cmd/go2go: panic with an embedded type param

[tenntenn]

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

$ go version
go version devel +79f7966688 Tue Jan 12 16:41:23 2021 +0000 darwin/amd64

Does this issue reproduce with the latest release?

N/A

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

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/tenntenn/Library/Caches/go-build"
GOENV="/Users/tenntenn/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/tenntenn/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/tenntenn/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/gotip"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/gotip/pkg/tool/darwin_amd64"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/usr/local/gotip/src/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 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/gh/r3m72st579d1z1trbmd6xfyc0000gp/T/go-build686441710=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

https://go2goplay.golang.org/p/iYVfYrwMPa3

package main

import (
	"fmt"
)

type C[T any] interface {
	type struct{ T }
}

func f[T any, _ C[T]](v T) {
	fmt.Println(v)
}

func main() {
	f(10)
}

What did you expect to see?

Print 10.

What did you see instead?

Panic.

panic: /var/folders/gh/r3m72st579d1z1trbmd6xfyc0000gp/T/go2go-run128067254/main.go2:12:2: unexpected type string character '=' in "struct{T /* = int */}"

goroutine 1 [running]:
go/go2go.(*translator).instantiatedName(0xc00014f678, 0x0, 0xc00000c4c0, 0xc00000c740, 0x2, 0x2, 0xc000061aa8, 0x0, 0x0, 0x0)
	/usr/local/gotip/src/go/go2go/names.go:62 +0x765
go/go2go.(*translator).instantiateFunction(0xc00014f678, 0x0, 0xc00000c4c0, 0xc00000c840, 0x2, 0x2, 0xc00000c740, 0x2, 0x2, 0x124c200, ...)
	/usr/local/gotip/src/go/go2go/instantiate.go:94 +0x85
go/go2go.(*translator).translateFunctionInstantiation(0xc00014f678, 0xc000048660)
	/usr/local/gotip/src/go/go2go/rewrite.go:906 +0x46e
go/go2go.(*translator).translateExpr(0xc00014f678, 0xc000048660)
	/usr/local/gotip/src/go/go2go/rewrite.go:687 +0x3cc
go/go2go.(*translator).translateStmt(0xc00014f678, 0xc000048670)
	/usr/local/gotip/src/go/go2go/rewrite.go:578 +0x3ac
go/go2go.(*translator).translateBlockStmt(0xc00014f678, 0xc000010db0)
	/usr/local/gotip/src/go/go2go/rewrite.go:547 +0x57
go/go2go.(*translator).translateFuncDecl(0xc00014f678, 0xc000020560)
	/usr/local/gotip/src/go/go2go/rewrite.go:538 +0xdb
go/go2go.(*translator).translate(0xc00014f678, 0xc00007c120)
	/usr/local/gotip/src/go/go2go/rewrite.go:466 +0x391
go/go2go.rewriteAST(0xc0000202c0, 0xc0000543c0, 0x0, 0x0, 0xc00005f770, 0xc00007c120, 0x14ac201, 0xc000020300, 0x140b480)
	/usr/local/gotip/src/go/go2go/rewrite.go:257 +0xe5
go/go2go.rewriteFile(0xc0000160f0, 0x43, 0xc0000202c0, 0xc0000543c0, 0x0, 0x0, 0xc00005f770, 0xc000016280, 0x4c, 0xc00007c120, ...)
	/usr/local/gotip/src/go/go2go/rewrite.go:221 +0xb8
go/go2go.rewriteFilesInPath(0xc0000543c0, 0x0, 0x0, 0xc0000160f0, 0x43, 0xc000048490, 0x1, 0x1, 0x0, 0x0, ...)
	/usr/local/gotip/src/go/go2go/go2go.go:115 +0xc5c
go/go2go.rewriteToPkgs(0xc0000543c0, 0x0, 0x0, 0xc0000160f0, 0x43, 0xc0000101d0, 0xc0000160f0, 0x43, 0x7ffeefbffb79, 0x8)
	/usr/local/gotip/src/go/go2go/go2go.go:46 +0x165
go/go2go.Rewrite(...)
	/usr/local/gotip/src/go/go2go/go2go.go:30
main.translate(0xc0000543c0, 0xc0000160f0, 0x43)
	/usr/local/gotip/src/cmd/go2go/translate.go:15 +0x47
main.main()
	/usr/local/gotip/src/cmd/go2go/main.go:63 +0xb2f

[tenntenn]

I tried adding = to nameCodes, it works.

diff --git a/src/go/go2go/names.go b/src/go/go2go/names.go
index ec3bef2db7..c054fb5a93 100644
--- a/src/go/go2go/names.go
+++ b/src/go/go2go/names.go
@@ -34,8 +34,9 @@ var nameCodes = map[rune]int{
 	'<':       11,
 	'-':       12,
 	'/':       13,
-	nameSep:   14,
-	nameIntro: 15,
+	'=':       14,
+	nameSep:   15,
+	nameIntro: 16,
 }
 
 // instantiatedName returns the name of a newly instantiated function.

[ianlancetaylor]

CC @griesemer

I'm not sure where the /* = int */ is coming from.

In general the go2go playground does not have good support for embedded type parameters.

[tenntenn]

/* = int */ comes from types.WriteType.

[findleyr]

I'm working on updating the playground this week; I can take a look at this particular panic.

[KeKe-Li]

also i have the same prombles,but i think is just embedded type parameters not have good support