diff options
Diffstat (limited to '')
-rw-r--r-- | dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/apidiff/compatibility.go | 364 |
1 files changed, 364 insertions, 0 deletions
diff --git a/dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/apidiff/compatibility.go b/dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/apidiff/compatibility.go new file mode 100644 index 0000000..44238fb --- /dev/null +++ b/dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/apidiff/compatibility.go @@ -0,0 +1,364 @@ +package apidiff + +import ( + "fmt" + "go/types" + "reflect" +) + +func (d *differ) checkCompatible(otn *types.TypeName, old, new types.Type) { + switch old := old.(type) { + case *types.Interface: + if new, ok := new.(*types.Interface); ok { + d.checkCompatibleInterface(otn, old, new) + return + } + + case *types.Struct: + if new, ok := new.(*types.Struct); ok { + d.checkCompatibleStruct(otn, old, new) + return + } + + case *types.Chan: + if new, ok := new.(*types.Chan); ok { + d.checkCompatibleChan(otn, old, new) + return + } + + case *types.Basic: + if new, ok := new.(*types.Basic); ok { + d.checkCompatibleBasic(otn, old, new) + return + } + + case *types.Named: + panic("unreachable") + + default: + d.checkCorrespondence(otn, "", old, new) + return + + } + // Here if old and new are different kinds of types. + d.typeChanged(otn, "", old, new) +} + +func (d *differ) checkCompatibleChan(otn *types.TypeName, old, new *types.Chan) { + d.checkCorrespondence(otn, ", element type", old.Elem(), new.Elem()) + if old.Dir() != new.Dir() { + if new.Dir() == types.SendRecv { + d.compatible(otn, "", "removed direction") + } else { + d.incompatible(otn, "", "changed direction") + } + } +} + +func (d *differ) checkCompatibleBasic(otn *types.TypeName, old, new *types.Basic) { + // Certain changes to numeric types are compatible. Approximately, the info must + // be the same, and the new values must be a superset of the old. + if old.Kind() == new.Kind() { + // old and new are identical + return + } + if compatibleBasics[[2]types.BasicKind{old.Kind(), new.Kind()}] { + d.compatible(otn, "", "changed from %s to %s", old, new) + } else { + d.typeChanged(otn, "", old, new) + } +} + +// All pairs (old, new) of compatible basic types. +var compatibleBasics = map[[2]types.BasicKind]bool{ + {types.Uint8, types.Uint16}: true, + {types.Uint8, types.Uint32}: true, + {types.Uint8, types.Uint}: true, + {types.Uint8, types.Uint64}: true, + {types.Uint16, types.Uint32}: true, + {types.Uint16, types.Uint}: true, + {types.Uint16, types.Uint64}: true, + {types.Uint32, types.Uint}: true, + {types.Uint32, types.Uint64}: true, + {types.Uint, types.Uint64}: true, + {types.Int8, types.Int16}: true, + {types.Int8, types.Int32}: true, + {types.Int8, types.Int}: true, + {types.Int8, types.Int64}: true, + {types.Int16, types.Int32}: true, + {types.Int16, types.Int}: true, + {types.Int16, types.Int64}: true, + {types.Int32, types.Int}: true, + {types.Int32, types.Int64}: true, + {types.Int, types.Int64}: true, + {types.Float32, types.Float64}: true, + {types.Complex64, types.Complex128}: true, +} + +// Interface compatibility: +// If the old interface has an unexported method, the new interface is compatible +// if its exported method set is a superset of the old. (Users could not implement, +// only embed.) +// +// If the old interface did not have an unexported method, the new interface is +// compatible if its exported method set is the same as the old, and it has no +// unexported methods. (Adding an unexported method makes the interface +// unimplementable outside the package.) +// +// TODO: must also check that if any methods were added or removed, every exposed +// type in the package that implemented the interface in old still implements it in +// new. Otherwise external assignments could fail. +func (d *differ) checkCompatibleInterface(otn *types.TypeName, old, new *types.Interface) { + // Method sets are checked in checkCompatibleDefined. + + // Does the old interface have an unexported method? + if unexportedMethod(old) != nil { + d.checkMethodSet(otn, old, new, additionsCompatible) + } else { + // Perform an equivalence check, but with more information. + d.checkMethodSet(otn, old, new, additionsIncompatible) + if u := unexportedMethod(new); u != nil { + d.incompatible(otn, u.Name(), "added unexported method") + } + } +} + +// Return an unexported method from the method set of t, or nil if there are none. +func unexportedMethod(t *types.Interface) *types.Func { + for i := 0; i < t.NumMethods(); i++ { + if m := t.Method(i); !m.Exported() { + return m + } + } + return nil +} + +// We need to check three things for structs: +// +// 1. The set of exported fields must be compatible. This ensures that keyed struct +// literals continue to compile. (There is no compatibility guarantee for unkeyed +// struct literals.) +// +// 2. The set of exported *selectable* fields must be compatible. This includes the exported +// fields of all embedded structs. This ensures that selections continue to compile. +// +// 3. If the old struct is comparable, so must the new one be. This ensures that equality +// expressions and uses of struct values as map keys continue to compile. +// +// An unexported embedded struct can't appear in a struct literal outside the +// package, so it doesn't have to be present, or have the same name, in the new +// struct. +// +// Field tags are ignored: they have no compile-time implications. +func (d *differ) checkCompatibleStruct(obj types.Object, old, new *types.Struct) { + d.checkCompatibleObjectSets(obj, exportedFields(old), exportedFields(new)) + d.checkCompatibleObjectSets(obj, exportedSelectableFields(old), exportedSelectableFields(new)) + // Removing comparability from a struct is an incompatible change. + if types.Comparable(old) && !types.Comparable(new) { + d.incompatible(obj, "", "old is comparable, new is not") + } +} + +// exportedFields collects all the immediate fields of the struct that are exported. +// This is also the set of exported keys for keyed struct literals. +func exportedFields(s *types.Struct) map[string]types.Object { + m := map[string]types.Object{} + for i := 0; i < s.NumFields(); i++ { + f := s.Field(i) + if f.Exported() { + m[f.Name()] = f + } + } + return m +} + +// exportedSelectableFields collects all the exported fields of the struct, including +// exported fields of embedded structs. +// +// We traverse the struct breadth-first, because of the rule that a lower-depth field +// shadows one at a higher depth. +func exportedSelectableFields(s *types.Struct) map[string]types.Object { + var ( + m = map[string]types.Object{} + next []*types.Struct // embedded structs at the next depth + seen []*types.Struct // to handle recursive embedding + ) + for cur := []*types.Struct{s}; len(cur) > 0; cur, next = next, nil { + seen = append(seen, cur...) + // We only want to consider unambiguous fields. Ambiguous fields (where there + // is more than one field of the same name at the same level) are legal, but + // cannot be selected. + for name, f := range unambiguousFields(cur) { + // Record an exported field we haven't seen before. If we have seen it, + // it occurred a lower depth, so it shadows this field. + if f.Exported() && m[name] == nil { + m[name] = f + } + // Remember embedded structs for processing at the next depth, + // but only if we haven't seen the struct at this depth or above. + if !f.Anonymous() { + continue + } + t := f.Type().Underlying() + if p, ok := t.(*types.Pointer); ok { + t = p.Elem().Underlying() + } + if t, ok := t.(*types.Struct); ok && !contains(seen, t) { + next = append(next, t) + } + } + } + return m +} + +func contains(ts []*types.Struct, t *types.Struct) bool { + for _, s := range ts { + if types.Identical(s, t) { + return true + } + } + return false +} + +// Given a set of structs at the same depth, the unambiguous fields are the ones whose +// names appear exactly once. +func unambiguousFields(structs []*types.Struct) map[string]*types.Var { + fields := map[string]*types.Var{} + seen := map[string]bool{} + for _, s := range structs { + for i := 0; i < s.NumFields(); i++ { + f := s.Field(i) + name := f.Name() + if seen[name] { + delete(fields, name) + } else { + seen[name] = true + fields[name] = f + } + } + } + return fields +} + +// Anything removed or change from the old set is an incompatible change. +// Anything added to the new set is a compatible change. +func (d *differ) checkCompatibleObjectSets(obj types.Object, old, new map[string]types.Object) { + for name, oldo := range old { + newo := new[name] + if newo == nil { + d.incompatible(obj, name, "removed") + } else { + d.checkCorrespondence(obj, name, oldo.Type(), newo.Type()) + } + } + for name := range new { + if old[name] == nil { + d.compatible(obj, name, "added") + } + } +} + +func (d *differ) checkCompatibleDefined(otn *types.TypeName, old *types.Named, new types.Type) { + // We've already checked that old and new correspond. + d.checkCompatible(otn, old.Underlying(), new.Underlying()) + // If there are different kinds of types (e.g. struct and interface), don't bother checking + // the method sets. + if reflect.TypeOf(old.Underlying()) != reflect.TypeOf(new.Underlying()) { + return + } + // Interface method sets are checked in checkCompatibleInterface. + if _, ok := old.Underlying().(*types.Interface); ok { + return + } + + // A new method set is compatible with an old if the new exported methods are a superset of the old. + d.checkMethodSet(otn, old, new, additionsCompatible) + d.checkMethodSet(otn, types.NewPointer(old), types.NewPointer(new), additionsCompatible) +} + +const ( + additionsCompatible = true + additionsIncompatible = false +) + +func (d *differ) checkMethodSet(otn *types.TypeName, oldt, newt types.Type, addcompat bool) { + // TODO: find a way to use checkCompatibleObjectSets for this. + oldMethodSet := exportedMethods(oldt) + newMethodSet := exportedMethods(newt) + msname := otn.Name() + if _, ok := oldt.(*types.Pointer); ok { + msname = "*" + msname + } + for name, oldMethod := range oldMethodSet { + newMethod := newMethodSet[name] + if newMethod == nil { + var part string + // Due to embedding, it's possible that the method's receiver type is not + // the same as the defined type whose method set we're looking at. So for + // a type T with removed method M that is embedded in some other type U, + // we will generate two "removed" messages for T.M, one for its own type + // T and one for the embedded type U. We want both messages to appear, + // but the messageSet dedup logic will allow only one message for a given + // object. So use the part string to distinguish them. + if receiverNamedType(oldMethod).Obj() != otn { + part = fmt.Sprintf(", method set of %s", msname) + } + d.incompatible(oldMethod, part, "removed") + } else { + obj := oldMethod + // If a value method is changed to a pointer method and has a signature + // change, then we can get two messages for the same method definition: one + // for the value method set that says it's removed, and another for the + // pointer method set that says it changed. To keep both messages (since + // messageSet dedups), use newMethod for the second. (Slight hack.) + if !hasPointerReceiver(oldMethod) && hasPointerReceiver(newMethod) { + obj = newMethod + } + d.checkCorrespondence(obj, "", oldMethod.Type(), newMethod.Type()) + } + } + + // Check for added methods. + for name, newMethod := range newMethodSet { + if oldMethodSet[name] == nil { + if addcompat { + d.compatible(newMethod, "", "added") + } else { + d.incompatible(newMethod, "", "added") + } + } + } +} + +// exportedMethods collects all the exported methods of type's method set. +func exportedMethods(t types.Type) map[string]types.Object { + m := map[string]types.Object{} + ms := types.NewMethodSet(t) + for i := 0; i < ms.Len(); i++ { + obj := ms.At(i).Obj() + if obj.Exported() { + m[obj.Name()] = obj + } + } + return m +} + +func receiverType(method types.Object) types.Type { + return method.Type().(*types.Signature).Recv().Type() +} + +func receiverNamedType(method types.Object) *types.Named { + switch t := receiverType(method).(type) { + case *types.Pointer: + return t.Elem().(*types.Named) + case *types.Named: + return t + default: + panic("unreachable") + } +} + +func hasPointerReceiver(method types.Object) bool { + _, ok := receiverType(method).(*types.Pointer) + return ok +} |