/internal/ir"
)
// QuerySet represents the input to the planner.
type QuerySet struct {
Name string
Queries []ast.Body
RewrittenVars map[ast.Var]ast.Var
}
type planiter func() error
type binaryiter func(ir.Local, ir.Local) error
type wasmBuiltin struct {
*ast.Builtin
WasmFunction string
}
// Planner implements a query planner for Rego queries.
type Planner struct {
policy *ir.Policy // result of planning
queries []QuerySet // input queries to plan
modules []*ast.Module // input modules to support queries
strings map[string]int // global string constant indices
externs map[string]struct{} // built-in functions that are required in execution environment
decls map[string]*ast.Builtin // built-in functions that may be provided in execution environment
rules *ruletrie // rules that may be planned
funcs *funcstack // functions that have been planned
plan *ir.Plan // in-progress query plan
curr *ir.Block // in-progress query block
vars *varstack // in-scope variables
ltarget ir.Local // target variable of last planned statement
lnext ir.Local // next variable to use
}
// New returns a new Planner object.
func New() *Planner {
return &Planner{
policy: &ir.Policy{
Static: &ir.Static{},
Plans: &ir.Plans{},
Funcs: &ir.Funcs{},
},
strings: map[string]int{},
externs: map[string]struct{}{},
lnext: ir.Unused,
vars: newVarstack(map[ast.Var]ir.Local{
ast.InputRootDocument.Value.(ast.Var): ir.Input,
ast.DefaultRootDocument.Value.(ast.Var): ir.Data,
}),
rules: newRuletrie(),
funcs: newFuncstack(),
}
}
// WithBuiltinDecls tells the planner what built-in function may be available
// inside the execution environment.
func (p *Planner) WithBuiltinDecls(decls map[string]*ast.Builtin) *Planner {
p.decls = decls
return p
}
// WithQueries sets the query sets to generate a plan for. The rewritten collection provides
// a mapping of rewritten query vars for each query set. The planner uses rewritten variables
// but the result set key will be the original variable name.
func (p *Planner) WithQueries(queries []QuerySet) *Planner {
p.queries = queries
return p
}
// WithModules sets the module set that contains query dependencies.
func (p *Planner) WithModules(modules []*ast.Module) *Planner {
p.modules = modules
return p
}
// Plan returns a IR plan for the policy query.
func (p *Planner) Plan() (*ir.Policy, error) {
if err := p.buildFunctrie(); err != nil {
return nil, err
}
if err := p.planQueries(); err != nil {
return nil, err
}
if err := p.planExterns(); err != nil {
return nil, err
}
return p.policy, nil
}
func (p *Planner) buildFunctrie() error {
for _, module := range p.modules {
// Create functrie node for empty packages so that extent queries return
// empty objects. For example:
//
// package x.y
//
// Query: data.x
//
// Expected result: {"y": {}}
if len(module.Rules) == 0 {
_ = p.rules.LookupOrInsert(module.Package.Path)
continue
}
for _, rule := range module.Rules {
val := p.rules.LookupOrInsert(rule.Path())
val.rules = append(val.rules, rule)
}
}
return nil
}
func (p *Planner) planRules(rules []*ast.Rule) (string, error) {
path := rules[0].Path().String()
if funcName, ok := p.funcs.Get(path); ok {
return funcName, nil
}
// Save current state of planner.
//
// TODO(tsandall): perhaps we would be better off using stacks here or
// splitting block planner into separate struct that could be instantiated
// for rule and comprehension bodies.
pvars := p.vars
pcurr := p.curr
pltarget := p.ltarget
plnext := p.lnext
// Reset the variable counter for the function plan.
p.lnext = ir.Input
// Create function definition for rules.
fn := &ir.Func{
Name: fmt.Sprintf("g%d.%s", p.funcs.gen, path),
Params: []ir.Local{
p.newLocal(), // input document
p.newLocal(), // data document
},
Return: p.newLocal(),
}
// Initialize parameters for functions.
for i := 0; i < len(rules[0].Head.Args); i++ {
fn.Params = append(fn.Params, p.newLocal())
}
params := fn.Params[2:]
// Initialize return value for partial set/object rules. Complete docs do
// not require their return value to be initialized.
