cmd/compile/internal/types2: disallow lone type parameter on RHS of type declaration

We may revisit this decision in a future release. By disallowing this
for Go 1.18 we are ensuring that we don't lock in the generics design
in a place that may need to change later. (Type declarations are the
primary construct where it crucially matters what the underlying type
of a type parameter is.)

Comment out all tests that rely on this feature; add comments referring
to issue so we can find all places easily should we change our minds.

Fixes #45639.

Change-Id: I730510e4da66d3716d455a9071c7778a1e4a1152
Reviewed-on: https://go-review.googlesource.com/c/go/+/359177
Trust: Robert Griesemer <gri@golang.org>
Trust: Dan Scales <danscales@google.com>
Reviewed-by: Dan Scales <danscales@google.com>
This commit is contained in:
Robert Griesemer 2021-10-27 13:55:15 -07:00
parent 79ff663754
commit a91d0b649c
20 changed files with 297 additions and 309 deletions

View file

@ -622,13 +622,6 @@ func TestDefsInfo(t *testing.T) {
{`package p3; type x int`, `x`, `type p3.x int`},
{`package p4; func f()`, `f`, `func p4.f()`},
{`package p5; func f() int { x, _ := 1, 2; return x }`, `_`, `var _ int`},
// generic types must be sanitized
// (need to use sufficiently nested types to provoke unexpanded types)
{genericPkg + `g0; type t[P any] P; const x = t[int](42)`, `x`, `const generic_g0.x generic_g0.t[int]`},
{genericPkg + `g1; type t[P any] P; var x = t[int](42)`, `x`, `var generic_g1.x generic_g1.t[int]`},
{genericPkg + `g2; type t[P any] P; type x struct{ f t[int] }`, `x`, `type generic_g2.x struct{f generic_g2.t[int]}`},
{genericPkg + `g3; type t[P any] P; func f(x struct{ f t[string] }); var g = f`, `g`, `var generic_g3.g func(x struct{f generic_g3.t[string]})`},
}
for _, test := range tests {
@ -667,13 +660,6 @@ func TestUsesInfo(t *testing.T) {
{`package p2; func _() { _ = x }; var x int`, `x`, `var p2.x int`},
{`package p3; func _() { type _ x }; type x int`, `x`, `type p3.x int`},
{`package p4; func _() { _ = f }; func f()`, `f`, `func p4.f()`},
// generic types must be sanitized
// (need to use sufficiently nested types to provoke unexpanded types)
{genericPkg + `g0; func _() { _ = x }; type t[P any] P; const x = t[int](42)`, `x`, `const generic_g0.x generic_g0.t[int]`},
{genericPkg + `g1; func _() { _ = x }; type t[P any] P; var x = t[int](42)`, `x`, `var generic_g1.x generic_g1.t[int]`},
{genericPkg + `g2; func _() { type _ x }; type t[P any] P; type x struct{ f t[int] }`, `x`, `type generic_g2.x struct{f generic_g2.t[int]}`},
{genericPkg + `g3; func _() { _ = f }; type t[P any] P; func f(x struct{ f t[string] })`, `f`, `func generic_g3.f(x struct{f generic_g3.t[string]})`},
}
for _, test := range tests {

View file

@ -604,9 +604,12 @@ func (check *Checker) typeDecl(obj *TypeName, tdecl *syntax.TypeDecl, def *Named
named.underlying = Typ[Invalid]
}
// If the RHS is a type parameter, it must be from this type declaration.
if tpar, _ := named.underlying.(*TypeParam); tpar != nil && tparamIndex(named.TypeParams().list(), tpar) < 0 {
check.errorf(tdecl.Type, "cannot use function type parameter %s as RHS in type declaration", tpar)
// Disallow a lone type parameter as the RHS of a type declaration (issue #45639).
// We can look directly at named.underlying because even if it is still a *Named
// type (underlying not fully resolved yet) it cannot become a type parameter due
// to this very restriction.
if tpar, _ := named.underlying.(*TypeParam); tpar != nil {
check.error(tdecl.Type, "cannot use a type parameter as RHS in type declaration")
named.underlying = Typ[Invalid]
}
}

