1 files changed, 310 insertions, 247 deletions

diff --git a/vendor/github.com/google/go-cmp/cmp/compare.go b/vendor/github.com/google/go-cmp/cmp/compare.go
index 7e215f2..2133562 100644
--- a/vendor/github.com/google/go-cmp/cmp/compare.go
+++ b/vendor/github.com/google/go-cmp/cmp/compare.go
@@ -29,26 +29,17 @@ package cmp
 import (
         "fmt"
         "reflect"
+        "strings"
 
         "github.com/google/go-cmp/cmp/internal/diff"
+        "github.com/google/go-cmp/cmp/internal/flags"
         "github.com/google/go-cmp/cmp/internal/function"
         "github.com/google/go-cmp/cmp/internal/value"
 )
 
-// BUG(dsnet): Maps with keys containing NaN values cannot be properly compared due to
-// the reflection package's inability to retrieve such entries. Equal will panic
-// anytime it comes across a NaN key, but this behavior may change.
-//
-// See https://golang.org/issue/11104 for more details.
-
-var nothing = reflect.Value{}
-
 // Equal reports whether x and y are equal by recursively applying the
 // following rules in the given order to x and y and all of their sub-values:
 //
-// • If two values are not of the same type, then they are never equal
-// and the overall result is false.
-//
 // • Let S be the set of all Ignore, Transformer, and Comparer options that
 // remain after applying all path filters, value filters, and type filters.
 // If at least one Ignore exists in S, then the comparison is ignored.
@@ -61,43 +52,79 @@ var nothing = reflect.Value{}
 //
 // • If the values have an Equal method of the form "(T) Equal(T) bool" or
 // "(T) Equal(I) bool" where T is assignable to I, then use the result of
-// x.Equal(y) even if x or y is nil.
-// Otherwise, no such method exists and evaluation proceeds to the next rule.
+// x.Equal(y) even if x or y is nil. Otherwise, no such method exists and
+// evaluation proceeds to the next rule.
 //
 // • Lastly, try to compare x and y based on their basic kinds.
 // Simple kinds like booleans, integers, floats, complex numbers, strings, and
 // channels are compared using the equivalent of the == operator in Go.
 // Functions are only equal if they are both nil, otherwise they are unequal.
-// Pointers are equal if the underlying values they point to are also equal.
-// Interfaces are equal if their underlying concrete values are also equal.
 //
-// Structs are equal if all of their fields are equal. If a struct contains
-// unexported fields, Equal panics unless the AllowUnexported option is used or
-// an Ignore option (e.g., cmpopts.IgnoreUnexported) ignores that field.
+// Structs are equal if recursively calling Equal on all fields report equal.
+// If a struct contains unexported fields, Equal panics unless an Ignore option
+// (e.g., cmpopts.IgnoreUnexported) ignores that field or the AllowUnexported
+// option explicitly permits comparing the unexported field.
+//
+// Slices are equal if they are both nil or both non-nil, where recursively
+// calling Equal on all non-ignored slice or array elements report equal.
+// Empty non-nil slices and nil slices are not equal; to equate empty slices,
+// consider using cmpopts.EquateEmpty.
 //
-// Arrays, slices, and maps are equal if they are both nil or both non-nil
-// with the same length and the elements at each index or key are equal.
-// Note that a non-nil empty slice and a nil slice are not equal.
-// To equate empty slices and maps, consider using cmpopts.EquateEmpty.
+// Maps are equal if they are both nil or both non-nil, where recursively
+// calling Equal on all non-ignored map entries report equal.
 // Map keys are equal according to the == operator.
 // To use custom comparisons for map keys, consider using cmpopts.SortMaps.
+// Empty non-nil maps and nil maps are not equal; to equate empty maps,
+// consider using cmpopts.EquateEmpty.
+//
+// Pointers and interfaces are equal if they are both nil or both non-nil,
+// where they have the same underlying concrete type and recursively
+// calling Equal on the underlying values reports equal.
 func Equal(x, y interface{}, opts ...Option) bool {
+        vx := reflect.ValueOf(x)
+        vy := reflect.ValueOf(y)
+
+        // If the inputs are different types, auto-wrap them in an empty interface
+        // so that they have the same parent type.
+        var t reflect.Type
+        if !vx.IsValid() || !vy.IsValid() || vx.Type() != vy.Type() {
+                t = reflect.TypeOf((*interface{})(nil)).Elem()
+                if vx.IsValid() {
+                        vvx := reflect.New(t).Elem()
+                        vvx.Set(vx)
+                        vx = vvx
+                }
+                if vy.IsValid() {
+                        vvy := reflect.New(t).Elem()
+                        vvy.Set(vy)
+                        vy = vvy
+                }
+        } else {
+                t = vx.Type()
+        }
+
         s := newState(opts)
-        s.compareAny(reflect.ValueOf(x), reflect.ValueOf(y))
+        s.compareAny(&pathStep{t, vx, vy})
         return s.result.Equal()
 }
 
