Initial commit: Go 1.23 release state

test/typeparam/absdiff.go

@@ -0,0 +1,94 @@
+// run
+
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type Numeric interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64 |
+		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
+		~float32 | ~float64 |
+		~complex64 | ~complex128
+}
+
+// numericAbs matches numeric types with an Abs method.
+type numericAbs[T any] interface {
+	Numeric
+	Abs() T
+}
+
+// AbsDifference computes the absolute value of the difference of
+// a and b, where the absolute value is determined by the Abs method.
+func absDifference[T numericAbs[T]](a, b T) T {
+	d := a - b
+	return d.Abs()
+}
+
+// orderedNumeric matches numeric types that support the < operator.
+type orderedNumeric interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64 |
+		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
+		~float32 | ~float64
+}
+
+// Complex matches the two complex types, which do not have a < operator.
+type Complex interface {
+	~complex64 | ~complex128
+}
+
+// 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() {
+	// // 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))
+	// }
+}

test/typeparam/absdiff2.go

@@ -0,0 +1,135 @@
+// run
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// absdiff example in which an Abs method is attached to a generic type, which is a
+// structure with a single field that may be a list of possible basic types.
+
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+type Numeric interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64 |
+		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
+		~float32 | ~float64 |
+		~complex64 | ~complex128
+}
+
+// numericAbs matches a struct containing a numeric type that has an Abs method.
+type numericAbs[T Numeric] interface {
+	~struct{ Value_ T }
+	Abs() T
+	Value() T
+}
+
+// absDifference computes the absolute value of the difference of
+// a and b, where the absolute value is determined by the Abs method.
+func absDifference[T Numeric, U numericAbs[T]](a, b U) T {
+	d := a.Value() - b.Value()
+	dt := U{Value_: d}
+	return dt.Abs()
+}
+
+// orderedNumeric matches numeric types that support the < operator.
+type orderedNumeric interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64 |
+		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
+		~float32 | ~float64
+}
+
+// Complex matches the two complex types, which do not have a < operator.
+type Complex interface {
+	~complex64 | ~complex128
+}
+
+// orderedAbs is a helper type that defines an Abs method for
+// a struct containing an ordered numeric type.
+type orderedAbs[T orderedNumeric] struct {
+	Value_ T
+}
+
+func (a orderedAbs[T]) Abs() T {
+	if a.Value_ < 0 {
+		return -a.Value_
+	}
+	return a.Value_
+}
+
+// Field accesses through type parameters are disabled
+// until we have a more thorough understanding of the
+// implications on the spec. See issue #51576.
+// Use accessor method instead.
+
+func (a orderedAbs[T]) Value() T {
+	return a.Value_
+}
+
+// complexAbs is a helper type that defines an Abs method for
+// a struct containing a complex type.
+type complexAbs[T Complex] struct {
+	Value_ T
+}
+
+func realimag(x any) (re, im float64) {
+	switch z := x.(type) {
+	case complex64:
+		re = float64(real(z))
+		im = float64(imag(z))
+	case complex128:
+		re = real(z)
+		im = imag(z)
+	default:
+		panic("unknown complex type")
+	}
+	return
+}
+
+func (a complexAbs[T]) Abs() T {
+	// TODO use direct conversion instead of realimag once #50937 is fixed
+	r, i := realimag(a.Value_)
+	// r := float64(real(a.Value))
+	// i := float64(imag(a.Value))
+	d := math.Sqrt(r*r + i*i)
+	return T(complex(d, 0))
+}
+
+func (a complexAbs[T]) Value() T {
+	return a.Value_
+}
+
+// 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 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 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))
+	}
+}

test/typeparam/absdiff3.go

@@ -0,0 +1,98 @@
+// run
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// absdiff example using a function argument rather than attaching an
+// Abs method to a structure containing base types.
+
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+type Numeric interface {
+	OrderedNumeric | Complex
+}
+
+// absDifference computes the absolute value of the difference of
+// a and b, where the absolute value is determined by the abs function.
+func absDifference[T Numeric](a, b T, abs func(a T) T) T {
+	return abs(a - b)
+}
+
+// OrderedNumeric matches numeric types that support the < operator.
+type OrderedNumeric interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64 |
+		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
+		~float32 | ~float64
+}
+
+func Abs[T OrderedNumeric](a T) T {
+	if a < 0 {
+		return -a
+	}
+	return a
+}
+
+// Complex matches the two complex types, which do not have a < operator.
+type Complex interface {
+	~complex64 | ~complex128
+}
+
+func realimag(x any) (re, im float64) {
+	switch z := x.(type) {
+	case complex64:
+		re = float64(real(z))
+		im = float64(imag(z))
+	case complex128:
+		re = real(z)
+		im = imag(z)
+	default:
+		panic("unknown complex type")
+	}
+	return
+}
+
+func ComplexAbs[T Complex](a T) T {
+	// TODO use direct conversion instead of realimag once #50937 is fixed
+	r, i := realimag(a)
+	// r := float64(real(a))
+	// i := float64(imag(a))
+	d := math.Sqrt(r*r + i*i)
+	return 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 absDifference(a, b, Abs[T])
+}
+
+// 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 absDifference(a, b, ComplexAbs[T])
+}
+
+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))
+	}
+}

test/typeparam/absdiffimp.dir/a.go

@@ -0,0 +1,72 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+type Numeric interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64 |
+		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
+		~float32 | ~float64 |
+		~complex64 | ~complex128
+}
+
+// numericAbs matches numeric types with an Abs method.
+type numericAbs[T any] interface {
+	Numeric
+	Abs() T
+}
+
+// AbsDifference computes the absolute value of the difference of
+// a and b, where the absolute value is determined by the Abs method.
+func absDifference[T numericAbs[T]](a, b T) T {
+	d := a - b
+	return d.Abs()
+}
+
+// orderedNumeric matches numeric types that support the < operator.
+type orderedNumeric interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64 |
+		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
+		~float32 | ~float64
+}
+
+// Complex matches the two complex types, which do not have a < operator.
+type Complex interface {
+	~complex64 | ~complex128
+}
+
+// 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)))
+// }

test/typeparam/absdiffimp.dir/main.go

@@ -0,0 +1,25 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func main() {
+	// 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))
+	// }
+}

test/typeparam/absdiffimp.go

@@ -0,0 +1,7 @@
+// rundir
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ignored

test/typeparam/absdiffimp2.dir/a.go

@@ -0,0 +1,110 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+import (
+	"math"
+)
+
+type Numeric interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64 |
+		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
+		~float32 | ~float64 |
+		~complex64 | ~complex128
+}
+
+// numericAbs matches a struct containing a numeric type that has an Abs method.
+type numericAbs[T Numeric] interface {
+	~struct{ Value_ T }
+	Abs() T
+	Value() T
+}
+
+// absDifference computes the absolute value of the difference of
+// a and b, where the absolute value is determined by the Abs method.
+func absDifference[T Numeric, U numericAbs[T]](a, b U) T {
+	d := a.Value() - b.Value()
+	dt := U{Value_: d}
+	return dt.Abs()
+}
+
+// orderedNumeric matches numeric types that support the < operator.
+type orderedNumeric interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64 |
+		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
+		~float32 | ~float64
+}
+
+// Complex matches the two complex types, which do not have a < operator.
+type Complex interface {
+	~complex64 | ~complex128
+}
+
+// orderedAbs is a helper type that defines an Abs method for
+// a struct containing an ordered numeric type.
+type orderedAbs[T orderedNumeric] struct {
+	Value_ T
+}
+
+func (a orderedAbs[T]) Abs() T {
+	if a.Value_ < 0 {
+		return -a.Value_
+	}
+	return a.Value_
+}
+
+// Field accesses through type parameters are disabled
+// until we have a more thorough understanding of the
+// implications on the spec. See issue #51576.
+// Use accessor method instead.
+
+func (a orderedAbs[T]) Value() T {
+	return a.Value_
+}
+
+// complexAbs is a helper type that defines an Abs method for
+// a struct containing a complex type.
+type complexAbs[T Complex] struct {
+	Value_ T
+}
+
+func realimag(x any) (re, im float64) {
+	switch z := x.(type) {
+	case complex64:
+		re = float64(real(z))
+		im = float64(imag(z))
+	case complex128:
+		re = real(z)
+		im = imag(z)
+	default:
+		panic("unknown complex type")
+	}
+	return
+}
+
+func (a complexAbs[T]) Abs() T {
+	// TODO use direct conversion instead of realimag once #50937 is fixed
+	r, i := realimag(a.Value_)
+	// r := float64(real(a.Value))
+	// i := float64(imag(a.Value))
+	d := math.Sqrt(r*r + i*i)
+	return T(complex(d, 0))
+}
+
+func (a complexAbs[T]) Value() T {
+	return a.Value_
+}
+
+// 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 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 absDifference(complexAbs[T]{a}, complexAbs[T]{b})
+}

test/typeparam/absdiffimp2.dir/main.go

@@ -0,0 +1,29 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+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))
+	}
+}

test/typeparam/absdiffimp2.go

@@ -0,0 +1,7 @@
+// rundir
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ignored

test/typeparam/adder.go

@@ -0,0 +1,29 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"fmt"
+)
+
+type AddType interface {
+	int | int64 | string
+}
+
+// Add can add numbers or strings
+func Add[T AddType](a, b T) T {
+	return a + b
+}
+
+func main() {
+	if got, want := Add(5, 3), 8; got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+	if got, want := Add("ab", "cd"), "abcd"; got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+}

test/typeparam/aliasimp.dir/a.go

@@ -0,0 +1,9 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+type Rimp[T any] struct {
+	F T
+}

test/typeparam/aliasimp.dir/main.go

@@ -0,0 +1,41 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "./a"
+
+type R[T any] struct {
+	F T
+}
+
+// type S = R // disallowed for now
+
+type Sint = R[int]
+
+// type Simp = a.Rimp // disallowed for now
+
+// type SimpString Simp[string] // disallowed for now
+type SimpString a.Rimp[string]
+
+func main() {
+	// var s S[int] // disallowed for now
+	var s R[int]
+	if s.F != 0 {
+		panic(s.F)
+	}
+	var s2 Sint
+	if s2.F != 0 {
+		panic(s2.F)
+	}
+	// var s3 Simp[string] // disallowed for now
+	var s3 a.Rimp[string]
+	if s3.F != "" {
+		panic(s3.F)
+	}
+	var s4 SimpString
+	if s4.F != "" {
+		panic(s4.F)
+	}
+}

test/typeparam/aliasimp.go

@@ -0,0 +1,7 @@
+// rundir
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ignored

test/typeparam/append.go

@@ -0,0 +1,31 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type Recv <-chan int
+
+type sliceOf[E any] interface {
+	~[]E
+}
+
+func _Append[S sliceOf[T], T any](s S, t ...T) S {
+	return append(s, t...)
+}
+
+func main() {
+	recv := make(Recv)
+	a := _Append([]Recv{recv}, recv)
+	if len(a) != 2 || a[0] != recv || a[1] != recv {
+		panic(a)
+	}
+
+	recv2 := make(chan<- int)
+	a2 := _Append([]chan<- int{recv2}, recv2)
+	if len(a2) != 2 || a2[0] != recv2 || a2[1] != recv2 {
+		panic(a)
+	}
+}

test/typeparam/boundmethod.go

@@ -0,0 +1,108 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This test illustrates how a type bound method (String below) can be implemented
+// either by a concrete type (myint below) or an instantiated generic type
+// (StringInt[myint] below).
+
+package main
+
+import (
+	"fmt"
+	"reflect"
+	"strconv"
+)
+
+type myint int
+
+//go:noinline
+func (m myint) String() string {
+	return strconv.Itoa(int(m))
+}
+
+type Stringer interface {
+	String() string
+}
+
+func stringify[T Stringer](s []T) (ret []string) {
+	for _, v := range s {
+		// Test normal bounds method call on type param
+		x1 := v.String()
+
+		// Test converting type param to its bound interface first
+		v1 := Stringer(v)
+		x2 := v1.String()
+
+		// Test method expression with type param type
+		f1 := T.String
+		x3 := f1(v)
+
+		// Test creating and calling closure equivalent to the method expression
+		f2 := func(v1 T) string {
+			return Stringer(v1).String()
+		}
+		x4 := f2(v)
+
+		if x1 != x2 || x2 != x3 || x3 != x4 {
+			panic(fmt.Sprintf("Mismatched values %v, %v, %v, %v\n", x1, x2, x3, x4))
+		}
+
+		ret = append(ret, v.String())
+	}
+	return ret
+}
+
+type Ints interface {
+	~int32 | ~int
+}
+
+// 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
+}
+
+func (m StringStruct[T]) String() string {
+	return strconv.Itoa(int(m.f))
+}
+
+func main() {
+	x := []myint{myint(1), myint(2), myint(3)}
+
+	// stringify on a normal type, whose bound method is associated with the base type.
+	got := stringify(x)
+	want := []string{"1", "2", "3"}
+	if !reflect.DeepEqual(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).
+	// 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"}
+	if !reflect.DeepEqual(got3, want3) {
+		panic(fmt.Sprintf("got %s, want %s", got3, want3))
+	}
+}

