Constant Evaluation of len with Type Assertion Causes Panic

[omarsy]

Description

The following code works as expected in Go, producing the output "ok 2". However, in Gno, it fails with a runtime panic and generates a lengthy stack trace.

package main

func main() {
	var i interface{} = [2]int{0, 1}
	const a = len(i.([2]int))
	println("ok", a)
}

Expected Behavior

In Go, the code executes without errors and produces the output:

ok 2

This is because the len function correctly evaluates the length of the array type assertion i.([2]int) during compilation.

Actual Behavior

In Gno, the code fails with a runtime panic. The stack trace includes the following:

/Users/ghost/go/pkg/mod/golang.org/[email protected]/src/runtime/debug/stack.go:24 +0x64
        github.com/gnolang/gno/gnovm/pkg/test.(*TestOptions).runTest.func1()
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/test/filetest.go:196 +0xac
        panic({0x105106360?, 0x140002a7800?})
                /Users/ghost/go/pkg/mod/golang.org/[email protected]/src/runtime/panic.go:770 +0x124
        github.com/gnolang/gno/gnovm/pkg/gnolang.doRecover({0x14000245c00, 0x3, 0x20}, {0x1051bcb60, 0x14000271b90})
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/preprocess.go:377 +0xb4
        panic({0x105106360?, 0x140002a7800?})
                /Users/ghost/go/pkg/mod/golang.org/[email protected]/src/runtime/panic.go:770 +0x124
        github.com/gnolang/gno/gnovm/pkg/gnolang.doRecover({0x14000195980, 0x1, 0x1}, {0x1051bcb60, 0x14000271b90})
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/preprocess.go:377 +0xb4
        panic({0x105106360?, 0x140002a7800?})
                /Users/ghost/go/pkg/mod/golang.org/[email protected]/src/runtime/panic.go:770 +0x124
        github.com/gnolang/gno/gnovm/pkg/gnolang.doRecover({0x14000370a00, 0x1, 0x20}, {0x1051bcb60, 0x14000271b90})
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/preprocess.go:399 +0x304
        panic({0x1050be360?, 0x14000195930?})
                /Users/ghost/go/pkg/mod/golang.org/[email protected]/src/runtime/panic.go:770 +0x124
        github.com/gnolang/gno/gnovm/pkg/gnolang.assertValidConstValue({0x1051c6be8, 0x140002bafa0}, {0x1051c7808, 0x140003ae808}, {0x1051bf128, 0x14000229770}, {0x1051be820?, 0x140001ab320?})
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/type_check.go:378 +0x680
        github.com/gnolang/gno/gnovm/pkg/gnolang.assertValidConstValue({0x1051c6be8, 0x140002bafa0}, {0x1051c7808, 0x140003ae808}, {0x1051be820?, 0x140001ab320}, {0x0, 0x0?})
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/type_check.go:289 +0x468
        github.com/gnolang/gno/gnovm/pkg/gnolang.assertValidConstExpr({0x1051c6be8, 0x140002bafa0}, {0x1051c7808, 0x140003ae808}, 0x1051bcb60?, {0x1051be820, 0x140001ab320})
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/type_check.go:243 +0x120
        github.com/gnolang/gno/gnovm/pkg/gnolang.preprocess1.func1({0x14000370c00, 0x0, 0x20}, 0x0, 0x0, {0x1051bcb60, 0x14000271b90}, 0x3)
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/preprocess.go:2302 +0x5c1c
        github.com/gnolang/gno/gnovm/pkg/gnolang.transcribe(0x1400037d3a0, {0x14000370c00, 0x0, 0x20}, 0x0, 0x0, {0x1051bcb60, 0x14000271b90}, 0x1400037d2a7)
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/transcribe.go:752 +0x18a8
        github.com/gnolang/gno/gnovm/pkg/gnolang.Transcribe({0x1051bcb60, 0x14000271b90}, 0x1400037d3a0)
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/transcribe.go:136 +0xb4
        github.com/gnolang/gno/gnovm/pkg/gnolang.preprocess1({0x1051c6be8, 0x140002bafa0}, {0x1051c7808, 0x140003ae808}, {0x1051bcb60, 0x14000271b90?})
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/preprocess.go:476 +0x250
        github.com/gnolang/gno/gnovm/pkg/gnolang.Preprocess({0x1051c6be8?, 0x140002bafa0?}, {0x1051c7808, 0x140003ae808}, {0x1051bcb60?, 0x14000271b90?})
