Type assertion to empty interface type crashes with `type assert failed`

[eliasnaur]

Reproducer program,

package main

import "fmt"

type Empty interface {
}

func main() {
	var intf interface{} = new(int)
	typed := intf.(Empty)
	fmt.Println(typed)
}

crashes on my stm32f469disco target with:

panic: runtime error: type assert failed

Issue found while running (more) Gio code.

[aykevl]

Did a quick test and this is also present in the release branch (so it isn't caused by #2753).

[aykevl]

Simplified to avoid use of fmt:

package main

type Empty interface {
}

func main() {
        var intf interface{} = 3
        typed := intf.(Empty)
        use(typed)
}

func use(typed Empty) {
        print("use: ")
        println(typed.(int))
}

It panics on the interface type assert in the main function.

[inindev]

I ran into this same issue today using an esp32c3. My output is via uart1 and I am using a local build of the dev branch which was built at commit 33489d6. I see the same issue using dev commit 776dabb. Let me know if it would be helpful to test against a different branch or commit.

The first call to fmt.Printf succeeds, then the second call results in: "panic: runtime error: type assert failed"

package main

import (
    "fmt"
    "time"
)

func main() {
    fmt.Printf("hello world 1\r\n")
    fmt.Printf("hello world 2\r\n")

    for {
        time.Sleep(time.Second)
    }
}

output

hello world 1
panic: runtime error: type assert failed

[aykevl]

Probably unrelated to #5438 but yeah, this bug was probably fixed in the meantime.