cmd/go2go: panic in type checker

[candlerb]

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

go2go playground

Does this issue reproduce with the latest release?

N/A

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

N/A

What did you do?

https://go2goplay.golang.org/p/VH5SLJNxw3X

package main

import (
	"fmt"
)

type MyMap[KT, VT comparable] struct {
    data map[KT]VT
}

func NewMap[KT, VT comparable]() *MyMap[KT, VT] {
    var m MyMap[KT, VT]
    m.data = make(map[KT]VT)
    return &m
}

func (m *MyMap[KT,VT]) set(k KT, v VT) {
    m.data[k] = v
}

func main() {
    m := NewMap[string, int]
    m[int] = 123
    fmt.Println("Got ", m["foo"])
}

What did you expect to see?

An error message about the nonsense line m[int] = 123

What did you see instead?

Panic - from the type checker according to @ianlancetaylor here.

panic: assertion failed [recovered]
	panic: assertion failed [recovered]
	panic: assertion failed

goroutine 1 [running]:
go/types.(*Checker).handleBailout(0xc0000d4280, 0xc000159be0)
	/usr/local/go-faketime/src/go/types/check.go:252 +0x9b
panic(0x645460, 0x6d5ad0)
	/usr/local/go-faketime/src/runtime/panic.go:969 +0x175
go/types.(*Checker).stmt.func1(0xc0000d4280, 0xc00013db80)
	/usr/local/go-faketime/src/go/types/stmt.go:307 +0x85
panic(0x645460, 0x6d5ad0)
	/usr/local/go-faketime/src/runtime/panic.go:975 +0x3e9
go/types.assert(...)
	/usr/local/go-faketime/src/go/types/errors.go:19
go/types.(*Checker).call(0xc0000d4280, 0xc0000af180, 0xc00013def0, 0x6de1e0, 0xc000084fc0, 0x9)
	/usr/local/go-faketime/src/go/types/call.go:188 +0x172d
go/types.(*Checker).exprInternal(0xc0000d4280, 0xc0000af180, 0x6de1e0, 0xc000084fc0, 0x0, 0x0, 0x6462e0)
	/usr/local/go-faketime/src/go/types/expr.go:1359 +0x2b9e
go/types.(*Checker).rawExpr(0xc0000d4280, 0xc0000af180, 0x6de1e0, 0xc000084fc0, 0x0, 0x0, 0x0)
	/usr/local/go-faketime/src/go/types/expr.go:1043 +0xc5
go/types.(*Checker).expr(0xc0000d4280, 0xc0000af180, 0x6de1e0, 0xc000084fc0)
	/usr/local/go-faketime/src/go/types/expr.go:1753 +0x55
go/types.(*Checker).assignVar(0xc0000d4280, 0x6de1e0, 0xc000084fc0, 0xc0000af140, 0xc00013db00, 0xc0000a8328)
	/usr/local/go-faketime/src/go/types/assignments.go:176 +0x29b
go/types.(*Checker).assignVars(0xc0000d4280, 0xc000082820, 0x1, 0x1, 0xc000082830, 0x1, 0x1)
	/usr/local/go-faketime/src/go/types/assignments.go:283 +0x22f
go/types.(*Checker).stmt(0xc0000d4280, 0x0, 0x6ddae0, 0xc0000ae700)
	/usr/local/go-faketime/src/go/types/stmt.go:409 +0x351d
go/types.(*Checker).stmtList(0xc0000d4280, 0x0, 0xc0000ae740, 0x3, 0x4)
	/usr/local/go-faketime/src/go/types/stmt.go:125 +0xd1
go/types.(*Checker).funcBody(0xc0000d4280, 0xc00013e840, 0xc0000a445c, 0x4, 0xc00013ea20, 0xc000085020, 0x0, 0x0)
	/usr/local/go-faketime/src/go/types/stmt.go:42 +0x257
go/types.(*Checker).funcDecl.func1()
	/usr/local/go-faketime/src/go/types/decl.go:813 +0x67
go/types.(*Checker).processDelayed(0xc0000d4280, 0x0)
	/usr/local/go-faketime/src/go/types/check.go:327 +0x3e
go/types.(*Checker).checkFiles(0xc0000d4280, 0xc000105cb8, 0x1, 0x1, 0x0, 0x0)
	/usr/local/go-faketime/src/go/types/check.go:295 +0x205
go/types.(*Checker).Files(...)
	/usr/local/go-faketime/src/go/types/check.go:257
go/types.(*Config).Check(0xc0000ae780, 0xc0000a43a0, 0x4, 0xc0000ae280, 0xc000105cb8, 0x1, 0x1, 0xc0000b1360, 0x0, 0x4b70cf, ...)
	/usr/local/go-faketime/src/go/types/api.go:392 +0x188
go/go2go.RewriteBuffer(0xc0000aa360, 0x7fff446f6dec, 0x1e, 0xc0000fa000, 0x174, 0x374, 0x0, 0xc000084a50, 0xc000084a20, 0xc0000849f0, ...)
	/usr/local/go-faketime/src/go/go2go/go2go.go:139 +0x257
main.translateFile(0xc0000aa360, 0x7fff446f6dec, 0x1e)
	/usr/local/go-faketime/src/cmd/go2go/translate.go:26 +0xa9
main.main()
	/usr/local/go-faketime/src/cmd/go2go/main.go:74 +0x309

[griesemer]

This works fine with cmd/compile/internal/types2 and the compiler (dev.typeparams branch).