if rules[0].Head.DocKind() == ast.PartialObjectDoc {
fn.Blocks = append(fn.Blocks, &ir.Block{
Stmts: []ir.Stmt{
&ir.MakeObjectStmt{
Target: fn.Return,
},
},
})
} else if rules[0].Head.DocKind() == ast.PartialSetDoc {
fn.Blocks = append(fn.Blocks, &ir.Block{
Stmts: []ir.Stmt{
&ir.MakeSetStmt{
Target: fn.Return,
},
},
})
}
// At this point the locals for the params and return value have been
// allocated. This will be the first local that can be used in each block.
lnext := p.lnext
var defaultRule *ast.Rule
// Generate function blocks for rules.
for i := range rules {
// Save default rule for the end.
if rules[i].Default {
defaultRule = rules[i]
continue
}
// Ordered rules are nested inside an additional block so that execution
// can short-circuit. For unordered rules blocks can be added directly
// to the function.
var blocks *[]*ir.Block
if rules[i].Else == nil {
blocks = &fn.Blocks
} else {
stmt := &ir.BlockStmt{}
block := &ir.Block{Stmts: []ir.Stmt{stmt}}
fn.Blocks = append(fn.Blocks, block)
blocks = &stmt.Blocks
}
var prev *ast.Rule
// Unordered rules are treated as a special case of ordered rules.
for rule := rules[i]; rule != nil; prev, rule = rule, rule.Else {
// Setup planner for block.
p.lnext = lnext
p.vars = newVarstack(map[ast.Var]ir.Local{
ast.InputRootDocument.Value.(ast.Var): fn.Params[0],
ast.DefaultRootDocument.Value.(ast.Var): fn.Params[1],
})
curr := &ir.Block{}
*blocks = append(*blocks, curr)
p.curr = curr
if prev != nil {
// Ordered rules are handled by short circuiting execution. The
// plan will jump out to the extra block that was planned above.
p.appendStmt(&ir.IsUndefinedStmt{Source: fn.Return})
}
// Complete and partial rules are treated as special cases of
// functions. If there are args, the first step is a no-op.
err := p.planFuncParams(params, rule.Head.Args, 0, func() error {
// Run planner on the rule body.
err := p.planQuery(rule.Body, 0, func() error {
// Run planner on the result.
switch rule.Head.DocKind() {
case ast.CompleteDoc:
return p.planTerm(rule.Head.Value, func() error {
p.appendStmt(&ir.AssignVarOnceStmt{
Target: fn.Return,
Source: p.ltarget,
})
return nil
})
case ast.PartialSetDoc:
return p.planTerm(rule.Head.Key, func() error {
p.appendStmt(&ir.SetAddStmt{
Set: fn.Return,
Value: p.ltarget,
})
return nil
})
case ast.PartialObjectDoc:
return p.planTerm(rule.Head.Key, func() error {
key := p.ltarget
return p.planTerm(rule.Head.Value, func() error {
value := p.ltarget
p.appendStmt(&ir.ObjectInsertOnceStmt{
Object: fn.Return,
Key: key,
Value: value,
})
return nil
})
})
default:
return fmt.Errorf("illegal rule kind")
}
})
if err != nil {
return err
}
return nil
})
if err != nil {
return "", err
}
}
}
// Default rules execute if the return is undefined.
if defaultRule != nil {
fn.Blocks = append(fn.Blocks, &ir.Block{
Stmts: []ir.Stmt{
&ir.IsUndefinedStmt{Source: fn.Return},
},
})
p.curr = fn.Blocks[len(fn.Blocks)-1]
err := p.planQuery(defaultRule.Body, 0, func() error {
return p.planTerm(defaultRule.Head.Value, func() error {
p.appendStmt(&ir.AssignVarOnceStmt{
Target: fn.Return,
Source: p.ltarget,
})
return nil
})
})
if err != nil {
return "", err
}
}
// All rules return a value.
fn.Blocks = append(fn.Blocks, &ir.Block{
Stmts: []ir.Stmt{
&ir.ReturnLocalStmt{
Source: fn.Return,
},
},
})
p.appendFunc(fn)
p.funcs.Add(path, fn.Name)
// Restore the state of the planner.