 // Diff returns a human-readable report of the differences between two values.
 // It returns an empty string if and only if Equal returns true for the same
-// input values and options. The output string will use the "-" symbol to
-// indicate elements removed from x, and the "+" symbol to indicate elements
-// added to y.
+// input values and options.
+//
+// The output is displayed as a literal in pseudo-Go syntax.
+// At the start of each line, a "-" prefix indicates an element removed from x,
+// a "+" prefix to indicates an element added to y, and the lack of a prefix
+// indicates an element common to both x and y. If possible, the output
+// uses fmt.Stringer.String or error.Error methods to produce more humanly
+// readable outputs. In such cases, the string is prefixed with either an
+// 's' or 'e' character, respectively, to indicate that the method was called.
 //
-// Do not depend on this output being stable.
+// Do not depend on this output being stable. If you need the ability to
+// programmatically interpret the difference, consider using a custom Reporter.
 func Diff(x, y interface{}, opts ...Option) string {
         r := new(defaultReporter)
-        opts = Options{Options(opts), r}
-        eq := Equal(x, y, opts...)
+        eq := Equal(x, y, Options(opts), Reporter(r))
         d := r.String()
         if (d == "") != eq {
                 panic("inconsistent difference and equality results")
@@ -108,9 +135,13 @@ func Diff(x, y interface{}, opts ...Option) string {
 type state struct {
         // These fields represent the "comparison state".
         // Calling statelessCompare must not result in observable changes to these.
-        result   diff.Result // The current result of comparison
-        curPath  Path        // The current path in the value tree
-        reporter reporter    // Optional reporter used for difference formatting
+        result    diff.Result // The current result of comparison
+        curPath   Path        // The current path in the value tree
+        reporters []reporter  // Optional reporters
+
+        // recChecker checks for infinite cycles applying the same set of
+        // transformers upon the output of itself.
+        recChecker recChecker
 
         // dynChecker triggers pseudo-random checks for option correctness.
         // It is safe for statelessCompare to mutate this value.
@@ -122,10 +153,9 @@ type state struct {
 }
 
 func newState(opts []Option) *state {
-        s := new(state)
-        for _, opt := range opts {
-                s.processOption(opt)
-        }
+        // Always ensure a validator option exists to validate the inputs.
+        s := &state{opts: Options{validator{}}}
+        s.processOption(Options(opts))
         return s
 }
 
@@ -152,10 +182,7 @@ func (s *state) processOption(opt Option) {
                         s.exporters[t] = true
                 }
         case reporter:
-                if s.reporter != nil {
-                        panic("difference reporter already registered")
-                }
-                s.reporter = opt
+                s.reporters = append(s.reporters, opt)
         default:
                 panic(fmt.Sprintf("unknown option %T", opt))
         }
@@ -164,153 +191,88 @@ func (s *state) processOption(opt Option) {
 // statelessCompare compares two values and returns the result.
 // This function is stateless in that it does not alter the current result,
 // or output to any registered reporters.
-func (s *state) statelessCompare(vx, vy reflect.Value) diff.Result {
+func (s *state) statelessCompare(step PathStep) diff.Result {
         // We do not save and restore the curPath because all of the compareX
         // methods should properly push and pop from the path.
         // It is an implementation bug if the contents of curPath differs from
         // when calling this function to when returning from it.
 
