Merge pull request #107 from google/mod

Use Go Modules and support Go 1.11 building

5 files changed, 0 insertions, 2129 deletions

diff --git a/vendor/honnef.co/go/tools/staticcheck/vrp/channel.go b/vendor/honnef.co/go/tools/staticcheck/vrp/channel.go
deleted file mode 100644
index c8fbacb..0000000
--- a/vendor/honnef.co/go/tools/staticcheck/vrp/channel.go
+++ /dev/null
@@ -1,73 +0,0 @@
-package vrp
-
-import (
-	"fmt"
-
-	"honnef.co/go/tools/ssa"
-)
-
-type ChannelInterval struct {
-	Size IntInterval
-}
-
-func (c ChannelInterval) Union(other Range) Range {
-	i, ok := other.(ChannelInterval)
-	if !ok {
-		i = ChannelInterval{EmptyIntInterval}
-	}
-	if c.Size.Empty() || !c.Size.IsKnown() {
-		return i
-	}
-	if i.Size.Empty() || !i.Size.IsKnown() {
-		return c
-	}
-	return ChannelInterval{
-		Size: c.Size.Union(i.Size).(IntInterval),
-	}
-}
-
-func (c ChannelInterval) String() string {
-	return c.Size.String()
-}
-
-func (c ChannelInterval) IsKnown() bool {
-	return c.Size.IsKnown()
-}
-
-type MakeChannelConstraint struct {
-	aConstraint
-	Buffer ssa.Value
-}
-type ChannelChangeTypeConstraint struct {
-	aConstraint
-	X ssa.Value
-}
-
-func NewMakeChannelConstraint(buffer, y ssa.Value) Constraint {
-	return &MakeChannelConstraint{NewConstraint(y), buffer}
-}
-func NewChannelChangeTypeConstraint(x, y ssa.Value) Constraint {
-	return &ChannelChangeTypeConstraint{NewConstraint(y), x}
-}
-
-func (c *MakeChannelConstraint) Operands() []ssa.Value       { return []ssa.Value{c.Buffer} }
-func (c *ChannelChangeTypeConstraint) Operands() []ssa.Value { return []ssa.Value{c.X} }
-
-func (c *MakeChannelConstraint) String() string {
-	return fmt.Sprintf("%s = make(chan, %s)", c.Y().Name, c.Buffer.Name())
-}
-func (c *ChannelChangeTypeConstraint) String() string {
-	return fmt.Sprintf("%s = changetype(%s)", c.Y().Name, c.X.Name())
-}
-
-func (c *MakeChannelConstraint) Eval(g *Graph) Range {
-	i, ok := g.Range(c.Buffer).(IntInterval)
-	if !ok {
-		return ChannelInterval{NewIntInterval(NewZ(0), PInfinity)}
-	}
-	if i.Lower.Sign() == -1 {
-		i.Lower = NewZ(0)
-	}
-	return ChannelInterval{i}
-}
-func (c *ChannelChangeTypeConstraint) Eval(g *Graph) Range { return g.Range(c.X) }
diff --git a/vendor/honnef.co/go/tools/staticcheck/vrp/int.go b/vendor/honnef.co/go/tools/staticcheck/vrp/int.go
deleted file mode 100644
index 926bb7a..0000000
--- a/vendor/honnef.co/go/tools/staticcheck/vrp/int.go
+++ /dev/null
@@ -1,476 +0,0 @@
-package vrp
-
-import (
-	"fmt"
-	"go/token"
-	"go/types"
-	"math/big"
-
-	"honnef.co/go/tools/ssa"
-)
-
-type Zs []Z
-
-func (zs Zs) Len() int {
-	return len(zs)
-}
-
-func (zs Zs) Less(i int, j int) bool {
-	return zs[i].Cmp(zs[j]) == -1
-}
-
-func (zs Zs) Swap(i int, j int) {
-	zs[i], zs[j] = zs[j], zs[i]
-}
-
-type Z struct {
-	infinity int8
-	integer  *big.Int
-}
-
-func NewZ(n int64) Z {
-	return NewBigZ(big.NewInt(n))
-}
-
-func NewBigZ(n *big.Int) Z {
-	return Z{integer: n}
-}
-
-func (z1 Z) Infinite() bool {
-	return z1.infinity != 0
-}
-
-func (z1 Z) Add(z2 Z) Z {
-	if z2.Sign() == -1 {
-		return z1.Sub(z2.Negate())
-	}
-	if z1 == NInfinity {
-		return NInfinity
-	}
-	if z1 == PInfinity {
-		return PInfinity
-	}
-	if z2 == PInfinity {
-		return PInfinity
-	}
-
-	if !z1.Infinite() && !z2.Infinite() {
-		n := &big.Int{}
-		n.Add(z1.integer, z2.integer)
-		return NewBigZ(n)
-	}
-
-	panic(fmt.Sprintf("%s + %s is not defined", z1, z2))
-}
-
-func (z1 Z) Sub(z2 Z) Z {
-	if z2.Sign() == -1 {
-		return z1.Add(z2.Negate())
-	}
-	if !z1.Infinite() && !z2.Infinite() {
-		n := &big.Int{}
-		n.Sub(z1.integer, z2.integer)
-		return NewBigZ(n)
-	}
-
-	if z1 != PInfinity && z2 == PInfinity {
-		return NInfinity
-	}
-	if z1.Infinite() && !z2.Infinite() {
-		return Z{infinity: z1.infinity}
-	}
-	if z1 == PInfinity && z2 == PInfinity {
-		return PInfinity
-	}
-	panic(fmt.Sprintf("%s - %s is not defined", z1, z2))
-}
-
-func (z1 Z) Mul(z2 Z) Z {
-	if (z1.integer != nil && z1.integer.Sign() == 0) ||
-		(z2.integer != nil && z2.integer.Sign() == 0) {
-		return NewBigZ(&big.Int{})
-	}
-
-	if z1.infinity != 0 || z2.infinity != 0 {
-		return Z{infinity: int8(z1.Sign() * z2.Sign())}
-	}
-
-	n := &big.Int{}
-	n.Mul(z1.integer, z2.integer)
-	return NewBigZ(n)
-}
-
-func (z1 Z) Negate() Z {
-	if z1.infinity == 1 {
-		return NInfinity
-	}
-	if z1.infinity == -1 {
-		return PInfinity
-	}
-	n := &big.Int{}
-	n.Neg(z1.integer)
-	return NewBigZ(n)
-}
-
-func (z1 Z) Sign() int {
-	if z1.infinity != 0 {
-		return int(z1.infinity)
-	}
-	return z1.integer.Sign()
-}
-
-func (z1 Z) String() string {
-	if z1 == NInfinity {
-		return "-∞"
-	}
-	if z1 == PInfinity {
-		return "∞"
-	}
-	return fmt.Sprintf("%d", z1.integer)
-}
-
-func (z1 Z) Cmp(z2 Z) int {
-	if z1.infinity == z2.infinity && z1.infinity != 0 {
-		return 0
-	}
-	if z1 == PInfinity {
-		return 1
-	}
-	if z1 == NInfinity {
-		return -1
-	}
-	if z2 == NInfinity {
-		return 1
-	}
-	if z2 == PInfinity {
-		return -1
-	}
-	return z1.integer.Cmp(z2.integer)
-}
-
-func MaxZ(zs ...Z) Z {
-	if len(zs) == 0 {
-		panic("Max called with no arguments")
-	}
-	if len(zs) == 1 {
-		return zs[0]
-	}
-	ret := zs[0]
-	for _, z := range zs[1:] {
-		if z.Cmp(ret) == 1 {
-			ret = z
-		}
-	}
-	return ret
-}
-
-func MinZ(zs ...Z) Z {
-	if len(zs) == 0 {
-		panic("Min called with no arguments")
-	}
-	if len(zs) == 1 {
-		return zs[0]
-	}
-	ret := zs[0]
-	for _, z := range zs[1:] {
-		if z.Cmp(ret) == -1 {
-			ret = z
-		}
-	}
-	return ret
-}
-
-var NInfinity = Z{infinity: -1}
-var PInfinity = Z{infinity: 1}
-var EmptyIntInterval = IntInterval{true, PInfinity, NInfinity}
-
-func InfinityFor(v ssa.Value) IntInterval {
-	if b, ok := v.Type().Underlying().(*types.Basic); ok {
-		if (b.Info() & types.IsUnsigned) != 0 {
-			return NewIntInterval(NewZ(0), PInfinity)
-		}
-	}
-	return NewIntInterval(NInfinity, PInfinity)
-}
-
-type IntInterval struct {
-	known bool
-	Lower Z
-	Upper Z
-}
-
-func NewIntInterval(l, u Z) IntInterval {
-	if u.Cmp(l) == -1 {
-		return EmptyIntInterval
-	}
-	return IntInterval{known: true, Lower: l, Upper: u}
-}
-
-func (i IntInterval) IsKnown() bool {
-	return i.known
-}
-
-func (i IntInterval) Empty() bool {
-	return i.Lower == PInfinity && i.Upper == NInfinity
-}
-
-func (i IntInterval) IsMaxRange() bool {
-	return i.Lower == NInfinity && i.Upper == PInfinity
-}
-
-func (i1 IntInterval) Intersection(i2 IntInterval) IntInterval {
-	if !i1.IsKnown() {
-		return i2
-	}
-	if !i2.IsKnown() {