test/typeparam/builtins.go

@@ -0,0 +1,112 @@
+// compile
+
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file tests built-in calls on generic types.
+
+// derived and expanded from cmd/compile/internal/types2/testdata/check/builtins.go2
+
+package builtins
+
+// close
+
+type C0 interface{ int }
+type C1 interface{ chan int }
+type C2 interface{ chan int | <-chan int }
+type C3 interface{ chan int | chan float32 }
+type C4 interface{ chan int | chan<- int }
+type C5[T any] interface{ ~chan T | chan<- T }
+
+func f1[T C1](ch T) {
+	close(ch)
+}
+
+func f2[T C3](ch T) {
+	close(ch)
+}
+
+func f3[T C4](ch T) {
+	close(ch)
+}
+
+func f4[T C5[X], X any](ch T) {
+	close(ch)
+}
+
+// delete
+
+type M0 interface{ int }
+type M1 interface{ map[string]int }
+type M2 interface {
+	map[string]int | map[string]float64
+}
+type M3 interface{ map[string]int | map[rune]int }
+type M4[K comparable, V any] interface{ map[K]V | map[rune]V }
+
+func g1[T M1](m T) {
+	delete(m, "foo")
+}
+
+func g2[T M2](m T) {
+	delete(m, "foo")
+}
+
+func g3[T M4[rune, V], V any](m T) {
+	delete(m, 'k')
+}
+
+// make
+
+func m1[
+	S1 interface{ []int },
+	S2 interface{ []int | chan int },
+
+	M1 interface{ map[string]int },
+	M2 interface{ map[string]int | chan int },
+
+	C1 interface{ chan int },
+	C2 interface{ chan int | chan string },
+]() {
+	type m1S0 []int
+	type m1M0 map[string]int
+	type m1C0 chan int
+
+	_ = make([]int, 10)
+	_ = make(m1S0, 10)
+	_ = make(S1, 10)
+	_ = make(S1, 10, 20)
+
+	_ = make(map[string]int)
+	_ = make(m1M0)
+	_ = make(M1)
+	_ = make(M1, 10)
+
+	_ = make(chan int)
+	_ = make(m1C0)
+	_ = make(C1)
+	_ = make(C1, 10)
+}
+
+// len/cap
+
+type Slice[T any] interface {
+	[]T
+}
+
+func c1[T any, S Slice[T]]() {
+	x := make(S, 5, 10)
+	_ = len(x)
+	_ = cap(x)
+}
+
+// append
+
+func a1[T any, S Slice[T]]() {
+	x := make(S, 5)
+	y := make(S, 2)
+	var z T
+	_ = append(x, y...)
+	_ = append(x, z)
+}

test/typeparam/chans.go

@@ -0,0 +1,413 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package chans provides utility functions for working with channels.
+package main
+
+import (
+	"context"
+	"fmt"
+	"runtime"
+	"sort"
+	"sync"
+	"time"
+)
+
+// _Equal reports whether two slices are equal: the same length and all
+// elements equal. All floating point NaNs are considered equal.
+func _SliceEqual[Elem comparable](s1, s2 []Elem) bool {
+	if len(s1) != len(s2) {
+		return false
+	}
+	for i, v1 := range s1 {
+		v2 := s2[i]
+		if v1 != v2 {
+			isNaN := func(f Elem) bool { return f != f }
+			if !isNaN(v1) || !isNaN(v2) {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+// _ReadAll reads from c until the channel is closed or the context is
+// canceled, returning all the values read.
+func _ReadAll[Elem any](ctx context.Context, c <-chan Elem) []Elem {
+	var r []Elem
+	for {
+		select {
+		case <-ctx.Done():
+			return r
+		case v, ok := <-c:
+			if !ok {
+				return r
+			}
+			r = append(r, v)
+		}
+	}
+}
+
+// _Merge merges two channels into a single channel.
+// This will leave a goroutine running until either both channels are closed
+// or the context is canceled, at which point the returned channel is closed.
+func _Merge[Elem any](ctx context.Context, c1, c2 <-chan Elem) <-chan Elem {
+	r := make(chan Elem)
+	go func(ctx context.Context, c1, c2 <-chan Elem, r chan<- Elem) {
+		defer close(r)
+		for c1 != nil || c2 != nil {
+			select {
+			case <-ctx.Done():
+				return
+			case v1, ok := <-c1:
+				if ok {
+					r <- v1
+				} else {
+					c1 = nil
+				}
+			case v2, ok := <-c2:
+				if ok {
+					r <- v2
+				} else {
+					c2 = nil
+				}
+			}
+		}
+	}(ctx, c1, c2, r)
+	return r
+}
+
+// _Filter calls f on each value read from c. If f returns true the value
+// is sent on the returned channel. This will leave a goroutine running
+// until c is closed or the context is canceled, at which point the
+// returned channel is closed.
+func _Filter[Elem any](ctx context.Context, c <-chan Elem, f func(Elem) bool) <-chan Elem {
+	r := make(chan Elem)
+	go func(ctx context.Context, c <-chan Elem, f func(Elem) bool, r chan<- Elem) {
+		defer close(r)
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case v, ok := <-c:
+				if !ok {
+					return
+				}
+				if f(v) {
+					r <- v
+				}
+			}
+		}
+	}(ctx, c, f, r)
+	return r
+}
+
+// _Sink returns a channel that discards all values sent to it.
+// This will leave a goroutine running until the context is canceled
+// or the returned channel is closed.
+func _Sink[Elem any](ctx context.Context) chan<- Elem {
+	r := make(chan Elem)
+	go func(ctx context.Context, r <-chan Elem) {
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case _, ok := <-r:
+				if !ok {
+					return
+				}
+			}
+		}
+	}(ctx, r)
+	return r
+}
+
+// An Exclusive is a value that may only be used by a single goroutine
+// at a time. This is implemented using channels rather than a mutex.
+type _Exclusive[Val any] struct {
+	c chan Val
+}
+
+// _MakeExclusive makes an initialized exclusive value.
+func _MakeExclusive[Val any](initial Val) *_Exclusive[Val] {
+	r := &_Exclusive[Val]{
+		c: make(chan Val, 1),
+	}
+	r.c <- initial
+	return r
+}
+
+// _Acquire acquires the exclusive value for private use.
+// It must be released using the Release method.
+func (e *_Exclusive[Val]) Acquire() Val {
+	return <-e.c
+}
+
+// TryAcquire attempts to acquire the value. The ok result reports whether
+// the value was acquired. If the value is acquired, it must be released
+// using the Release method.
+func (e *_Exclusive[Val]) TryAcquire() (v Val, ok bool) {
+	select {
+	case r := <-e.c:
+		return r, true
+	default:
+		return v, false
+	}
+}
+
+// Release updates and releases the value.
+// This method panics if the value has not been acquired.
+func (e *_Exclusive[Val]) Release(v Val) {
+	select {
+	case e.c <- v:
+	default:
+		panic("_Exclusive Release without Acquire")
+	}
+}
+
+// Ranger returns a Sender and a Receiver. The Receiver provides a
+// Next method to retrieve values. The Sender provides a Send method
+// to send values and a Close method to stop sending values. The Next
+// method indicates when the Sender has been closed, and the Send
+// method indicates when the Receiver has been freed.
+//
+// This is a convenient way to exit a goroutine sending values when
+// the receiver stops reading them.
+func _Ranger[Elem any]() (*_Sender[Elem], *_Receiver[Elem]) {
+	c := make(chan Elem)
+	d := make(chan struct{})
+	s := &_Sender[Elem]{
+		values: c,
+		done:   d,
+	}
+	r := &_Receiver[Elem]{
+		values: c,
+		done:   d,
+	}
+	runtime.SetFinalizer(r, (*_Receiver[Elem]).finalize)
+	return s, r
+}
+
+// A _Sender is used to send values to a Receiver.
+type _Sender[Elem any] struct {
+	values chan<- Elem
+	done   <-chan struct{}
+}
+
+// Send sends a value to the receiver. It reports whether the value was sent.
+// The value will not be sent if the context is closed or the receiver
+// is freed.
+func (s *_Sender[Elem]) Send(ctx context.Context, v Elem) bool {
+	select {
+	case <-ctx.Done():
+		return false
+	case s.values <- v:
+		return true
+	case <-s.done:
+		return false
+	}
+}
+
+// Close tells the receiver that no more values will arrive.
+// After Close is called, the _Sender may no longer be used.
+func (s *_Sender[Elem]) Close() {
+	close(s.values)
+}
+
+// A _Receiver receives values from a _Sender.
+type _Receiver[Elem any] struct {
+	values <-chan Elem
+	done   chan<- struct{}
+}
+
+// Next returns the next value from the channel. The bool result indicates
+// whether the value is valid.
+func (r *_Receiver[Elem]) Next(ctx context.Context) (v Elem, ok bool) {
+	select {
+	case <-ctx.Done():
+	case v, ok = <-r.values:
+	}
+	return v, ok
+}
+
+// finalize is a finalizer for the receiver.
+func (r *_Receiver[Elem]) finalize() {
+	close(r.done)
+}
+
+func TestReadAll() {
+	c := make(chan int)
+	go func() {
+		c <- 4
+		c <- 2
+		c <- 5
+		close(c)
+	}()
+	got := _ReadAll(context.Background(), c)
+	want := []int{4, 2, 5}
+	if !_SliceEqual(got, want) {
+		panic(fmt.Sprintf("_ReadAll returned %v, want %v", got, want))
+	}
+}
+
+func TestMerge() {
+	c1 := make(chan int)
+	c2 := make(chan int)
+	go func() {
+		c1 <- 1
+		c1 <- 3
+		c1 <- 5
+		close(c1)
+	}()
+	go func() {
+		c2 <- 2
+		c2 <- 4
+		c2 <- 6
+		close(c2)
+	}()
+	ctx := context.Background()
+	got := _ReadAll(ctx, _Merge(ctx, c1, c2))
+	sort.Ints(got)
+	want := []int{1, 2, 3, 4, 5, 6}
+	if !_SliceEqual(got, want) {
+		panic(fmt.Sprintf("_Merge returned %v, want %v", got, want))
+	}
+}
+
+func TestFilter() {
+	c := make(chan int)
+	go func() {
+		c <- 1
+		c <- 2
+		c <- 3
+		close(c)
+	}()
+	even := func(i int) bool { return i%2 == 0 }
+	ctx := context.Background()
+	got := _ReadAll(ctx, _Filter(ctx, c, even))
+	want := []int{2}
+	if !_SliceEqual(got, want) {
+		panic(fmt.Sprintf("_Filter returned %v, want %v", got, want))
+	}
+}
+
+func TestSink() {
+	c := _Sink[int](context.Background())
+	after := time.NewTimer(time.Minute)
+	defer after.Stop()
+	send := func(v int) {
+		select {
+		case c <- v:
+		case <-after.C:
+			panic("timed out sending to _Sink")
+		}
+	}
+	send(1)
+	send(2)
+	send(3)
+	close(c)
+}
+
+func TestExclusive() {
+	val := 0
+	ex := _MakeExclusive(&val)
+
+	var wg sync.WaitGroup
+	f := func() {
+		defer wg.Done()
+		for i := 0; i < 10; i++ {
+			p := ex.Acquire()
+			(*p)++
+			ex.Release(p)
+		}
+	}
+
+	wg.Add(2)
+	go f()
+	go f()
+
+	wg.Wait()
+	if val != 20 {
+		panic(fmt.Sprintf("after Acquire/Release loop got %d, want 20", val))
+	}
+}
+
+func TestExclusiveTry() {
+	s := ""
+	ex := _MakeExclusive(&s)
+	p, ok := ex.TryAcquire()
+	if !ok {
+		panic("TryAcquire failed")
+	}
+	*p = "a"
+
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		_, ok := ex.TryAcquire()
+		if ok {
+			panic(fmt.Sprintf("TryAcquire succeeded unexpectedly"))
+		}
+	}()
+	wg.Wait()
+
+	ex.Release(p)
+
+	p, ok = ex.TryAcquire()
+	if !ok {
+		panic(fmt.Sprintf("TryAcquire failed"))
+	}
+}
+
+func TestRanger() {
+	s, r := _Ranger[int]()
+
+	ctx := context.Background()
+	go func() {
+		// Receive one value then exit.
+		v, ok := r.Next(ctx)
+		if !ok {
+			panic(fmt.Sprintf("did not receive any values"))
+		} else if v != 1 {
+			panic(fmt.Sprintf("received %d, want 1", v))
+		}
+	}()
+
+	c1 := make(chan bool)
+	c2 := make(chan bool)
+	go func() {
+		defer close(c2)
+		if !s.Send(ctx, 1) {
+			panic(fmt.Sprintf("Send failed unexpectedly"))
+		}
+		close(c1)
+		if s.Send(ctx, 2) {
+			panic(fmt.Sprintf("Send succeeded unexpectedly"))
+		}
+	}()
+
+	<-c1
+
+	// Force a garbage collection to try to get the finalizers to run.
+	runtime.GC()
+
+	select {
+	case <-c2:
+	case <-time.After(time.Minute):
+		panic("_Ranger Send should have failed, but timed out")
+	}
+}
+
+func main() {
+	TestReadAll()
+	TestMerge()
+	TestFilter()
+	TestSink()
+	TestExclusive()
+	TestExclusiveTry()
+	TestRanger()
+}

