cmd/compile: internal compiler error: assertion failed

[4ad]

On 48dfddb.

Repro:

package main

import "fmt"

type Foo[t any] interface {
	Foo(Bar[t])
}
type Bar[t any] interface {
	Int(Int[t]) Foo[int]
}

type Int[t any] int

func (n Int[t]) Foo(v Bar[t])   { v.Int(n) }
func (n Int[_]) String() string { return fmt.Sprintf("(int %d)", n) }

func main() {
	fmt.Println("hello")
}

with -gcflags='-G=3' this fails with

go run -gcflags='-G=3' e.go
# command-line-arguments
<unknown line number>: internal compiler error: assertion failed

goroutine 1 [running]:
runtime/debug.Stack()
	/Users/aram/go/src/runtime/debug/stack.go:24 +0x65
cmd/compile/internal/base.FatalfAt({0xab6c0, 0xc0}, {0x18ef5c4, 0x10}, {0x0, 0x0, 0x0})
	/Users/aram/go/src/cmd/compile/internal/base/print.go:227 +0x154
cmd/compile/internal/base.Fatalf(...)
	/Users/aram/go/src/cmd/compile/internal/base/print.go:196
cmd/compile/internal/base.Assert(...)
	/Users/aram/go/src/cmd/compile/internal/base/print.go:239
cmd/compile/internal/typecheck.assert(...)
	/Users/aram/go/src/cmd/compile/internal/typecheck/subr.go:976
cmd/compile/internal/typecheck.(*Tsubster).Typ(0xc0000e83d8, 0xc0000aae70)
	/Users/aram/go/src/cmd/compile/internal/typecheck/subr.go:1065 +0x1325
cmd/compile/internal/typecheck.(*Tsubster).tstruct(0xc0000e83d8, 0xc0000ab180, 0x0)
	/Users/aram/go/src/cmd/compile/internal/typecheck/subr.go:1266 +0x15c
cmd/compile/internal/typecheck.(*Tsubster).Typ(0xc0000e83d8, 0xc0000ab030)
	/Users/aram/go/src/cmd/compile/internal/typecheck/subr.go:1111 +0x185
cmd/compile/internal/noder.(*irgen).fillinMethods(0xc0000ec000, 0xc0000caaa0, 0xc0000ab570)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:317 +0x645
cmd/compile/internal/noder.(*irgen).typ0(0xc0000ec000, {0x1a47090, 0xc0000caaa0})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:151 +0x1295
cmd/compile/internal/noder.(*irgen).typ1(0xc0000ec000, {0x1a47090, 0xc0000caaa0})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:61 +0x65
cmd/compile/internal/noder.(*irgen).typ(0xc0000d0780, {0x1a47090, 0xc0000caaa0})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:33 +0x27
cmd/compile/internal/noder.(*irgen).obj(0xc0000ec000, {0x1a58158, 0xc0000d0780})
	/Users/aram/go/src/cmd/compile/internal/noder/object.go:100 +0x7cf
cmd/compile/internal/noder.(*irgen).fillinMethods(0xc0000ec000, 0xc0000cac80, 0xc0000aafc0)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:286 +0x1ff
cmd/compile/internal/noder.(*irgen).typ0(0xc0000ec000, {0x1a47090, 0xc0000cac80})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:151 +0x1295
cmd/compile/internal/noder.(*irgen).typ1(0xc0000ec000, {0x1a47090, 0xc0000cac80})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:61 +0x65
cmd/compile/internal/noder.(*irgen).param(0xc0000ec000, 0xc0000d1620)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:362 +0x74
cmd/compile/internal/noder.(*irgen).signature.func1(0xc0000989f0)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:348 +0xa5
cmd/compile/internal/noder.(*irgen).signature(0xc0000ec000, 0x0, 0xc0000a3400)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:352 +0x233
cmd/compile/internal/noder.(*irgen).typ0(0xc0000ec000, {0x1a47040, 0xc0000ccc30})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:205 +0xefc
cmd/compile/internal/noder.(*irgen).typ1(0xc0000ec000, {0x1a47040, 0xc0000ccc30})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:61 +0x65
cmd/compile/internal/noder.(*irgen).typ0(0xc0000ec000, {0x1a47090, 0xc0000cab40})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:150 +0x1268
cmd/compile/internal/noder.(*irgen).typ1(0xc0000ec000, {0x1a47090, 0xc0000cab40})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:61 +0x65
cmd/compile/internal/noder.(*irgen).param(0xc0000ec000, 0xc0000d16e0)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:362 +0x74