-		return i1
-	}
-	if i1.Empty() || i2.Empty() {
-		return EmptyIntInterval
-	}
-	i3 := NewIntInterval(MaxZ(i1.Lower, i2.Lower), MinZ(i1.Upper, i2.Upper))
-	if i3.Lower.Cmp(i3.Upper) == 1 {
-		return EmptyIntInterval
-	}
-	return i3
-}
-
-func (i1 IntInterval) Union(other Range) Range {
-	i2, ok := other.(IntInterval)
-	if !ok {
-		i2 = EmptyIntInterval
-	}
-	if i1.Empty() || !i1.IsKnown() {
-		return i2
-	}
-	if i2.Empty() || !i2.IsKnown() {
-		return i1
-	}
-	return NewIntInterval(MinZ(i1.Lower, i2.Lower), MaxZ(i1.Upper, i2.Upper))
-}
-
-func (i1 IntInterval) Add(i2 IntInterval) IntInterval {
-	if i1.Empty() || i2.Empty() {
-		return EmptyIntInterval
-	}
-	l1, u1, l2, u2 := i1.Lower, i1.Upper, i2.Lower, i2.Upper
-	return NewIntInterval(l1.Add(l2), u1.Add(u2))
-}
-
-func (i1 IntInterval) Sub(i2 IntInterval) IntInterval {
-	if i1.Empty() || i2.Empty() {
-		return EmptyIntInterval
-	}
-	l1, u1, l2, u2 := i1.Lower, i1.Upper, i2.Lower, i2.Upper
-	return NewIntInterval(l1.Sub(u2), u1.Sub(l2))
-}
-
-func (i1 IntInterval) Mul(i2 IntInterval) IntInterval {
-	if i1.Empty() || i2.Empty() {
-		return EmptyIntInterval
-	}
-	x1, x2 := i1.Lower, i1.Upper
-	y1, y2 := i2.Lower, i2.Upper
-	return NewIntInterval(
-		MinZ(x1.Mul(y1), x1.Mul(y2), x2.Mul(y1), x2.Mul(y2)),
-		MaxZ(x1.Mul(y1), x1.Mul(y2), x2.Mul(y1), x2.Mul(y2)),
-	)
-}
-
-func (i1 IntInterval) String() string {
-	if !i1.IsKnown() {
-		return "[⊥, ⊥]"
-	}
-	if i1.Empty() {
-		return "{}"
-	}
-	return fmt.Sprintf("[%s, %s]", i1.Lower, i1.Upper)
-}
-
-type IntArithmeticConstraint struct {
-	aConstraint
-	A  ssa.Value
-	B  ssa.Value
-	Op token.Token
-	Fn func(IntInterval, IntInterval) IntInterval
-}
-
-type IntAddConstraint struct{ *IntArithmeticConstraint }
-type IntSubConstraint struct{ *IntArithmeticConstraint }
-type IntMulConstraint struct{ *IntArithmeticConstraint }
-
-type IntConversionConstraint struct {
-	aConstraint
-	X ssa.Value
-}
-
-type IntIntersectionConstraint struct {
-	aConstraint
-	ranges   Ranges
-	A        ssa.Value
-	B        ssa.Value
-	Op       token.Token
-	I        IntInterval
-	resolved bool
-}
-
-type IntIntervalConstraint struct {
-	aConstraint
-	I IntInterval
-}
-
-func NewIntArithmeticConstraint(a, b, y ssa.Value, op token.Token, fn func(IntInterval, IntInterval) IntInterval) *IntArithmeticConstraint {
-	return &IntArithmeticConstraint{NewConstraint(y), a, b, op, fn}
-}
-func NewIntAddConstraint(a, b, y ssa.Value) Constraint {
-	return &IntAddConstraint{NewIntArithmeticConstraint(a, b, y, token.ADD, IntInterval.Add)}
-}
-func NewIntSubConstraint(a, b, y ssa.Value) Constraint {
-	return &IntSubConstraint{NewIntArithmeticConstraint(a, b, y, token.SUB, IntInterval.Sub)}
-}
-func NewIntMulConstraint(a, b, y ssa.Value) Constraint {
-	return &IntMulConstraint{NewIntArithmeticConstraint(a, b, y, token.MUL, IntInterval.Mul)}
-}
-func NewIntConversionConstraint(x, y ssa.Value) Constraint {
-	return &IntConversionConstraint{NewConstraint(y), x}
-}
-func NewIntIntersectionConstraint(a, b ssa.Value, op token.Token, ranges Ranges, y ssa.Value) Constraint {
-	return &IntIntersectionConstraint{
-		aConstraint: NewConstraint(y),
-		ranges:      ranges,
-		A:           a,
-		B:           b,
-		Op:          op,
-	}
-}
-func NewIntIntervalConstraint(i IntInterval, y ssa.Value) Constraint {
-	return &IntIntervalConstraint{NewConstraint(y), i}
-}
-
-func (c *IntArithmeticConstraint) Operands() []ssa.Value   { return []ssa.Value{c.A, c.B} }
-func (c *IntConversionConstraint) Operands() []ssa.Value   { return []ssa.Value{c.X} }
-func (c *IntIntersectionConstraint) Operands() []ssa.Value { return []ssa.Value{c.A} }
-func (s *IntIntervalConstraint) Operands() []ssa.Value     { return nil }
-
-func (c *IntArithmeticConstraint) String() string {
-	return fmt.Sprintf("%s = %s %s %s", c.Y().Name(), c.A.Name(), c.Op, c.B.Name())
-}
-func (c *IntConversionConstraint) String() string {
-	return fmt.Sprintf("%s = %s(%s)", c.Y().Name(), c.Y().Type(), c.X.Name())
-}
-func (c *IntIntersectionConstraint) String() string {
-	return fmt.Sprintf("%s = %s %s %s (%t branch)", c.Y().Name(), c.A.Name(), c.Op, c.B.Name(), c.Y().(*ssa.Sigma).Branch)
-}
-func (c *IntIntervalConstraint) String() string { return fmt.Sprintf("%s = %s", c.Y().Name(), c.I) }
-
-func (c *IntArithmeticConstraint) Eval(g *Graph) Range {
-	i1, i2 := g.Range(c.A).(IntInterval), g.Range(c.B).(IntInterval)
-	if !i1.IsKnown() || !i2.IsKnown() {
-		return IntInterval{}
-	}
-	return c.Fn(i1, i2)
-}
-func (c *IntConversionConstraint) Eval(g *Graph) Range {
-	s := &types.StdSizes{
-		// XXX is it okay to assume the largest word size, or do we
-		// need to be platform specific?
-		WordSize: 8,
-		MaxAlign: 1,
-	}
-	fromI := g.Range(c.X).(IntInterval)
-	toI := g.Range(c.Y()).(IntInterval)
-	fromT := c.X.Type().Underlying().(*types.Basic)
-	toT := c.Y().Type().Underlying().(*types.Basic)
-	fromB := s.Sizeof(c.X.Type())
-	toB := s.Sizeof(c.Y().Type())
-
-	if !fromI.IsKnown() {
-		return toI
-	}
-	if !toI.IsKnown() {
-		return fromI
-	}
-
-	// uint<N> -> sint/uint<M>, M > N: [max(0, l1), min(2**N-1, u2)]
-	if (fromT.Info()&types.IsUnsigned != 0) &&
-		toB > fromB {
-
-		n := big.NewInt(1)
-		n.Lsh(n, uint(fromB*8))
-		n.Sub(n, big.NewInt(1))
-		return NewIntInterval(
-			MaxZ(NewZ(0), fromI.Lower),
-			MinZ(NewBigZ(n), toI.Upper),
-		)
-	}
-
-	// sint<N> -> sint<M>, M > N; [max(-∞, l1), min(2**N-1, u2)]
-	if (fromT.Info()&types.IsUnsigned == 0) &&
-		(toT.Info()&types.IsUnsigned == 0) &&
-		toB > fromB {
-
-		n := big.NewInt(1)
-		n.Lsh(n, uint(fromB*8))
-		n.Sub(n, big.NewInt(1))
-		return NewIntInterval(
-			MaxZ(NInfinity, fromI.Lower),
-			MinZ(NewBigZ(n), toI.Upper),
-		)
-	}
-
-	return fromI
-}
-func (c *IntIntersectionConstraint) Eval(g *Graph) Range {
-	xi := g.Range(c.A).(IntInterval)
-	if !xi.IsKnown() {
-		return c.I
-	}
-	return xi.Intersection(c.I)
-}
-func (c *IntIntervalConstraint) Eval(*Graph) Range { return c.I }
-
-func (c *IntIntersectionConstraint) Futures() []ssa.Value {
-	return []ssa.Value{c.B}
-}
-
-func (c *IntIntersectionConstraint) Resolve() {
-	r, ok := c.ranges[c.B].(IntInterval)
-	if !ok {
-		c.I = InfinityFor(c.Y())
-		return
-	}
-
-	switch c.Op {
-	case token.EQL:
-		c.I = r
-	case token.GTR:
-		c.I = NewIntInterval(r.Lower.Add(NewZ(1)), PInfinity)
-	case token.GEQ:
-		c.I = NewIntInterval(r.Lower, PInfinity)
-	case token.LSS:
-		// TODO(dh): do we need 0 instead of NInfinity for uints?
