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https://github.com/golang/go
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d31f85009c
The nounified frontend currently tries to construct dictionaries that correspond to invalid instantiations (i.e., instantiations T[X] where X does not satisfy the constraints specified on T's type parameter). As a consequence, we may fail to find method expressions needed by the dictionary. The real fix for this is to avoid creating those dictionaries in the first place, because they should never actually be needed at runtime. But that seems scary for a backport: we've repeatedly attempted to backport generics fixes, which have fixed one issue but introduced another. This CL is a minimally invasive solution to #54225, which avoids the ICE by instead skipping emitting the invalid dictionary. If the dictionary ends up not being needed (which I believe will always be the case), then the linker's reachability analysis will simply ignore its absence. Or worst case, if the dictionary *is* reachable somehow, we've simply turned an ICE into a link-time missing symbol failure. That's not great for user experience, but it seems like a small trade off to avoid risking breaking any other currently working code. Updates #54225. Change-Id: Ic379696079f4729b1dd6a66994a58cca50281a84 Reviewed-on: https://go-review.googlesource.com/c/go/+/429655 Reviewed-by: Michael Knyszek <mknyszek@google.com> Reviewed-by: Keith Randall <khr@golang.org> Run-TryBot: Matthew Dempsky <mdempsky@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
34 lines
532 B
Go
34 lines
532 B
Go
// run
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// Copyright 2022 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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func main() {
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One[TextValue]()
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}
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func One[V Value]() { Two[Node[V]]() }
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func Two[V interface{ contentLen() int }]() {
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var v V
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v.contentLen()
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}
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type Value interface {
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Len() int
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}
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type Node[V Value] struct{}
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func (Node[V]) contentLen() int {
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var value V
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return value.Len()
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}
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type TextValue struct{}
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func (TextValue) Len() int { return 0 }
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