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go/types, types2: missing error for invalid (but empty) expression switch #43110

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griesemer opened this issue Dec 10, 2020 · 2 comments
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go/types, types2: missing error for invalid (but empty) expression switch #43110

griesemer opened this issue Dec 10, 2020 · 2 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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Go1.17

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@griesemer
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For

package main

func _() {
	var a struct{ _ func() }
	switch a {
	}
}

the compiler reports

main.go:5:2: cannot switch on a (type struct { _ func() }) (struct containing func() cannot be compared)

go/types and types2 don't report an error.

For

var a struct{ _ func() }
switch a {
case a:
}

go/types and types2 report an error with case a:

main.go:6:7: cannot compare a == a (operator == not defined for struct{_ func()})

Empty switches like this are unlikely, but we should report an error at the top (and than avoid the respective errors for the cases).

cc: @findleyr
@griesemer griesemer added the NeedsFix The path to resolution is known, but the work has not been done. label Dec 10, 2020
@griesemer griesemer added this to the Go1.17 milestone Dec 10, 2020
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Change https://golang.org/cl/278132 mentions this issue: [dev.typeparams] cmd/compile/internal/types2: report error for invalid (but empty) expr switch

@griesemer griesemer mentioned this issue Dec 15, 2020
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gopherbot pushed a commit that referenced this issue Dec 15, 2020
@griesemer
[dev.typeparams] cmd/compile/internal/types2: report error for invali…
14e4267 
…d (but empty) expr switch

Enable one more errorcheck test.

Updates #43110.
Updates #43200.

Change-Id: Ib7b971d5e9989c65320579f75d65266bbbbeec53
Reviewed-on: https://go-review.googlesource.com/c/go/+/278132
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
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Change https://golang.org/cl/278813 mentions this issue: go/types: report error for invalid (but empty) expr switch

@golang golang locked and limited conversation to collaborators Dec 16, 2021
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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