View file

@ -4,8 +4,6 @@
package linalg
import "math"
// Numeric is type bound that matches any numeric type.
// It would likely be in a constraints package in the standard library.
type Numeric interface {
@ -52,32 +50,33 @@ type Complex interface {
~complex64 | ~complex128
}
// OrderedAbs is a helper type that defines an Abs method for
// ordered numeric types.
type OrderedAbs[T OrderedNumeric] T
func (a OrderedAbs[T]) Abs() OrderedAbs[T] {
if a < 0 {
return -a
}
return a
}
// ComplexAbs is a helper type that defines an Abs method for
// complex types.
type ComplexAbs[T Complex] T
func (a ComplexAbs[T]) Abs() ComplexAbs[T] {
r := float64(real(a))
i := float64(imag(a))
d := math.Sqrt(r * r + i * i)
return ComplexAbs[T](complex(d, 0))
}
func OrderedAbsDifference[T OrderedNumeric](a, b T) T {
return T(AbsDifference(OrderedAbs[T](a), OrderedAbs[T](b)))
}
func ComplexAbsDifference[T Complex](a, b T) T {
return T(AbsDifference(ComplexAbs[T](a), ComplexAbs[T](b)))
}
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// // OrderedAbs is a helper type that defines an Abs method for
// // ordered numeric types.
// type OrderedAbs[T OrderedNumeric] T
//
// func (a OrderedAbs[T]) Abs() OrderedAbs[T] {
// if a < 0 {
// return -a
// }
// return a
// }
//
// // ComplexAbs is a helper type that defines an Abs method for
// // complex types.
// type ComplexAbs[T Complex] T
//
// func (a ComplexAbs[T]) Abs() ComplexAbs[T] {
// r := float64(real(a))
// i := float64(imag(a))
// d := math.Sqrt(r * r + i * i)
// return ComplexAbs[T](complex(d, 0))
// }
//
// func OrderedAbsDifference[T OrderedNumeric](a, b T) T {
// return T(AbsDifference(OrderedAbs[T](a), OrderedAbs[T](b)))
// }
//
// func ComplexAbsDifference[T Complex](a, b T) T {
// return T(AbsDifference(ComplexAbs[T](a), ComplexAbs[T](b)))
// }

View file

@ -8,7 +8,8 @@ type myInt int
// Parameterized type declarations
type T1[P any] P
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
type T1[P any] P // ERROR cannot use a type parameter as RHS in type declaration
type T2[P any] struct {
f P
@ -19,7 +20,7 @@ type List[P any] []P
// Alias type declarations cannot have type parameters.
// Issue #46477 proposses to change that.
type A1[P any] = /* ERROR cannot be alias */ P
type A1[P any] = /* ERROR cannot be alias */ struct{}
// Pending clarification of #46477 we disallow aliases
// of generic types.

View file

@ -87,25 +87,27 @@ type NumericAbs[T any] interface {
func AbsDifference[T NumericAbs[T]](x T) { panic(0) }
type OrderedAbs[T any] T
func (a OrderedAbs[T]) Abs() OrderedAbs[T]
func OrderedAbsDifference[T any](x T) {
AbsDifference(OrderedAbs[T](x))
}
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// type OrderedAbs[T any] T
//
// func (a OrderedAbs[T]) Abs() OrderedAbs[T]
//
// func OrderedAbsDifference[T any](x T) {
// AbsDifference(OrderedAbs[T](x))
// }
// same code, reduced to essence
func g[P interface{ m() P }](x P) { panic(0) }
type T4[P any] P
func (_ T4[P]) m() T4[P]
func _[Q any](x Q) {
g(T4[Q](x))
}
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// type T4[P any] P
//
// func (_ T4[P]) m() T4[P]
//
// func _[Q any](x Q) {
// g(T4[Q](x))
// }
// Another test case that caused problems in the past