-        oldResult, oldReporter := s.result, s.reporter
+        oldResult, oldReporters := s.result, s.reporters
         s.result = diff.Result{} // Reset result
-        s.reporter = nil         // Remove reporter to avoid spurious printouts
-        s.compareAny(vx, vy)
+        s.reporters = nil        // Remove reporters to avoid spurious printouts
+        s.compareAny(step)
         res := s.result
-        s.result, s.reporter = oldResult, oldReporter
+        s.result, s.reporters = oldResult, oldReporters
         return res
 }
 
-func (s *state) compareAny(vx, vy reflect.Value) {
-        // TODO: Support cyclic data structures.
-
-        // Rule 0: Differing types are never equal.
-        if !vx.IsValid() || !vy.IsValid() {
-                s.report(vx.IsValid() == vy.IsValid(), vx, vy)
-                return
-        }
-        if vx.Type() != vy.Type() {
-                s.report(false, vx, vy) // Possible for path to be empty
-                return
-        }
-        t := vx.Type()
-        if len(s.curPath) == 0 {
-                s.curPath.push(&pathStep{typ: t})
-                defer s.curPath.pop()
+func (s *state) compareAny(step PathStep) {
+        // Update the path stack.
+        s.curPath.push(step)
+        defer s.curPath.pop()
+        for _, r := range s.reporters {
+                r.PushStep(step)
+                defer r.PopStep()
         }
-        vx, vy = s.tryExporting(vx, vy)
+        s.recChecker.Check(s.curPath)
+
+        // Obtain the current type and values.
+        t := step.Type()
+        vx, vy := step.Values()
 
         // Rule 1: Check whether an option applies on this node in the value tree.
-        if s.tryOptions(vx, vy, t) {
+        if s.tryOptions(t, vx, vy) {
                 return
         }
 
         // Rule 2: Check whether the type has a valid Equal method.
-        if s.tryMethod(vx, vy, t) {
+        if s.tryMethod(t, vx, vy) {
                 return
         }
 
