diff options
Diffstat (limited to 'dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/apidiff/correspondence.go')
-rw-r--r-- | dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/apidiff/correspondence.go | 288 |
1 files changed, 288 insertions, 0 deletions
diff --git a/dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/apidiff/correspondence.go b/dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/apidiff/correspondence.go new file mode 100644 index 0000000..ee00bc0 --- /dev/null +++ b/dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/apidiff/correspondence.go @@ -0,0 +1,288 @@ +package apidiff + +import ( + "fmt" + "go/types" + "sort" +) + +// Two types are correspond if they are identical except for defined types, +// which must correspond. +// +// Two defined types correspond if they can be interchanged in the old and new APIs, +// possibly after a renaming. +// +// This is not a pure function. If we come across named types while traversing, +// we establish correspondence. +func (d *differ) correspond(old, new types.Type) bool { + return d.corr(old, new, nil) +} + +// corr determines whether old and new correspond. The argument p is a list of +// known interface identities, to avoid infinite recursion. +// +// corr calls itself recursively as much as possible, to establish more +// correspondences and so check more of the API. E.g. if the new function has more +// parameters than the old, compare all the old ones before returning false. +// +// Compare this to the implementation of go/types.Identical. +func (d *differ) corr(old, new types.Type, p *ifacePair) bool { + // Structure copied from types.Identical. + switch old := old.(type) { + case *types.Basic: + return types.Identical(old, new) + + case *types.Array: + if new, ok := new.(*types.Array); ok { + return d.corr(old.Elem(), new.Elem(), p) && old.Len() == new.Len() + } + + case *types.Slice: + if new, ok := new.(*types.Slice); ok { + return d.corr(old.Elem(), new.Elem(), p) + } + + case *types.Map: + if new, ok := new.(*types.Map); ok { + return d.corr(old.Key(), new.Key(), p) && d.corr(old.Elem(), new.Elem(), p) + } + + case *types.Chan: + if new, ok := new.(*types.Chan); ok { + return d.corr(old.Elem(), new.Elem(), p) && old.Dir() == new.Dir() + } + + case *types.Pointer: + if new, ok := new.(*types.Pointer); ok { + return d.corr(old.Elem(), new.Elem(), p) + } + + case *types.Signature: + if new, ok := new.(*types.Signature); ok { + pe := d.corr(old.Params(), new.Params(), p) + re := d.corr(old.Results(), new.Results(), p) + return old.Variadic() == new.Variadic() && pe && re + } + + case *types.Tuple: + if new, ok := new.(*types.Tuple); ok { + for i := 0; i < old.Len(); i++ { + if i >= new.Len() || !d.corr(old.At(i).Type(), new.At(i).Type(), p) { + return false + } + } + return old.Len() == new.Len() + } + + case *types.Struct: + if new, ok := new.(*types.Struct); ok { + for i := 0; i < old.NumFields(); i++ { + if i >= new.NumFields() { + return false + } + of := old.Field(i) + nf := new.Field(i) + if of.Anonymous() != nf.Anonymous() || + old.Tag(i) != new.Tag(i) || + !d.corr(of.Type(), nf.Type(), p) || + !d.corrFieldNames(of, nf) { + return false + } + } + return old.NumFields() == new.NumFields() + } + + case *types.Interface: + if new, ok := new.(*types.Interface); ok { + // Deal with circularity. See the comment in types.Identical. + q := &ifacePair{old, new, p} + for p != nil { + if p.identical(q) { + return true // same pair was compared before + } + p = p.prev + } + oldms := d.sortedMethods(old) + newms := d.sortedMethods(new) + for i, om := range oldms { + if i >= len(newms) { + return false + } + nm := newms[i] + if d.methodID(om) != d.methodID(nm) || !d.corr(om.Type(), nm.Type(), q) { + return false + } + } + return old.NumMethods() == new.NumMethods() + } + + case *types.Named: + if new, ok := new.(*types.Named); ok { + return d.establishCorrespondence(old, new) + } + if new, ok := new.(*types.Basic); ok { + // Basic types are defined types, too, so we have to support them. + + return d.establishCorrespondence(old, new) + } + + case *types.TypeParam: + if new, ok := new.(*types.TypeParam); ok { + if old.Index() == new.Index() { + return true + } + } + + default: + panic(fmt.Sprintf("unknown type kind %T", old)) + } + return false +} + +// Compare old and new field names. We are determining correspondence across packages, +// so just compare names, not packages. For an unexported, embedded field of named +// type (non-named embedded fields are possible with aliases), we check that the type +// names correspond. We check the types for correspondence before this is called, so +// we've established correspondence. +func (d *differ) corrFieldNames(of, nf *types.Var) bool { + if of.Anonymous() && nf.Anonymous() && !of.Exported() && !nf.Exported() { + if on, ok := of.Type().