test/typeparam/chansimp.dir/a.go

@@ -0,0 +1,232 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+import (
+	"context"
+	"runtime"
+)
+
+// Equal reports whether two slices are equal: the same length and all
+// elements equal. All floating point NaNs are considered equal.
+func SliceEqual[Elem comparable](s1, s2 []Elem) bool {
+	if len(s1) != len(s2) {
+		return false
+	}
+	for i, v1 := range s1 {
+		v2 := s2[i]
+		if v1 != v2 {
+			isNaN := func(f Elem) bool { return f != f }
+			if !isNaN(v1) || !isNaN(v2) {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+// ReadAll reads from c until the channel is closed or the context is
+// canceled, returning all the values read.
+func ReadAll[Elem any](ctx context.Context, c <-chan Elem) []Elem {
+	var r []Elem
+	for {
+		select {
+		case <-ctx.Done():
+			return r
+		case v, ok := <-c:
+			if !ok {
+				return r
+			}
+			r = append(r, v)
+		}
+	}
+}
+
+// Merge merges two channels into a single channel.
+// This will leave a goroutine running until either both channels are closed
+// or the context is canceled, at which point the returned channel is closed.
+func Merge[Elem any](ctx context.Context, c1, c2 <-chan Elem) <-chan Elem {
+	r := make(chan Elem)
+	go func(ctx context.Context, c1, c2 <-chan Elem, r chan<- Elem) {
+		defer close(r)
+		for c1 != nil || c2 != nil {
+			select {
+			case <-ctx.Done():
+				return
+			case v1, ok := <-c1:
+				if ok {
+					r <- v1
+				} else {
+					c1 = nil
+				}
+			case v2, ok := <-c2:
+				if ok {
+					r <- v2
+				} else {
+					c2 = nil
+				}
+			}
+		}
+	}(ctx, c1, c2, r)
+	return r
+}
+
+// Filter calls f on each value read from c. If f returns true the value
+// is sent on the returned channel. This will leave a goroutine running
+// until c is closed or the context is canceled, at which point the
+// returned channel is closed.
+func Filter[Elem any](ctx context.Context, c <-chan Elem, f func(Elem) bool) <-chan Elem {
+	r := make(chan Elem)
+	go func(ctx context.Context, c <-chan Elem, f func(Elem) bool, r chan<- Elem) {
+		defer close(r)
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case v, ok := <-c:
+				if !ok {
+					return
+				}
+				if f(v) {
+					r <- v
+				}
+			}
+		}
+	}(ctx, c, f, r)
+	return r
+}
+
+// Sink returns a channel that discards all values sent to it.
+// This will leave a goroutine running until the context is canceled
+// or the returned channel is closed.
+func Sink[Elem any](ctx context.Context) chan<- Elem {
+	r := make(chan Elem)
+	go func(ctx context.Context, r <-chan Elem) {
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case _, ok := <-r:
+				if !ok {
+					return
+				}
+			}
+		}
+	}(ctx, r)
+	return r
+}
+
+// An Exclusive is a value that may only be used by a single goroutine
+// at a time. This is implemented using channels rather than a mutex.
+type Exclusive[Val any] struct {
+	c chan Val
+}
+
+// MakeExclusive makes an initialized exclusive value.
+func MakeExclusive[Val any](initial Val) *Exclusive[Val] {
+	r := &Exclusive[Val]{
+		c: make(chan Val, 1),
+	}
+	r.c <- initial
+	return r
+}
+
+// Acquire acquires the exclusive value for private use.
+// It must be released using the Release method.
+func (e *Exclusive[Val]) Acquire() Val {
+	return <-e.c
+}
+
+// TryAcquire attempts to acquire the value. The ok result reports whether
+// the value was acquired. If the value is acquired, it must be released
+// using the Release method.
+func (e *Exclusive[Val]) TryAcquire() (v Val, ok bool) {
+	select {
+	case r := <-e.c:
+		return r, true
+	default:
+		return v, false
+	}
+}
+
+// Release updates and releases the value.
+// This method panics if the value has not been acquired.
+func (e *Exclusive[Val]) Release(v Val) {
+	select {
+	case e.c <- v:
+	default:
+		panic("Exclusive Release without Acquire")
+	}
+}
+
+// Ranger returns a Sender and a Receiver. The Receiver provides a
+// Next method to retrieve values. The Sender provides a Send method
+// to send values and a Close method to stop sending values. The Next
+// method indicates when the Sender has been closed, and the Send
+// method indicates when the Receiver has been freed.
+//
+// This is a convenient way to exit a goroutine sending values when
+// the receiver stops reading them.
+func Ranger[Elem any]() (*Sender[Elem], *Receiver[Elem]) {
+	c := make(chan Elem)
+	d := make(chan struct{})
+	s := &Sender[Elem]{
+		values: c,
+		done:   d,
+	}
+	r := &Receiver[Elem]{
+		values: c,
+		done:   d,
+	}
+	runtime.SetFinalizer(r, (*Receiver[Elem]).finalize)
+	return s, r
+}
+
+// A Sender is used to send values to a Receiver.
+type Sender[Elem any] struct {
+	values chan<- Elem
+	done   <-chan struct{}
+}
+
+// Send sends a value to the receiver. It reports whether the value was sent.
+// The value will not be sent if the context is closed or the receiver
+// is freed.
+func (s *Sender[Elem]) Send(ctx context.Context, v Elem) bool {
+	select {
+	case <-ctx.Done():
+		return false
+	case s.values <- v:
+		return true
+	case <-s.done:
+		return false
+	}
+}
+
+// Close tells the receiver that no more values will arrive.
+// After Close is called, the Sender may no longer be used.
+func (s *Sender[Elem]) Close() {
+	close(s.values)
+}
+
+// A Receiver receives values from a Sender.
+type Receiver[Elem any] struct {
+	values <-chan Elem
+	done   chan<- struct{}
+}
+
+// Next returns the next value from the channel. The bool result indicates
+// whether the value is valid.
+func (r *Receiver[Elem]) Next(ctx context.Context) (v Elem, ok bool) {
+	select {
+	case <-ctx.Done():
+	case v, ok = <-r.values:
+	}
+	return v, ok
+}
+
+// finalize is a finalizer for the receiver.
+func (r *Receiver[Elem]) finalize() {
+	close(r.done)
+}

test/typeparam/chansimp.dir/main.go

@@ -0,0 +1,189 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"./a"
+	"context"
+	"fmt"
+	"runtime"
+	"sort"
+	"sync"
+	"time"
+)
+
+func TestReadAll() {
+	c := make(chan int)
+	go func() {
+		c <- 4
+		c <- 2
+		c <- 5
+		close(c)
+	}()
+	got := a.ReadAll(context.Background(), c)
+	want := []int{4, 2, 5}
+	if !a.SliceEqual(got, want) {
+		panic(fmt.Sprintf("ReadAll returned %v, want %v", got, want))
+	}
+}
+
+func TestMerge() {
+	c1 := make(chan int)
+	c2 := make(chan int)
+	go func() {
+		c1 <- 1
+		c1 <- 3
+		c1 <- 5
+		close(c1)
+	}()
+	go func() {
+		c2 <- 2
+		c2 <- 4
+		c2 <- 6
+		close(c2)
+	}()
+	ctx := context.Background()
+	got := a.ReadAll(ctx, a.Merge(ctx, c1, c2))
+	sort.Ints(got)
+	want := []int{1, 2, 3, 4, 5, 6}
+	if !a.SliceEqual(got, want) {
+		panic(fmt.Sprintf("Merge returned %v, want %v", got, want))
+	}
+}
+
+func TestFilter() {
+	c := make(chan int)
+	go func() {
+		c <- 1
+		c <- 2
+		c <- 3
+		close(c)
+	}()
+	even := func(i int) bool { return i%2 == 0 }
+	ctx := context.Background()
+	got := a.ReadAll(ctx, a.Filter(ctx, c, even))
+	want := []int{2}
+	if !a.SliceEqual(got, want) {
+		panic(fmt.Sprintf("Filter returned %v, want %v", got, want))
+	}
+}
+
+func TestSink() {
+	c := a.Sink[int](context.Background())
+	after := time.NewTimer(time.Minute)
+	defer after.Stop()
+	send := func(v int) {
+		select {
+		case c <- v:
+		case <-after.C:
+			panic("timed out sending to Sink")
+		}
+	}
+	send(1)
+	send(2)
+	send(3)
+	close(c)
+}
+
+func TestExclusive() {
+	val := 0
+	ex := a.MakeExclusive(&val)
+
+	var wg sync.WaitGroup
+	f := func() {
+		defer wg.Done()
+		for i := 0; i < 10; i++ {
+			p := ex.Acquire()
+			(*p)++
+			ex.Release(p)
+		}
+	}
+
+	wg.Add(2)
+	go f()
+	go f()
+
+	wg.Wait()
+	if val != 20 {
+		panic(fmt.Sprintf("after Acquire/Release loop got %d, want 20", val))
+	}
+}
+
+func TestExclusiveTry() {
+	s := ""
+	ex := a.MakeExclusive(&s)
+	p, ok := ex.TryAcquire()
+	if !ok {
+		panic("TryAcquire failed")
+	}
+	*p = "a"
+
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		_, ok := ex.TryAcquire()
+		if ok {
+			panic(fmt.Sprintf("TryAcquire succeeded unexpectedly"))
+		}
+	}()
+	wg.Wait()
+
+	ex.Release(p)
+
+	p, ok = ex.TryAcquire()
+	if !ok {
+		panic(fmt.Sprintf("TryAcquire failed"))
+	}
+}
+
+func TestRanger() {
+	s, r := a.Ranger[int]()
+
+	ctx := context.Background()
+	go func() {
+		// Receive one value then exit.
+		v, ok := r.Next(ctx)
+		if !ok {
+			panic(fmt.Sprintf("did not receive any values"))
+		} else if v != 1 {
+			panic(fmt.Sprintf("received %d, want 1", v))
+		}
+	}()
+
+	c1 := make(chan bool)
+	c2 := make(chan bool)
+	go func() {
+		defer close(c2)
+		if !s.Send(ctx, 1) {
+			panic(fmt.Sprintf("Send failed unexpectedly"))
+		}
+		close(c1)
+		if s.Send(ctx, 2) {
+			panic(fmt.Sprintf("Send succeeded unexpectedly"))
+		}
+	}()
+
+	<-c1
+
+	// Force a garbage collection to try to get the finalizers to run.
+	runtime.GC()
+
+	select {
+	case <-c2:
+	case <-time.After(time.Minute):
+		panic("Ranger Send should have failed, but timed out")
+	}
+}
+
+func main() {
+	TestReadAll()
+	TestMerge()
+	TestFilter()
+	TestSink()
+	TestExclusive()
+	TestExclusiveTry()
+	TestRanger()
+}