p.lnext = plnext
p.ltarget = pltarget
p.vars = pvars
p.curr = pcurr
return fn.Name, nil
}
func (p *Planner) planFuncParams(params []ir.Local, args ast.Args, idx int, iter planiter) error {
if idx >= len(args) {
return iter()
}
return p.planUnifyLocal(params[idx], args[idx], func() error {
return p.planFuncParams(params, args, idx+1, iter)
})
}
func (p *Planner) planQueries() error {
for _, qs := range p.queries {
// Initialize the plan with a block that prepares the query result.
p.plan = &ir.Plan{Name: qs.Name}
p.policy.Plans.Plans = append(p.policy.Plans.Plans, p.plan)
p.curr = &ir.Block{}
// Build a set of variables appearing in the query and allocate strings for
// each one. The strings will be used in the result set objects.
qvs := ast.NewVarSet()
for _, q := range qs.Queries {
vs := q.Vars(ast.VarVisitorParams{SkipRefCallHead: true, SkipClosures: true}).Diff(ast.ReservedVars)
qvs.Update(vs)
}
lvarnames := make(map[ast.Var]ir.Local, len(qvs))
for _, qv := range qvs.Sorted() {
qv = rewrittenVar(qs.RewrittenVars, qv)
if !qv.IsGenerated() && !qv.IsWildcard() {
stmt := &ir.MakeStringStmt{
Index: p.getStringConst(string(qv)),
Target: p.newLocal(),
}
p.appendStmt(stmt)
lvarnames[qv] = stmt.Target
}
}
if len(p.curr.Stmts) > 0 {
p.appendBlock(p.curr)
}
lnext := p.lnext
for _, q := range qs.Queries {
p.lnext = lnext
p.vars.Push(map[ast.Var]ir.Local{})
p.curr = &ir.Block{}
defined := false
qvs := q.Vars(ast.VarVisitorParams{SkipRefCallHead: true, SkipClosures: true}).Diff(ast.ReservedVars).Sorted()
if err := p.planQuery(q, 0, func() error {
// Add an object containing variable bindings into the result set.
lr := p.newLocal()
p.appendStmt(&ir.MakeObjectStmt{
Target: lr,
})
for _, qv := range qvs {
rw := rewrittenVar(qs.RewrittenVars, qv)
if !rw.IsGenerated() && !rw.IsWildcard() {
p.appendStmt(&ir.ObjectInsertStmt{
Object: lr,
Key: lvarnames[rw],
Value: p.vars.GetOrEmpty(qv),
})
}
}
p.appendStmt(&ir.ResultSetAdd{
Value: lr,
})
defined = true
return nil
}); err != nil {
return err
}
p.vars.Pop()
if defined {
p.appendBlock(p.curr)
}
}
}
return nil
}
func (p *Planner) planQuery(q ast.Body, index int, iter planiter) error {
if index >= len(q) {
return iter()
}
return p.planExpr(q[index], func() error {
return p.planQuery(q, index+1, iter)
})
}
// TODO(tsandall): improve errors to include location information.
func (p *Planner) planExpr(e *ast.Expr, iter planiter) error {
if e.Negated {
return p.planNot(e, iter)
}
if len(e.With) > 0 {
return p.planWith(e, iter)
}
if e.IsCall() {
return p.planExprCall(e, iter)
}
return p.planExprTerm(e, iter)
}
func (p *Planner) planNot(e *ast.Expr, iter planiter) error {
not := &ir.NotStmt{
Block: &ir.Block{},
}
prev := p.curr
p.curr = not.Block
if err := p.planExpr(e.Complement(), func() error {
return nil
}); err != nil {
return err
}
p.curr = prev
p.appendStmt(not)
return iter()
}
func (p *Planner) planWith(e *ast.Expr, iter planiter) error {
// Plan the values that will be applied by the with modifiers. All values
// must be defined for the overall expression to evaluate.