View file

@ -353,15 +353,16 @@ func _() {
// the previous example was extracted from
func f12[T interface{m() T}]() {}
type A[T any] T
func (a A[T]) m() A[T]
func _[T any]() {
f12[A[T]]()
}
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// func f12[T interface{m() T}]() {}
//
// type A[T any] T
//
// func (a A[T]) m() A[T]
//
// func _[T any]() {
// f12[A[T]]()
// }
// method expressions

View file

@ -6,8 +6,6 @@
package p
import "unsafe"
// Parameterized types may have methods.
type T1[A any] struct{ a A }
@ -97,17 +95,18 @@ type T0 struct{}
func (T0) _() {}
func (T1[A]) _() {}
// A generic receiver type may constrain its type parameter such
// that it must be a pointer type. Such receiver types are not
// permitted.
type T3a[P interface{ ~int | ~string | ~float64 }] P
func (T3a[_]) m() {} // this is ok
type T3b[P interface{ ~unsafe.Pointer }] P
func (T3b /* ERROR invalid receiver */ [_]) m() {}
type T3c[P interface{ *int | *string }] P
func (T3c /* ERROR invalid receiver */ [_]) m() {}
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// // A generic receiver type may constrain its type parameter such
// // that it must be a pointer type. Such receiver types are not
// // permitted.
// type T3a[P interface{ ~int | ~string | ~float64 }] P
//
// func (T3a[_]) m() {} // this is ok
//
// type T3b[P interface{ ~unsafe.Pointer }] P
//
// func (T3b /* ERROR invalid receiver */ [_]) m() {}
//
// type T3c[P interface{ *int | *string }] P
//
// func (T3c /* ERROR invalid receiver */ [_]) m() {}

View file

@ -185,12 +185,13 @@ type _ struct {
// _ = y < 0
// }
// It is not permitted to declare a local type whose underlying
// type is a type parameter not declared by that type declaration.
func _[T any]() {
type _ T // ERROR cannot use function type parameter T as RHS in type declaration
type _ [_ any] T // ERROR cannot use function type parameter T as RHS in type declaration
}
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// // It is not permitted to declare a local type whose underlying
// // type is a type parameter not declared by that type declaration.
// func _[T any]() {
// type _ T // ERROR cannot use function type parameter T as RHS in type declaration
// type _ [_ any] T // ERROR cannot use function type parameter T as RHS in type declaration
// }
// As a special case, an explicit type argument may be omitted
// from a type parameter bound if the type bound expects exactly

View file

@ -74,9 +74,10 @@ func F20[t Z20]() { F20(t /* ERROR invalid composite literal type */ {}) }
type Z21 /* ERROR illegal cycle */ interface{ Z21 }
func F21[T Z21]() { ( /* ERROR not used */ F21[Z21]) }
// crash 24
type T24[P any] P
func (r T24[P]) m() { T24 /* ERROR without instantiation */ .m() }
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// // crash 24
// type T24[P any] P
// func (r T24[P]) m() { T24 /* ERROR without instantiation */ .m() }
// crash 25
type T25[A any] int

View file

@ -4,14 +4,15 @@
package p
type T[P any] P
type A = T // ERROR cannot use generic type
var x A[int]
var _ A
type B = T[int]
var y B = x
var _ B /* ERROR not a generic type */ [int]
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// type T[P any] P
// type A = T // ERROR cannot use generic type
// var x A[int]
// var _ A
//
// type B = T[int]
// var y B = x
// var _ B /* ERROR not a generic type */ [int]
// test case from issue

View file

@ -8,7 +8,7 @@
package p
type E0[P any] P
type E0[P any] []P
type E1[P any] *P
type E2[P any] struct{ _ P }
type E3[P any] struct{ _ *P }

