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https://github.com/golang/go
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fdded79e6e
In the case of partially inferred type arguments, we need to use the IndexExpr as the key in g.info.Inferred[] rather than the CallExpr. Added an extra fromStrings1 call in the settable.go test that tests partially inferred type arguments. This new call uses a new concrete type SettableString as well. I also added another implementation fromStrings3 (derived from a go2go tests) that typechecks but intentionally causes a panic. Change-Id: I74d35c5a741f72f37160a96fbec939451157f392 Reviewed-on: https://go-review.googlesource.com/c/go/+/300309 Run-TryBot: Dan Scales <danscales@google.com> TryBot-Result: Go Bot <gobot@golang.org> Trust: Dan Scales <danscales@google.com> Trust: Robert Griesemer <gri@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>
105 lines
2.7 KiB
Go
105 lines
2.7 KiB
Go
// run -gcflags=-G=3
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// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package main
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import (
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"fmt"
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"strconv"
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)
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// Various implementations of fromStrings().
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type _Setter[B any] interface {
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Set(string)
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type *B
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}
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// Takes two type parameters where PT = *T
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func fromStrings1[T any, PT _Setter[T]](s []string) []T {
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result := make([]T, len(s))
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for i, v := range s {
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// The type of &result[i] is *T which is in the type list
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// of Setter, so we can convert it to PT.
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p := PT(&result[i])
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// PT has a Set method.
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p.Set(v)
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}
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return result
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}
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// Takes one type parameter and a set function
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func fromStrings2[T any](s []string, set func(*T, string)) []T {
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results := make([]T, len(s))
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for i, v := range s {
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set(&results[i], v)
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}
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return results
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}
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type _Setter2 interface {
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Set(string)
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}
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// Takes only one type parameter, but causes a panic (see below)
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func fromStrings3[T _Setter2](s []string) []T {
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results := make([]T, len(s))
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for i, v := range s {
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// Panics if T is a pointer type because receiver is T(nil).
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results[i].Set(v)
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}
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return results
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}
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// Two concrete types with the appropriate Set method.
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type SettableInt int
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func (p *SettableInt) Set(s string) {
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i, err := strconv.Atoi(s)
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if err != nil {
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panic(err)
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}
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*p = SettableInt(i)
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}
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type SettableString struct {
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s string
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}
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func (x *SettableString) Set(s string) {
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x.s = s
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}
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func main() {
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s := fromStrings1[SettableInt, *SettableInt]([]string{"1"})
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if len(s) != 1 || s[0] != 1 {
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panic(fmt.Sprintf("got %v, want %v", s, []int{1}))
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}
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// Test out constraint type inference, which should determine that the second
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// type param is *SettableString.
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ps := fromStrings1[SettableString]([]string{"x", "y"})
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if len(ps) != 2 || ps[0] != (SettableString{"x"}) || ps[1] != (SettableString{"y"}) {
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panic(s)
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}
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s = fromStrings2([]string{"1"}, func(p *SettableInt, s string) { p.Set(s) })
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if len(s) != 1 || s[0] != 1 {
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panic(fmt.Sprintf("got %v, want %v", s, []int{1}))
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}
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defer func() {
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if recover() == nil {
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panic("did not panic as expected")
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}
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}()
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// This should type check but should panic at run time,
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// because it will make a slice of *SettableInt and then call
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// Set on a nil value.
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fromStrings3[*SettableInt]([]string{"1"})
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}
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