values := make([]*ast.Term, len(e.With))
for i := range e.With {
values[i] = e.With[i].Value
}
return p.planTermSlice(values, func(locals []ir.Local) error {
paths := make([][]int, len(e.With))
saveVars := ast.NewVarSet()
dataRefs := []ast.Ref{}
for i := range e.With {
target := e.With[i].Target.Value.(ast.Ref)
paths[i] = make([]int, len(target)-1)
for j := 1; j < len(target); j++ {
if s, ok := target[j].Value.(ast.String); ok {
paths[i][j-1] = p.getStringConst(string(s))
} else {
return errors.New("invalid with target")
}
}
head := target[0].Value.(ast.Var)
saveVars.Add(head)
if head.Equal(ast.DefaultRootDocument.Value) {
dataRefs = append(dataRefs, target)
}
}
restore := make([][2]ir.Local, len(saveVars))
for i, v := range saveVars.Sorted() {
lorig := p.vars.GetOrEmpty(v)
lsave := p.newLocal()
p.appendStmt(&ir.AssignVarStmt{Source: lorig, Target: lsave})
restore[i] = [2]ir.Local{lorig, lsave}
}
// If any of the with statements targeted the data document we shadow
// the existing planned functions during expression planning. This
// causes the planner to re-plan any rules that may be required during
// planning of this expression (transitively).
if len(dataRefs) > 0 {
p.funcs.Push(map[string]string{})
for _, ref := range dataRefs {
p.rules.Push(ref)
}
}
err := p.planWithRec(e, paths, locals, 0, func() error {
if len(dataRefs) > 0 {
p.funcs.Pop()
for i := len(dataRefs) - 1; i >= 0; i-- {
p.rules.Pop(dataRefs[i])
}
}
err := p.planWithUndoRec(restore, 0, func() error {
err := iter()
if len(dataRefs) > 0 {
p.funcs.Push(map[string]string{})
for _, ref := range dataRefs {
p.rules.Push(ref)
}
}
return err
})
return err
})
if len(dataRefs) > 0 {
p.funcs.Pop()
for i := len(dataRefs) - 1; i >= 0; i-- {
p.rules.Pop(dataRefs[i])
}
}
return err
})
}
func (p *Planner) planWithRec(e *ast.Expr, targets [][]int, values []ir.Local, index int, iter planiter) error {
if index >= len(e.With) {
return p.planExpr(e.NoWith(), iter)
}
prev := p.curr
p.curr = &ir.Block{}
err := p.planWithRec(e, targets, values, index+1, iter)
if err != nil {
return err
}
block := p.curr
p.curr = prev
target := e.With[index].Target.Value.(ast.Ref)
head := target[0].Value.(ast.Var)
stmt := &ir.WithStmt{
Local: p.vars.GetOrEmpty(head),
Path: targets[index],
Value: values[index],
Block: block,
}
p.appendStmt(stmt)
return nil
}
func (p *Planner) planWithUndoRec(restore [][2]ir.Local, index int, iter planiter) error {
if index >= len(restore) {
return iter()
}
prev := p.curr
p.curr = &ir.Block{}
if err := p.planWithUndoRec(restore, index+1, iter); err != nil {
return err
}
block := p.curr
p.curr = prev
lorig := restore[index][0]
lsave := restore[index][1]
p.appendStmt(&ir.WithStmt{
Local: lorig,
Value: lsave,
Block: block,
})
return nil
}
func (p *Planner) planExprTerm(e *ast.Expr, iter planiter) error {
return p.planTerm(e.Terms.(*ast.Term), func() error {
falsy := p.newLocal()
p.appendStmt(&ir.MakeBooleanStmt{
Value: false,
Target: falsy,
})
p.appendStmt(&ir.NotEqualStmt{
A: p.ltarget,
B: falsy,
})
return iter()
})
}
func (p *Planner) planExprCall(e *ast.Expr, iter planiter) error {
operator := e.Operator().String()
switch operator {
case ast.Equality.Name:
return p.planUnify(e.Operand(0), e.Operand(1), iter)
case ast.Equal.Name:
return p.planBinaryExpr(e, func(a, b ir.Local) error {
p.appendStmt(&ir.EqualStmt{
A: a,
B: b,
})
return iter()
})
