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cmd/compile: unified IR needs to treat conversion of constants to type parameter type as non-constant #54307

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mdempsky opened this issue Aug 5, 2022 · 1 comment
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cmd/compile: unified IR needs to treat conversion of constants to type parameter type as non-constant #54307

mdempsky opened this issue Aug 5, 2022 · 1 comment
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compiler/runtime Issues related to the Go compiler and/or runtime. FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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Go1.20

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mdempsky commented Aug 5, 2022 •
edited

This code compiles with Go 1.19, but currently fails with GOEXPERIMENT=unified because -1 is not representable by type uint.

package p

func f[Int int, Uint uint]() {
	_ = uint(Int(-1))
	_ = uint(Uint(0) - 1)
}

var _ = f[int, uint]

Per the Go spec, "If the type is a type parameter, the constant is converted into a non-constant value of the type parameter."

(Noticed at https://github.com/lightstep/otel-launcher-go/blob/448fc6822e81fdde2763f224bd9c7f3bbf72309c/lightstep/sdk/metric/aggregator/histogram/structure/exponential.go#L640, while investigating #54302.)
@mdempsky mdempsky added the NeedsFix The path to resolution is known, but the work has not been done. label Aug 5, 2022
@mdempsky mdempsky added this to the Go1.20 milestone Aug 5, 2022
@mdempsky mdempsky self-assigned this Aug 5, 2022
@gopherbot gopherbot added the compiler/runtime Issues related to the Go compiler and/or runtime. label Aug 5, 2022
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Change https://go.dev/cl/421874 mentions this issue: cmd/compile: treat constants to type parameter conversion as non-constant in Unified IR

jproberts pushed a commit to jproberts/go that referenced this issue Aug 10, 2022
@cuonglm @jproberts
cmd/compile: treat constants to type parameter conversion as non-cons…
2994661 
…tant in Unified IR

Fixes golang#54307

Change-Id: Idcbdb3b1cf7c7fd147cc079659f29a9b5d17e6e0
Reviewed-on: https://go-review.googlesource.com/c/go/+/421874
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
@golang golang locked and limited conversation to collaborators Aug 8, 2023
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compiler/runtime Issues related to the Go compiler and/or runtime. FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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