-		c.I = NewIntInterval(NInfinity, r.Upper.Sub(NewZ(1)))
-	case token.LEQ:
-		c.I = NewIntInterval(NInfinity, r.Upper)
-	case token.NEQ:
-		c.I = InfinityFor(c.Y())
-	default:
-		panic("unsupported op " + c.Op.String())
-	}
-}
-
-func (c *IntIntersectionConstraint) IsKnown() bool {
-	return c.I.IsKnown()
-}
-
-func (c *IntIntersectionConstraint) MarkUnresolved() {
-	c.resolved = false
-}
-
-func (c *IntIntersectionConstraint) MarkResolved() {
-	c.resolved = true
-}
-
-func (c *IntIntersectionConstraint) IsResolved() bool {
-	return c.resolved
-}
diff --git a/vendor/honnef.co/go/tools/staticcheck/vrp/slice.go b/vendor/honnef.co/go/tools/staticcheck/vrp/slice.go
deleted file mode 100644
index 40658dd..0000000
--- a/vendor/honnef.co/go/tools/staticcheck/vrp/slice.go
+++ /dev/null
@@ -1,273 +0,0 @@
-package vrp
-
-// TODO(dh): most of the constraints have implementations identical to
-// that of strings. Consider reusing them.
-
-import (
-	"fmt"
-	"go/types"
-
-	"honnef.co/go/tools/ssa"
-)
-
-type SliceInterval struct {
-	Length IntInterval
-}
-
-func (s SliceInterval) Union(other Range) Range {
-	i, ok := other.(SliceInterval)
-	if !ok {
-		i = SliceInterval{EmptyIntInterval}
-	}
-	if s.Length.Empty() || !s.Length.IsKnown() {
-		return i
-	}
-	if i.Length.Empty() || !i.Length.IsKnown() {
-		return s
-	}
-	return SliceInterval{
-		Length: s.Length.Union(i.Length).(IntInterval),
-	}
-}
-func (s SliceInterval) String() string { return s.Length.String() }
-func (s SliceInterval) IsKnown() bool  { return s.Length.IsKnown() }
-
-type SliceAppendConstraint struct {
-	aConstraint
-	A ssa.Value
-	B ssa.Value
-}
-
-type SliceSliceConstraint struct {
-	aConstraint
-	X     ssa.Value
-	Lower ssa.Value
-	Upper ssa.Value
-}
-
-type ArraySliceConstraint struct {
-	aConstraint
-	X     ssa.Value
-	Lower ssa.Value
-	Upper ssa.Value
-}
-
-type SliceIntersectionConstraint struct {
-	aConstraint
-	X ssa.Value
-	I IntInterval
-}
-
-type SliceLengthConstraint struct {
-	aConstraint
-	X ssa.Value
-}
-
-type MakeSliceConstraint struct {
-	aConstraint
-	Size ssa.Value
-}
-
-type SliceIntervalConstraint struct {
-	aConstraint
-	I IntInterval
-}
-
-func NewSliceAppendConstraint(a, b, y ssa.Value) Constraint {
-	return &SliceAppendConstraint{NewConstraint(y), a, b}
-}
-func NewSliceSliceConstraint(x, lower, upper, y ssa.Value) Constraint {
-	return &SliceSliceConstraint{NewConstraint(y), x, lower, upper}
-}
-func NewArraySliceConstraint(x, lower, upper, y ssa.Value) Constraint {
-	return &ArraySliceConstraint{NewConstraint(y), x, lower, upper}
-}
-func NewSliceIntersectionConstraint(x ssa.Value, i IntInterval, y ssa.Value) Constraint {
-	return &SliceIntersectionConstraint{NewConstraint(y), x, i}
-}
-func NewSliceLengthConstraint(x, y ssa.Value) Constraint {
-	return &SliceLengthConstraint{NewConstraint(y), x}
-}
-func NewMakeSliceConstraint(size, y ssa.Value) Constraint {
-	return &MakeSliceConstraint{NewConstraint(y), size}
-}
-func NewSliceIntervalConstraint(i IntInterval, y ssa.Value) Constraint {
-	return &SliceIntervalConstraint{NewConstraint(y), i}
-}
-
-func (c *SliceAppendConstraint) Operands() []ssa.Value { return []ssa.Value{c.A, c.B} }
-func (c *SliceSliceConstraint) Operands() []ssa.Value {
-	ops := []ssa.Value{c.X}
-	if c.Lower != nil {
-		ops = append(ops, c.Lower)
-	}
-	if c.Upper != nil {
-		ops = append(ops, c.Upper)
-	}
-	return ops
-}
-func (c *ArraySliceConstraint) Operands() []ssa.Value {
-	ops := []ssa.Value{c.X}
-	if c.Lower != nil {
-		ops = append(ops, c.Lower)
-	}
-	if c.Upper != nil {
-		ops = append(ops, c.Upper)
-	}
-	return ops
-}
-func (c *SliceIntersectionConstraint) Operands() []ssa.Value { return []ssa.Value{c.X} }
-func (c *SliceLengthConstraint) Operands() []ssa.Value       { return []ssa.Value{c.X} }
-func (c *MakeSliceConstraint) Operands() []ssa.Value         { return []ssa.Value{c.Size} }
-func (s *SliceIntervalConstraint) Operands() []ssa.Value     { return nil }
-
-func (c *SliceAppendConstraint) String() string {
-	return fmt.Sprintf("%s = append(%s, %s)", c.Y().Name(), c.A.Name(), c.B.Name())
-}
-func (c *SliceSliceConstraint) String() string {
-	var lname, uname string
-	if c.Lower != nil {
-		lname = c.Lower.Name()
-	}
-	if c.Upper != nil {
-		uname = c.Upper.Name()
-	}
-	return fmt.Sprintf("%s[%s:%s]", c.X.Name(), lname, uname)
-}
-func (c *ArraySliceConstraint) String() string {
-	var lname, uname string
-	if c.Lower != nil {
-		lname = c.Lower.Name()
-	}
-	if c.Upper != nil {
-		uname = c.Upper.Name()
-	}
-	return fmt.Sprintf("%s[%s:%s]", c.X.Name(), lname, uname)
-}
-func (c *SliceIntersectionConstraint) String() string {
-	return fmt.Sprintf("%s = %s.%t ⊓ %s", c.Y().Name(), c.X.Name(), c.Y().(*ssa.Sigma).Branch, c.I)
-}
-func (c *SliceLengthConstraint) String() string {
-	return fmt.Sprintf("%s = len(%s)", c.Y().Name(), c.X.Name())
-}
-func (c *MakeSliceConstraint) String() string {
-	return fmt.Sprintf("%s = make(slice, %s)", c.Y().Name(), c.Size.Name())
-}
-func (c *SliceIntervalConstraint) String() string { return fmt.Sprintf("%s = %s", c.Y().Name(), c.I) }
-
-func (c *SliceAppendConstraint) Eval(g *Graph) Range {
-	l1 := g.Range(c.A).(SliceInterval).Length
-	var l2 IntInterval
-	switch r := g.Range(c.B).(type) {
-	case SliceInterval:
-		l2 = r.Length
-	case StringInterval:
-		l2 = r.Length
-	default:
-		return SliceInterval{}
-	}
-	if !l1.IsKnown() || !l2.IsKnown() {
-		return SliceInterval{}
-	}
-	return SliceInterval{
-		Length: l1.Add(l2),
-	}
-}
-func (c *SliceSliceConstraint) Eval(g *Graph) Range {
-	lr := NewIntInterval(NewZ(0), NewZ(0))
-	if c.Lower != nil {
-		lr = g.Range(c.Lower).(IntInterval)
-	}
-	ur := g.Range(c.X).(SliceInterval).Length
-	if c.Upper != nil {
-		ur = g.Range(c.Upper).(IntInterval)
-	}
-	if !lr.IsKnown() || !ur.IsKnown() {
-		return SliceInterval{}
-	}
-
-	ls := []Z{
-		ur.Lower.Sub(lr.Lower),
-		ur.Upper.Sub(lr.Lower),
-		ur.Lower.Sub(lr.Upper),
-		ur.Upper.Sub(lr.Upper),
-	}
-	// TODO(dh): if we don't truncate lengths to 0 we might be able to
-	// easily detect slices with high < low. we'd need to treat -∞
-	// specially, though.