test/typeparam/chansimp.go

@@ -0,0 +1,7 @@
+// rundir
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ignored

test/typeparam/combine.go

@@ -0,0 +1,65 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"fmt"
+)
+
+type Gen[A any] func() (A, bool)
+
+func Combine[T1, T2, T any](g1 Gen[T1], g2 Gen[T2], join func(T1, T2) T) Gen[T] {
+	return func() (T, bool) {
+		var t T
+		t1, ok := g1()
+		if !ok {
+			return t, false
+		}
+		t2, ok := g2()
+		if !ok {
+			return t, false
+		}
+		return join(t1, t2), true
+	}
+}
+
+type Pair[A, B any] struct {
+	A A
+	B B
+}
+
+func _NewPair[A, B any](a A, b B) Pair[A, B] {
+	return Pair[A, B]{a, b}
+}
+
+func Combine2[A, B any](ga Gen[A], gb Gen[B]) Gen[Pair[A, B]] {
+	return Combine(ga, gb, _NewPair[A, B])
+}
+
+func main() {
+	var g1 Gen[int] = func() (int, bool) { return 3, true }
+	var g2 Gen[string] = func() (string, bool) { return "x", false }
+	var g3 Gen[string] = func() (string, bool) { return "y", true }
+
+	gc := Combine(g1, g2, _NewPair[int, string])
+	if got, ok := gc(); ok {
+		panic(fmt.Sprintf("got %v, %v, wanted -/false", got, ok))
+	}
+	gc2 := Combine2(g1, g2)
+	if got, ok := gc2(); ok {
+		panic(fmt.Sprintf("got %v, %v, wanted -/false", got, ok))
+	}
+
+	gc3 := Combine(g1, g3, _NewPair[int, string])
+	if got, ok := gc3(); !ok || got.A != 3 || got.B != "y" {
+		panic(fmt.Sprintf("got %v, %v, wanted {3, y}, true", got, ok))
+	}
+	gc4 := Combine2(g1, g3)
+	if got, ok := gc4(); !ok || got.A != 3 || got.B != "y" {
+		panic(fmt.Sprintf("got %v, %v, wanted {3, y}, true", got, ok))
+	}
+}

test/typeparam/cons.go

@@ -0,0 +1,100 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "fmt"
+
+// Overriding the predeclare "any", so it can be used as a type constraint or a type
+// argument
+type any interface{}
+
+type Function[a, b any] interface {
+	Apply(x a) b
+}
+
+type incr struct{ n int }
+
+func (this incr) Apply(x int) int {
+	return x + this.n
+}
+
+type pos struct{}
+
+func (this pos) Apply(x int) bool {
+	return x > 0
+}
+
+type compose[a, b, c any] struct {
+	f Function[a, b]
+	g Function[b, c]
+}
+
+func (this compose[a, b, c]) Apply(x a) c {
+	return this.g.Apply(this.f.Apply(x))
+}
+
+type _Eq[a any] interface {
+	Equal(a) bool
+}
+
+type Int int
+
+func (this Int) Equal(that int) bool {
+	return int(this) == that
+}
+
+type List[a any] interface {
+	Match(casenil Function[Nil[a], any], casecons Function[Cons[a], any]) any
+}
+
+type Nil[a any] struct {
+}
+
+func (xs Nil[a]) Match(casenil Function[Nil[a], any], casecons Function[Cons[a], any]) any {
+	return casenil.Apply(xs)
+}
+
+type Cons[a any] struct {
+	Head a
+	Tail List[a]
+}
+
+func (xs Cons[a]) Match(casenil Function[Nil[a], any], casecons Function[Cons[a], any]) any {
+	return casecons.Apply(xs)
+}
+
+type mapNil[a, b any] struct {
+}
+
+func (m mapNil[a, b]) Apply(_ Nil[a]) any {
+	return Nil[b]{}
+}
+
+type mapCons[a, b any] struct {
+	f Function[a, b]
+}
+
+func (m mapCons[a, b]) Apply(xs Cons[a]) any {
+	return Cons[b]{m.f.Apply(xs.Head), Map[a, b](m.f, xs.Tail)}
+}
+
+func Map[a, b any](f Function[a, b], xs List[a]) List[b] {
+	return xs.Match(mapNil[a, b]{}, mapCons[a, b]{f}).(List[b])
+}
+
+func main() {
+	var xs List[int] = Cons[int]{3, Cons[int]{6, Nil[int]{}}}
+	var ys List[int] = Map[int, int](incr{-5}, xs)
+	var xz List[bool] = Map[int, bool](pos{}, ys)
+	cs1 := xz.(Cons[bool])
+	cs2 := cs1.Tail.(Cons[bool])
+	_, ok := cs2.Tail.(Nil[bool])
+	if cs1.Head != false || cs2.Head != true || !ok {
+		panic(fmt.Sprintf("got %v, %v, %v, expected false, true, true",
+			cs1.Head, cs2.Head, ok))
+	}
+}

test/typeparam/dedup.dir/a.go

@@ -0,0 +1,10 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+//go:noinline
+func F[T comparable](a, b T) bool {
+	return a == b
+}

test/typeparam/dedup.dir/b.go

@@ -0,0 +1,14 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package b
+
+import "./a"
+
+func B() {
+	var x int64
+	println(a.F(&x, &x))
+	var y int32
+	println(a.F(&y, &y))
+}

test/typeparam/dedup.dir/c.go

@@ -0,0 +1,14 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package c
+
+import "./a"
+
+func C() {
+	var x int64
+	println(a.F(&x, &x))
+	var y int32
+	println(a.F(&y, &y))
+}

test/typeparam/dedup.dir/main.go

@@ -0,0 +1,15 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"./b"
+	"./c"
+)
+
+func main() {
+	b.B()
+	c.C()
+}

test/typeparam/dedup.go

@@ -0,0 +1,12 @@
+// rundir
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Note: this doesn't really test the deduplication of
+// instantiations. It just provides an easy mechanism to build a
+// binary that you can then check with objdump manually to make sure
+// deduplication is happening. TODO: automate this somehow?
+
+package ignored

test/typeparam/dedup.out

@@ -0,0 +1,4 @@
+true
+true
+true
+true

test/typeparam/devirtualize1.go

@@ -0,0 +1,22 @@
+// run
+
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type S struct {
+	x int
+}
+
+func (t *S) M1() {
+}
+
+func F[T any](x T) any {
+	return x
+}
+
+func main() {
+	F(&S{}).(interface{ M1() }).M1()
+}

test/typeparam/devirtualize2.go

@@ -0,0 +1,28 @@
+// run
+
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type S struct {
+	x int
+}
+
+func (t *S) M1() {
+}
+func (t *S) M2() {
+}
+
+type I interface {
+	M1()
+}
+
+func F[T I](x T) I {
+	return x
+}
+
+func main() {
+	F(&S{}).(interface{ M2() }).M2()
+}

test/typeparam/dictionaryCapture-noinline.go

@@ -0,0 +1,126 @@
+// run -gcflags="-l"
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test situations where functions/methods are not
+// immediately called and we need to capture the dictionary
+// required for later invocation.
+
+package main
+
+func main() {
+	functions()
+	methodExpressions()
+	methodValues()
+	interfaceMethods()
+	globals()
+}
+
+func g0[T any](x T) {
+}
+func g1[T any](x T) T {
+	return x
+}
+func g2[T any](x T) (T, T) {
+	return x, x
+}
+
+func functions() {
+	f0 := g0[int]
+	f0(7)
+	f1 := g1[int]
+	is7(f1(7))
+	f2 := g2[int]
+	is77(f2(7))
+}
+
+func is7(x int) {
+	if x != 7 {
+		println(x)
+		panic("assertion failed")
+	}
+}
+func is77(x, y int) {
+	if x != 7 || y != 7 {
+		println(x, y)
+		panic("assertion failed")
+	}
+}
+
+type s[T any] struct {
+	a T
+}
+
+func (x s[T]) g0() {
+}
+func (x s[T]) g1() T {
+	return x.a
+}
+func (x s[T]) g2() (T, T) {
+	return x.a, x.a
+}
+
+func methodExpressions() {
+	x := s[int]{a: 7}
+	f0 := s[int].g0
+	f0(x)
+	f1 := s[int].g1
+	is7(f1(x))
+	f2 := s[int].g2
+	is77(f2(x))
+}
+
+func methodValues() {
+	x := s[int]{a: 7}
+	f0 := x.g0
+	f0()
+	f1 := x.g1
+	is7(f1())
+	f2 := x.g2
+	is77(f2())
+}
+
+var x interface {
+	g0()
+	g1() int
+	g2() (int, int)
+} = s[int]{a: 7}
+var y interface{} = s[int]{a: 7}
+
+func interfaceMethods() {
+	x.g0()
+	is7(x.g1())
+	is77(x.g2())
+	y.(interface{ g0() }).g0()
+	is7(y.(interface{ g1() int }).g1())
+	is77(y.(interface{ g2() (int, int) }).g2())
+}
+
+// Also check for instantiations outside functions.
+var gg0 = g0[int]
+var gg1 = g1[int]
+var gg2 = g2[int]
+
+var hh0 = s[int].g0
+var hh1 = s[int].g1
+var hh2 = s[int].g2
+
+var xtop = s[int]{a: 7}
+var ii0 = x.g0
+var ii1 = x.g1
+var ii2 = x.g2
+
+func globals() {
+	gg0(7)
+	is7(gg1(7))
+	is77(gg2(7))
+	x := s[int]{a: 7}
+	hh0(x)
+	is7(hh1(x))
+	is77(hh2(x))
+	ii0()
+	is7(ii1())
+	is77(ii2())
+}

