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go/types/types2: generic functions must have a function body #47069

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griesemer opened this issue Jul 6, 2021 · 4 comments
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go/types/types2: generic functions must have a function body #47069

griesemer opened this issue Jul 6, 2021 · 4 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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Go1.18

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@griesemer
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Reminder issue: Currently, the type checkers permit generic functions without function body. We (probably) can't/won't permit external implementations of generic functions.

The linker will probably complain if a generic function body is missing, but we should report a nice error during type checking. The fix is trivial, but there are many generic function type checker tests that don't use function bodies.

cc: @findleyr, @mdempsky, @ianlancetaylor
@griesemer griesemer added NeedsFix The path to resolution is known, but the work has not been done. NeedsDecision Feedback is required from experts, contributors, and/or the community before a change can be made. labels Jul 6, 2021
@griesemer griesemer added this to the Go1.18 milestone Jul 6, 2021
@griesemer griesemer self-assigned this Jul 6, 2021
@gopherbot gopherbot removed the NeedsFix The path to resolution is known, but the work has not been done. label Jul 6, 2021
@griesemer
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@ianlancetaylor Do you see any reason why we would want to allow leaving away the function body for a generic function? (I don't know how an external implementation would work.)

@ianlancetaylor
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I can't think of any way that it would make sense to omit the body of a generic function. A generic function can only be used if it is instantiated, and the compiler can't instantiate without a body.

@griesemer griesemer added NeedsFix The path to resolution is known, but the work has not been done. and removed NeedsDecision Feedback is required from experts, contributors, and/or the community before a change can be made. labels Aug 9, 2021
@gopherbot
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Change https://golang.org/cl/340911 mentions this issue: [dev.typeparams] cmd/compile/internal/types2: parameterized functions must have a body

gopherbot pushed a commit that referenced this issue Aug 10, 2021
@griesemer
[dev.typeparams] cmd/compile/internal/types2: parameterized functions…
e4cfa2f 
… must have a body

Add the respective check and add missing bodies to tests.
Use {} as body for functions that don't return a result.
Use { panic(0) } as body for functions that return a result.

For #47069.

Change-Id: Ia5d7525c9c036baf8a955d13bff448401e08235e
Reviewed-on: https://go-review.googlesource.com/c/go/+/340911
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
@griesemer
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This was fixed in types2 with the above CL, and in go/types with CL 342475.

@golang golang locked and limited conversation to collaborators Jun 23, 2023
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