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go/types, types2: Simple generic code makes compiler loop forever #48671

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aDotInTheVoid opened this issue Sep 28, 2021 · 3 comments
Closed

go/types, types2: Simple generic code makes compiler loop forever #48671

aDotInTheVoid opened this issue Sep 28, 2021 · 3 comments
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FrozenDueToAge NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. release-blocker
Milestone
Go1.18

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@aDotInTheVoid
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What version of Go are you using (go version)?

$ go version
go version devel go1.18-534dfb2 Tue Sep 28 03:21:58 2021 +0000 darwin/amd64

Does this issue reproduce with the latest release?

No, requires generics

What operating system and processor architecture are you using (go env)?

go env Output
$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/nixon/Library/Caches/go-build"
GOENV="/Users/nixon/Library/Application Support/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/nixon/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/nixon/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/Users/nixon/sdk/gotip"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/Users/nixon/sdk/gotip/pkg/tool/darwin_amd64"
GOVCS=""
GOVERSION="devel go1.18-534dfb2 Tue Sep 28 03:21:58 2021 +0000"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/nixon/dev/go/gnom/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/14/bhp6wfld6f9gyw31rw492_p40000gn/T/go-build1866204895=/tmp/go-build -gno-record-gcc-switches -fno-common"
GOROOT/bin/go version: go version devel go1.18-534dfb2 Tue Sep 28 03:21:58 2021 +0000 darwin/amd64
GOROOT/bin/go tool compile -V: compile version devel go1.18-534dfb2 Tue Sep 28 03:21:58 2021 +0000
uname -v: Darwin Kernel Version 19.6.0: Tue Aug 24 20:28:00 PDT 2021; root:xnu-6153.141.40~1/RELEASE_X86_64
ProductName:	Mac OS X
ProductVersion:	10.15.7
BuildVersion:	19H1417
lldb --version: lldb-1103.0.22.10
Apple Swift version 5.2.4 (swiftlang-1103.0.32.9 clang-1103.0.32.53)

What did you do?

package slow

type Maker[T any] func() T

func (m Maker[T]) Culprit() Maker[[]T] {
	return nil
}

What did you expect to see?

Program compiles sucessfully

What did you see instead?

Compiller loops forever. I stoped it after 9 mins.

Other potentialy usefull things

package slow

type Maker[T any] func() T

func (m Maker[T]) Culprit() Maker[T] {
	return nil
}

both compiles fine
@findleyr findleyr changed the title Simple generic code makes compiler loop forever go/types, types2: Simple generic code makes compiler loop forever Sep 28, 2021
@findleyr
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This is an infinite recursion in the type checker.

CC @griesemer

@findleyr findleyr added release-blocker NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. labels Sep 28, 2021
@findleyr findleyr added this to the Go1.18 milestone Sep 28, 2021
@findleyr
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Thank you for the report.

Simpler reproducer:

type N[T any] N[*T]

We recurse while expanding N[*T].

This can probably be duped to #48098, though it is important to note that we must also detect this recursion through method declarations.

@findleyr findleyr mentioned this issue Sep 28, 2021
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@findleyr
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Closing as a dupe of #48098

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