// makeBound returns a bound method wrapper (or "bound"), a synthetic
// function that delegates to a concrete or interface method denoted
// by obj. The resulting function has no receiver, but has one free
// variable which will be used as the method's receiver in the
// tail-call.
//
// Use MakeClosure with such a wrapper to construct a bound method
// closure. e.g.:
//
// type T int or: type T interface { meth() }
// func (t T) meth()
// var t T
// f := t.meth
// f() // calls t.meth()
//
// f is a closure of a synthetic wrapper defined as if by:
//
// f := func() { return t.meth() }
//
// Unlike makeWrapper, makeBound need perform no indirection or field
// selections because that can be done before the closure is
// constructed.
//
// EXCLUSIVE_LOCKS_ACQUIRED(meth.Prog.methodsMu)
//
func makeBound(prog *Program, obj *types.Func) *Function {
prog.methodsMu.Lock()
defer prog.methodsMu.Unlock()
fn, ok := prog.bounds[obj]
if !ok {
description := fmt.Sprintf("bound method wrapper for %s", obj)
if prog.mode&LogSource != 0 {
defer logStack("%s", description)()
}
fn = &Function{
name: obj.Name() + "$bound",
object: obj,
Signature: changeRecv(obj.Type().(*types.Signature), nil), // drop receiver
Synthetic: description,
Prog: prog,
pos: obj.Pos(),
}
fv := &FreeVar{name: "recv", typ: recvType(obj), parent: fn}
fn.FreeVars = []*FreeVar{fv}
fn.startBody()
createParams(fn, 0)
var c Call
if !isInterface(recvType(obj)) { // concrete
c.Call.Value = prog.declaredFunc(obj)
c.Call.Args = []Value{fv}
} else {
c.Call.Value = fv
c.Call.Method = obj
}
for _, arg := range fn.Params {
c.Call.Args = append(c.Call.Args, arg)
}
emitTailCall(fn, &c)
fn.finishBody()
prog.bounds[obj] = fn
}
return fn
}
// checkMethod performs safety checks for renaming a method.
// There are three hazards:
// - declaration conflicts
// - selection ambiguity/changes
// - entailed renamings of assignable concrete/interface types.
// We reject renamings initiated at concrete methods if it would
// change the assignability relation. For renamings of abstract
// methods, we rename all methods transitively coupled to it via
// assignability.
func (r *Unexporter) checkMethod(objsToUpdate map[types.Object]string, from *types.Func, to string) {
// e.g. error.Error
if from.Pkg() == nil {
r.warn(from, r.errorf(from.Pos(), "you cannot rename built-in method %s", from))
return
}
// ASSIGNABILITY: We reject renamings of concrete methods that
// would break a 'satisfy' constraint; but renamings of abstract
// methods are allowed to proceed, and we rename affected
// concrete and abstract methods as necessary. It is the
// initial method that determines the policy.
// Check for conflict at point of declaration.
// Check to ensure preservation of assignability requirements.
R := recv(from).Type()
if isInterface(R) {
// Abstract method
// declaration
prev, _, _ := types.LookupFieldOrMethod(R, false, from.Pkg(), to)
if prev != nil {
r.warn(from,
r.errorf(from.Pos(), "renaming this interface method %q to %q",
from.Name(), to),
r.errorf(prev.Pos(), "\twould conflict with this method"))
return
}
// Check all interfaces that embed this one for
// declaration conflicts too.
for _, info := range r.packages {
// Start with named interface types (better errors)
for _, obj := range info.Defs {
if obj, ok := obj.(*types.TypeName); ok && isInterface(obj.Type()) {
f, _, _ := types.LookupFieldOrMethod(
obj.Type(), false, from.Pkg(), from.Name())
if f == nil {
continue
}
t, _, _ := types.LookupFieldOrMethod(
obj.Type(), false, from.Pkg(), to)
if t == nil {
continue
}
r.warn(from,
r.errorf(from.Pos(), "renaming this interface method %q to %q",
from.Name(), to),
r.errorf(t.Pos(), "\twould conflict with this method"),
r.errorf(obj.Pos(), "\tin named interface type %q", obj.Name()))
}
}
// Now look at all literal interface types (includes named ones again).
for e, tv := range info.Types {
if e, ok := e.(*ast.InterfaceType); ok {
_ = e
_ = tv.Type.(*types.Interface)
// TODO(adonovan): implement same check as above.
