Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

reflect: reflect.StructOf makes types that violate reflect.Type contracts #61433

Open
g7r opened this issue Jul 19, 2023 · 5 comments
Open

reflect: reflect.StructOf makes types that violate reflect.Type contracts #61433

g7r opened this issue Jul 19, 2023 · 5 comments
Assignees
@cherrymui
Labels
compiler/runtime Issues related to the Go compiler and/or runtime. NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
Milestone
Go1.23

Comments

@g7r
Copy link
Contributor

g7r commented Jul 19, 2023

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

$ go version
go version go1.20.6 linux/amd64

Does this issue reproduce with the latest release?

Yes

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

go env Output
$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/sz/.cache/go-build"
GOENV="/home/sz/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/sz/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/sz/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/lib/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.20.6"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
GOWORK=""
CGO_CFLAGS="-O2 -g"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-O2 -g"
CGO_FFLAGS="-O2 -g"
CGO_LDFLAGS="-O2 -g"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build2006396805=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Consider the following code: https://go.dev/play/p/6MPHjq0B5km

It invokes reflect.StructOf method with two embedded fields, a struct and an interface. The resulting type has three methods, according to reflect.Type.NumMethod() function. The method list isn't lexicographically sorted and contains duplicates.

reflect.StructOf has its limitations documented in godoc, but it doesn't explain the observed behavior.

What did you expect to see?

Output:

Method 0: M1
Method 1: M2

What did you see instead?

Output:

Method 0: M1
Method 1: M2
Method 2: M1
@gopherbot gopherbot added the compiler/runtime Issues related to the Go compiler and/or runtime. label Jul 19, 2023
@seankhliao
Copy link
Member

looks like a known limitation: https://cs.opensource.google/go/go/+/refs/tags/go1.20.6:src/reflect/type.go;l=2685

@g7r
Copy link
Contributor Author

g7r commented Jul 19, 2023

@seankhliao, kind of yes. reflect.StructOf is really limited when it comes to embedding fields with methods. Nonetheless, reflect.StructOf allows me to create types that break contracts.

@heschi heschi added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Jul 20, 2023
@heschi heschi added this to the Go1.22 milestone Jul 20, 2023
@heschi
Copy link
Contributor

heschi commented Jul 20, 2023

cc @golang/runtime

@cherrymui
Copy link
Member

If we create such a struct in Go, it only has the M2 method: https://go.dev/play/p/wpUZ9HSrQQC . The ambiguous M1 method is not included in the method set of the outer struct. I think the reflect package should do that as well. I.e. the expected output would be just

Method 0: M2

@cherrymui
Copy link
Member

As we currently don't support embedding multiple non-interface fields, the duplicates must be from interface fields. I'm curious about your use case. As far as I can tell, calling embedded interface method doesn't seem to work.

@odeke-em odeke-em modified the milestones: Go1.22, Go1.23 Dec 13, 2023
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Assignees

@cherrymui cherrymui

Labels
compiler/runtime Issues related to the Go compiler and/or runtime. NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
Projects
Go Compiler / Runtime
Status: Todo
Milestone
Go1.23
Development

No branches or pull requests
6 participants
@g7r @odeke-em @gopherbot @seankhliao @cherrymui @heschi