(*types.Named); ok { + nn := nf.Type().(*types.Named) + return d.establishCorrespondence(on, nn) + } + } + return of.Name() == nf.Name() +} + +// Establish that old corresponds with new if it does not already +// correspond to something else. +func (d *differ) establishCorrespondence(old *types.Named, new types.Type) bool { + oldname := old.Obj() + oldc := d.correspondMap[oldname] + if oldc == nil { + // For now, assume the types don't correspond unless they are from the old + // and new packages, respectively. + // + // This is too conservative. For instance, + // [old] type A = q.B; [new] type A q.C + // could be OK if in package q, B is an alias for C. + // Or, using p as the name of the current old/new packages: + // [old] type A = q.B; [new] type A int + // could be OK if in q, + // [old] type B int; [new] type B = p.A + // In this case, p.A and q.B name the same type in both old and new worlds. + // Note that this case doesn't imply circular package imports: it's possible + // that in the old world, p imports q, but in the new, q imports p. + // + // However, if we didn't do something here, then we'd incorrectly allow cases + // like the first one above in which q.B is not an alias for q.C + // + // What we should do is check that the old type, in the new world's package + // of the same path, doesn't correspond to something other than the new type. + // That is a bit hard, because there is no easy way to find a new package + // matching an old one. + if newn, ok := new.(*types.Named); ok { + if old.Obj().Pkg() != d.old || newn.Obj().Pkg() != d.new { + return old.Obj().Id() == newn.Obj().Id() + } + // Prior to generics, any two named types could correspond. + // Two named types cannot correspond if their type parameter lists don't match. + if !typeParamListsMatch(old.TypeParams(), newn.TypeParams()) { + return false + } + } + // If there is no correspondence, create one. + d.correspondMap[oldname] = new + // Check that the corresponding types are compatible. + d.checkCompatibleDefined(oldname, old, new) + return true + } + return typesEquivalent(oldc, new) +} + +// Two list of type parameters match if they are the same length, and +// the constraints of corresponding type parameters are identical. +func typeParamListsMatch(tps1, tps2 *types.TypeParamList) bool { + if tps1.Len() != tps2.Len() { + return false + } + for i := 0; i < tps1.Len(); i++ { + if !types.Identical(tps1.At(i).Constraint(), tps2.At(i).Constraint()) { + return false + } + } + return true +} + +// typesEquivalent reports whether two types are identical, or if +// the types have identical type param lists except that one type has nil +// constraints. +// +// This allows us to match a Type from a method receiver or arg to the Type from +// the declaration. +func typesEquivalent(old, new types.Type) bool { + if types.Identical(old, new) { + return true + } + // Handle two types with the same type params, one + // having constraints and one not. + oldn, ok := old.(*types.Named) + if !ok { + return false + } + newn, ok := new.(*types.Named) + if !ok { + return false + } + oldps := oldn.TypeParams() + newps := newn.TypeParams() + if oldps.Len() != newps.Len() { + return false + } + if oldps.Len() == 0 { + // Not generic types. + return false + } + for i := 0; i < oldps.Len(); i++ { + oldp := oldps.At(i) + newp := newps.At(i) + if oldp.Constraint() == nil || newp.Constraint() == nil { + return true + } + if !types.Identical(oldp.Constraint(), newp.Constraint()) { + return false + } + } + return true +} + +func (d *differ) sortedMethods(iface *types.Interface) []*types.Func { + ms := make([]*types.Func, iface.NumMethods()) + for i := 0; i < iface.NumMethods(); i++ { + ms[i] = iface.Method(i) + } + sort.Slice(ms, func(i, j int) bool { return d.methodID(ms[i]) < d.methodID(ms[j]) }) + return ms +} + +func (d *differ) methodID(m *types.Func) string { + // If the method belongs to one of the two packages being compared, use + // just its name even if it's unexported. That lets us treat unexported names + // from the old and new packages as equal. + if m.Pkg() == d.old || m.Pkg() == d.new { + return m.Name() + } + return m.Id() +} + +// Copied from the go/types package: + +// An ifacePair is a node in a stack of interface type pairs compared for identity. +type ifacePair struct { + x, y *types.Interface + prev *ifacePair +} + +func (p *ifacePair) identical(q *ifacePair) bool { + return p.x == q.x && p.y == q.y || p.x == q.y && p.y == q.x +} |