}
}
}
// assignability
//
// Find the set of concrete or abstract methods directly
// coupled to abstract method 'from' by some
// satisfy.Constraint, and rename them too.
for key := range r.satisfy() {
// key = (lhs, rhs) where lhs is always an interface.
lsel := r.msets.MethodSet(key.LHS).Lookup(from.Pkg(), from.Name())
if lsel == nil {
continue
}
rmethods := r.msets.MethodSet(key.RHS)
rsel := rmethods.Lookup(from.Pkg(), from.Name())
if rsel == nil {
continue
}
// If both sides have a method of this name,
// and one of them is m, the other must be coupled.
var coupled *types.Func
switch from {
case lsel.Obj():
coupled = rsel.Obj().(*types.Func)
case rsel.Obj():
coupled = lsel.Obj().(*types.Func)
default:
continue
}
// We must treat concrete-to-interface
// constraints like an implicit selection C.f of
// each interface method I.f, and check that the
// renaming leaves the selection unchanged and
// unambiguous.
//
// Fun fact: the implicit selection of C.f
// type I interface{f()}
// type C struct{I}
// func (C) g()
// var _ I = C{} // here
// yields abstract method I.f. This can make error
// messages less than obvious.
//
if !isInterface(key.RHS) {
// The logic below was derived from checkSelections.
rtosel := rmethods.Lookup(from.Pkg(), to)
if rtosel != nil {
rto := rtosel.Obj().(*types.Func)
delta := len(rsel.Index()) - len(rtosel.Index())
if delta < 0 {
continue // no ambiguity
}
// TODO(adonovan): record the constraint's position.
keyPos := token.NoPos
rename := r.errorf(from.Pos(), "renaming this method %q to %q",
from.Name(), to)
if delta == 0 {
// analogous to same-block conflict
r.warn(from, rename,
r.errorf(keyPos, "\twould make the %s method of %s invoked via interface %s ambiguous",
to, key.RHS, key.LHS),
r.errorf(rto.Pos(), "\twith (%s).%s",
recv(rto).Type(), to))
} else {
// analogous to super-block conflict
r.warn(from, rename,
r.errorf(keyPos, "\twould change the %s method of %s invoked via interface %s",
to, key.RHS, key.LHS),
r.errorf(coupled.Pos(), "\tfrom (%s).%s",
recv(coupled).Type(), to),
r.errorf(rto.Pos(), "\tto (%s).%s",
recv(rto).Type(), to))
}
return // one error is enough
}
}
if !r.changeMethods {
// This should be unreachable.
r.warn(from,
r.errorf(from.Pos(), "internal error: during renaming of abstract method %s", from),
r.errorf(coupled.Pos(), "\tchangedMethods=false, coupled method=%s", coupled),
r.errorf(from.Pos(), "\tPlease file a bug report"))
return
}
// Rename the coupled method to preserve assignability.
r.check(objsToUpdate, coupled, to)
}
} else {
// Concrete method
// declaration
prev, indices, _ := types.LookupFieldOrMethod(R, true, from.Pkg(), to)
if prev != nil && len(indices) == 1 {
r.warn(from,
r.errorf(from.Pos(), "renaming this method %q to %q",
from.Name(), to),
r.errorf(prev.Pos(), "\twould conflict with this %s",
objectKind(prev)))
return
}
// assignability
//
// Find the set of abstract methods coupled to concrete
// method 'from' by some satisfy.Constraint, and rename
// them too.
//
// Coupling may be indirect, e.g. I.f <-> C.f via type D.
//
// type I interface {f()}
// type C int
// type (C) f()
// type D struct{C}
// var _ I = D{}
//
for key := range r.satisfy() {
// key = (lhs, rhs) where lhs is always an interface.
if isInterface(key.RHS) {
continue
}
rsel := r.msets.MethodSet(key.RHS).Lookup(from.Pkg(), from.Name())
if rsel == nil || rsel.Obj() != from {
continue // rhs does not have the method
}
lsel := r.msets.MethodSet(key.LHS).Lookup(from.Pkg(), from.Name())
if lsel == nil {
continue
}
imeth := lsel.Obj().(*types.Func)
// imeth is the abstract method (e.g. I.f)
// and key.RHS is the concrete coupling type (e.g. D).
if !r.changeMethods {
rename := r.errorf(from.Pos(), "renaming this method %q to %q",
from.Name(), to)
var pos token.Pos
var iface string
i := recv(imeth).Type()
if named, ok := i.(*types.Named); ok {
pos = named.Obj().Pos()
iface = "interface " + named.Obj().Name()
} else {
pos = from.Pos()
iface = i.String()
}
r.warn(from, rename,
r.errorf(pos, "\twould make %s no longer assignable to %s",
key.RHS, iface),
r.errorf(imeth.Pos(), "\t(rename %s.%s if you intend to change both types)",
i, from.Name()))
return // one error is enough
}
// Rename the coupled interface method to preserve assignability.
r.check(objsToUpdate, imeth, to)
}
}
// Check integrity of existing (field and method) selections.
// We skip this if there were errors above, to avoid redundant errors.
r.checkSelections(objsToUpdate, from, to)
}
// checkMethod performs safety checks for renaming a method.