View file

@ -4,9 +4,10 @@
package P
// It is not permitted to declare a local type whose underlying
// type is a type parameters not declared by that type declaration.
func _[T any]() {
type _ T // ERROR cannot use function type parameter T as RHS in type declaration
type _ [_ any] T // ERROR cannot use function type parameter T as RHS in type declaration
}
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// // It is not permitted to declare a local type whose underlying
// // type is a type parameters not declared by that type declaration.
// func _[T any]() {
// type _ T // ERROR cannot use function type parameter T as RHS in type declaration
// type _ [_ any] T // ERROR cannot use function type parameter T as RHS in type declaration
// }

View file

@ -4,15 +4,16 @@
package p
type T1[P any] P
func (T1[_]) m() {}
func _[P any](x *T1[P]) {
// x.m exists because x is of type *T1 where T1 is a defined type
// (even though under(T1) is a type parameter)
x.m()
}
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// type T1[P any] P
//
// func (T1[_]) m() {}
//
// func _[P any](x *T1[P]) {
// // x.m exists because x is of type *T1 where T1 is a defined type
// // (even though under(T1) is a type parameter)
// x.m()
// }
func _[P interface{ m() }](x P) {
@ -40,29 +41,31 @@ type Barer[t any] interface {
Bar(t)
}
type Foo1[t any] t
type Bar[t any] t
func (l Foo1[t]) Foo(v Barer[t]) { v.Bar(t(l)) }
func (b *Bar[t]) Bar(l t) { *b = Bar[t](l) }
func _[t any](f Fooer1[t]) t {
var b Bar[t]
f.Foo(&b)
return t(b)
}
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// type Foo1[t any] t
// type Bar[t any] t
//
// func (l Foo1[t]) Foo(v Barer[t]) { v.Bar(t(l)) }
// func (b *Bar[t]) Bar(l t) { *b = Bar[t](l) }
//
// func _[t any](f Fooer1[t]) t {
// var b Bar[t]
// f.Foo(&b)
// return t(b)
// }
// Test case 2 from issue
type Fooer2[t any] interface {
Foo()
}
type Foo2[t any] t
func (f *Foo2[t]) Foo() {}
func _[t any](v t) {
var f = Foo2[t](v)
_ = Fooer2[t](&f)
}
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// type Fooer2[t any] interface {
// Foo()
// }
//
// type Foo2[t any] t
//
// func (f *Foo2[t]) Foo() {}
//
// func _[t any](v t) {
// var f = Foo2[t](v)
// _ = Fooer2[t](&f)
// }