test/typeparam/dictionaryCapture.go

@@ -0,0 +1,203 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test situations where functions/methods are not
+// immediately called and we need to capture the dictionary
+// required for later invocation.
+
+package main
+
+import (
+	"fmt"
+)
+
+func main() {
+	functions()
+	methodExpressions()
+	genMethodExpressions[int](7)
+	methodValues()
+	genMethodValues[int](7)
+	interfaceMethods()
+	globals()
+	recursive()
+}
+
+func g0[T any](x T) {
+}
+func g1[T any](x T) T {
+	return x
+}
+func g2[T any](x T) (T, T) {
+	return x, x
+}
+
+func functions() {
+	f0 := g0[int]
+	f0(7)
+	f1 := g1[int]
+	is7(f1(7))
+	f2 := g2[int]
+	is77(f2(7))
+}
+
+func is7(x int) {
+	if x != 7 {
+		println(x)
+		panic("assertion failed")
+	}
+}
+func is77(x, y int) {
+	if x != 7 || y != 7 {
+		println(x, y)
+		panic("assertion failed")
+	}
+}
+
+type s[T any] struct {
+	a T
+}
+
+func (x s[T]) g0() {
+}
+func (x s[T]) g1() T {
+	return x.a
+}
+func (x s[T]) g2() (T, T) {
+	return x.a, x.a
+}
+
+func methodExpressions() {
+	x := s[int]{a: 7}
+	f0 := s[int].g0
+	f0(x)
+	f0p := (*s[int]).g0
+	f0p(&x)
+	f1 := s[int].g1
+	is7(f1(x))
+	f1p := (*s[int]).g1
+	is7(f1p(&x))
+	f2 := s[int].g2
+	is77(f2(x))
+	f2p := (*s[int]).g2
+	is77(f2p(&x))
+}
+
+func genMethodExpressions[T comparable](want T) {
+	x := s[T]{a: want}
+	f0 := s[T].g0
+	f0(x)
+	f0p := (*s[T]).g0
+	f0p(&x)
+	f1 := s[T].g1
+	if got := f1(x); got != want {
+		panic(fmt.Sprintf("f1(x) == %d, want %d", got, want))
+	}
+	f1p := (*s[T]).g1
+	if got := f1p(&x); got != want {
+		panic(fmt.Sprintf("f1p(&x) == %d, want %d", got, want))
+	}
+	f2 := s[T].g2
+	if got1, got2 := f2(x); got1 != want || got2 != want {
+		panic(fmt.Sprintf("f2(x) == %d, %d, want %d, %d", got1, got2, want, want))
+	}
+}
+
+func methodValues() {
+	x := s[int]{a: 7}
+	f0 := x.g0
+	f0()
+	f1 := x.g1
+	is7(f1())
+	f2 := x.g2
+	is77(f2())
+}
+
+func genMethodValues[T comparable](want T) {
+	x := s[T]{a: want}
+	f0 := x.g0
+	f0()
+	f1 := x.g1
+	if got := f1(); got != want {
+		panic(fmt.Sprintf("f1() == %d, want %d", got, want))
+	}
+	f2 := x.g2
+	if got1, got2 := f2(); got1 != want || got2 != want {
+		panic(fmt.Sprintf("f2() == %d, %d, want %d, %d", got1, got2, want, want))
+	}
+}
+
+var x interface {
+	g0()
+	g1() int
+	g2() (int, int)
+} = s[int]{a: 7}
+var y interface{} = s[int]{a: 7}
+
+func interfaceMethods() {
+	x.g0()
+	is7(x.g1())
+	is77(x.g2())
+	y.(interface{ g0() }).g0()
+	is7(y.(interface{ g1() int }).g1())
+	is77(y.(interface{ g2() (int, int) }).g2())
+}
+
+// Also check for instantiations outside functions.
+var gg0 = g0[int]
+var gg1 = g1[int]
+var gg2 = g2[int]
+
+var hh0 = s[int].g0
+var hh1 = s[int].g1
+var hh2 = s[int].g2
+
+var xtop = s[int]{a: 7}
+var ii0 = x.g0
+var ii1 = x.g1
+var ii2 = x.g2
+
+func globals() {
+	gg0(7)
+	is7(gg1(7))
+	is77(gg2(7))
+	x := s[int]{a: 7}
+	hh0(x)
+	is7(hh1(x))
+	is77(hh2(x))
+	ii0()
+	is7(ii1())
+	is77(ii2())
+}
+
+func recursive() {
+	if got, want := recur1[int](5), 110; got != want {
+		panic(fmt.Sprintf("recur1[int](5) = %d, want = %d", got, want))
+	}
+}
+
+type Integer interface {
+	int | int32 | int64
+}
+
+func recur1[T Integer](n T) T {
+	if n == 0 || n == 1 {
+		return T(1)
+	} else {
+		return n * recur2(n-1)
+	}
+}
+
+func recur2[T Integer](n T) T {
+	list := make([]T, n)
+	for i, _ := range list {
+		list[i] = T(i + 1)
+	}
+	var sum T
+	for _, elt := range list {
+		sum += elt
+	}
+	return sum + recur1(n-1)
+}

test/typeparam/dottype.go

@@ -0,0 +1,86 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func f[T any](x interface{}) T {
+	return x.(T)
+}
+func f2[T any](x interface{}) (T, bool) {
+	t, ok := x.(T)
+	return t, ok
+}
+
+type I interface {
+	foo()
+}
+
+type myint int
+
+func (myint) foo() {
+}
+
+type myfloat float64
+
+func (myfloat) foo() {
+}
+
+func g[T I](x I) T {
+	return x.(T)
+}
+func g2[T I](x I) (T, bool) {
+	t, ok := x.(T)
+	return t, ok
+}
+
+func h[T any](x interface{}) struct{ a, b T } {
+	return x.(struct{ a, b T })
+}
+
+func k[T any](x interface{}) interface{ bar() T } {
+	return x.(interface{ bar() T })
+}
+
+type mybar int
+
+func (x mybar) bar() int {
+	return int(x)
+}
+
+func main() {
+	var i interface{} = int(3)
+	var j I = myint(3)
+	var x interface{} = float64(3)
+	var y I = myfloat(3)
+
+	println(f[int](i))
+	shouldpanic(func() { f[int](x) })
+	println(f2[int](i))
+	println(f2[int](x))
+
+	println(g[myint](j))
+	shouldpanic(func() { g[myint](y) })
+	println(g2[myint](j))
+	println(g2[myint](y))
+
+	println(h[int](struct{ a, b int }{3, 5}).a)
+
+	println(k[int](mybar(3)).bar())
+
+	type large struct {a,b,c,d,e,f int}
+	println(f[large](large{}).a)
+	l2, ok := f2[large](large{})
+	println(l2.a, ok)
+}
+func shouldpanic(x func()) {
+	defer func() {
+		e := recover()
+		if e == nil {
+			panic("didn't panic")
+		}
+	}()
+	x()
+}

test/typeparam/dottype.out

@@ -0,0 +1,10 @@
+3
+3 true
+0 false
+3
+3 true
+0 false
+3
+3
+0
+0 true

test/typeparam/double.go

@@ -0,0 +1,72 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"fmt"
+	"reflect"
+)
+
+type Number interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64 | ~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr | ~float32 | ~float64
+}
+
+type MySlice []int
+type MyFloatSlice []float64
+
+type _SliceOf[E any] interface {
+	~[]E
+}
+
+func _DoubleElems[S _SliceOf[E], E Number](s S) S {
+	r := make(S, len(s))
+	for i, v := range s {
+		r[i] = v + v
+	}
+	return r
+}
+
+// Test use of untyped constant in an expression with a generically-typed parameter
+func _DoubleElems2[S _SliceOf[E], E Number](s S) S {
+	r := make(S, len(s))
+	for i, v := range s {
+		r[i] = v * 2
+	}
+	return r
+}
+
+func main() {
+	arg := MySlice{1, 2, 3}
+	want := MySlice{2, 4, 6}
+	got := _DoubleElems[MySlice, int](arg)
+	if !reflect.DeepEqual(got, want) {
+		panic(fmt.Sprintf("got %s, want %s", got, want))
+	}
+
+	// constraint type inference
+	got = _DoubleElems[MySlice](arg)
+	if !reflect.DeepEqual(got, want) {
+		panic(fmt.Sprintf("got %s, want %s", got, want))
+	}
+
+	got = _DoubleElems(arg)
+	if !reflect.DeepEqual(got, want) {
+		panic(fmt.Sprintf("got %s, want %s", got, want))
+	}
+
+	farg := MyFloatSlice{1.2, 2.0, 3.5}
+	fwant := MyFloatSlice{2.4, 4.0, 7.0}
+	fgot := _DoubleElems(farg)
+	if !reflect.DeepEqual(fgot, fwant) {
+		panic(fmt.Sprintf("got %s, want %s", fgot, fwant))
+	}
+
+	fgot = _DoubleElems2(farg)
+	if !reflect.DeepEqual(fgot, fwant) {
+		panic(fmt.Sprintf("got %s, want %s", fgot, fwant))
+	}
+}

test/typeparam/eface.go

@@ -0,0 +1,67 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Make sure we handle instantiated empty interfaces.
+
+package main
+
+type E[T any] interface {
+}
+
+//go:noinline
+func f[T any](x E[T]) interface{} {
+	return x
+}
+
+//go:noinline
+func g[T any](x interface{}) E[T] {
+	return x
+}
+
+type I[T any] interface {
+	foo()
+}
+
+type myint int
+
+func (x myint) foo() {}
+
+//go:noinline
+func h[T any](x I[T]) interface{ foo() } {
+	return x
+}
+
+//go:noinline
+func i[T any](x interface{ foo() }) I[T] {
+	return x
+}
+
+func main() {
+	if f[int](1) != 1 {
+		println("test 1 failed")
+	}
+	if f[int](2) != (interface{})(2) {
+		println("test 2 failed")
+	}
+	if g[int](3) != 3 {
+		println("test 3 failed")
+	}
+	if g[int](4) != (E[int])(4) {
+		println("test 4 failed")
+	}
+	if h[int](myint(5)) != myint(5) {
+		println("test 5 failed")
+	}
+	if h[int](myint(6)) != interface{ foo() }(myint(6)) {
+		println("test 6 failed")
+	}
+	if i[int](myint(7)) != myint(7) {
+		println("test 7 failed")
+	}
+	if i[int](myint(8)) != I[int](myint(8)) {
+		println("test 8 failed")
+	}
+}

test/typeparam/equal.go

@@ -0,0 +1,69 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// comparisons of type parameters to interfaces
+
+package main
+
+func f[T comparable](t, u T) bool {
+	// Comparing two type parameters directly.
+	// (Not really testing comparisons to interfaces, but just 'cause we're here.)
+	return t == u
+}
+
+func g[T comparable](t T, i interface{}) bool {
+	// Compare type parameter value to empty interface.
+	return t == i
+}
+
+type I interface {
+	foo()
+}
+
+type C interface {
+	comparable
+	I
+}
+
+func h[T C](t T, i I) bool {
+	// Compare type parameter value to nonempty interface.
+	return t == i
+}
+
+type myint int
+
+func (x myint) foo() {
+}
+
+func k[T comparable](t T, i interface{}) bool {
+	// Compare derived type value to interface.
+	return struct{ a, b T }{t, t} == i
+}
+
+func main() {
+	assert(f(3, 3))
+	assert(!f(3, 5))
+	assert(g(3, 3))
+	assert(!g(3, 5))
+	assert(h(myint(3), myint(3)))
+	assert(!h(myint(3), myint(5)))
+
+	type S struct{ a, b float64 }
+
+	assert(f(S{3, 5}, S{3, 5}))
+	assert(!f(S{3, 5}, S{4, 6}))
+	assert(g(S{3, 5}, S{3, 5}))
+	assert(!g(S{3, 5}, S{4, 6}))
+
+	assert(k(3, struct{ a, b int }{3, 3}))
+	assert(!k(3, struct{ a, b int }{3, 4}))
+}
+
+func assert(b bool) {
+	if !b {
+		panic("assertion failed")
+	}
+}

test/typeparam/fact.go

@@ -0,0 +1,32 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "fmt"
+
+func fact[T interface{ ~int | ~int64 | ~float64 }](n T) T {
+	if n == 1 {
+		return 1
+	}
+	return n * fact(n-1)
+}
+
+func main() {
+	const want = 120
+
+	if got := fact(5); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+
+	if got := fact[int64](5); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+
+	if got := fact(5.0); got != want {
+		panic(fmt.Sprintf("got %f, want %f", got, want))
+	}
+}

test/typeparam/factimp.dir/a.go

@@ -0,0 +1,12 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+func Fact[T interface{ int | int64 | float64 }](n T) T {
+	if n == 1 {
+		return 1
+	}
+	return n * Fact(n-1)
+}

test/typeparam/factimp.dir/main.go

@@ -0,0 +1,26 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"./a"
+	"fmt"
+)
+
+func main() {
+	const want = 120
+
+	if got := a.Fact(5); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+
+	if got := a.Fact[int64](5); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+
+	if got := a.Fact(5.0); got != want {
+		panic(fmt.Sprintf("got %f, want %f", got, want))
+	}
+}

test/typeparam/factimp.go

@@ -0,0 +1,7 @@
+// rundir
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ignored

test/typeparam/gencrawler.dir/a.go

@@ -0,0 +1,27 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+var V val[int]
+
+type val[T any] struct {
+	valx T
+}
+
+func (v *val[T]) Print() {
+	v.print1()
+}
+
+func (v *val[T]) print1() {
+	println(v.valx)
+}
+
+func (v *val[T]) fnprint1() {
+	println(v.valx)
+}
+
+func FnPrint[T any](v *val[T]) {
+	v.fnprint1()
+}

test/typeparam/gencrawler.dir/main.go

@@ -0,0 +1,12 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "./a"
+
+func main() {
+	a.V.Print()
+	a.FnPrint(&a.V)
+}

test/typeparam/gencrawler.go

@@ -0,0 +1,10 @@
+// rundir
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Testing that all methods of a private generic type are exported, if a variable
+// with that type is exported.
+
+package ignored