// There are three hazards:
// - declaration conflicts
// - selection ambiguity/changes
// - entailed renamings of assignable concrete/interface types (for now, just reject)
func (r *renamer) checkMethod(from *types.Func) {
// e.g. error.Error
if from.Pkg() == nil {
r.errorf(from.Pos(), "you cannot rename built-in method %s", from)
return
}
// As always, having to support concrete methods with pointer
// and non-pointer receivers, and named vs unnamed types with
// methods, makes tooling fun.
// ASSIGNABILITY
//
// For now, if any method renaming breaks a required
// assignability to another type, we reject it.
//
// TODO(adonovan): probably we should compute the entailed
// renamings so that an interface method renaming causes
// concrete methods to change too. But which ones?
//
// There is no correct answer, only heuristics, because Go's
// "duck typing" doesn't distinguish intentional from contingent
// assignability. There are two obvious approaches:
//
// (1) Update the minimum set of types to preserve the
// assignability of types all syntactic assignments
// (incl. implicit ones in calls, returns, sends, etc).
// The satisfy.Finder enumerates these.
// This is likely to be an underapproximation.
//
// (2) Update all types that are assignable to/from the changed
// type. This requires computing the "implements" relation
// for all pairs of types (as godoc and oracle do).
// This is likely to be an overapproximation.
//
// If a concrete type is renamed, we probably do not want to
// rename corresponding interfaces; interface renamings should
// probably be initiated at the interface. (But what if a
// concrete type implements multiple interfaces with the same
// method? Then the user is stuck.)
//
// We need some experience before we decide how to implement this.
// Check for conflict at point of declaration.
// Check to ensure preservation of assignability requirements.
recv := from.Type().(*types.Signature).Recv().Type()
if isInterface(recv) {
// Abstract method
// declaration
prev, _, _ := types.LookupFieldOrMethod(recv, false, from.Pkg(), r.to)
if prev != nil {
r.errorf(from.Pos(), "renaming this interface method %q to %q",
from.Name(), r.to)
r.errorf(prev.Pos(), "\twould conflict with this method")
return
}
// Check all interfaces that embed this one for
// declaration conflicts too.
for _, info := range r.packages {
// Start with named interface types (better errors)
for _, obj := range info.Defs {
if obj, ok := obj.(*types.TypeName); ok && isInterface(obj.Type()) {
f, _, _ := types.LookupFieldOrMethod(
obj.Type(), false, from.Pkg(), from.Name())
if f == nil {
continue
}
t, _, _ := types.LookupFieldOrMethod(
obj.Type(), false, from.Pkg(), r.to)
if t == nil {
continue
}
r.errorf(from.Pos(), "renaming this interface method %q to %q",
from.Name(), r.to)
r.errorf(t.Pos(), "\twould conflict with this method")
r.errorf(obj.Pos(), "\tin named interface type %q", obj.Name())
}
}
// Now look at all literal interface types (includes named ones again).
for e, tv := range info.Types {
if e, ok := e.(*ast.InterfaceType); ok {
_ = e
_ = tv.Type.(*types.Interface)
// TODO(adonovan): implement same check as above.
}
}
}
// assignability
for T := range r.findAssignments(recv) {
if obj, _, _ := types.LookupFieldOrMethod(T, false, from.Pkg(), from.Name()); obj == nil {
continue
}
r.errorf(from.Pos(), "renaming this method %q to %q",
from.Name(), r.to)
var pos token.Pos
var other string
if named, ok := T.(*types.Named); ok {
pos = named.Obj().Pos()
other = named.Obj().Name()
} else {
pos = from.Pos()
other = T.String()
}
r.errorf(pos, "\twould make %s no longer assignable to it", other)
return
}
} else {
// Concrete method
// declaration
prev, indices, _ := types.LookupFieldOrMethod(recv, true, from.Pkg(), r.to)
if prev != nil && len(indices) == 1 {
r.errorf(from.Pos(), "renaming this method %q to %q",
from.Name(), r.to)
r.errorf(prev.Pos(), "\twould conflict with this %s",
objectKind(prev))
return
}
// assignability (of both T and *T)
recvBase := deref(recv)
for _, R := range []types.Type{recvBase, types.NewPointer(recvBase)} {
for I := range r.findAssignments(R) {
if obj, _, _ := types.LookupFieldOrMethod(I, true, from.Pkg(), from.Name()); obj == nil {
continue
}
r.errorf(from.Pos(), "renaming this method %q to %q",
from.Name(), r.to)
var pos token.Pos
var iface string
if named, ok := I.(*types.Named); ok {
pos = named.Obj().Pos()
iface = "interface " + named.Obj().Name()
} else {
pos = from.Pos()
iface = I.String()
}
r.errorf(pos, "\twould make it no longer assignable to %s", iface)
return // one is enough
}
}
}
// Check integrity of existing (field and method) selections.
// We skip this if there were errors above, to avoid redundant errors.
r.checkSelections(from)
}