View file

@ -6,11 +6,6 @@
package main
import (
"fmt"
"math"
)
type Numeric interface {
~int | ~int8 | ~int16 | ~int32 | ~int64 |
~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
@ -43,55 +38,57 @@ type Complex interface {
~complex64 | ~complex128
}
// orderedAbs is a helper type that defines an Abs method for
// ordered numeric types.
type orderedAbs[T orderedNumeric] T
func (a orderedAbs[T]) Abs() orderedAbs[T] {
if a < 0 {
return -a
}
return a
}
// complexAbs is a helper type that defines an Abs method for
// complex types.
type complexAbs[T Complex] T
func (a complexAbs[T]) Abs() complexAbs[T] {
r := float64(real(a))
i := float64(imag(a))
d := math.Sqrt(r*r + i*i)
return complexAbs[T](complex(d, 0))
}
// OrderedAbsDifference returns the absolute value of the difference
// between a and b, where a and b are of an ordered type.
func orderedAbsDifference[T orderedNumeric](a, b T) T {
return T(absDifference(orderedAbs[T](a), orderedAbs[T](b)))
}
// ComplexAbsDifference returns the absolute value of the difference
// between a and b, where a and b are of a complex type.
func complexAbsDifference[T Complex](a, b T) T {
return T(absDifference(complexAbs[T](a), complexAbs[T](b)))
}
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// // orderedAbs is a helper type that defines an Abs method for
// // ordered numeric types.
// type orderedAbs[T orderedNumeric] T
//
// func (a orderedAbs[T]) Abs() orderedAbs[T] {
// if a < 0 {
// return -a
// }
// return a
// }
//
// // complexAbs is a helper type that defines an Abs method for
// // complex types.
// type complexAbs[T Complex] T
//
// func (a complexAbs[T]) Abs() complexAbs[T] {
// r := float64(real(a))
// i := float64(imag(a))
// d := math.Sqrt(r*r + i*i)
// return complexAbs[T](complex(d, 0))
// }
//
// // OrderedAbsDifference returns the absolute value of the difference
// // between a and b, where a and b are of an ordered type.
// func orderedAbsDifference[T orderedNumeric](a, b T) T {
// return T(absDifference(orderedAbs[T](a), orderedAbs[T](b)))
// }
//
// // ComplexAbsDifference returns the absolute value of the difference
// // between a and b, where a and b are of a complex type.
// func complexAbsDifference[T Complex](a, b T) T {
// return T(absDifference(complexAbs[T](a), complexAbs[T](b)))
// }
func main() {
if got, want := orderedAbsDifference(1.0, -2.0), 3.0; got != want {
panic(fmt.Sprintf("got = %v, want = %v", got, want))
}
if got, want := orderedAbsDifference(-1.0, 2.0), 3.0; got != want {
panic(fmt.Sprintf("got = %v, want = %v", got, want))
}
if got, want := orderedAbsDifference(-20, 15), 35; got != want {
panic(fmt.Sprintf("got = %v, want = %v", got, want))
}
if got, want := complexAbsDifference(5.0+2.0i, 2.0-2.0i), 5+0i; got != want {
panic(fmt.Sprintf("got = %v, want = %v", got, want))
}
if got, want := complexAbsDifference(2.0-2.0i, 5.0+2.0i), 5+0i; got != want {
panic(fmt.Sprintf("got = %v, want = %v", got, want))
}
// // For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// if got, want := orderedAbsDifference(1.0, -2.0), 3.0; got != want {
// panic(fmt.Sprintf("got = %v, want = %v", got, want))
// }
// if got, want := orderedAbsDifference(-1.0, 2.0), 3.0; got != want {
// panic(fmt.Sprintf("got = %v, want = %v", got, want))
// }
// if got, want := orderedAbsDifference(-20, 15), 35; got != want {
// panic(fmt.Sprintf("got = %v, want = %v", got, want))
// }
//
// if got, want := complexAbsDifference(5.0+2.0i, 2.0-2.0i), 5+0i; got != want {
// panic(fmt.Sprintf("got = %v, want = %v", got, want))
// }
// if got, want := complexAbsDifference(2.0-2.0i, 5.0+2.0i), 5+0i; got != want {
// panic(fmt.Sprintf("got = %v, want = %v", got, want))
// }
}

View file

@ -4,10 +4,6 @@
package a
import (
"math"
)
type Numeric interface {
~int | ~int8 | ~int16 | ~int32 | ~int64 |
~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
@ -40,36 +36,37 @@ type Complex interface {
~complex64 | ~complex128
}
// orderedAbs is a helper type that defines an Abs method for
// ordered numeric types.
type orderedAbs[T orderedNumeric] T
func (a orderedAbs[T]) Abs() orderedAbs[T] {
if a < 0 {
return -a
}
return a
}
// complexAbs is a helper type that defines an Abs method for
// complex types.
type complexAbs[T Complex] T
func (a complexAbs[T]) Abs() complexAbs[T] {
r := float64(real(a))
i := float64(imag(a))
d := math.Sqrt(r*r + i*i)
return complexAbs[T](complex(d, 0))
}
// OrderedAbsDifference returns the absolute value of the difference
// between a and b, where a and b are of an ordered type.
func OrderedAbsDifference[T orderedNumeric](a, b T) T {
return T(absDifference(orderedAbs[T](a), orderedAbs[T](b)))
}
// ComplexAbsDifference returns the absolute value of the difference
// between a and b, where a and b are of a complex type.
func ComplexAbsDifference[T Complex](a, b T) T {
return T(absDifference(complexAbs[T](a), complexAbs[T](b)))
}
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// // orderedAbs is a helper type that defines an Abs method for
// // ordered numeric types.
// type orderedAbs[T orderedNumeric] T
//
// func (a orderedAbs[T]) Abs() orderedAbs[T] {
// if a < 0 {
// return -a
// }
// return a
// }
//
// // complexAbs is a helper type that defines an Abs method for
// // complex types.
// type complexAbs[T Complex] T
//
// func (a complexAbs[T]) Abs() complexAbs[T] {
// r := float64(real(a))
// i := float64(imag(a))
// d := math.Sqrt(r*r + i*i)
// return complexAbs[T](complex(d, 0))
// }
//
// // OrderedAbsDifference returns the absolute value of the difference
// // between a and b, where a and b are of an ordered type.
// func OrderedAbsDifference[T orderedNumeric](a, b T) T {
// return T(absDifference(orderedAbs[T](a), orderedAbs[T](b)))
// }
//
// // ComplexAbsDifference returns the absolute value of the difference
// // between a and b, where a and b are of a complex type.
// func ComplexAbsDifference[T Complex](a, b T) T {
// return T(absDifference(complexAbs[T](a), complexAbs[T](b)))
// }