-        // Rule 3: Recursively descend into each value's underlying kind.
+        // Rule 3: Compare based on the underlying kind.
         switch t.Kind() {
         case reflect.Bool:
-                s.report(vx.Bool() == vy.Bool(), vx, vy)
-                return
+                s.report(vx.Bool() == vy.Bool(), 0)
         case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-                s.report(vx.Int() == vy.Int(), vx, vy)
-                return
+                s.report(vx.Int() == vy.Int(), 0)
         case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
-                s.report(vx.Uint() == vy.Uint(), vx, vy)
-                return
+                s.report(vx.Uint() == vy.Uint(), 0)
         case reflect.Float32, reflect.Float64:
-                s.report(vx.Float() == vy.Float(), vx, vy)
-                return
+                s.report(vx.Float() == vy.Float(), 0)
         case reflect.Complex64, reflect.Complex128:
-                s.report(vx.Complex() == vy.Complex(), vx, vy)
-                return
+                s.report(vx.Complex() == vy.Complex(), 0)
         case reflect.String:
-                s.report(vx.String() == vy.String(), vx, vy)
-                return
+                s.report(vx.String() == vy.String(), 0)
         case reflect.Chan, reflect.UnsafePointer:
-                s.report(vx.Pointer() == vy.Pointer(), vx, vy)
-                return
+                s.report(vx.Pointer() == vy.Pointer(), 0)
         case reflect.Func:
-                s.report(vx.IsNil() && vy.IsNil(), vx, vy)
-                return
+                s.report(vx.IsNil() && vy.IsNil(), 0)
+        case reflect.Struct:
+                s.compareStruct(t, vx, vy)
+        case reflect.Slice, reflect.Array:
+                s.compareSlice(t, vx, vy)
+        case reflect.Map:
+                s.compareMap(t, vx, vy)
         case reflect.Ptr:
-                if vx.IsNil() || vy.IsNil() {
-                        s.report(vx.IsNil() && vy.IsNil(), vx, vy)
-                        return
-                }
-                s.curPath.push(&indirect{pathStep{t.Elem()}})
-                defer s.curPath.pop()
-                s.compareAny(vx.Elem(), vy.Elem())
-                return
+                s.comparePtr(t, vx, vy)
         case reflect.Interface:
-                if vx.IsNil() || vy.IsNil() {
-                        s.report(vx.IsNil() && vy.IsNil(), vx, vy)
-                        return
-                }
-                if vx.Elem().Type() != vy.Elem().Type() {
-                        s.report(false, vx.Elem(), vy.Elem())
-                        return
-                }
-                s.curPath.push(&typeAssertion{pathStep{vx.Elem().Type()}})
-                defer s.curPath.pop()
-                s.compareAny(vx.Elem(), vy.Elem())
-                return
-        case reflect.Slice:
-                if vx.IsNil() || vy.IsNil() {
-                        s.report(vx.IsNil() && vy.IsNil(), vx, vy)
-                        return
-                }
-                fallthrough
-        case reflect.Array:
-                s.compareArray(vx, vy, t)
-                return
-        case reflect.Map:
-                s.compareMap(vx, vy, t)
-                return
-        case reflect.Struct:
-                s.compareStruct(vx, vy, t)
-                return
+                s.compareInterface(t, vx, vy)
         default:
                 panic(fmt.Sprintf("%v kind not handled", t.Kind()))
         }
 }
 
-func (s *state) tryExporting(vx, vy reflect.Value) (reflect.Value, reflect.Value) {
-        if sf, ok := s.curPath[len(s.curPath)-1].(*structField); ok && sf.unexported {
-                if sf.force {
-                        // Use unsafe pointer arithmetic to get read-write access to an
-                        // unexported field in the struct.
-                        vx = unsafeRetrieveField(sf.pvx, sf.field)
-                        vy = unsafeRetrieveField(sf.pvy, sf.field)
-                } else {
-                        // We are not allowed to export the value, so invalidate them
-                        // so that tryOptions can panic later if not explicitly ignored.
-                        vx = nothing
-                        vy = nothing
-                }
-        }
-        return vx, vy
-}
-
-func (s *state) tryOptions(vx, vy reflect.Value, t reflect.Type) bool {
-        // If there were no FilterValues, we will not detect invalid inputs,
-        // so manually check for them and append invalid if necessary.
-        // We still evaluate the options since an ignore can override invalid.
-        opts := s.opts
-        if !vx.IsValid() || !vy.IsValid() {
-                opts = Options{opts, invalid{}}
-        }
-
+func (s *state) tryOptions(t reflect.Type, vx, vy reflect.Value) bool {
         // Evaluate all filters and apply the remaining options.
-        if opt := opts.filter(s, vx, vy, t); opt != nil {
+        if opt := s.opts.filter(s, t, vx, vy); opt != nil {
                 opt.apply(s, vx, vy)
                 return true
         }
         return false
 }
 
-func (s *state) tryMethod(vx, vy reflect.Value, t reflect.Type) bool {
+func (s *state) tryMethod(t reflect.Type, vx, vy reflect.Value) bool {
         // Check if this type even has an Equal method.
         m, ok := t.MethodByName("Equal")
         if !ok || !function.IsType(m.Type, function.EqualAssignable) {
@@ -318,11 +280,11 @@ func (s *state) tryMethod(vx, vy reflect.Value, t reflect.Type) bool {
         }
 
         eq := s.callTTBFunc(m.Func, vx, vy)
-        s.report(eq, vx, vy)
+        s.report(eq, reportByMethod)
         return true
 }
 