case ast.LessThan.Name:
return p.planBinaryExpr(e, func(a, b ir.Local) error {
p.appendStmt(&ir.LessThanStmt{
A: a,
B: b,
})
return iter()
})
case ast.LessThanEq.Name:
return p.planBinaryExpr(e, func(a, b ir.Local) error {
p.appendStmt(&ir.LessThanEqualStmt{
A: a,
B: b,
})
return iter()
})
case ast.GreaterThan.Name:
return p.planBinaryExpr(e, func(a, b ir.Local) error {
p.appendStmt(&ir.GreaterThanStmt{
A: a,
B: b,
})
return iter()
})
case ast.GreaterThanEq.Name:
return p.planBinaryExpr(e, func(a, b ir.Local) error {
p.appendStmt(&ir.GreaterThanEqualStmt{
A: a,
B: b,
})
return iter()
})
case ast.NotEqual.Name:
return p.planBinaryExpr(e, func(a, b ir.Local) error {
p.appendStmt(&ir.NotEqualStmt{
A: a,
B: b,
})
return iter()
})
default:
var relation bool
var name string
var arity int
var args []ir.Local
node := p.rules.Lookup(e.Operator())
if node != nil {
var err error
name, err = p.planRules(node.Rules())
if err != nil {
return err
}
arity = node.Arity()
args = []ir.Local{
p.vars.GetOrEmpty(ast.InputRootDocument.Value.(ast.Var)),
p.vars.GetOrEmpty(ast.DefaultRootDocument.Value.(ast.Var)),
}
} else if decl, ok := p.decls[operator]; ok {
relation = decl.Relation
arity = len(decl.Decl.Args())
name = operator
p.externs[operator] = struct{}{}
} else {
return fmt.Errorf("illegal call: unknown operator %q", operator)
}
operands := e.Operands()
if len(operands) < arity || len(operands) > arity+1 {
return fmt.Errorf("illegal call: wrong number of operands: got %v, want %v)", len(operands), arity)
}
if relation {
return p.planExprCallRelation(name, arity, operands, args, iter)
}
return p.planExprCallFunc(name, arity, operands, args, iter)
}
}
func (p *Planner) planExprCallRelation(name string, arity int, operands []*ast.Term, args []ir.Local, iter planiter) error {
if len(operands) == arity {
return p.planCallArgs(operands, 0, args, func(args []ir.Local) error {
p.ltarget = p.newLocal()
p.appendStmt(&ir.CallStmt{
Func: name,
Args: args,
Result: p.ltarget,
})
lsize := p.newLocal()
p.appendStmt(&ir.LenStmt{
Source: p.ltarget,
Target: lsize,
})
lzero := p.newLocal()
p.appendStmt(&ir.MakeNumberIntStmt{
Value: 0,
Target: lzero,
})
p.appendStmt(&ir.NotEqualStmt{
A: lsize,
B: lzero,
})
return iter()
})
}
return p.planCallArgs(operands[:len(operands)-1], 0, args, func(args []ir.Local) error {
p.ltarget = p.newLocal()
p.appendStmt(&ir.CallStmt{
Func: name,
Args: args,
Result: p.ltarget,
})
return p.planScanValues(operands[len(operands)-1], func(ir.Local) error {
return iter()
})
})
}
func (p *Planner) planExprCallFunc(name string, arity int, operands []*ast.Term, args []ir.Local, iter planiter) error {
if len(operands) == arity {
// definition: f(x) = x { ... }
// call: f(x) # result not captured
return p.planCallArgs(operands, 0, args, func(args []ir.Local) error {
p.ltarget = p.newLocal()
p.appendStmt(&ir.CallStmt{
Func: name,
Args: args,
Result: p.ltarget,
})
falsy := p.newLocal()
p.appendStmt(&ir.MakeBooleanStmt{
Value: false,
Target: falsy,
})
p.appendStmt(&ir.NotEqualStmt{
A: p.ltarget,
B: falsy,
})
return iter()
})
}
// definition: f(x) = x { ... }
// call: f(x, 1) # caller captures result
return p.planCallArgs(operands[:len(operands)-1], 0, args, func(args []ir.Local) error {
result := p.newLocal()
p.appendStmt(&ir.CallStmt{
Func: name,
Args: args,
Result: result,
})
return p.planUnifyLocal(result, operands[len(operands)-1], iter)