-	for i, l := range ls {
-		if l.Sign() == -1 {
-			ls[i] = NewZ(0)
-		}
-	}
-
-	return SliceInterval{
-		Length: NewIntInterval(MinZ(ls...), MaxZ(ls...)),
-	}
-}
-func (c *ArraySliceConstraint) Eval(g *Graph) Range {
-	lr := NewIntInterval(NewZ(0), NewZ(0))
-	if c.Lower != nil {
-		lr = g.Range(c.Lower).(IntInterval)
-	}
-	var l int64
-	switch typ := c.X.Type().(type) {
-	case *types.Array:
-		l = typ.Len()
-	case *types.Pointer:
-		l = typ.Elem().(*types.Array).Len()
-	}
-	ur := NewIntInterval(NewZ(l), NewZ(l))
-	if c.Upper != nil {
-		ur = g.Range(c.Upper).(IntInterval)
-	}
-	if !lr.IsKnown() || !ur.IsKnown() {
-		return SliceInterval{}
-	}
-
-	ls := []Z{
-		ur.Lower.Sub(lr.Lower),
-		ur.Upper.Sub(lr.Lower),
-		ur.Lower.Sub(lr.Upper),
-		ur.Upper.Sub(lr.Upper),
-	}
-	// TODO(dh): if we don't truncate lengths to 0 we might be able to
-	// easily detect slices with high < low. we'd need to treat -∞
-	// specially, though.
-	for i, l := range ls {
-		if l.Sign() == -1 {
-			ls[i] = NewZ(0)
-		}
-	}
-
-	return SliceInterval{
-		Length: NewIntInterval(MinZ(ls...), MaxZ(ls...)),
-	}
-}
-func (c *SliceIntersectionConstraint) Eval(g *Graph) Range {
-	xi := g.Range(c.X).(SliceInterval)
-	if !xi.IsKnown() {
-		return c.I
-	}
-	return SliceInterval{
-		Length: xi.Length.Intersection(c.I),
-	}
-}
-func (c *SliceLengthConstraint) Eval(g *Graph) Range {
-	i := g.Range(c.X).(SliceInterval).Length
-	if !i.IsKnown() {
-		return NewIntInterval(NewZ(0), PInfinity)
-	}
-	return i
-}
-func (c *MakeSliceConstraint) Eval(g *Graph) Range {
-	i, ok := g.Range(c.Size).(IntInterval)
-	if !ok {
-		return SliceInterval{NewIntInterval(NewZ(0), PInfinity)}
-	}
-	if i.Lower.Sign() == -1 {
-		i.Lower = NewZ(0)
-	}
-	return SliceInterval{i}
-}
-func (c *SliceIntervalConstraint) Eval(*Graph) Range { return SliceInterval{c.I} }
diff --git a/vendor/honnef.co/go/tools/staticcheck/vrp/string.go b/vendor/honnef.co/go/tools/staticcheck/vrp/string.go
deleted file mode 100644
index e05877f..0000000
--- a/vendor/honnef.co/go/tools/staticcheck/vrp/string.go
+++ /dev/null
@@ -1,258 +0,0 @@
-package vrp
-
-import (
-	"fmt"
-	"go/token"
-	"go/types"
-
-	"honnef.co/go/tools/ssa"
-)
-
-type StringInterval struct {
-	Length IntInterval
-}
-
-func (s StringInterval) Union(other Range) Range {
-	i, ok := other.(StringInterval)
-	if !ok {
-		i = StringInterval{EmptyIntInterval}
-	}
-	if s.Length.Empty() || !s.Length.IsKnown() {
-		return i
-	}
-	if i.Length.Empty() || !i.Length.IsKnown() {
-		return s
-	}
-	return StringInterval{
-		Length: s.Length.Union(i.Length).(IntInterval),
-	}
-}
-
-func (s StringInterval) String() string {
-	return s.Length.String()
-}
-
-func (s StringInterval) IsKnown() bool {
-	return s.Length.IsKnown()
-}
-
-type StringSliceConstraint struct {
-	aConstraint
-	X     ssa.Value
-	Lower ssa.Value
-	Upper ssa.Value
-}
-
-type StringIntersectionConstraint struct {
-	aConstraint
-	ranges   Ranges
-	A        ssa.Value
-	B        ssa.Value
-	Op       token.Token
-	I        IntInterval
-	resolved bool
-}
-
-type StringConcatConstraint struct {
-	aConstraint
-	A ssa.Value
-	B ssa.Value
-}
-
-type StringLengthConstraint struct {
-	aConstraint
-	X ssa.Value
-}
-
-type StringIntervalConstraint struct {
-	aConstraint
-	I IntInterval
-}
-
-func NewStringSliceConstraint(x, lower, upper, y ssa.Value) Constraint {
-	return &StringSliceConstraint{NewConstraint(y), x, lower, upper}
-}
-func NewStringIntersectionConstraint(a, b ssa.Value, op token.Token, ranges Ranges, y ssa.Value) Constraint {
-	return &StringIntersectionConstraint{
-		aConstraint: NewConstraint(y),
-		ranges:      ranges,
-		A:           a,
-		B:           b,
-		Op:          op,
-	}
-}
-func NewStringConcatConstraint(a, b, y ssa.Value) Constraint {
-	return &StringConcatConstraint{NewConstraint(y), a, b}
-}
-func NewStringLengthConstraint(x ssa.Value, y ssa.Value) Constraint {
-	return &StringLengthConstraint{NewConstraint(y), x}
-}
-func NewStringIntervalConstraint(i IntInterval, y ssa.Value) Constraint {
-	return &StringIntervalConstraint{NewConstraint(y), i}
-}
-
-func (c *StringSliceConstraint) Operands() []ssa.Value {
-	vs := []ssa.Value{c.X}
-	if c.Lower != nil {
-		vs = append(vs, c.Lower)
-	}
-	if c.Upper != nil {
-		vs = append(vs, c.Upper)
-	}
-	return vs
-}
-func (c *StringIntersectionConstraint) Operands() []ssa.Value { return []ssa.Value{c.A} }
-func (c StringConcatConstraint) Operands() []ssa.Value        { return []ssa.Value{c.A, c.B} }
-func (c *StringLengthConstraint) Operands() []ssa.Value       { return []ssa.Value{c.X} }
-func (s *StringIntervalConstraint) Operands() []ssa.Value     { return nil }
-
-func (c *StringSliceConstraint) String() string {
-	var lname, uname string
-	if c.Lower != nil {
-		lname = c.Lower.Name()
-	}
-	if c.Upper != nil {
-		uname = c.Upper.Name()
-	}
-	return fmt.Sprintf("%s[%s:%s]", c.X.Name(), lname, uname)
-}
-func (c *StringIntersectionConstraint) String() string {
-	return fmt.Sprintf("%s = %s %s %s (%t branch)", c.Y().Name(), c.A.Name(), c.Op, c.B.Name(), c.Y().(*ssa.Sigma).Branch)
-}
-func (c StringConcatConstraint) String() string {
-	return fmt.Sprintf("%s = %s + %s", c.Y().Name(), c.A.Name(), c.B.Name())
-}
-func (c *StringLengthConstraint) String() string {
-	return fmt.Sprintf("%s = len(%s)", c.Y().Name(), c.X.Name())
-}
-func (c *StringIntervalConstraint) String() string { return fmt.Sprintf("%s = %s", c.Y().Name(), c.I) }
-
-func (c *StringSliceConstraint) Eval(g *Graph) Range {
-	lr := NewIntInterval(NewZ(0), NewZ(0))
-	if c.Lower != nil {
-		lr = g.Range(c.Lower).(IntInterval)
-	}
-	ur := g.Range(c.X).(StringInterval).Length
-	if c.Upper != nil {
-		ur = g.Range(c.Upper).(IntInterval)
-	}
-	if !lr.IsKnown() || !ur.IsKnown() {
-		return StringInterval{}
-	}
-
-	ls := []Z{
-		ur.Lower.Sub(lr.Lower),
-		ur.Upper.Sub(lr.Lower),
-		ur.Lower.Sub(lr.Upper),
-		ur.Upper.Sub(lr.Upper),
-	}
-	// TODO(dh): if we don't truncate lengths to 0 we might be able to
-	// easily detect slices with high < low. we'd need to treat -∞
-	// specially, though.