cmd/compile/internal/noder.(*irgen).signature.func1(0xc000098a08)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:348 +0xa5
cmd/compile/internal/noder.(*irgen).signature(0xc0000ec000, 0x2c, 0xc0000a3440)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:352 +0x233
cmd/compile/internal/noder.(*irgen).typ0(0xc0000ec000, {0x1a47040, 0xc0000ccc80})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:205 +0xefc
cmd/compile/internal/noder.(*irgen).typ1(0xc0000ec000, {0x1a47040, 0xc0000ccc80})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:61 +0x65
cmd/compile/internal/noder.(*irgen).typ0(0xc0000ec000, {0x1a47090, 0xc0000ca820})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:150 +0x1268
cmd/compile/internal/noder.(*irgen).typ1(0xc0000ec000, {0x1a47090, 0xc0000ca820})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:61 +0x65
cmd/compile/internal/noder.(*irgen).param(0xc0000ec000, 0xc0000d0cc0)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:362 +0x74
cmd/compile/internal/noder.(*irgen).signature.func1(0xc0000988d0)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:348 +0xa5
cmd/compile/internal/noder.(*irgen).signature(0xc0000ec000, 0x10ce30a, 0xc0000a3580)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:353 +0x269
cmd/compile/internal/noder.(*irgen).typ0(0xc0000ec000, {0x1a47040, 0xc0000cccd0})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:205 +0xefc
cmd/compile/internal/noder.(*irgen).typ1(0xc0000ec000, {0x1a47040, 0xc0000cccd0})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:61 +0x65
cmd/compile/internal/noder.(*irgen).typ0(0xc0000ec000, {0x1a47090, 0xc0000caa00})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:150 +0x1268
cmd/compile/internal/noder.(*irgen).typ1(0xc0000ec000, {0x1a47090, 0xc0000caa00})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:61 +0x65
cmd/compile/internal/noder.(*irgen).param(0xc0000ec000, 0xc0000d1200)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:362 +0x74
cmd/compile/internal/noder.(*irgen).signature.func1(0xc000098948)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:348 +0xa5
cmd/compile/internal/noder.(*irgen).signature(0xc0000ec000, 0xc0000d10e0, 0xc0000a3000)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:352 +0x233
cmd/compile/internal/noder.(*irgen).obj(0xc0000ec000, {0x1a58158, 0xc0000d06c0})
	/Users/aram/go/src/cmd/compile/internal/noder/object.go:102 +0x805
cmd/compile/internal/noder.(*irgen).fillinMethods(0xc0000ec000, 0xc0000ca960, 0xc0000aad90)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:286 +0x1ff
cmd/compile/internal/noder.(*irgen).typ0(0xc0000ec000, {0x1a47090, 0xc0000ca960})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:151 +0x1295
cmd/compile/internal/noder.(*irgen).typ1(0xc0000ec000, {0x1a47090, 0xc0000ca960})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:61 +0x65
cmd/compile/internal/noder.(*irgen).typ(0xc0000d06c0, {0x1a47090, 0xc0000ca960})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:33 +0x27
cmd/compile/internal/noder.(*irgen).obj(0xc0000ec000, {0x1a58158, 0xc0000d06c0})
	/Users/aram/go/src/cmd/compile/internal/noder/object.go:100 +0x7cf
cmd/compile/internal/noder.(*irgen).fillinMethods(0xc0000ec000, 0xc0000cabe0, 0xc0000aad20)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:286 +0x1ff
cmd/compile/internal/noder.(*irgen).typ0(0xc0000ec000, {0x1a47090, 0xc0000cabe0})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:151 +0x1295
cmd/compile/internal/noder.(*irgen).typ1(0xc0000ec000, {0x1a47090, 0xc0000cabe0})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:61 +0x65
cmd/compile/internal/noder.(*irgen).param(0xc0000ec000, 0xc0000d1500)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:362 +0x74
