{`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 {
{`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 {
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]
}
}
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 {
~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)))
+// }
// 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
// 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.
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
// 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
package p
-import "unsafe"
-
// Parameterized types may have methods.
type T1[A any] struct{ a A }
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() {}
// _ = 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
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
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
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 }
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
+// }
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) {
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)
+// }
package main
-import (
- "fmt"
- "math"
-)
-
type Numeric interface {
~int | ~int8 | ~int16 | ~int32 | ~int64 |
~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
~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))
+ // }
}
package a
-import (
- "math"
-)
-
type Numeric interface {
~int | ~int8 | ~int16 | ~int32 | ~int64 |
~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
~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)))
+// }
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))
+ // }
}
~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
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))
}
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))
+ // }
}
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]
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)
}
-(eq (lit 128) (lit 64))
-(eq (lit true) (lit true))