-	for i, l := range ls {
-		if l.Sign() == -1 {
-			ls[i] = NewZ(0)
-		}
-	}
-
-	return StringInterval{
-		Length: NewIntInterval(MinZ(ls...), MaxZ(ls...)),
-	}
-}
-func (c *StringIntersectionConstraint) Eval(g *Graph) Range {
-	var l IntInterval
-	switch r := g.Range(c.A).(type) {
-	case StringInterval:
-		l = r.Length
-	case IntInterval:
-		l = r
-	}
-
-	if !l.IsKnown() {
-		return StringInterval{c.I}
-	}
-	return StringInterval{
-		Length: l.Intersection(c.I),
-	}
-}
-func (c StringConcatConstraint) Eval(g *Graph) Range {
-	i1, i2 := g.Range(c.A).(StringInterval), g.Range(c.B).(StringInterval)
-	if !i1.Length.IsKnown() || !i2.Length.IsKnown() {
-		return StringInterval{}
-	}
-	return StringInterval{
-		Length: i1.Length.Add(i2.Length),
-	}
-}
-func (c *StringLengthConstraint) Eval(g *Graph) Range {
-	i := g.Range(c.X).(StringInterval).Length
-	if !i.IsKnown() {
-		return NewIntInterval(NewZ(0), PInfinity)
-	}
-	return i
-}
-func (c *StringIntervalConstraint) Eval(*Graph) Range { return StringInterval{c.I} }
-
-func (c *StringIntersectionConstraint) Futures() []ssa.Value {
-	return []ssa.Value{c.B}
-}
-
-func (c *StringIntersectionConstraint) Resolve() {
-	if (c.A.Type().Underlying().(*types.Basic).Info() & types.IsString) != 0 {
-		// comparing two strings
-		r, ok := c.ranges[c.B].(StringInterval)
-		if !ok {
-			c.I = NewIntInterval(NewZ(0), PInfinity)
-			return
-		}
-		switch c.Op {
-		case token.EQL:
-			c.I = r.Length
-		case token.GTR, token.GEQ:
-			c.I = NewIntInterval(r.Length.Lower, PInfinity)
-		case token.LSS, token.LEQ:
-			c.I = NewIntInterval(NewZ(0), r.Length.Upper)
-		case token.NEQ:
-		default:
-			panic("unsupported op " + c.Op.String())
-		}
-	} else {
-		r, ok := c.ranges[c.B].(IntInterval)
-		if !ok {
-			c.I = NewIntInterval(NewZ(0), PInfinity)
-			return
-		}
-		// comparing two lengths
-		switch c.Op {
-		case token.EQL:
-			c.I = r
-		case token.GTR:
-			c.I = NewIntInterval(r.Lower.Add(NewZ(1)), PInfinity)
-		case token.GEQ:
-			c.I = NewIntInterval(r.Lower, PInfinity)
-		case token.LSS:
-			c.I = NewIntInterval(NInfinity, r.Upper.Sub(NewZ(1)))
-		case token.LEQ:
-			c.I = NewIntInterval(NInfinity, r.Upper)
-		case token.NEQ:
-		default:
-			panic("unsupported op " + c.Op.String())
-		}
-	}
-}
-
-func (c *StringIntersectionConstraint) IsKnown() bool {
-	return c.I.IsKnown()
-}
-
-func (c *StringIntersectionConstraint) MarkUnresolved() {
-	c.resolved = false
-}
-
-func (c *StringIntersectionConstraint) MarkResolved() {
-	c.resolved = true
-}
-
-func (c *StringIntersectionConstraint) IsResolved() bool {
-	return c.resolved
-}
diff --git a/vendor/honnef.co/go/tools/staticcheck/vrp/vrp.go b/vendor/honnef.co/go/tools/staticcheck/vrp/vrp.go
deleted file mode 100644
index cb17f04..0000000
--- a/vendor/honnef.co/go/tools/staticcheck/vrp/vrp.go
+++ /dev/null
@@ -1,1049 +0,0 @@
-package vrp
-
-// TODO(dh) widening and narrowing have a lot of code in common. Make
-// it reusable.
-
-import (
-	"fmt"
-	"go/constant"
-	"go/token"
-	"go/types"
-	"math/big"
-	"sort"
-	"strings"
-
-	"honnef.co/go/tools/ssa"
-)
-
-type Future interface {
-	Constraint
-	Futures() []ssa.Value
-	Resolve()
-	IsKnown() bool
-	MarkUnresolved()
-	MarkResolved()
-	IsResolved() bool
-}
-
-type Range interface {
-	Union(other Range) Range
-	IsKnown() bool
-}
-
-type Constraint interface {
-	Y() ssa.Value
-	isConstraint()
-	String() string
-	Eval(*Graph) Range
-	Operands() []ssa.Value
-}
-
-type aConstraint struct {
-	y ssa.Value
-}
-
-func NewConstraint(y ssa.Value) aConstraint {
-	return aConstraint{y}
-}
-
-func (aConstraint) isConstraint()  {}
-func (c aConstraint) Y() ssa.Value { return c.y }
-
-type PhiConstraint struct {
-	aConstraint
-	Vars []ssa.Value
-}
-
-func NewPhiConstraint(vars []ssa.Value, y ssa.Value) Constraint {
-	uniqm := map[ssa.Value]struct{}{}
-	for _, v := range vars {
-		uniqm[v] = struct{}{}
-	}
-	var uniq []ssa.Value
-	for v := range uniqm {
-		uniq = append(uniq, v)
-	}
-	return &PhiConstraint{
-		aConstraint: NewConstraint(y),
-		Vars:        uniq,
-	}
-}
-
-func (c *PhiConstraint) Operands() []ssa.Value {
-	return c.Vars
-}
-
-func (c *PhiConstraint) Eval(g *Graph) Range {
-	i := Range(nil)
-	for _, v := range c.Vars {
-		i = g.Range(v).Union(i)
-	}
-	return i
-}
-
-func (c *PhiConstraint) String() string {
-	names := make([]string, len(c.Vars))
-	for i, v := range c.Vars {
-		names[i] = v.Name()
-	}
-	return fmt.Sprintf("%s = φ(%s)", c.Y().Name(), strings.Join(names, ", "))
-}
-
-func isSupportedType(typ types.Type) bool {
-	switch typ := typ.Underlying().(type) {
-	case *types.Basic:
-		switch typ.Kind() {
-		case types.String, types.UntypedString:
-			return true
-		default:
-			if (typ.Info() & types.IsInteger) == 0 {
-				return false
-			}
-		}
-	case *types.Chan:
-		return true
-	case *types.Slice:
-		return true
-	default:
-		return false
-	}
-	return true
-}
-
-func ConstantToZ(c constant.Value) Z {
-	s := constant.ToInt(c).ExactString()
-	n := &big.Int{}
-	n.SetString(s, 10)
-	return NewBigZ(n)
-}
-
-func sigmaInteger(g *Graph, ins *ssa.Sigma, cond *ssa.BinOp, ops []*ssa.Value) Constraint {
-	op := cond.Op
-	if !ins.Branch {
-		op = (invertToken(op))
-	}
-
-	switch op {
-	case token.EQL, token.GTR, token.GEQ, token.LSS, token.LEQ:
-	default:
-		return nil
-	}
-	var a, b ssa.Value
-	if (*ops[0]) == ins.X {
-		a = *ops[0]
-		b = *ops[1]
-	} else {
-		a = *ops[1]
-		b = *ops[0]
-		op = flipToken(op)
-	}
-	return NewIntIntersectionConstraint(a, b, op, g.ranges, ins)
-}
-
-func sigmaString(g *Graph, ins *ssa.Sigma, cond *ssa.BinOp, ops []*ssa.Value) Constraint {
-	op := cond.Op
-	if !ins.Branch {
-		op = (invertToken(op))
-	}
-
-	switch op {
-	case token.EQL, token.GTR, token.GEQ, token.LSS, token.LEQ:
-	default:
-		return nil
-	}
-
-	if ((*ops[0]).Type().Underlying().(*types.Basic).Info() & types.IsString) == 0 {
-		var a, b ssa.Value
-		call, ok := (*ops[0]).(*ssa.Call)
-		if ok && call.Common().Args[0] == ins.X {
-			a = *ops[0]
-			b = *ops[1]
-		} else {
-			a = *ops[1]
-			b = *ops[0]
-			op = flipToken(op)
-		}
-		return NewStringIntersectionConstraint(a, b, op, g.ranges, ins)
-	}
-	var a, b ssa.Value
-	if (*ops[0]) == ins.X {
-		a = *ops[0]
-		b = *ops[1]
-	} else {
-		a = *ops[1]
-		b = *ops[0]
-		op = flipToken(op)
-	}
-	return NewStringIntersectionConstraint(a, b, op, g.ranges, ins)
-}
-
-func sigmaSlice(g *Graph, ins *ssa.Sigma, cond *ssa.BinOp, ops []*ssa.Value) Constraint {
-	// TODO(dh) sigmaSlice and sigmaString are a lot alike. Can they
-	// be merged?
-	//
-	// XXX support futures
-
-	op := cond.Op
-	if !ins.Branch {
-		op = (invertToken(op))
-	}
-
-	k, ok := (*ops[1]).(*ssa.Const)
-	// XXX investigate in what cases this wouldn't be a Const
-	//
-	// XXX what if left and right are swapped?