})
}
func (p *Planner) planCallArgs(terms []*ast.Term, idx int, args []ir.Local, iter func([]ir.Local) error) error {
if idx >= len(terms) {
return iter(args)
}
return p.planTerm(terms[idx], func() error {
args = append(args, p.ltarget)
return p.planCallArgs(terms, idx+1, args, iter)
})
}
func (p *Planner) planUnify(a, b *ast.Term, iter planiter) error {
switch va := a.Value.(type) {
case ast.Null, ast.Boolean, ast.Number, ast.String, ast.Ref, ast.Set, *ast.SetComprehension, *ast.ArrayComprehension, *ast.ObjectComprehension:
return p.planTerm(a, func() error {
return p.planUnifyLocal(p.ltarget, b, iter)
})
case ast.Var:
return p.planUnifyVar(va, b, iter)
case *ast.Array:
switch vb := b.Value.(type) {
case ast.Var:
return p.planUnifyVar(vb, a, iter)
case ast.Ref:
return p.planTerm(b, func() error {
return p.planUnifyLocalArray(p.ltarget, va, iter)
})
case *ast.Array:
if va.Len() == vb.Len() {
return p.planUnifyArraysRec(va, vb, 0, iter)
}
return nil
}
case ast.Object:
switch vb := b.Value.(type) {
case ast.Var:
return p.planUnifyVar(vb, a, iter)
case ast.Ref:
return p.planTerm(b, func() error {
return p.planUnifyLocalObject(p.ltarget, va, iter)
})
case ast.Object:
if va.Len() == vb.Len() {
return p.planUnifyObjectsRec(va, vb, va.Keys(), 0, iter)
}
return nil
}
}
return fmt.Errorf("not implemented: unify(%v, %v)", a, b)
}
func (p *Planner) planUnifyVar(a ast.Var, b *ast.Term, iter planiter) error {
if la, ok := p.vars.Get(a); ok {
return p.planUnifyLocal(la, b, iter)
}
return p.planTerm(b, func() error {
target := p.newLocal()
p.vars.Put(a, target)
p.appendStmt(&ir.AssignVarStmt{
Source: p.ltarget,
Target: target,
})
return iter()
})
}
func (p *Planner) planUnifyLocal(a ir.Local, b *ast.Term, iter planiter) error {
switch vb := b.Value.(type) {
case ast.Null, ast.Boolean, ast.Number, ast.String, ast.Ref, ast.Set, *ast.SetComprehension, *ast.ArrayComprehension, *ast.ObjectComprehension:
return p.planTerm(b, func() error {
p.appendStmt(&ir.EqualStmt{
A: a,
B: p.ltarget,
})
return iter()
})
case ast.Var:
if lv, ok := p.vars.Get(vb); ok {
p.appendStmt(&ir.EqualStmt{
A: a,
B: lv,
})
return iter()
}
lv := p.newLocal()
p.vars.Put(vb, lv)
p.appendStmt(&ir.AssignVarStmt{
Source: a,
Target: lv,
})
return iter()
case *ast.Array:
return p.planUnifyLocalArray(a, vb, iter)
case ast.Object:
return p.planUnifyLocalObject(a, vb, iter)
}
return fmt.Errorf("not implemented: unifyLocal(%v, %v)", a, b)
}
func (p *Planner) planUnifyLocalArray(a ir.Local, b *ast.Array, iter planiter) error {
p.appendStmt(&ir.IsArrayStmt{
Source: a,
})
blen := p.newLocal()
alen := p.newLocal()
p.appendStmt(&ir.LenStmt{
Source: a,
Target: alen,
})
p.appendStmt(&ir.MakeNumberIntStmt{
Value: int64(b.Len()),
Target: blen,
})
p.appendStmt(&ir.EqualStmt{
A: alen,
B: blen,
})
lkey := p.newLocal()
p.appendStmt(&ir.MakeNumberIntStmt{
Target: lkey,
})
lval := p.newLocal()
return p.planUnifyLocalArrayRec(a, 0, b, lkey, lval, iter)
}
func (p *Planner) planUnifyLocalArrayRec(a ir.Local, index int, b *ast.Array, lkey, lval ir.Local, iter planiter) error {
if b.Len() == index {
return iter()
}
p.appendStmt(&ir.AssignIntStmt{
Value: int64(index),
Target: lkey,
})
p.appendStmt(&ir.DotStmt{
Source: a,
Key: lkey,
Target: lval,
})
return p.planUnifyLocal(lval, b.Elem(index), func() error {
return p.planUnifyLocalArrayRec(a, index+1, b, lkey, lval, iter)
})
}