-func (s *state) callTRFunc(f, v reflect.Value) reflect.Value {
+func (s *state) callTRFunc(f, v reflect.Value, step Transform) reflect.Value {
         v = sanitizeValue(v, f.Type().In(0))
         if !s.dynChecker.Next() {
                 return f.Call([]reflect.Value{v})[0]
@@ -333,15 +295,15 @@ func (s *state) callTRFunc(f, v reflect.Value) reflect.Value {
         // unsafe mutations to the input.
         c := make(chan reflect.Value)
         go detectRaces(c, f, v)
+        got := <-c
         want := f.Call([]reflect.Value{v})[0]
-        if got := <-c; !s.statelessCompare(got, want).Equal() {
+        if step.vx, step.vy = got, want; !s.statelessCompare(step).Equal() {
                 // To avoid false-positives with non-reflexive equality operations,
                 // we sanity check whether a value is equal to itself.
-                if !s.statelessCompare(want, want).Equal() {
+                if step.vx, step.vy = want, want; !s.statelessCompare(step).Equal() {
                         return want
                 }
-                fn := getFuncName(f.Pointer())
-                panic(fmt.Sprintf("non-deterministic function detected: %s", fn))
+                panic(fmt.Sprintf("non-deterministic function detected: %s", function.NameOf(f)))
         }
         return want
 }
@@ -359,10 +321,10 @@ func (s *state) callTTBFunc(f, x, y reflect.Value) bool {
         // unsafe mutations to the input.
         c := make(chan reflect.Value)
         go detectRaces(c, f, y, x)
+        got := <-c
         want := f.Call([]reflect.Value{x, y})[0].Bool()
-        if got := <-c; !got.IsValid() || got.Bool() != want {
-                fn := getFuncName(f.Pointer())
-                panic(fmt.Sprintf("non-deterministic or non-symmetric function detected: %s", fn))
+        if !got.IsValid() || got.Bool() != want {
+                panic(fmt.Sprintf("non-deterministic or non-symmetric function detected: %s", function.NameOf(f)))
         }
         return want
 }
@@ -380,140 +342,241 @@ func detectRaces(c chan<- reflect.Value, f reflect.Value, vs ...reflect.Value) {
 // assuming that T is assignable to R.
 // Otherwise, it returns the input value as is.
 func sanitizeValue(v reflect.Value, t reflect.Type) reflect.Value {
-        // TODO(dsnet): Remove this hacky workaround.
-        // See https://golang.org/issue/22143
-        if v.Kind() == reflect.Interface && v.IsNil() && v.Type() != t {
-                return reflect.New(t).Elem()
+        // TODO(dsnet): Workaround for reflect bug (https://golang.org/issue/22143).
+        if !flags.AtLeastGo110 {
+                if v.Kind() == reflect.Interface && v.IsNil() && v.Type() != t {
+                        return reflect.New(t).Elem()
+                }
         }
         return v
 }
 
-func (s *state) compareArray(vx, vy reflect.Value, t reflect.Type) {
-        step := &sliceIndex{pathStep{t.Elem()}, 0, 0}
-        s.curPath.push(step)
+func (s *state) compareStruct(t reflect.Type, vx, vy reflect.Value) {
+        var vax, vay reflect.Value // Addressable versions of vx and vy
 
-        // Compute an edit-script for slices vx and vy.
-        es := diff.Difference(vx.Len(), vy.Len(), func(ix, iy int) diff.Result {
-                step.xkey, step.ykey = ix, iy
-                return s.statelessCompare(vx.Index(ix), vy.Index(iy))
-        })
+        step := StructField{&structField{}}
+        for i := 0; i < t.NumField(); i++ {
+                step.typ = t.Field(i).Type
+                step.vx = vx.Field(i)
+                step.vy = vy.Field(i)
+                step.name = t.Field(i).Name
+                step.idx = i
+                step.unexported = !isExported(step.name)
+                if step.unexported {
+                        if step.name == "_" {
+                                continue
+                        }
+                        // Defer checking of unexported fields until later to give an
+                        // Ignore a chance to ignore the field.
+                        if !vax.IsValid() || !vay.IsValid() {
+                                // For retrieveUnexportedField to work, the parent struct must
+                                // be addressable. Create a new copy of the values if
+                                // necessary to make them addressable.
+                                vax = makeAddressable(vx)
+                                vay = makeAddressable(vy)
+                        }
+                        step.mayForce = s.exporters[t]
+                        step.pvx = vax
+                        step.pvy = vay
+                        step.field = t.Field(i)
+                }
+                s.compareAny(step)
+        }
+}
 