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/preprocess.go:436 +0x34
        github.com/gnolang/gno/gnovm/pkg/gnolang.predefineNow2({0x1051c6be8, 0x140002bafa0}, {0x1051c7808, 0x140003ae808}, {0x1051c0ff0, 0x14000271b90}, 0x1400037d6a0)
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/preprocess.go:4189 +0x290
        github.com/gnolang/gno/gnovm/pkg/gnolang.predefineNow({0x1051c6be8?, 0x140002bafa0?}, {0x1051c7808?, 0x140003ae808?}, {0x1051c0ff0?, 0x14000271b90?})
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/preprocess.go:4061 +0xc4
        github.com/gnolang/gno/gnovm/pkg/gnolang.preprocess1.func1({0x14000370000, 0x3, 0x20}, 0x27, 0x0, {0x1051bcb60, 0x14000271b90}, 0x0)
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/preprocess.go:529 +0xad80
        github.com/gnolang/gno/gnovm/pkg/gnolang.transcribe(0x1400037f150, {0x14000370000, 0x3, 0x20}, 0x27, 0x0, {0x1051bcb60, 0x14000271b90}, 0x1400037e8a7)
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/transcribe.go:143 +0x74
        github.com/gnolang/gno/gnovm/pkg/gnolang.transcribe(0x1400037f150, {0x14000370000, 0x2, 0x20}, 0x47, 0x0, {0x1051bd860, 0x14000364080}, 0x1400037eb37)
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/transcribe.go:411 +0x25fc
        github.com/gnolang/gno/gnovm/pkg/gnolang.transcribe(0x1400037f150, {0x14000370000, 0x1, 0x20}, 0x4f, 0x0, {0x1051bcae0, 0x140003ae808}, 0x1400037edc7)
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/transcribe.go:690 +0x73d0
        github.com/gnolang/gno/gnovm/pkg/gnolang.transcribe(0x1400037f150, {0x14000370000, 0x0, 0x20}, 0x0, 0x0, {0x1051be1e0, 0x14000334608}, 0x1400037f057)
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/transcribe.go:732 +0x2d4c
        github.com/gnolang/gno/gnovm/pkg/gnolang.Transcribe({0x1051be1e0, 0x14000334608}, 0x1400037f150)
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/transcribe.go:136 +0xb4
        github.com/gnolang/gno/gnovm/pkg/gnolang.preprocess1({0x1051c6be8, 0x140002bafa0}, {0x1051c76e0, 0x14000334008}, {0x1051be1e0, 0x14000334608?})
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/preprocess.go:476 +0x250
        github.com/gnolang/gno/gnovm/pkg/gnolang.Preprocess({0x1051c6be8?, 0x140002bafa0?}, {0x1051c76e0, 0x14000334008}, {0x1051be1e0?, 0x14000334608?})
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/preprocess.go:436 +0x34
        github.com/gnolang/gno/gnovm/pkg/gnolang.(*Machine).runFileDecls(0x140001f2008, {0x14000197b18, 0x1, 0x1})
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/machine.go:495 +0x254
        github.com/gnolang/gno/gnovm/pkg/gnolang.(*Machine).RunFiles(0x140001f2008, {0x14000197b18?, 0x140000422a0?, 0x6c?})
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/machine.go:446 +0x30
        github.com/gnolang/gno/gnovm/pkg/test.(*TestOptions).runTest(0x140003b6b40, 0x140001f2008, {0x104e34320, 0x4}, {0x140004a0990, 0x11}, {0x1400026b200, 0x6c, 0x140002bafa0?})
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/test/filetest.go:222 +0x46c
        github.com/gnolang/gno/gnovm/pkg/test.(*TestOptions).runFiletest(0x140003b6b40, {0x140004a0990, 0x11}, {0x1400026b200, 0x6c, 0x200})
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/test/filetest.go:68 +0x50c
        github.com/gnolang/gno/gnovm/pkg/test.(*TestOptions).RunFiletest(...)
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/test/filetest.go:28
        github.com/gnolang/gno/gnovm/pkg/gnolang_test.TestFiles.func2.2(0x1400039e000)
                /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/files_test.go:90 +0xfc
        testing.tRunner(0x1400039e000, 0x14000271880)
                /Users/ghost/go/pkg/mod/golang.org/[email protected]/src/testing/testing.go:1689 +0xec
        created by testing.(*T).Run in goroutine 35
                /Users/ghost/go/pkg/mod/golang.org/[email protected]/src/testing/testing.go:1742 +0x318