mirror of
https://github.com/golang/go
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90b1ed1602
types2 will give us a constant with a type T, if an untyped constant is used with another operand of type T (in a provably correct way). When we substitute in the type args during stenciling, we now know the real type of the constant. We may then need to change the BasicLit.val to be the correct type (e.g. convert an int64Val constant to a floatVal constant). Otherwise, later parts of the compiler will be confused. Updated tests list.go and double.go with uses of untyped constants. Change-Id: I9966bbb0dea3a7de1c5a6420f8ad8af9ca84a33e Reviewed-on: https://go-review.googlesource.com/c/go/+/303089 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>
73 lines
1.6 KiB
Go
73 lines
1.6 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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"reflect"
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)
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type Number interface {
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type int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64, uintptr, float32, float64
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}
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type MySlice []int
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type MyFloatSlice []float64
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type _SliceOf[E any] interface {
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type []E
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}
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func _DoubleElems[S _SliceOf[E], E Number](s S) S {
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r := make(S, len(s))
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for i, v := range s {
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r[i] = v + v
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}
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return r
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}
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// Test use of untyped constant in an expression with a generically-typed parameter
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func _DoubleElems2[S _SliceOf[E], E Number](s S) S {
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r := make(S, len(s))
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for i, v := range s {
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r[i] = v * 2
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}
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return r
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}
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func main() {
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arg := MySlice{1, 2, 3}
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want := MySlice{2, 4, 6}
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got := _DoubleElems[MySlice, int](arg)
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if !reflect.DeepEqual(got, want) {
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panic(fmt.Sprintf("got %s, want %s", got, want))
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}
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// constraint type inference
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got = _DoubleElems[MySlice](arg)
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if !reflect.DeepEqual(got, want) {
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panic(fmt.Sprintf("got %s, want %s", got, want))
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}
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got = _DoubleElems(arg)
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if !reflect.DeepEqual(got, want) {
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panic(fmt.Sprintf("got %s, want %s", got, want))
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}
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farg := MyFloatSlice{1.2, 2.0, 3.5}
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fwant := MyFloatSlice{2.4, 4.0, 7.0}
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fgot := _DoubleElems(farg)
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if !reflect.DeepEqual(fgot, fwant) {
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panic(fmt.Sprintf("got %s, want %s", fgot, fwant))
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}
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fgot = _DoubleElems2(farg)
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if !reflect.DeepEqual(fgot, fwant) {
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panic(fmt.Sprintf("got %s, want %s", fgot, fwant))
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}
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}
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