-        // Report the entire slice as is if the arrays are of primitive kind,
-        // and the arrays are different enough.
-        isPrimitive := false
-        switch t.Elem().Kind() {
-        case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
-                reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr,
-                reflect.Bool, reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128:
-                isPrimitive = true
-        }
-        if isPrimitive && es.Dist() > (vx.Len()+vy.Len())/4 {
-                s.curPath.pop() // Pop first since we are reporting the whole slice
-                s.report(false, vx, vy)
+func (s *state) compareSlice(t reflect.Type, vx, vy reflect.Value) {
+        isSlice := t.Kind() == reflect.Slice
+        if isSlice && (vx.IsNil() || vy.IsNil()) {
+                s.report(vx.IsNil() && vy.IsNil(), 0)
                 return
         }
 
-        // Replay the edit-script.
+        // TODO: Support cyclic data structures.
+
+        step := SliceIndex{&sliceIndex{pathStep: pathStep{typ: t.Elem()}}}
+        withIndexes := func(ix, iy int) SliceIndex {
+                if ix >= 0 {
+                        step.vx, step.xkey = vx.Index(ix), ix
+                } else {
+                        step.vx, step.xkey = reflect.Value{}, -1
+                }
+                if iy >= 0 {
+                        step.vy, step.ykey = vy.Index(iy), iy
+                } else {
+                        step.vy, step.ykey = reflect.Value{}, -1
+                }
+                return step
+        }
+
+        // Ignore options are able to ignore missing elements in a slice.
+        // However, detecting these reliably requires an optimal differencing
+        // algorithm, for which diff.Difference is not.
+        //
+        // Instead, we first iterate through both slices to detect which elements
+        // would be ignored if standing alone. The index of non-discarded elements
+        // are stored in a separate slice, which diffing is then performed on.
+        var indexesX, indexesY []int
+        var ignoredX, ignoredY []bool
+        for ix := 0; ix < vx.Len(); ix++ {
+                ignored := s.statelessCompare(withIndexes(ix, -1)).NumDiff == 0
+                if !ignored {
+                        indexesX = append(indexesX, ix)
+                }
+                ignoredX = append(ignoredX, ignored)
+        }
+        for iy := 0; iy < vy.Len(); iy++ {
+                ignored := s.statelessCompare(withIndexes(-1, iy)).NumDiff == 0
+                if !ignored {
+                        indexesY = append(indexesY, iy)
+                }
+                ignoredY = append(ignoredY, ignored)
+        }
+
+        // Compute an edit-script for slices vx and vy (excluding ignored elements).
+        edits := diff.Difference(len(indexesX), len(indexesY), func(ix, iy int) diff.Result {
+                return s.statelessCompare(withIndexes(indexesX[ix], indexesY[iy]))
+        })
+
+        // Replay the ignore-scripts and the edit-script.
         var ix, iy int
-        for _, e := range es {
+        for ix < vx.Len() || iy < vy.Len() {
+                var e diff.EditType
+                switch {
+                case ix < len(ignoredX) && ignoredX[ix]:
+                        e = diff.UniqueX
+                case iy < len(ignoredY) && ignoredY[iy]:
+                        e = diff.UniqueY
+                default:
+                        e, edits = edits[0], edits[1:]
+                }
                 switch e {
                 case diff.UniqueX:
-                        step.xkey, step.ykey = ix, -1
-                        s.report(false, vx.Index(ix), nothing)
+                        s.compareAny(withIndexes(ix, -1))
                         ix++
                 case diff.UniqueY:
-                        step.xkey, step.ykey = -1, iy
-                        s.report(false, nothing, vy.Index(iy))
+                        s.compareAny(withIndexes(-1, iy))
                         iy++
                 default:
-                        step.xkey, step.ykey = ix, iy
-                        if e == diff.Identity {
-                                s.report(true, vx.Index(ix), vy.Index(iy))
-                        } else {
-                                s.compareAny(vx.Index(ix), vy.Index(iy))
-                        }
+                        s.compareAny(withIndexes(ix, iy))
                         ix++
                         iy++
                 }
         }
-        s.curPath.pop()
-        return
 }
 
