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go/types: avoid infinite recursion in Comparable #43088

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findleyr opened this issue Dec 9, 2020 · 3 comments
Closed

go/types: avoid infinite recursion in Comparable #43088

findleyr opened this issue Dec 9, 2020 · 3 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done. release-blocker
Milestone
Go1.16

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@findleyr
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findleyr commented Dec 9, 2020

https://golang.org/cl/276374 fixes an infinite recursion in the Comparable function of the cmd/compile/internal/types2 package in the dev.typeparams branch, which is based on go/types.

This bug is present in go/types as well, though it can't be hit via normal type-checking. However, it is possible to reach via the API, for example

name := types.NewTypeName(token.NoPos, nil, "T", nil)
T := types.NewNamed(name, nil, nil)
S := types.NewStruct([]*types.Var{types.NewField(token.NoPos, nil, "x", T, false)}, nil)
T.SetUnderlying(S)
_ = types.Comparable(T)

We should probably port CL 276374 to go/types for 1.16.

CC @griesemer
@findleyr findleyr self-assigned this Dec 9, 2020
@findleyr findleyr added this to the Go1.16 milestone Dec 9, 2020
@findleyr findleyr added release-blocker NeedsFix The path to resolution is known, but the work has not been done. labels Dec 9, 2020
@griesemer
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Agreed. The fix is straight-forward and safe to include into 1.16 at this time.

@gopherbot
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Change https://golang.org/cl/276374 mentions this issue: [dev.typeparams] cmd/compile/internal/types2: avoid endless recursion in Comparable predicate

@gopherbot
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Change https://golang.org/cl/276552 mentions this issue: go/types: avoid endless recursion in the Comparable predicate

gopherbot pushed a commit that referenced this issue Dec 9, 2020
@griesemer
[dev.typeparams] cmd/compile/internal/types2: avoid endless recursion…
c32566c 
… in Comparable predicate

Use a map to detect recursive types.
With this we can now typecheck fixedbugs/issue8501.go.

Updates #43088.

Change-Id: I7fad6ccf6c94268473ff72b09a3158e13a7f4cc3
Reviewed-on: https://go-review.googlesource.com/c/go/+/276374
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
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