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go/types: implement Checker.implements

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This is a port of CL 363837 from types2 to go/types. As usual, test
error messages had to be repositioned on the operand.

Change-Id: I2b53fae7aa30f9147f8d05f75b0ab252338320bb
Reviewed-on: https://go-review.googlesource.com/c/go/+/364934
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Robert Findley 2021-11-17 20:01:16 -05:00
parent 14c3f749be
commit 9ea939be60
2 changed files with 72 additions and 63 deletions
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131
src/go/types/instantiate.go
View File

@ -133,34 +133,6 @@ func (check *Checker) validateTArgLen(pos token.Pos, ntparams, ntargs int) bool
} }
func (check *Checker) verify(pos token.Pos, tparams []*TypeParam, targs []Type) (int, error) { func (check *Checker) verify(pos token.Pos, tparams []*TypeParam, targs []Type) (int, error) {
smap := makeSubstMap(tparams, targs)
for i, tpar := range tparams {
// stop checking bounds after the first failure
if err := check.satisfies(pos, targs[i], tpar, smap); err != nil {
return i, err
}
}
return -1, nil
}
// satisfies reports whether the type argument targ satisfies the constraint of type parameter
// parameter tpar (after any of its type parameters have been substituted through smap).
// A suitable error is reported if the result is false.
// TODO(gri) This should be a method of interfaces or type sets.
func (check *Checker) satisfies(pos token.Pos, targ Type, tpar *TypeParam, smap substMap) error {
iface := tpar.iface()
// Every type argument satisfies interface{}.
if iface.Empty() {
return nil
}
// A type argument that is a type parameter with an empty type set satisfies any constraint.
// (The empty set is a subset of any set.)
if targ, _ := targ.(*TypeParam); targ != nil && targ.iface().typeSet().IsEmpty() {
return nil
}
// TODO(rfindley): it would be great if users could pass in a qualifier here, // TODO(rfindley): it would be great if users could pass in a qualifier here,
// rather than falling back to verbose qualification. Maybe this can be part // rather than falling back to verbose qualification. Maybe this can be part
// of the shared context. // of the shared context.
@ -168,78 +140,115 @@ func (check *Checker) satisfies(pos token.Pos, targ Type, tpar *TypeParam, smap
if check != nil { if check != nil {
qf = check.qualifier qf = check.qualifier
} }
smap := makeSubstMap(tparams, targs)
for i, tpar := range tparams {
// The type parameter bound is parameterized with the same type parameters
// as the instantiated type; before we can use it for bounds checking we
// need to instantiate it with the type arguments with which we instantiated
// the parameterized type.
bound := check.subst(pos, tpar.bound, smap, nil)
if err := check.implements(targs[i], bound, qf); err != nil {
return i, err
}
}
return -1, nil
}
// implements checks if V implements T and reports an error if it doesn't.
// If a qualifier is provided, it is used in error formatting.
func (check *Checker) implements(V, T Type, qf Qualifier) error {
Vu := under(V)
Tu := under(T)
if Vu == Typ[Invalid] || Tu == Typ[Invalid] {
return nil
}
errorf := func(format string, args ...interface{}) error { errorf := func(format string, args ...interface{}) error {
return errors.New(sprintf(nil, qf, false, format, args...)) return errors.New(sprintf(nil, qf, false, format, args...))
} }
// No type argument with non-empty type set satisfies the empty type set. Ti, _ := Tu.(*Interface)
if iface.typeSet().IsEmpty() { if Ti == nil {
return errorf("%s does not satisfy %s (constraint type set is empty)", targ, tpar.bound) return errorf("%s is not an interface", T)
} }
// The type parameter bound is parameterized with the same type parameters // Every type satisfies the empty interface.
// as the instantiated type; before we can use it for bounds checking we if Ti.Empty() {
// need to instantiate it with the type arguments with which we instantiate return nil
// the parameterized type. }
iface = check.subst(pos, iface, smap, nil).(*Interface) // T is not the empty interface (i.e., the type set of T is restricted)
// if iface is comparable, targ must be comparable // An interface V with an empty type set satisfies any interface.
// (The empty set is a subset of any set.)
Vi, _ := Vu.(*Interface)
if Vi != nil && Vi.typeSet().IsEmpty() {
return nil
}
// type set of V is not empty
// No type with non-empty type set satisfies the empty type set.
// TODO(gri) should use "implements" rather than "satisfies" throughout
if Ti.typeSet().IsEmpty() {
return errorf("%s does not satisfy %s (constraint type set is empty)", V, T)
}
// If T is comparable, V must be comparable.
// TODO(gri) the error messages needs to be better, here // TODO(gri) the error messages needs to be better, here
if iface.IsComparable() && !Comparable(targ) { if Ti.IsComparable() && !Comparable(V) {