View file

@ -4,26 +4,22 @@
package main
import (
"a"
"fmt"
)
func main() {
if got, want := a.OrderedAbsDifference(1.0, -2.0), 3.0; got != want {
panic(fmt.Sprintf("got = %v, want = %v", got, want))
}
if got, want := a.OrderedAbsDifference(-1.0, 2.0), 3.0; got != want {
panic(fmt.Sprintf("got = %v, want = %v", got, want))
}
if got, want := a.OrderedAbsDifference(-20, 15), 35; got != want {
panic(fmt.Sprintf("got = %v, want = %v", got, want))
}
if got, want := a.ComplexAbsDifference(5.0+2.0i, 2.0-2.0i), 5+0i; got != want {
panic(fmt.Sprintf("got = %v, want = %v", got, want))
}
if got, want := a.ComplexAbsDifference(2.0-2.0i, 5.0+2.0i), 5+0i; got != want {
panic(fmt.Sprintf("got = %v, want = %v", got, want))
}
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// if got, want := a.OrderedAbsDifference(1.0, -2.0), 3.0; got != want {
// panic(fmt.Sprintf("got = %v, want = %v", got, want))
// }
// if got, want := a.OrderedAbsDifference(-1.0, 2.0), 3.0; got != want {
// panic(fmt.Sprintf("got = %v, want = %v", got, want))
// }
// if got, want := a.OrderedAbsDifference(-20, 15), 35; got != want {
// panic(fmt.Sprintf("got = %v, want = %v", got, want))
// }
//
// if got, want := a.ComplexAbsDifference(5.0+2.0i, 2.0-2.0i), 5+0i; got != want {
// panic(fmt.Sprintf("got = %v, want = %v", got, want))
// }
// if got, want := a.ComplexAbsDifference(2.0-2.0i, 5.0+2.0i), 5+0i; got != want {
// panic(fmt.Sprintf("got = %v, want = %v", got, want))
// }
}