cmd/compile/internal/noder.(*irgen).signature.func1(0xc0000989a8)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:348 +0xa5
cmd/compile/internal/noder.(*irgen).signature(0xc0000ec000, 0x1a47040, 0xc0000a33c0)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:352 +0x233
cmd/compile/internal/noder.(*irgen).typ0(0xc0000ec000, {0x1a47040, 0xc0000ccbe0})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:205 +0xefc
cmd/compile/internal/noder.(*irgen).typ1(0xc0000ec000, {0x1a47040, 0xc0000ccbe0})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:61 +0x65
cmd/compile/internal/noder.(*irgen).typ0(0xc0000ec000, {0x1a47090, 0xc0000ca8c0})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:150 +0x1268
cmd/compile/internal/noder.(*irgen).typ1(0xc0000ec000, {0x1a47090, 0xc0000ca8c0})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:61 +0x65
cmd/compile/internal/noder.(*irgen).param(0xc0000ec000, 0xc0000d0ea0)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:362 +0x74
cmd/compile/internal/noder.(*irgen).signature.func1(0xc000098900)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:348 +0xa5
cmd/compile/internal/noder.(*irgen).signature(0xc0000ec000, 0x120, 0xc0000a2d40)
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:352 +0x233
cmd/compile/internal/noder.(*irgen).typ0(0xc0000ec000, {0x1a47040, 0xc0000ccb40})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:205 +0xefc
cmd/compile/internal/noder.(*irgen).typ1(0xc0000ec000, {0x1a47040, 0xc0000ccb40})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:61 +0x65
cmd/compile/internal/noder.(*irgen).typ(0x1871200, {0x1a47040, 0xc0000ccb40})
	/Users/aram/go/src/cmd/compile/internal/noder/types.go:33 +0x27
cmd/compile/internal/noder.(*irgen).expr(0xc0000ec000, {0x1a48048, 0xc00008c090})
	/Users/aram/go/src/cmd/compile/internal/noder/expr.go:46 +0x90a
cmd/compile/internal/noder.(*irgen).typeExpr(0xc0000ec000, {0x1a48048, 0xc00008c090})
	/Users/aram/go/src/cmd/compile/internal/noder/expr.go:483 +0x31
cmd/compile/internal/noder.(*irgen).typeDecl(0xc0000ec000, 0xc0001381b0, 0xc000092060)
	/Users/aram/go/src/cmd/compile/internal/noder/decl.go:171 +0x10f
cmd/compile/internal/noder.(*irgen).generate(0xc0000ec000, {0xc000064b70, 0x2, 0x203000})
	/Users/aram/go/src/cmd/compile/internal/noder/irgen.go:228 +0x729
cmd/compile/internal/noder.check2({0xc000064b70, 0x2, 0x2})
	/Users/aram/go/src/cmd/compile/internal/noder/irgen.go:92 +0x16d
cmd/compile/internal/noder.LoadPackage({0xc00001e260, 0x2, 0x0})
	/Users/aram/go/src/cmd/compile/internal/noder/noder.go:90 +0x365
cmd/compile/internal/gc.Main(0x1916550)
	/Users/aram/go/src/cmd/compile/internal/gc/main.go:190 +0xaf3
main.main()
	/Users/aram/go/src/cmd/compile/main.go:55 +0xdd

Works on go2go playground: https://go2goplay.golang.org/p/kPeQ-34axPT

Removing either one of Int's methods makes the compiler happy.

[griesemer]

Slightly simpler reproducer:

package p

type Foo[t any] interface {
	Foo(Bar[t])
}
type Bar[t any] interface {
	Int(Int[t]) Foo[int]
}

type Int[t any] int

func (n Int[t]) Foo(Bar[t]) {}
func (n Int[_]) String()    {}

Looks like an issue with types2 to types(1) translation.
cc: @danscales

[danscales]

Yes, this is a types2-to-types1 translation problem. I'll take this one. Adding Type to the end of the type names to be clearer, we have FooType's definition depends on BarType, BarType's definition depends on IntType and FooType, and IntType's methods depend on BarType. I think we may just need a "delay" queue to call fillinMethods on types that have been translated recursively after the top-level (possibly mutually recursive) types have been translated.

[gopherbot]

Change https://golang.org/cl/345149 mentions this issue: cmd/compile: delay fillinMethods to deal with mutually-recursive types