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>
104 lines
2.6 KiB
Go
104 lines
2.6 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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)
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type Ordered interface {
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type int, int8, int16, int32, int64,
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uint, uint8, uint16, uint32, uint64, uintptr,
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float32, float64,
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string
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}
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// _List is a linked list of ordered values of type T.
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type _List[T Ordered] struct {
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next *_List[T]
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val T
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}
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func (l *_List[T]) Largest() T {
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var max T
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for p := l; p != nil; p = p.next {
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if p.val > max {
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max = p.val
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}
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}
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return max
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}
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type OrderedNum interface {
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type int, int8, int16, int32, int64,
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uint, uint8, uint16, uint32, uint64, uintptr,
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float32, float64
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}
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// _ListNum is a linked _List of ordered numeric values of type T.
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type _ListNum[T OrderedNum] struct {
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next *_ListNum[T]
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val T
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}
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const Clip = 5
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// clippedLargest returns the largest in the list of OrderNums, but a max of 5.
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// Test use of untyped constant in an expression with a generically-typed parameter
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func (l *_ListNum[T]) ClippedLargest() T {
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var max T
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for p := l; p != nil; p = p.next {
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if p.val > max && p.val < Clip {
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max = p.val
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}
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}
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return max
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}
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func main() {
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i3 := &_List[int]{nil, 1}
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i2 := &_List[int]{i3, 3}
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i1 := &_List[int]{i2, 2}
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if got, want := i1.Largest(), 3; got != want {
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panic(fmt.Sprintf("got %d, want %d", got, want))
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}
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b3 := &_List[byte]{nil, byte(1)}
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b2 := &_List[byte]{b3, byte(3)}
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b1 := &_List[byte]{b2, byte(2)}
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if got, want := b1.Largest(), byte(3); got != want {
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panic(fmt.Sprintf("got %d, want %d", got, want))
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}
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f3 := &_List[float64]{nil, 13.5}
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f2 := &_List[float64]{f3, 1.2}
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f1 := &_List[float64]{f2, 4.5}
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if got, want := f1.Largest(), 13.5; got != want {
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panic(fmt.Sprintf("got %f, want %f", got, want))
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}
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s3 := &_List[string]{nil, "dd"}
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s2 := &_List[string]{s3, "aa"}
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s1 := &_List[string]{s2, "bb"}
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if got, want := s1.Largest(), "dd"; got != want {
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panic(fmt.Sprintf("got %s, want %s", got, want))
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}
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j3 := &_ListNum[int]{nil, 1}
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j2 := &_ListNum[int]{j3, 32}
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j1 := &_ListNum[int]{j2, 2}
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if got, want := j1.ClippedLargest(), 2; got != want {
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panic(fmt.Sprintf("got %d, want %d", got, want))
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}
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g3 := &_ListNum[float64]{nil, 13.5}
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g2 := &_ListNum[float64]{g3, 1.2}
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g1 := &_ListNum[float64]{g2, 4.5}
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if got, want := g1.ClippedLargest(), 4.5; got != want {
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panic(fmt.Sprintf("got %f, want %f", got, want))
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}
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}
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