View file

@ -59,12 +59,13 @@ type Ints interface {
~int32 | ~int
}
type StringInt[T Ints] T
//go:noinline
func (m StringInt[T]) String() string {
return strconv.Itoa(int(m))
}
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// type StringInt[T Ints] T
//
// //go:noinline
// func (m StringInt[T]) String() string {
// return strconv.Itoa(int(m))
// }
type StringStruct[T Ints] struct {
f T
@ -84,22 +85,23 @@ func main() {
panic(fmt.Sprintf("got %s, want %s", got, want))
}
x2 := []StringInt[myint]{StringInt[myint](5), StringInt[myint](7), StringInt[myint](6)}
// stringify on an instantiated type, whose bound method is associated with
// the generic type StringInt[T], which maps directly to T.
got2 := stringify(x2)
want2 := []string{ "5", "7", "6" }
if !reflect.DeepEqual(got2, want2) {
panic(fmt.Sprintf("got %s, want %s", got2, want2))
}
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// x2 := []StringInt[myint]{StringInt[myint](5), StringInt[myint](7), StringInt[myint](6)}
//
// // stringify on an instantiated type, whose bound method is associated with
// // the generic type StringInt[T], which maps directly to T.
// got2 := stringify(x2)
// want2 := []string{"5", "7", "6"}
// if !reflect.DeepEqual(got2, want2) {
// panic(fmt.Sprintf("got %s, want %s", got2, want2))
// }
// stringify on an instantiated type, whose bound method is associated with
// the generic type StringStruct[T], which maps to a struct containing T.
x3 := []StringStruct[myint]{StringStruct[myint]{f: 11}, StringStruct[myint]{f: 10}, StringStruct[myint]{f: 9}}
got3 := stringify(x3)
want3 := []string{ "11", "10", "9" }
want3 := []string{"11", "10", "9"}
if !reflect.DeepEqual(got3, want3) {
panic(fmt.Sprintf("got %s, want %s", got3, want3))
}

View file

@ -6,35 +6,32 @@
package main
import (
"fmt"
)
type FooType[T any] interface {
Foo(BarType[T])string
Foo(BarType[T]) string
}
type BarType[T any] interface {
Bar(FooType[T])string
}
type Baz[T any] T
func (l Baz[T]) Foo(v BarType[T]) string {
return v.Bar(l)
}
type Bob[T any] T
func (l Bob[T]) Bar(v FooType[T]) string {
if v,ok := v.(Baz[T]);ok{
return fmt.Sprintf("%v%v",v,l)
}
return ""
Bar(FooType[T]) string
}
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// type Baz[T any] T
// func (l Baz[T]) Foo(v BarType[T]) string {
// return v.Bar(l)
// }
// type Bob[T any] T
// func (l Bob[T]) Bar(v FooType[T]) string {
// if v,ok := v.(Baz[T]);ok{
// return fmt.Sprintf("%v%v",v,l)
// }
// return ""
// }
func main() {
var baz Baz[int] = 123
var bob Bob[int] = 456
if got, want := baz.Foo(bob), "123456"; got != want {
panic(fmt.Sprintf("got %s want %s", got, want))
}
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// var baz Baz[int] = 123
// var bob Bob[int] = 456
//
// if got, want := baz.Foo(bob), "123456"; got != want {
// panic(fmt.Sprintf("got %s want %s", got, want))
// }
}

View file

@ -12,10 +12,11 @@ type Exp[Ty any] interface {
Eval() Ty
}
type Lit[Ty any] Ty
func (lit Lit[Ty]) Eval() Ty { return Ty(lit) }
func (lit Lit[Ty]) String() string { return fmt.Sprintf("(lit %v)", Ty(lit)) }
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// type Lit[Ty any] Ty
//
// func (lit Lit[Ty]) Eval() Ty { return Ty(lit) }
// func (lit Lit[Ty]) String() string { return fmt.Sprintf("(lit %v)", Ty(lit)) }
type Eq[Ty any] struct {
a Exp[Ty]
@ -26,12 +27,14 @@ func (e Eq[Ty]) String() string {
return fmt.Sprintf("(eq %v %v)", e.a, e.b)
}
var (
e0 = Eq[int]{Lit[int](128), Lit[int](64)}
e1 = Eq[bool]{Lit[bool](true), Lit[bool](true)}
)
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// var (
// e0 = Eq[int]{Lit[int](128), Lit[int](64)}
// e1 = Eq[bool]{Lit[bool](true), Lit[bool](true)}
// )
func main() {
fmt.Printf("%v\n", e0)
fmt.Printf("%v\n", e1)
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
// fmt.Printf("%v\n", e0)
// fmt.Printf("%v\n", e1)
}

View file

@ -1,2 +0,0 @@
(eq (lit 128) (lit 64))
(eq (lit true) (lit true))