test/typeparam/gencrawler.out

@@ -0,0 +1,2 @@
+0
+0

test/typeparam/genembed.go

@@ -0,0 +1,52 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test wrappers/interfaces for generic type embedding another generic type.
+
+package main
+
+import "fmt"
+
+type A[T any] struct {
+	B[T]
+}
+
+type B[T any] struct {
+	val T
+}
+
+func (b *B[T]) get() T {
+	return b.val
+}
+
+type getter[T any] interface {
+	get() T
+}
+
+//go:noinline
+func doGet[T any](i getter[T]) T {
+	return i.get()
+}
+
+//go:noline
+func doGet2[T any](i interface{}) T {
+	i2 := i.(getter[T])
+	return i2.get()
+}
+
+func main() {
+	a := A[int]{B: B[int]{3}}
+	var i getter[int] = &a
+
+	if got, want := doGet(i), 3; got != want {
+		panic(fmt.Sprintf("got %v, want %v", got, want))
+	}
+
+	as := A[string]{B: B[string]{"abc"}}
+	if got, want := doGet2[string](&as), "abc"; got != want {
+		panic(fmt.Sprintf("got %v, want %v", got, want))
+	}
+}

test/typeparam/genembed2.go

@@ -0,0 +1,46 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test for declaration and use of a parameterized embedded field.
+
+package main
+
+import (
+	"fmt"
+	"sync"
+)
+
+type MyStruct[T any] struct {
+	val T
+}
+
+type Lockable[T any] struct {
+	MyStruct[T]
+	mu sync.Mutex
+}
+
+// Get returns the value stored in a Lockable.
+func (l *Lockable[T]) Get() T {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	return l.MyStruct.val
+}
+
+// Set sets the value in a Lockable.
+func (l *Lockable[T]) Set(v T) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	l.MyStruct = MyStruct[T]{v}
+}
+
+func main() {
+	var li Lockable[int]
+
+	li.Set(5)
+	if got, want := li.Get(), 5; got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+}

test/typeparam/geninline.dir/a.go

@@ -0,0 +1,56 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+type IVal[T comparable] interface {
+	check(want T)
+}
+
+type Val[T comparable] struct {
+	val T
+}
+
+//go:noinline
+func (l *Val[T]) check(want T) {
+	if l.val != want {
+		panic("hi")
+	}
+}
+
+func Test1() {
+	var l Val[int]
+	if l.val != 0 {
+		panic("hi")
+	}
+	_ = IVal[int](&l)
+}
+
+func Test2() {
+	var l Val[float64]
+	l.val = 3.0
+	l.check(float64(3))
+	_ = IVal[float64](&l)
+}
+
+type privateVal[T comparable] struct {
+	val T
+}
+
+//go:noinline
+func (l *privateVal[T]) check(want T) {
+	if l.val != want {
+		panic("hi")
+	}
+}
+
+type Outer struct {
+	val privateVal[string]
+}
+
+func Test3() {
+	var o Outer
+	o.val.check("")
+	_ = IVal[string](&o.val)
+}

test/typeparam/geninline.dir/main.go

@@ -0,0 +1,16 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "./a"
+
+// Testing inlining of functions that refer to instantiated exported and non-exported
+// generic types.
+
+func main() {
+	a.Test1()
+	a.Test2()
+	a.Test3()
+}

test/typeparam/geninline.go

@@ -0,0 +1,7 @@
+// rundir
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ignored

test/typeparam/graph.go

@@ -0,0 +1,231 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"errors"
+	"fmt"
+)
+
+// _SliceEqual reports whether two slices are equal: the same length and all
+// elements equal. All floating point NaNs are considered equal.
+func _SliceEqual[Elem comparable](s1, s2 []Elem) bool {
+	if len(s1) != len(s2) {
+		return false
+	}
+	for i, v1 := range s1 {
+		v2 := s2[i]
+		if v1 != v2 {
+			isNaN := func(f Elem) bool { return f != f }
+			if !isNaN(v1) || !isNaN(v2) {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+// A Graph is a collection of nodes. A node may have an arbitrary number
+// of edges. An edge connects two nodes. Both nodes and edges must be
+// comparable. This is an undirected simple graph.
+type _Graph[_Node _NodeC[_Edge], _Edge _EdgeC[_Node]] struct {
+	nodes []_Node
+}
+
+// _NodeC is the constraints on a node in a graph, given the _Edge type.
+type _NodeC[_Edge any] interface {
+	comparable
+	Edges() []_Edge
+}
+
+// _EdgeC is the constraints on an edge in a graph, given the _Node type.
+type _EdgeC[_Node any] interface {
+	comparable
+	Nodes() (a, b _Node)
+}
+
+// _New creates a new _Graph from a collection of Nodes.
+func _New[_Node _NodeC[_Edge], _Edge _EdgeC[_Node]](nodes []_Node) *_Graph[_Node, _Edge] {
+	return &_Graph[_Node, _Edge]{nodes: nodes}
+}
+
+// nodePath holds the path to a node during ShortestPath.
+// This should ideally be a type defined inside ShortestPath,
+// but the translator tool doesn't support that.
+type nodePath[_Node _NodeC[_Edge], _Edge _EdgeC[_Node]] struct {
+	node _Node
+	path []_Edge
+}
+
+// ShortestPath returns the shortest path between two nodes,
+// as an ordered list of edges. If there are multiple shortest paths,
+// which one is returned is unpredictable.
+func (g *_Graph[_Node, _Edge]) ShortestPath(from, to _Node) ([]_Edge, error) {
+	visited := make(map[_Node]bool)
+	visited[from] = true
+	workqueue := []nodePath[_Node, _Edge]{nodePath[_Node, _Edge]{from, nil}}
+	for len(workqueue) > 0 {
+		current := workqueue
+		workqueue = nil
+		for _, np := range current {
+			edges := np.node.Edges()
+			for _, edge := range edges {
+				a, b := edge.Nodes()
+				if a == np.node {
+					a = b
+				}
+				if !visited[a] {
+					ve := append([]_Edge(nil), np.path...)
+					ve = append(ve, edge)
+					if a == to {
+						return ve, nil
+					}
+					workqueue = append(workqueue, nodePath[_Node, _Edge]{a, ve})
+					visited[a] = true
+				}
+			}
+		}
+	}
+	return nil, errors.New("no path")
+}
+
+type direction int
+
+const (
+	north direction = iota
+	ne
+	east
+	se
+	south
+	sw
+	west
+	nw
+	up
+	down
+)
+
+func (dir direction) String() string {
+	strs := map[direction]string{
+		north: "north",
+		ne:    "ne",
+		east:  "east",
+		se:    "se",
+		south: "south",
+		sw:    "sw",
+		west:  "west",
+		nw:    "nw",
+		up:    "up",
+		down:  "down",
+	}
+	if str, ok := strs[dir]; ok {
+		return str
+	}
+	return fmt.Sprintf("direction %d", dir)
+}
+
+type mazeRoom struct {
+	index int
+	exits [10]int
+}
+
+type mazeEdge struct {
+	from, to int
+	dir      direction
+}
+
+// Edges returns the exits from the room.
+func (m mazeRoom) Edges() []mazeEdge {
+	var r []mazeEdge
+	for i, exit := range m.exits {
+		if exit != 0 {
+			r = append(r, mazeEdge{
+				from: m.index,
+				to:   exit,
+				dir:  direction(i),
+			})
+		}
+	}
+	return r
+}
+
+// Nodes returns the rooms connected by an edge.
+//
+//go:noinline
+func (e mazeEdge) Nodes() (mazeRoom, mazeRoom) {
+	m1, ok := zork[e.from]
+	if !ok {
+		panic("bad edge")
+	}
+	m2, ok := zork[e.to]
+	if !ok {
+		panic("bad edge")
+	}
+	return m1, m2
+}
+
+// The first maze in Zork. Room indexes based on original Fortran data file.
+// You are in a maze of twisty little passages, all alike.
+var zork = map[int]mazeRoom{
+	11: {exits: [10]int{north: 11, south: 12, east: 14}}, // west to Troll Room
+	12: {exits: [10]int{south: 11, north: 14, east: 13}},
+	13: {exits: [10]int{west: 12, north: 14, up: 16}},
+	14: {exits: [10]int{west: 13, north: 11, east: 15}},
+	15: {exits: [10]int{south: 14}},                   // Dead End
+	16: {exits: [10]int{east: 17, north: 13, sw: 18}}, // skeleton, etc.
+	17: {exits: [10]int{west: 16}},                    // Dead End
+	18: {exits: [10]int{down: 16, east: 19, west: 18, up: 22}},
+	19: {exits: [10]int{up: 29, west: 18, ne: 15, east: 20, south: 30}},
+	20: {exits: [10]int{ne: 19, west: 20, se: 21}},
+	21: {exits: [10]int{north: 20}}, // Dead End
+	22: {exits: [10]int{north: 18, east: 24, down: 23, south: 28, west: 26, nw: 22}},
+	23: {exits: [10]int{east: 22, west: 28, up: 24}},
+	24: {exits: [10]int{ne: 25, down: 23, nw: 28, sw: 26}},
+	25: {exits: [10]int{sw: 24}}, // Grating room (up to Clearing)
+	26: {exits: [10]int{west: 16, sw: 24, east: 28, up: 22, north: 27}},
+	27: {exits: [10]int{south: 26}}, // Dead End
+	28: {exits: [10]int{east: 22, down: 26, south: 23, west: 24}},
+	29: {exits: [10]int{west: 30, nw: 29, ne: 19, south: 19}},
+	30: {exits: [10]int{west: 29, south: 19}}, // ne to Cyclops Room
+}
+
+func TestShortestPath() {
+	// The Zork maze is not a proper undirected simple graph,
+	// as there are some one way paths (e.g., 19 -> 15),
+	// but for this test that doesn't matter.
+
+	// Set the index field in the map. Simpler than doing it in the
+	// composite literal.
+	for k := range zork {
+		r := zork[k]
+		r.index = k
+		zork[k] = r
+	}
+
+	var nodes []mazeRoom
+	for idx, room := range zork {
+		mridx := room
+		mridx.index = idx
+		nodes = append(nodes, mridx)
+	}
+	g := _New[mazeRoom, mazeEdge](nodes)
+	path, err := g.ShortestPath(zork[11], zork[30])
+	if err != nil {
+		panic(fmt.Sprintf("%v", err))
+	}
+	var steps []direction
+	for _, edge := range path {
+		steps = append(steps, edge.dir)
+	}
+	want := []direction{east, west, up, sw, east, south}
+	if !_SliceEqual(steps, want) {
+		panic(fmt.Sprintf("ShortestPath returned %v, want %v", steps, want))
+	}
+}
+
+func main() {
+	TestShortestPath()
+}

test/typeparam/ifaceconv.go

@@ -0,0 +1,83 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test that we can convert type parameters to both empty
+// and nonempty interfaces, and named and nonnamed versions
+// thereof.
+
+package main
+
+import "fmt"
+
+type E interface{}
+
+func f[T any](x T) interface{} {
+	var i interface{} = x
+	return i
+}
+
+func fs[T any](x T) interface{} {
+	y := []T{x}
+	var i interface{} = y
+	return i
+}
+
+func g[T any](x T) E {
+	var i E = x
+	return i
+}
+
+type C interface {
+	foo() int
+}
+
+type myInt int
+
+func (x myInt) foo() int {
+	return int(x + 1)
+}
+
+func h[T C](x T) interface{ foo() int } {
+	var i interface{ foo() int } = x
+	return i
+}
+func i[T C](x T) C {
+	var i C = x // conversion in assignment
+	return i
+}
+
+func j[T C](t T) C {
+	return C(t) // explicit conversion
+}
+
+func js[T any](x T) interface{} {
+	y := []T{x}
+	return interface{}(y)
+}
+
+func main() {
+	if got, want := f[int](7), 7; got != want {
+		panic(fmt.Sprintf("got %d want %d", got, want))
+	}
+	if got, want := fs[int](7), []int{7}; got.([]int)[0] != want[0] {
+		panic(fmt.Sprintf("got %d want %d", got, want))
+	}
+	if got, want := g[int](7), 7; got != want {
+		panic(fmt.Sprintf("got %d want %d", got, want))
+	}
+	if got, want := h[myInt](7).foo(), 8; got != want {
+		panic(fmt.Sprintf("got %d want %d", got, want))
+	}
+	if got, want := i[myInt](7).foo(), 8; got != want {
+		panic(fmt.Sprintf("got %d want %d", got, want))
+	}
+	if got, want := j[myInt](7).foo(), 8; got != want {
+		panic(fmt.Sprintf("got %d want %d", got, want))
+	}
+	if got, want := js[int](7), []int{7}; got.([]int)[0] != want[0] {
+		panic(fmt.Sprintf("got %d want %d", got, want))
+	}
+}

