--- /dev/null
+package apidiff
+
+import (
+ "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)
+ }
+
+ default:
+ panic("unknown type kind")
+ }
+ 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()
+ }
+ }
+ // 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 types.Identical(oldc, new)
+}
+
+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
+}
projects / dotfiles / .git / blobdiff