-	if !ok {
-		return nil
-	}
-
-	call, ok := (*ops[0]).(*ssa.Call)
-	if !ok {
-		return nil
-	}
-	builtin, ok := call.Common().Value.(*ssa.Builtin)
-	if !ok {
-		return nil
-	}
-	if builtin.Name() != "len" {
-		return nil
-	}
-	callops := call.Operands(nil)
-
-	v := ConstantToZ(k.Value)
-	c := NewSliceIntersectionConstraint(*callops[1], IntInterval{}, ins).(*SliceIntersectionConstraint)
-	switch op {
-	case token.EQL:
-		c.I = NewIntInterval(v, v)
-	case token.GTR, token.GEQ:
-		off := int64(0)
-		if cond.Op == token.GTR {
-			off = 1
-		}
-		c.I = NewIntInterval(
-			v.Add(NewZ(off)),
-			PInfinity,
-		)
-	case token.LSS, token.LEQ:
-		off := int64(0)
-		if cond.Op == token.LSS {
-			off = -1
-		}
-		c.I = NewIntInterval(
-			NInfinity,
-			v.Add(NewZ(off)),
-		)
-	default:
-		return nil
-	}
-	return c
-}
-
-func BuildGraph(f *ssa.Function) *Graph {
-	g := &Graph{
-		Vertices: map[interface{}]*Vertex{},
-		ranges:   Ranges{},
-	}
-
-	var cs []Constraint
-
-	ops := make([]*ssa.Value, 16)
-	seen := map[ssa.Value]bool{}
-	for _, block := range f.Blocks {
-		for _, ins := range block.Instrs {
-			ops = ins.Operands(ops[:0])
-			for _, op := range ops {
-				if c, ok := (*op).(*ssa.Const); ok {
-					if seen[c] {
-						continue
-					}
-					seen[c] = true
-					if c.Value == nil {
-						switch c.Type().Underlying().(type) {
-						case *types.Slice:
-							cs = append(cs, NewSliceIntervalConstraint(NewIntInterval(NewZ(0), NewZ(0)), c))
-						}
-						continue
-					}
-					switch c.Value.Kind() {
-					case constant.Int:
-						v := ConstantToZ(c.Value)
-						cs = append(cs, NewIntIntervalConstraint(NewIntInterval(v, v), c))
-					case constant.String:
-						s := constant.StringVal(c.Value)
-						n := NewZ(int64(len(s)))
-						cs = append(cs, NewStringIntervalConstraint(NewIntInterval(n, n), c))
-					}
-				}
-			}
-		}
-	}
-	for _, block := range f.Blocks {
-		for _, ins := range block.Instrs {
-			switch ins := ins.(type) {
-			case *ssa.Convert:
-				switch v := ins.Type().Underlying().(type) {
-				case *types.Basic:
-					if (v.Info() & types.IsInteger) == 0 {
-						continue
-					}
-					cs = append(cs, NewIntConversionConstraint(ins.X, ins))
-				}
-			case *ssa.Call:
-				if static := ins.Common().StaticCallee(); static != nil {
-					if fn, ok := static.Object().(*types.Func); ok {
-						switch fn.FullName() {
-						case "bytes.Index", "bytes.IndexAny", "bytes.IndexByte",
-							"bytes.IndexFunc", "bytes.IndexRune", "bytes.LastIndex",
-							"bytes.LastIndexAny", "bytes.LastIndexByte", "bytes.LastIndexFunc",
-							"strings.Index", "strings.IndexAny", "strings.IndexByte",
-							"strings.IndexFunc", "strings.IndexRune", "strings.LastIndex",
-							"strings.LastIndexAny", "strings.LastIndexByte", "strings.LastIndexFunc":
-							// TODO(dh): instead of limiting by +∞,
-							// limit by the upper bound of the passed
-							// string
-							cs = append(cs, NewIntIntervalConstraint(NewIntInterval(NewZ(-1), PInfinity), ins))
-						case "bytes.Title", "bytes.ToLower", "bytes.ToTitle", "bytes.ToUpper",
-							"strings.Title", "strings.ToLower", "strings.ToTitle", "strings.ToUpper":
-							cs = append(cs, NewCopyConstraint(ins.Common().Args[0], ins))
-						case "bytes.ToLowerSpecial", "bytes.ToTitleSpecial", "bytes.ToUpperSpecial",
-							"strings.ToLowerSpecial", "strings.ToTitleSpecial", "strings.ToUpperSpecial":
-							cs = append(cs, NewCopyConstraint(ins.Common().Args[1], ins))
-						case "bytes.Compare", "strings.Compare":
-							cs = append(cs, NewIntIntervalConstraint(NewIntInterval(NewZ(-1), NewZ(1)), ins))
-						case "bytes.Count", "strings.Count":
-							// TODO(dh): instead of limiting by +∞,
-							// limit by the upper bound of the passed
-							// string.
-							cs = append(cs, NewIntIntervalConstraint(NewIntInterval(NewZ(0), PInfinity), ins))
-						case "bytes.Map", "bytes.TrimFunc", "bytes.TrimLeft", "bytes.TrimLeftFunc",
-							"bytes.TrimRight", "bytes.TrimRightFunc", "bytes.TrimSpace",
-							"strings.Map", "strings.TrimFunc", "strings.TrimLeft", "strings.TrimLeftFunc",
-							"strings.TrimRight", "strings.TrimRightFunc", "strings.TrimSpace":
-							// TODO(dh): lower = 0, upper = upper of passed string
-						case "bytes.TrimPrefix", "bytes.TrimSuffix",
-							"strings.TrimPrefix", "strings.TrimSuffix":
-							// TODO(dh) range between "unmodified" and len(cutset) removed
-						case "(*bytes.Buffer).Cap", "(*bytes.Buffer).Len", "(*bytes.Reader).Len", "(*bytes.Reader).Size":
-							cs = append(cs, NewIntIntervalConstraint(NewIntInterval(NewZ(0), PInfinity), ins))
-						}
-					}
-				}
-				builtin, ok := ins.Common().Value.(*ssa.Builtin)
-				ops := ins.Operands(nil)
-				if !ok {
-					continue
-				}
-				switch builtin.Name() {
-				case "len":
-					switch op1 := (*ops[1]).Type().Underlying().(type) {
-					case *types.Basic:
-						if op1.Kind() == types.String || op1.Kind() == types.UntypedString {
-							cs = append(cs, NewStringLengthConstraint(*ops[1], ins))
-						}
-					case *types.Slice:
-						cs = append(cs, NewSliceLengthConstraint(*ops[1], ins))
-					}
-
-				case "append":
-					cs = append(cs, NewSliceAppendConstraint(ins.Common().Args[0], ins.Common().Args[1], ins))
-				}
-			case *ssa.BinOp:
-				ops := ins.Operands(nil)
-				basic, ok := (*ops[0]).Type().Underlying().(*types.Basic)
-				if !ok {
-					continue
-				}
-				switch basic.Kind() {
-				case types.Int, types.Int8, types.Int16, types.Int32, types.Int64,
-					types.Uint, types.Uint8, types.Uint16, types.Uint32, types.Uint64, types.UntypedInt:
-					fns := map[token.Token]func(ssa.Value, ssa.Value, ssa.Value) Constraint{
-						token.ADD: NewIntAddConstraint,
-						token.SUB: NewIntSubConstraint,
-						token.MUL: NewIntMulConstraint,
-						// XXX support QUO, REM, SHL, SHR
-					}
-					fn, ok := fns[ins.Op]
-					if ok {
-						cs = append(cs, fn(*ops[0], *ops[1], ins))
-					}
-				case types.String, types.UntypedString:
-					if ins.Op == token.ADD {
-						cs = append(cs, NewStringConcatConstraint(*ops[0], *ops[1], ins))
-					}
-				}
-			case *ssa.Slice:
-				typ := ins.X.Type().Underlying()
-				switch typ := typ.(type) {
-				case *types.Basic:
-					cs = append(cs, NewStringSliceConstraint(ins.X, ins.Low, ins.High, ins))
-				case *types.Slice:
-					cs = append(cs, NewSliceSliceConstraint(ins.X, ins.Low, ins.High, ins))
-				case *types.Array:
-					cs = append(cs, NewArraySliceConstraint(ins.X, ins.Low, ins.High, ins))
-				case *types.Pointer:
-					if _, ok := typ.Elem().(*types.Array); !ok {
-						continue
-					}
-					cs = append(cs, NewArraySliceConstraint(ins.X, ins.Low, ins.High, ins))
-				}
-			case *ssa.Phi:
-				if !isSupportedType(ins.Type()) {
-					continue
-				}
-				ops := ins.Operands(nil)
-				dops := make([]ssa.Value, len(ops))
-				for i, op := range ops {
-					dops[i] = *op
-				}
-				cs = append(cs, NewPhiConstraint(dops, ins))
-			case *ssa.Sigma:
-				pred := ins.Block().Preds[0]
-				instrs := pred.Instrs
-				cond, ok := instrs[len(instrs)-1].(*ssa.If).Cond.(*ssa.BinOp)
-				ops := cond.Operands(nil)
-				if !ok {
-					continue
-				}
-				switch typ := ins.Type().Underlying().(type) {
-				case *types.Basic:
-					var c Constraint
-					switch typ.Kind() {