test/typeparam/importtest.go

@@ -0,0 +1,16 @@
+// compile
+
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file checks that basic importing works in -G mode.
+
+package p
+
+import "fmt"
+import "math"
+
+func f(x float64) {
+	fmt.Println(math.Sin(x))
+}

test/typeparam/index.go

@@ -0,0 +1,81 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"fmt"
+)
+
+// Index returns the index of x in s, or -1 if not found.
+func Index[T comparable](s []T, x T) int {
+	for i, v := range s {
+		// v and x are type T, which has the comparable
+		// constraint, so we can use == here.
+		if v == x {
+			return i
+		}
+	}
+	return -1
+}
+
+type obj struct {
+	x int
+}
+
+type obj2 struct {
+	x int8
+	y float64
+}
+
+type obj3 struct {
+	x int64
+	y int8
+}
+
+type inner struct {
+	y int64
+	z int32
+}
+
+type obj4 struct {
+	x int32
+	s inner
+}
+
+func main() {
+	want := 2
+
+	vec1 := []string{"ab", "cd", "ef"}
+	if got := Index(vec1, "ef"); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+
+	vec2 := []byte{'c', '6', '@'}
+	if got := Index(vec2, '@'); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+
+	vec3 := []*obj{&obj{2}, &obj{42}, &obj{1}}
+	if got := Index(vec3, vec3[2]); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+
+	vec4 := []obj2{obj2{2, 3.0}, obj2{3, 4.0}, obj2{4, 5.0}}
+	if got := Index(vec4, vec4[2]); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+
+	vec5 := []obj3{obj3{2, 3}, obj3{3, 4}, obj3{4, 5}}
+	if got := Index(vec5, vec5[2]); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+
+	vec6 := []obj4{obj4{2, inner{3, 4}}, obj4{3, inner{4, 5}}, obj4{4, inner{5, 6}}}
+	if got := Index(vec6, vec6[2]); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+}

test/typeparam/index2.go

@@ -0,0 +1,67 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Testing various generic uses of indexing, both for reads and writes.
+
+package main
+
+import "fmt"
+
+// Can index an argument (read/write) constrained to be a slice or an array.
+func Index1[T interface{ []int64 | [5]int64 }](x T) int64 {
+	x[2] = 5
+	return x[3]
+}
+
+// Can index an argument (read) constrained to be a byte array or a string.
+func Index2[T interface{ []byte | string }](x T) byte {
+	return x[3]
+}
+
+// Can index an argument (write) constrained to be a byte array, but not a string.
+func Index2a[T interface{ []byte }](x T) byte {
+	x[2] = 'b'
+	return x[3]
+}
+
+// Can index an argument (read/write) constrained to be a map. Maps can't
+// be combined with any other type for indexing purposes.
+func Index3[T interface{ map[int]int64 }](x T) int64 {
+	x[2] = 43
+	return x[3]
+}
+
+// But the type of the map keys or values can be parameterized.
+func Index4[T any](x map[int]T) T {
+	var zero T
+	x[2] = zero
+	return x[3]
+}
+
+func test[T comparable](got, want T) {
+	if got != want {
+		panic(fmt.Sprintf("got %v, want %v", got, want))
+	}
+}
+
+func main() {
+	x := make([]int64, 4)
+	x[3] = 2
+	y := [5]int64{1, 2, 3, 4, 5}
+	z := "abcd"
+	w := make([]byte, 4)
+	w[3] = 5
+	v := make(map[int]int64)
+	v[3] = 18
+
+	test(Index1(x), int64(2))
+	test(Index1(y), int64(4))
+	test(Index2(z), byte(100))
+	test(Index2(w), byte(5))
+	test(Index2a(w), byte(5))
+	test(Index3(v), int64(18))
+	test(Index4(v), int64(18))
+}

test/typeparam/interfacearg.go

@@ -0,0 +1,46 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type I interface{}
+
+type _S[T any] struct {
+	x *T
+}
+
+// F is a non-generic function, but has a type _S[I] which is instantiated from a
+// generic type. Test that _S[I] is successfully exported.
+func F() {
+	v := _S[I]{}
+	if v.x != nil {
+		panic(v)
+	}
+}
+
+// Testing the various combinations of method expressions.
+type S1 struct{}
+
+func (*S1) M() {}
+
+type S2 struct{}
+
+func (S2) M() {}
+
+func _F1[T interface{ M() }](t T) {
+	_ = T.M
+}
+
+func F2() {
+	_F1(&S1{})
+	_F1(S2{})
+	_F1(&S2{})
+}
+
+func main() {
+	F()
+	F2()
+}

test/typeparam/issue23536.go

@@ -0,0 +1,32 @@
+// run
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test case where a slice of a user-defined byte type (not uint8 or byte) is
+// converted to a string.  Same for slice of runes.
+
+package main
+
+type MyByte byte
+
+type MyRune rune
+
+func f[T []MyByte](x T) string {
+	return string(x)
+}
+
+func g[T []MyRune](x T) string {
+	return string(x)
+}
+
+func main() {
+	var y []MyByte
+	_ = f(y)
+	_ = string(y)
+
+	var z []MyRune
+	_ = g(z)
+	_ = string(z)
+}

test/typeparam/issue376214.go

@@ -0,0 +1,20 @@
+// run
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func add[S ~string | ~[]byte](buf *[]byte, s S) {
+	*buf = append(*buf, s...)
+}
+
+func main() {
+	var buf []byte
+	add(&buf, "foo")
+	add(&buf, []byte("bar"))
+	if string(buf) != "foobar" {
+		panic("got " + string(buf))
+	}
+}

test/typeparam/issue39755.go

@@ -0,0 +1,27 @@
+// compile
+
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// copied from cmd/compile/internal/types2/testdata/fixedbugs/issue39755.go
+
+package p
+
+func _[T interface{ ~map[string]int }](x T) {
+	_ = x == nil
+}
+
+// simplified test case from issue
+
+type PathParamsConstraint interface {
+	~map[string]string | ~[]struct{ key, value string }
+}
+
+type PathParams[T PathParamsConstraint] struct {
+	t T
+}
+
+func (pp *PathParams[T]) IsNil() bool {
+	return pp.t == nil // this must succeed
+}

test/typeparam/issue42758.go

@@ -0,0 +1,19 @@
+// run
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func F[T, U int]() interface{} {
+	switch interface{}(nil) {
+	case int(0), T(0), U(0):
+	}
+
+	return map[interface{}]int{int(0): 0, T(0): 0, U(0): 0}
+}
+
+func main() {
+	F[int, int]()
+}

test/typeparam/issue44688.go

@@ -0,0 +1,149 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// derived & expanded from cmd/compile/internal/types2/testdata/fixedbugs/issue44688.go2
+
+package main
+
+type A1[T any] struct {
+	val T
+}
+
+func (p *A1[T]) m1(val T) {
+	p.val = val
+}
+
+type A2[T any] interface {
+	m2(T)
+}
+
+type B1[T any] struct {
+	filler int
+	*A1[T]
+	A2[T]
+}
+
+type B2[T any] interface {
+	A2[T]
+}
+
+type ImpA2[T any] struct {
+	f T
+}
+
+func (a2 *ImpA2[T]) m2(s T) {
+	a2.f = s
+}
+
+type C[T any] struct {
+	filler1 int
+	filler2 int
+	B1[T]
+}
+
+type D[T any] struct {
+	filler1 int
+	filler2 int
+	filler3 int
+	C[T]
+}
+
+func test1[T any](arg T) {
+	// calling embedded methods
+	var b1 B1[T]
+	b1.A1 = &A1[T]{}
+	b1.A2 = &ImpA2[T]{}
+
+	b1.A1.m1(arg)
+	b1.m1(arg)
+
+	b1.A2.m2(arg)
+	b1.m2(arg)
+
+	var b2 B2[T]
+	b2 = &ImpA2[T]{}
+	b2.m2(arg)
+
+	// a deeper nesting
+	var d D[T]
+	d.C.B1.A1 = &A1[T]{}
+	d.C.B1.A2 = &ImpA2[T]{}
+	d.m1(arg)
+	d.m2(arg)
+
+	// calling method expressions
+	m1x := B1[T].m1
+	m1x(b1, arg)
+	// TODO(khr): reenable these.
+	//m2x := B2[T].m2
+	//m2x(b2, arg)
+
+	// calling method values
+	m1v := b1.m1
+	m1v(arg)
+	m2v := b1.m2
+	m2v(arg)
+	b2v := b2.m2
+	b2v(arg)
+}
+
+func test2() {
+	// calling embedded methods
+	var b1 B1[string]
+	b1.A1 = &A1[string]{}
+	b1.A2 = &ImpA2[string]{}
+
+	b1.A1.m1("")
+	b1.m1("")
+
+	b1.A2.m2("")
+	b1.m2("")
+
+	var b2 B2[string]
+	b2 = &ImpA2[string]{}
+	b2.m2("")
+
+	// a deeper nesting
+	var d D[string]
+	d.C.B1.A1 = &A1[string]{}
+	d.C.B1.A2 = &ImpA2[string]{}
+	d.m1("")
+	d.m2("")
+
+	// calling method expressions
+	m1x := B1[string].m1
+	m1x(b1, "")
+	m2x := B2[string].m2
+	m2x(b2, "")
+
+	// calling method values
+	m1v := b1.m1
+	m1v("")
+	m2v := b1.m2
+	m2v("")
+	b2v := b2.m2
+	b2v("")
+}
+
+// actual test case from issue
+
+type A[T any] struct{}
+
+func (*A[T]) f(T) {}
+
+type B[T any] struct{ A[T] }
+
+func test3() {
+	var b B[string]
+	b.A.f("")
+	b.f("")
+}
+
+func main() {
+	test1[string]("")
+	test2()
+	test3()
+}

test/typeparam/issue45547.go

@@ -0,0 +1,20 @@
+// compile
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func f[T any]() (f, g T) { return f, g }
+
+// Tests for generic function instantiation on the right hande side of multi-value
+// assignments.
+
+func g() {
+	// Multi-value assignment within a function
+	var _, _ = f[int]()
+}
+
+// Multi-value assignment outside a function.
+var _, _ = f[int]()

test/typeparam/issue45722.go

@@ -0,0 +1,34 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"fmt"
+	"log"
+)
+
+func try[T any](v T, err error) T {
+	if err != nil {
+		panic(err)
+	}
+	return v
+}
+
+func handle(handle func(error)) {
+	if issue := recover(); issue != nil {
+		if e, ok := issue.(error); ok && e != nil {
+			handle(e)
+		} else {
+			handle(fmt.Errorf("%v", e))
+		}
+	}
+}
+
+func main() {
+	defer handle(func(e error) { log.Fatalln(e) })
+	_ = try(fmt.Print(""))
+}

test/typeparam/issue45738.go

@@ -0,0 +1,18 @@
+// compile
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+//go:noinline
+func f[T any]() {
+	x := 5
+	g := func() int { return x }
+	g()
+}
+
+func main() {
+	f[int]()
+}

test/typeparam/issue45817.go

@@ -0,0 +1,26 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"fmt"
+)
+
+type s[T any] struct {
+	a T
+}
+
+func (x s[T]) f() T {
+	return x.a
+}
+func main() {
+	x := s[int]{a: 7}
+	f := x.f
+	if got, want := f(), 7; got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+}

test/typeparam/issue46461.go

@@ -0,0 +1,13 @@
+// errorcheck
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type T[U interface{ M() T[U] }] int // ERROR "invalid recursive type: T refers to itself"
+
+type X int
+
+func (X) M() T[X] { return 0 }

test/typeparam/issue46461b.dir/a.go

@@ -0,0 +1,7 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+type T[U interface{ M() int }] int

test/typeparam/issue46461b.dir/b.go

@@ -0,0 +1,13 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package b
+
+import "./a"
+
+type X int
+
+func (X) M() int { return 0 }
+
+type _ a.T[X]

test/typeparam/issue46461b.go

@@ -0,0 +1,7 @@
+// compiledir
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ignored