-func (s *state) compareMap(vx, vy reflect.Value, t reflect.Type) {
+func (s *state) compareMap(t reflect.Type, vx, vy reflect.Value) {
         if vx.IsNil() || vy.IsNil() {
-                s.report(vx.IsNil() && vy.IsNil(), vx, vy)
+                s.report(vx.IsNil() && vy.IsNil(), 0)
                 return
         }
 
+        // TODO: Support cyclic data structures.
+
         // We combine and sort the two map keys so that we can perform the
         // comparisons in a deterministic order.
-        step := &mapIndex{pathStep: pathStep{t.Elem()}}
-        s.curPath.push(step)
-        defer s.curPath.pop()
+        step := MapIndex{&mapIndex{pathStep: pathStep{typ: t.Elem()}}}
         for _, k := range value.SortKeys(append(vx.MapKeys(), vy.MapKeys()...)) {
+                step.vx = vx.MapIndex(k)
+                step.vy = vy.MapIndex(k)
                 step.key = k
-                vvx := vx.MapIndex(k)
-                vvy := vy.MapIndex(k)
-                switch {
-                case vvx.IsValid() && vvy.IsValid():
-                        s.compareAny(vvx, vvy)
-                case vvx.IsValid() && !vvy.IsValid():
-                        s.report(false, vvx, nothing)
-                case !vvx.IsValid() && vvy.IsValid():
-                        s.report(false, nothing, vvy)
-                default:
-                        // It is possible for both vvx and vvy to be invalid if the
-                        // key contained a NaN value in it. There is no way in
-                        // reflection to be able to retrieve these values.
-                        // See https://golang.org/issue/11104
-                        panic(fmt.Sprintf("%#v has map key with NaNs", s.curPath))
+                if !step.vx.IsValid() && !step.vy.IsValid() {
+                        // It is possible for both vx and vy to be invalid if the
+                        // key contained a NaN value in it.
+                        //
+                        // Even with the ability to retrieve NaN keys in Go 1.12,
+                        // there still isn't a sensible way to compare the values since
+                        // a NaN key may map to multiple unordered values.
+                        // The most reasonable way to compare NaNs would be to compare the
+                        // set of values. However, this is impossible to do efficiently
+                        // since set equality is provably an O(n^2) operation given only
+                        // an Equal function. If we had a Less function or Hash function,
+                        // this could be done in O(n*log(n)) or O(n), respectively.
+                        //
+                        // Rather than adding complex logic to deal with NaNs, make it
+                        // the user's responsibility to compare such obscure maps.
+                        const help = "consider providing a Comparer to compare the map"
+                        panic(fmt.Sprintf("%#v has map key with NaNs\n%s", s.curPath, help))
                 }
+                s.compareAny(step)
         }
 }
 
-func (s *state) compareStruct(vx, vy reflect.Value, t reflect.Type) {
-        var vax, vay reflect.Value // Addressable versions of vx and vy
+func (s *state) comparePtr(t reflect.Type, vx, vy reflect.Value) {
+        if vx.IsNil() || vy.IsNil() {
+                s.report(vx.IsNil() && vy.IsNil(), 0)
+                return
+        }
 