-					case types.Int, types.Int8, types.Int16, types.Int32, types.Int64,
-						types.Uint, types.Uint8, types.Uint16, types.Uint32, types.Uint64, types.UntypedInt:
-						c = sigmaInteger(g, ins, cond, ops)
-					case types.String, types.UntypedString:
-						c = sigmaString(g, ins, cond, ops)
-					}
-					if c != nil {
-						cs = append(cs, c)
-					}
-				case *types.Slice:
-					c := sigmaSlice(g, ins, cond, ops)
-					if c != nil {
-						cs = append(cs, c)
-					}
-				default:
-					//log.Printf("unsupported sigma type %T", typ) // XXX
-				}
-			case *ssa.MakeChan:
-				cs = append(cs, NewMakeChannelConstraint(ins.Size, ins))
-			case *ssa.MakeSlice:
-				cs = append(cs, NewMakeSliceConstraint(ins.Len, ins))
-			case *ssa.ChangeType:
-				switch ins.X.Type().Underlying().(type) {
-				case *types.Chan:
-					cs = append(cs, NewChannelChangeTypeConstraint(ins.X, ins))
-				}
-			}
-		}
-	}
-
-	for _, c := range cs {
-		if c == nil {
-			panic("nil constraint")
-		}
-		// If V is used in constraint C, then we create an edge V->C
-		for _, op := range c.Operands() {
-			g.AddEdge(op, c, false)
-		}
-		if c, ok := c.(Future); ok {
-			for _, op := range c.Futures() {
-				g.AddEdge(op, c, true)
-			}
-		}
-		// If constraint C defines variable V, then we create an edge
-		// C->V
-		g.AddEdge(c, c.Y(), false)
-	}
-
-	g.FindSCCs()
-	g.sccEdges = make([][]Edge, len(g.SCCs))
-	g.futures = make([][]Future, len(g.SCCs))
-	for _, e := range g.Edges {
-		g.sccEdges[e.From.SCC] = append(g.sccEdges[e.From.SCC], e)
-		if !e.control {
-			continue
-		}
-		if c, ok := e.To.Value.(Future); ok {
-			g.futures[e.From.SCC] = append(g.futures[e.From.SCC], c)
-		}
-	}
-	return g
-}
-
-func (g *Graph) Solve() Ranges {
-	var consts []Z
-	off := NewZ(1)
-	for _, n := range g.Vertices {
-		if c, ok := n.Value.(*ssa.Const); ok {
-			basic, ok := c.Type().Underlying().(*types.Basic)
-			if !ok {
-				continue
-			}
-			if (basic.Info() & types.IsInteger) != 0 {
-				z := ConstantToZ(c.Value)
-				consts = append(consts, z)
-				consts = append(consts, z.Add(off))
-				consts = append(consts, z.Sub(off))
-			}
-		}
-
-	}
-	sort.Sort(Zs(consts))
-
-	for scc, vertices := range g.SCCs {
-		n := 0
-		n = len(vertices)
-		if n == 1 {
-			g.resolveFutures(scc)
-			v := vertices[0]
-			if v, ok := v.Value.(ssa.Value); ok {
-				switch typ := v.Type().Underlying().(type) {
-				case *types.Basic:
-					switch typ.Kind() {
-					case types.String, types.UntypedString:
-						if !g.Range(v).(StringInterval).IsKnown() {
-							g.SetRange(v, StringInterval{NewIntInterval(NewZ(0), PInfinity)})
-						}
-					default:
-						if !g.Range(v).(IntInterval).IsKnown() {
-							g.SetRange(v, InfinityFor(v))
-						}
-					}
-				case *types.Chan:
-					if !g.Range(v).(ChannelInterval).IsKnown() {
-						g.SetRange(v, ChannelInterval{NewIntInterval(NewZ(0), PInfinity)})
-					}
-				case *types.Slice:
-					if !g.Range(v).(SliceInterval).IsKnown() {
-						g.SetRange(v, SliceInterval{NewIntInterval(NewZ(0), PInfinity)})
-					}
-				}
-			}
-			if c, ok := v.Value.(Constraint); ok {
-				g.SetRange(c.Y(), c.Eval(g))
-			}
-		} else {
-			uses := g.uses(scc)
-			entries := g.entries(scc)
-			for len(entries) > 0 {
-				v := entries[len(entries)-1]
-				entries = entries[:len(entries)-1]
-				for _, use := range uses[v] {
-					if g.widen(use, consts) {
-						entries = append(entries, use.Y())
-					}
-				}
-			}
-
-			g.resolveFutures(scc)
-
-			// XXX this seems to be necessary, but shouldn't be.
-			// removing it leads to nil pointer derefs; investigate
-			// where we're not setting values correctly.
-			for _, n := range vertices {
-				if v, ok := n.Value.(ssa.Value); ok {
-					i, ok := g.Range(v).(IntInterval)
-					if !ok {
-						continue
-					}
-					if !i.IsKnown() {
-						g.SetRange(v, InfinityFor(v))
-					}
-				}
-			}
-
-			actives := g.actives(scc)
-			for len(actives) > 0 {
-				v := actives[len(actives)-1]
-				actives = actives[:len(actives)-1]
-				for _, use := range uses[v] {
-					if g.narrow(use) {
-						actives = append(actives, use.Y())
-					}
-				}
-			}
-		}
-		// propagate scc
-		for _, edge := range g.sccEdges[scc] {
-			if edge.control {
-				continue
-			}
-			if edge.From.SCC == edge.To.SCC {
-				continue
-			}
-			if c, ok := edge.To.Value.(Constraint); ok {
-				g.SetRange(c.Y(), c.Eval(g))
-			}
-			if c, ok := edge.To.Value.(Future); ok {
-				if !c.IsKnown() {
-					c.MarkUnresolved()
-				}
-			}
-		}
-	}
-
-	for v, r := range g.ranges {
-		i, ok := r.(IntInterval)
-		if !ok {
-			continue
-		}
-		if (v.Type().Underlying().(*types.Basic).Info() & types.IsUnsigned) == 0 {
-			if i.Upper != PInfinity {
-				s := &types.StdSizes{
-					// XXX is it okay to assume the largest word size, or do we
-					// need to be platform specific?
-					WordSize: 8,
-					MaxAlign: 1,
-				}
-				bits := (s.Sizeof(v.Type()) * 8) - 1
-				n := big.NewInt(1)
-				n = n.Lsh(n, uint(bits))
-				upper, lower := &big.Int{}, &big.Int{}
-				upper.Sub(n, big.NewInt(1))
-				lower.Neg(n)
-
-				if i.Upper.Cmp(NewBigZ(upper)) == 1 {
-					i = NewIntInterval(NInfinity, PInfinity)
-				} else if i.Lower.Cmp(NewBigZ(lower)) == -1 {
-					i = NewIntInterval(NInfinity, PInfinity)
-				}
-			}
-		}
-
-		g.ranges[v] = i
-	}
-
-	return g.ranges
-}
-
-func VertexString(v *Vertex) string {
-	switch v := v.Value.(type) {
-	case Constraint:
-		return v.String()
-	case ssa.Value:
-		return v.Name()
-	case nil:
-		return "BUG: nil vertex value"
-	default:
-		panic(fmt.Sprintf("unexpected type %T", v))
-	}
-}
-
-type Vertex struct {
-	Value   interface{} // one of Constraint or ssa.Value
-	SCC     int
-	index   int
-	lowlink int
-	stack   bool
-
-	Succs []Edge
-}
-
-type Ranges map[ssa.Value]Range
-
-func (r Ranges) Get(x ssa.Value) Range {
-	if x == nil {
-		return nil
-	}
-	i, ok := r[x]
-	if !ok {
-		switch x := x.Type().Underlying().(type) {
-		case *types.Basic:
-			switch x.Kind() {
-			case types.String, types.UntypedString:
-				return StringInterval{}
-			default:
-				return IntInterval{}
-			}
-		case *types.Chan:
-			return ChannelInterval{}
-		case *types.Slice:
-			return SliceInterval{}
-		}
-	}
-	return i
-}
-
-type Graph struct {
-	Vertices map[interface{}]*Vertex
-	Edges    []Edge
-	SCCs     [][]*Vertex
-	ranges   Ranges
-
-	// map SCCs to futures
-	futures [][]Future
-	// map SCCs to edges
-	sccEdges [][]Edge
-}
-
-func (g Graph) Graphviz() string {
-	var lines []string
-	lines = append(lines, "digraph{")
-	ids := map[interface{}]int{}
-	i := 1
-	for _, v := range g.Vertices {
-		ids[v] = i
-		shape := "box"
-		if _, ok := v.Value.(ssa.Value); ok {
-			shape = "oval"
-		}
-		lines = append(lines, fmt.Sprintf(`n%d [shape="%s", label=%q, colorscheme=spectral11, style="filled", fillcolor="%d"]`,
-			i, shape, VertexString(v), (v.SCC%11)+1))
-		i++
-	}
-	for _, e := range g.Edges {
-		style := "solid"
-		if e.control {
-			style = "dashed"
-		}
-		lines = append(lines, fmt.Sprintf(`n%d -> n%d [style="%s"]`, ids[e.From], ids[e.To], style))
-	}
-	lines = append(lines, "}")
-	return strings.Join(lines, "\n")
-}
-
-func (g *Graph) SetRange(x ssa.Value, r Range) {
-	g.ranges[x] = r
-}
-
-func (g *Graph) Range(x ssa.Value) Range {
-	return g.ranges.Get(x)
-}
-
