cmd/compile: nil deref #24447
Description
go version devel +b61b1d2c57 Sun Mar 18 16:53:53 2018 +0000 linux/amd64
package n type R interface{S} type S=interface{R}go build crash.go
panic: runtime error: invalid memory address or nil pointer dereference goroutine 1 [running]: cmd/compile/internal/gc.dowidth() cmd/compile/internal/types.(*Type).Fields() cmd/compile/internal/gc.expandiface() cmd/compile/internal/gc.dowidth() cmd/compile/internal/types.(*Type).Fields() cmd/compile/internal/gc.expandiface() cmd/compile/internal/gc.dowidth() cmd/compile/internal/gc.resumecheckwidth() cmd/compile/internal/gc.Main() main.main() Found with go-fuzz. #19109