test/typeparam/issue46472.go

@@ -0,0 +1,20 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func foo[T any](d T) {
+	switch v := interface{}(d).(type) {
+	case string:
+		if v != "x" {
+			panic("unexpected v: " + v)
+		}
+	}
+
+}
+func main() {
+	foo("x")
+}

test/typeparam/issue46591.go

@@ -0,0 +1,22 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type T[_ any] struct{}
+
+var m = map[interface{}]int{
+	T[struct{ int }]{}: 0,
+	T[struct {
+		int "x"
+	}]{}: 0,
+}
+
+func main() {
+	if len(m) != 2 {
+		panic(len(m))
+	}
+}

test/typeparam/issue47258.go

@@ -0,0 +1,32 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"fmt"
+)
+
+type Numeric interface {
+	int32 | int64 | float64 | complex64
+}
+
+//go:noline
+func inc[T Numeric](x T) T {
+	x++
+	return x
+}
+func main() {
+	if got, want := inc(int32(5)), int32(6); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+	if got, want := inc(float64(5)), float64(6.0); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+	if got, want := inc(complex64(5)), complex64(6.0); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+}

test/typeparam/issue47272.go

@@ -0,0 +1,55 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"errors"
+	"fmt"
+)
+
+type Option[T any] struct {
+	ok  bool
+	val T
+}
+
+func (o Option[T]) String() string {
+	if o.ok {
+		return fmt.Sprintf("Some(%v)", o.val)
+	}
+	return "None"
+}
+
+func Some[T any](val T) Option[T] { return Option[T]{ok: true, val: val} }
+func None[T any]() Option[T]      { return Option[T]{ok: false} }
+
+type Result[T, E any] struct {
+	ok  bool
+	val T
+	err E
+}
+
+func (r Result[T, E]) String() string {
+	if r.ok {
+		return fmt.Sprintf("Ok(%v)", r.val)
+	}
+	return fmt.Sprintf("Err(%v)", r.err)
+}
+
+func Ok[T, E any](val T) Result[T, E]  { return Result[T, E]{ok: true, val: val} }
+func Err[T, E any](err E) Result[T, E] { return Result[T, E]{ok: false, err: err} }
+
+func main() {
+	a := Some[int](1)
+	b := None[int]()
+	fmt.Println(a, b)
+
+	x := Ok[int, error](1)
+	y := Err[int, error](errors.New("test"))
+	fmt.Println(x, y)
+	// fmt.Println(x)
+	_, _, _, _ = a, b, x, y
+}

test/typeparam/issue47272.out

@@ -0,0 +1,2 @@
+Some(1) None
+Ok(1) Err(test)

test/typeparam/issue47514.go

@@ -0,0 +1,20 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test that closures inside a generic function are not exported,
+// even though not themselves generic.
+
+package main
+
+func Do[T any]() {
+	_ = func() string {
+		return ""
+	}
+}
+
+func main() {
+	Do[int]()
+}

test/typeparam/issue47514b.go

@@ -0,0 +1,19 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func Do[T any](do func() (T, string)) {
+	_ = func() (T, string) {
+		return do()
+	}
+}
+
+func main() {
+	Do[int](func() (int, string) {
+		return 3, "3"
+	})
+}

test/typeparam/issue47514c.dir/a.go

@@ -0,0 +1,5 @@
+package a
+
+type Doer[T any] interface {
+	Do() T
+}

test/typeparam/issue47514c.dir/main.go

@@ -0,0 +1,10 @@
+package main
+
+import "./a"
+
+func Do[T any](doer a.Doer[T]) {
+	doer.Do()
+}
+
+func main() {
+}

test/typeparam/issue47514c.go

@@ -0,0 +1,7 @@
+// rundir
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ignored

test/typeparam/issue47631.go

@@ -0,0 +1,31 @@
+// compile
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func g[T any]() {
+	type U []T
+	type V []int
+}
+
+type S[T any] struct {
+}
+
+func (s S[T]) m() {
+	type U []T
+	type V []int
+}
+
+func f() {
+	type U []int
+}
+
+type X struct {
+}
+
+func (x X) m() {
+	type U []int
+}

test/typeparam/issue47676.go

@@ -0,0 +1,23 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func main() {
+	d := diff([]int{}, func(int) string {
+		return "foo"
+	})
+	d()
+}
+
+func diff[T any](previous []T, uniqueKey func(T) string) func() {
+	return func() {
+		newJSON := map[string]T{}
+		for _, prev := range previous {
+			delete(newJSON, uniqueKey(prev))
+		}
+	}
+}

test/typeparam/issue47684.go

@@ -0,0 +1,19 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func f[G any]() int {
+	return func() int {
+		return func() int {
+			return 0
+		}()
+	}()
+}
+
+func main() {
+	f[int]()
+}

test/typeparam/issue47684b.go

@@ -0,0 +1,23 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func f[G any]() interface{} {
+	return func() interface{} {
+		return func() interface{} {
+			var x G
+			return x
+		}()
+	}()
+}
+
+func main() {
+	x := f[int]()
+	if v, ok := x.(int); !ok || v != 0 {
+		panic("bad")
+	}
+}

test/typeparam/issue47684c.go

@@ -0,0 +1,19 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func f[G any]() func()func()int {
+	return func() func()int {
+		return func() int {
+			return 0
+		}
+	}
+}
+
+func main() {
+	f[int]()()()
+}

test/typeparam/issue47708.go

@@ -0,0 +1,37 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type FooType[T any] interface {
+	Foo(BarType[T]) string
+}
+type BarType[T any] interface {
+	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() {
+	// 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))
+	// }
+}

test/typeparam/issue47710.go

@@ -0,0 +1,19 @@
+// compile
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type FooType[t any] interface {
+	Foo(BarType[t])
+}
+type BarType[t any] interface {
+	Int(IntType[t]) FooType[int]
+}
+
+type IntType[t any] int
+
+func (n IntType[t]) Foo(BarType[t]) {}
+func (n IntType[_]) String()    {}

test/typeparam/issue47713.go

@@ -0,0 +1,52 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"encoding"
+	"fmt"
+)
+
+type Seralizable interface {
+	encoding.BinaryMarshaler
+	encoding.BinaryUnmarshaler
+}
+
+type SerDeString string
+
+func (s *SerDeString) UnmarshalBinary(in []byte) error {
+	*s = SerDeString(in)
+	return nil
+}
+
+func (s SerDeString) MarshalBinary() ([]byte, error) {
+	return []byte(s), nil
+}
+
+
+type GenericSerializable[T Seralizable] struct {
+	Key string
+	Value T
+}
+
+func (g GenericSerializable[T]) Send() {
+	out, err := g.Value.MarshalBinary()
+	if err != nil {
+		panic("bad")
+	}
+	var newval SerDeString
+	newval.UnmarshalBinary(out)
+	fmt.Printf("Sent %s\n", newval)
+}
+
+func main() {
+	val := SerDeString("asdf")
+	x := GenericSerializable[*SerDeString]{
+		Value: &val,
+	}
+	x.Send()
+}

test/typeparam/issue47713.out

@@ -0,0 +1 @@
+Sent asdf

test/typeparam/issue47716.go

@@ -0,0 +1,68 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"fmt"
+	"unsafe"
+)
+
+// size returns the size of type T
+func size[T any](x T) uintptr {
+	return unsafe.Sizeof(x)
+}
+
+// size returns the alignment of type T
+func align[T any](x T) uintptr {
+	return unsafe.Alignof(x)
+}
+
+type Tstruct[T any] struct {
+	f1 T
+	f2 int
+}
+
+// offset returns the offset of field f2 in the generic type Tstruct
+func (r *Tstruct[T]) offset() uintptr {
+	return unsafe.Offsetof(r.f2)
+}
+
+func main() {
+	v1 := int(5)
+	if got, want := size(v1), unsafe.Sizeof(v1); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+	if got, want := align(v1), unsafe.Alignof(v1); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+
+	v2 := "abc"
+	if got, want := size(v2), unsafe.Sizeof(v2); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+	if got, want := align(v2), unsafe.Alignof(v2); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+
+	var v3 Tstruct[int]
+	if got, want := unsafe.Offsetof(v3.f2), unsafe.Sizeof(v1); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+
+	var v4 Tstruct[interface{}]
+	var v5 interface{}
+	if got, want := unsafe.Offsetof(v4.f2), unsafe.Sizeof(v5); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+
+	if got, want := v3.offset(), unsafe.Offsetof(v3.f2); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+	if got, want := v4.offset(), unsafe.Offsetof(v4.f2); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+}

test/typeparam/issue47723.go

@@ -0,0 +1,23 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func f[_ any]() int {
+	var a [1]int
+	_ = func() int {
+		return func() int {
+			return 0
+		}()
+	}()
+	return a[func() int {
+		return 0
+	}()]
+}
+
+func main() {
+	f[int]()
+}

test/typeparam/issue47740.go

@@ -0,0 +1,40 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "fmt"
+
+type Exp[Ty any] interface {
+	Eval() Ty
+}
+
+// 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]
+	b Exp[Ty]
+}
+
+func (e Eq[Ty]) String() string {
+	return fmt.Sprintf("(eq %v %v)", e.a, e.b)
+}
+
+// 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() {
+	// 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)
+}

test/typeparam/issue47740b.go

@@ -0,0 +1,23 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "reflect"
+
+type S[T any] struct {
+	a interface{}
+}
+
+func (e S[T]) M() {
+	v := reflect.ValueOf(e.a)
+	_, _ = v.Interface().(int)
+}
+
+func main() {
+	e := S[int]{0}
+	e.M()
+}

test/typeparam/issue47775.dir/b.go

@@ -0,0 +1,19 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package b
+
+type C[T any] struct {
+}
+
+func (c *C[T]) reset() {
+}
+
+func New[T any]() {
+	c := &C[T]{}
+	z(c.reset)
+}
+
+func z(interface{}) {
+}

test/typeparam/issue47775.dir/main.go

@@ -0,0 +1,11 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "./b"
+
+func main() {
+	b.New[int]()
+}

test/typeparam/issue47775.go

@@ -0,0 +1,7 @@
+// rundir
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ignored

test/typeparam/issue47775b.go

@@ -0,0 +1,28 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type C[T any] struct {
+}
+
+func (c *C[T]) reset() {
+}
+
+func New[T any]() {
+	c := &C[T]{}
+	i = c.reset
+	z(c.reset)
+}
+
+var i interface{}
+
+func z(interface{}) {
+}
+
+func main() {
+	New[int]()
+}

test/typeparam/issue47797.go

@@ -0,0 +1,22 @@
+// compile
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type Foo[T any] struct {
+        Val T
+}
+
+func (f Foo[T]) Bat() {}
+
+type Bar struct {
+        Foo[int]
+}
+
+func foo() {
+        var b Bar
+        b.Bat()
+}

test/typeparam/issue47877.go

@@ -0,0 +1,23 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type Map[K comparable, V any] struct {
+        m map[K]V
+}
+
+func NewMap[K comparable, V any]() Map[K, V] {
+        return Map[K, V]{m: map[K]V{}}
+}
+
+func (m Map[K, V]) Get(key K) V {
+        return m.m[key]
+}
+
+func main() {
+        _ = NewMap[int, struct{}]()
+}

test/typeparam/issue47878.go

@@ -0,0 +1,56 @@
+// compile
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type Src1[T any] func() Src1[T]
+
+func (s *Src1[T]) Next() {
+	*s = (*s)()
+}
+
+type Src2[T any] []func() Src2[T]
+
+func (s Src2[T]) Next() {
+	_ = s[0]()
+}
+
+type Src3[T comparable] map[T]func() Src3[T]
+
+func (s Src3[T]) Next() {
+	var a T
+	_ = s[a]()
+}
+
+type Src4[T any] chan func() T
+
+func (s Src4[T]) Next() {
+	_ = (<-s)()
+}
+
+type Src5[T any] func() Src5[T]
+
+func (s Src5[T]) Next() {
+	var x interface{} = s
+	_ = (x.(Src5[T]))()
+}
+
+func main() {
+	var src1 Src1[int]
+	src1.Next()
+
+	var src2 Src2[int]
+	src2.Next()
+
+	var src3 Src3[string]
+	src3.Next()
+
+	var src4 Src4[int]
+	src4.Next()
+
+	var src5 Src5[int]
+	src5.Next()
+}