if tpar, _ := targ.(*TypeParam); tpar != nil && tpar.iface().typeSet().IsAll() { if Vi != nil && Vi.typeSet().IsAll() {
return errorf("%s has no constraints", targ) return errorf("%s has no constraints", V)
} }
return errorf("%s does not satisfy comparable", targ) return errorf("%s does not satisfy comparable", V)
} }
// targ must implement iface (methods) // V must implement T (methods)
// - check only if we have methods // - check only if we have methods
if iface.NumMethods() > 0 { if Ti.NumMethods() > 0 {
// If the type argument is a pointer to a type parameter, the type argument's // If the type argument is a pointer to a type parameter, the type argument's
// method set is empty. // method set is empty.
// TODO(gri) is this what we want? (spec question) // TODO(gri) is this what we want? (spec question)
if base, isPtr := deref(targ); isPtr && isTypeParam(base) { if base, isPtr := deref(V); isPtr && isTypeParam(base) {
return errorf("%s has no methods", targ) return errorf("%s has no methods", V)
} }
if m, wrong := check.missingMethod(targ, iface, true); m != nil { if m, wrong := check.missingMethod(V, Ti, true); m != nil {
// TODO(gri) needs to print updated name to avoid major confusion in error message! // TODO(gri) needs to print updated name to avoid major confusion in error message!
// (print warning for now) // (print warning for now)
// Old warning: // Old warning:
// check.softErrorf(pos, "%s does not satisfy %s (warning: name not updated) = %s (missing method %s)", targ, tpar.bound, iface, m) // check.softErrorf(pos, "%s does not satisfy %s (warning: name not updated) = %s (missing method %s)", V, T, Ti, m)
if wrong != nil { if wrong != nil {
// TODO(gri) This can still report uninstantiated types which makes the error message // TODO(gri) This can still report uninstantiated types which makes the error message
// more difficult to read then necessary. // more difficult to read then necessary.
// TODO(rFindley) should this use parentheses rather than ':' for qualification? // TODO(rFindley) should this use parentheses rather than ':' for qualification?
return errorf("%s does not satisfy %s: wrong method signature\n\tgot %s\n\twant %s", return errorf("%s does not satisfy %s: wrong method signature\n\tgot %s\n\twant %s",
targ, tpar.bound, wrong, m, V, T, wrong, m,
) )
} }
return errorf("%s does not satisfy %s (missing method %s)", targ, tpar.bound, m.name) return errorf("%s does not satisfy %s (missing method %s)", V, T, m.name)
} }
} }
// targ must also be in the set of types of iface, if any. // V must also be in the set of types of T, if any.
// Constraints with empty type sets were already excluded above. // Constraints with empty type sets were already excluded above.
if !iface.typeSet().hasTerms() { if !Ti.typeSet().hasTerms() {
return nil // nothing to do return nil // nothing to do
} }
// If targ is itself a type parameter, each of its possible types must be in the set // If V is itself an interface, each of its possible types must be in the set
// of iface types (i.e., the targ type set must be a subset of the iface type set). // of T types (i.e., the V type set must be a subset of the T type set).
// Type arguments with empty type sets were already excluded above. // Interfaces V with empty type sets were already excluded above.
if targ, _ := targ.(*TypeParam); targ != nil { if Vi != nil {
targBound := targ.iface() if !Vi.typeSet().subsetOf(Ti.typeSet()) {
if !targBound.typeSet().subsetOf(iface.typeSet()) {
// TODO(gri) report which type is missing // TODO(gri) report which type is missing
return errorf("%s does not satisfy %s", targ, tpar.bound) return errorf("%s does not satisfy %s", V, T)
} }
return nil return nil
} }
// Otherwise, targ's type must be included in the iface type set. // Otherwise, V's type must be included in the iface type set.
if !iface.typeSet().includes(targ) { if !Ti.typeSet().includes(V) {
// TODO(gri) report which type is missing // TODO(gri) report which type is missing
return errorf("%s does not satisfy %s", targ, tpar.bound) return errorf("%s does not satisfy %s", V, T)
} }
return nil return nil

4
src/go/types/testdata/fixedbugs/issue45920.go2 vendored
View File

@ -8,10 +8,10 @@ func f1[T any, C chan T | <-chan T](ch C) {}
func _(ch chan int) { f1(ch) } func _(ch chan int) { f1(ch) }
func _(ch <-chan int) { f1(ch) } func _(ch <-chan int) { f1(ch) }
func _(ch chan<- int) { f1 /* ERROR chan<- int does not satisfy chan T\|<-chan T */ (ch) } func _(ch chan<- int) { f1 /* ERROR chan<- int does not satisfy chan int\|<-chan int */ (ch) }
func f2[T any, C chan T | chan<- T](ch C) {} func f2[T any, C chan T | chan<- T](ch C) {}
func _(ch chan int) { f2(ch) } func _(ch chan int) { f2(ch) }
func _(ch <-chan int) { f2 /* ERROR <-chan int does not satisfy chan T\|chan<- T */ (ch)} func _(ch <-chan int) { f2 /* ERROR <-chan int does not satisfy chan int\|chan<- int */ (ch) }
func _(ch chan<- int) { f2(ch) } func _(ch chan<- int) { f2(ch) }