-        step := &structField{}
-        s.curPath.push(step)
-        defer s.curPath.pop()
-        for i := 0; i < t.NumField(); i++ {
-                vvx := vx.Field(i)
-                vvy := vy.Field(i)
-                step.typ = t.Field(i).Type
-                step.name = t.Field(i).Name
-                step.idx = i
-                step.unexported = !isExported(step.name)
-                if step.unexported {
-                        // Defer checking of unexported fields until later to give an
-                        // Ignore a chance to ignore the field.
-                        if !vax.IsValid() || !vay.IsValid() {
-                                // For unsafeRetrieveField to work, the parent struct must
-                                // be addressable. Create a new copy of the values if
-                                // necessary to make them addressable.
-                                vax = makeAddressable(vx)
-                                vay = makeAddressable(vy)
-                        }
-                        step.force = s.exporters[t]
-                        step.pvx = vax
-                        step.pvy = vay
-                        step.field = t.Field(i)
+        // TODO: Support cyclic data structures.
+
+        vx, vy = vx.Elem(), vy.Elem()
+        s.compareAny(Indirect{&indirect{pathStep{t.Elem(), vx, vy}}})
+}
+
+func (s *state) compareInterface(t reflect.Type, vx, vy reflect.Value) {
+        if vx.IsNil() || vy.IsNil() {
+                s.report(vx.IsNil() && vy.IsNil(), 0)
+                return
+        }
+        vx, vy = vx.Elem(), vy.Elem()
+        if vx.Type() != vy.Type() {
+                s.report(false, 0)
+                return
+        }
+        s.compareAny(TypeAssertion{&typeAssertion{pathStep{vx.Type(), vx, vy}}})
+}
+
+func (s *state) report(eq bool, rf resultFlags) {
+        if rf&reportByIgnore == 0 {
+                if eq {
+                        s.result.NumSame++
+                        rf |= reportEqual
+                } else {
+                        s.result.NumDiff++
+                        rf |= reportUnequal
                 }
-                s.compareAny(vvx, vvy)
+        }
+        for _, r := range s.reporters {
+                r.Report(Result{flags: rf})
         }
 }
 
-// report records the result of a single comparison.
-// It also calls Report if any reporter is registered.
-func (s *state) report(eq bool, vx, vy reflect.Value) {
-        if eq {
-                s.result.NSame++
-        } else {
-                s.result.NDiff++
+// recChecker tracks the state needed to periodically perform checks that
+// user provided transformers are not stuck in an infinitely recursive cycle.
+type recChecker struct{ next int }
+
+// Check scans the Path for any recursive transformers and panics when any
+// recursive transformers are detected. Note that the presence of a
+// recursive Transformer does not necessarily imply an infinite cycle.
+// As such, this check only activates after some minimal number of path steps.
+func (rc *recChecker) Check(p Path) {
+        const minLen = 1 << 16
+        if rc.next == 0 {
+                rc.next = minLen
+        }
+        if len(p) < rc.next {
+                return
+        }
+        rc.next <<= 1
+
+        // Check whether the same transformer has appeared at least twice.
+        var ss []string
+        m := map[Option]int{}
+        for _, ps := range p {
+                if t, ok := ps.(Transform); ok {
+                        t := t.Option()
+                        if m[t] == 1 { // Transformer was used exactly once before
+                                tf := t.(*transformer).fnc.Type()
+                                ss = append(ss, fmt.Sprintf("%v: %v => %v", t, tf.In(0), tf.Out(0)))
+                        }
+                        m[t]++
+                }
         }
-        if s.reporter != nil {
-                s.reporter.Report(vx, vy, eq, s.curPath)
+        if len(ss) > 0 {
+                const warning = "recursive set of Transformers detected"
+                const help = "consider using cmpopts.AcyclicTransformer"
+                set := strings.Join(ss, "\n\t")
+                panic(fmt.Sprintf("%s:\n\t%s\n%s", warning, set, help))
         }
 }