-func (g *Graph) widen(c Constraint, consts []Z) bool {
-	setRange := func(i Range) {
-		g.SetRange(c.Y(), i)
-	}
-	widenIntInterval := func(oi, ni IntInterval) (IntInterval, bool) {
-		if !ni.IsKnown() {
-			return oi, false
-		}
-		nlc := NInfinity
-		nuc := PInfinity
-		for _, co := range consts {
-			if co.Cmp(ni.Lower) <= 0 {
-				nlc = co
-				break
-			}
-		}
-		for _, co := range consts {
-			if co.Cmp(ni.Upper) >= 0 {
-				nuc = co
-				break
-			}
-		}
-
-		if !oi.IsKnown() {
-			return ni, true
-		}
-		if ni.Lower.Cmp(oi.Lower) == -1 && ni.Upper.Cmp(oi.Upper) == 1 {
-			return NewIntInterval(nlc, nuc), true
-		}
-		if ni.Lower.Cmp(oi.Lower) == -1 {
-			return NewIntInterval(nlc, oi.Upper), true
-		}
-		if ni.Upper.Cmp(oi.Upper) == 1 {
-			return NewIntInterval(oi.Lower, nuc), true
-		}
-		return oi, false
-	}
-	switch oi := g.Range(c.Y()).(type) {
-	case IntInterval:
-		ni := c.Eval(g).(IntInterval)
-		si, changed := widenIntInterval(oi, ni)
-		if changed {
-			setRange(si)
-			return true
-		}
-		return false
-	case StringInterval:
-		ni := c.Eval(g).(StringInterval)
-		si, changed := widenIntInterval(oi.Length, ni.Length)
-		if changed {
-			setRange(StringInterval{si})
-			return true
-		}
-		return false
-	case SliceInterval:
-		ni := c.Eval(g).(SliceInterval)
-		si, changed := widenIntInterval(oi.Length, ni.Length)
-		if changed {
-			setRange(SliceInterval{si})
-			return true
-		}
-		return false
-	default:
-		return false
-	}
-}
-
-func (g *Graph) narrow(c Constraint) bool {
-	narrowIntInterval := func(oi, ni IntInterval) (IntInterval, bool) {
-		oLower := oi.Lower
-		oUpper := oi.Upper
-		nLower := ni.Lower
-		nUpper := ni.Upper
-
-		if oLower == NInfinity && nLower != NInfinity {
-			return NewIntInterval(nLower, oUpper), true
-		}
-		if oUpper == PInfinity && nUpper != PInfinity {
-			return NewIntInterval(oLower, nUpper), true
-		}
-		if oLower.Cmp(nLower) == 1 {
-			return NewIntInterval(nLower, oUpper), true
-		}
-		if oUpper.Cmp(nUpper) == -1 {
-			return NewIntInterval(oLower, nUpper), true
-		}
-		return oi, false
-	}
-	switch oi := g.Range(c.Y()).(type) {
-	case IntInterval:
-		ni := c.Eval(g).(IntInterval)
-		si, changed := narrowIntInterval(oi, ni)
-		if changed {
-			g.SetRange(c.Y(), si)
-			return true
-		}
-		return false
-	case StringInterval:
-		ni := c.Eval(g).(StringInterval)
-		si, changed := narrowIntInterval(oi.Length, ni.Length)
-		if changed {
-			g.SetRange(c.Y(), StringInterval{si})
-			return true
-		}
-		return false
-	case SliceInterval:
-		ni := c.Eval(g).(SliceInterval)
-		si, changed := narrowIntInterval(oi.Length, ni.Length)
-		if changed {
-			g.SetRange(c.Y(), SliceInterval{si})
-			return true
-		}
-		return false
-	default:
-		return false
-	}
-}
-
-func (g *Graph) resolveFutures(scc int) {
-	for _, c := range g.futures[scc] {
-		c.Resolve()
-	}
-}
-
-func (g *Graph) entries(scc int) []ssa.Value {
-	var entries []ssa.Value
-	for _, n := range g.Vertices {
-		if n.SCC != scc {
-			continue
-		}
-		if v, ok := n.Value.(ssa.Value); ok {
-			// XXX avoid quadratic runtime
-			//
-			// XXX I cannot think of any code where the future and its
-			// variables aren't in the same SCC, in which case this
-			// code isn't very useful (the variables won't be resolved
-			// yet). Before we have a cross-SCC example, however, we
-			// can't really verify that this code is working
-			// correctly, or indeed doing anything useful.
-			for _, on := range g.Vertices {
-				if c, ok := on.Value.(Future); ok {
-					if c.Y() == v {
-						if !c.IsResolved() {
-							g.SetRange(c.Y(), c.Eval(g))
-							c.MarkResolved()
-						}
-						break
-					}
-				}
-			}
-			if g.Range(v).IsKnown() {
-				entries = append(entries, v)
-			}
-		}
-	}
-	return entries
-}
-
-func (g *Graph) uses(scc int) map[ssa.Value][]Constraint {
-	m := map[ssa.Value][]Constraint{}
-	for _, e := range g.sccEdges[scc] {
-		if e.control {
-			continue
-		}
-		if v, ok := e.From.Value.(ssa.Value); ok {
-			c := e.To.Value.(Constraint)
-			sink := c.Y()
-			if g.Vertices[sink].SCC == scc {
-				m[v] = append(m[v], c)
-			}
-		}
-	}
-	return m
-}
-
-func (g *Graph) actives(scc int) []ssa.Value {
-	var actives []ssa.Value
-	for _, n := range g.Vertices {
-		if n.SCC != scc {
-			continue
-		}
-		if v, ok := n.Value.(ssa.Value); ok {
-			if _, ok := v.(*ssa.Const); !ok {
-				actives = append(actives, v)
-			}
-		}
-	}
-	return actives
-}
-
-func (g *Graph) AddEdge(from, to interface{}, ctrl bool) {
-	vf, ok := g.Vertices[from]
-	if !ok {
-		vf = &Vertex{Value: from}
-		g.Vertices[from] = vf
-	}
-	vt, ok := g.Vertices[to]
-	if !ok {
-		vt = &Vertex{Value: to}
-		g.Vertices[to] = vt
-	}
-	e := Edge{From: vf, To: vt, control: ctrl}
-	g.Edges = append(g.Edges, e)
-	vf.Succs = append(vf.Succs, e)
-}
-
-type Edge struct {
-	From, To *Vertex
-	control  bool
-}
-
-func (e Edge) String() string {
-	return fmt.Sprintf("%s -> %s", VertexString(e.From), VertexString(e.To))
-}
-
-func (g *Graph) FindSCCs() {
-	// use Tarjan to find the SCCs
-
-	index := 1
-	var s []*Vertex
-
-	scc := 0
-	var strongconnect func(v *Vertex)
-	strongconnect = func(v *Vertex) {
-		// set the depth index for v to the smallest unused index
-		v.index = index
-		v.lowlink = index
-		index++
-		s = append(s, v)
-		v.stack = true
-
-		for _, e := range v.Succs {
-			w := e.To
-			if w.index == 0 {
-				// successor w has not yet been visited; recurse on it
-				strongconnect(w)
-				if w.lowlink < v.lowlink {
-					v.lowlink = w.lowlink
-				}
-			} else if w.stack {
-				// successor w is in stack s and hence in the current scc
-				if w.index < v.lowlink {
-					v.lowlink = w.index
-				}
-			}
-		}
-
-		if v.lowlink == v.index {
-			for {
-				w := s[len(s)-1]
-				s = s[:len(s)-1]
-				w.stack = false
-				w.SCC = scc
-				if w == v {
-					break
-				}
-			}
-			scc++
-		}
-	}
-	for _, v := range g.Vertices {
-		if v.index == 0 {
-			strongconnect(v)
-		}
-	}
-
-	g.SCCs = make([][]*Vertex, scc)
-	for _, n := range g.Vertices {
-		n.SCC = scc - n.SCC - 1
-		g.SCCs[n.SCC] = append(g.SCCs[n.SCC], n)
-	}
-}
-
-func invertToken(tok token.Token) token.Token {
-	switch tok {
-	case token.LSS:
-		return token.GEQ
-	case token.GTR:
-		return token.LEQ
-	case token.EQL:
-		return token.NEQ
-	case token.NEQ:
-		return token.EQL
-	case token.GEQ:
-		return token.LSS
-	case token.LEQ:
-		return token.GTR
-	default:
-		panic(fmt.Sprintf("unsupported token %s", tok))
-	}
-}
-
-func flipToken(tok token.Token) token.Token {
-	switch tok {
-	case token.LSS:
-		return token.GTR
-	case token.GTR:
-		return token.LSS
-	case token.EQL:
-		return token.EQL
-	case token.NEQ:
-		return token.NEQ
-	case token.GEQ:
-		return token.LEQ
-	case token.LEQ:
-		return token.GEQ
-	default:
-		panic(fmt.Sprintf("unsupported token %s", tok))
-	}
-}
-
-type CopyConstraint struct {
-	aConstraint
-	X ssa.Value
-}
-
-func (c *CopyConstraint) String() string {
-	return fmt.Sprintf("%s = copy(%s)", c.Y().Name(), c.X.Name())
-}
-
-func (c *CopyConstraint) Eval(g *Graph) Range {
-	return g.Range(c.X)
-}
-
-func (c *CopyConstraint) Operands() []ssa.Value {
-	return []ssa.Value{c.X}
-}
-
-func NewCopyConstraint(x, y ssa.Value) Constraint {
-	return &CopyConstraint{
-		aConstraint: aConstraint{
-			y: y,
-		},
-		X: x,
-	}
-}