opa eval panics when usinginput()

[srenatus]

open-policy-agent/opa % opa eval '[input() | input := 1]'
panic: interface conversion: ast.Value is ast.Var, not ast.Ref

goroutine 1 [running]:
github.com/open-policy-agent/opa/ast.(*Expr).Operator(...)
        /Users/stephan/Sources/open-policy-agent/opa/ast/policy.go:1178
github.com/open-policy-agent/opa/ast.checkUndefinedFuncs.func1(0xc000349080)
        /Users/stephan/Sources/open-policy-agent/opa/ast/compile.go:881 +0x689
github.com/open-policy-agent/opa/ast.WalkExprs.func1({0x5727500?, 0xc000349080?})
        /Users/stephan/Sources/open-policy-agent/opa/ast/visit.go:213 +0x36
github.com/open-policy-agent/opa/ast.(*GenericVisitor).Walk(0xc0007fe1f8, {0x5727500?, 0xc000349080?})
        /Users/stephan/Sources/open-policy-agent/opa/ast/visit.go:278 +0x5c
github.com/open-policy-agent/opa/ast.(*GenericVisitor).Walk(0xc0007fe1f8, {0x56ed420?, 0xc00026aae0?})
        /Users/stephan/Sources/open-policy-agent/opa/ast/visit.go:319 +0xac7
github.com/open-policy-agent/opa/ast.(*GenericVisitor).Walk(0xc0007fe1f8, {0x56a5c80?, 0xc00025b3a0?})
        /Users/stephan/Sources/open-policy-agent/opa/ast/visit.go:361 +0x80c
github.com/open-policy-agent/opa/ast.(*GenericVisitor).Walk(0xc0007fe1f8, {0x56ea840?, 0xc00026aa50?})
        /Users/stephan/Sources/open-policy-agent/opa/ast/visit.go:341 +0x545
github.com/open-policy-agent/opa/ast.(*GenericVisitor).Walk(0xc0007fe1f8, {0x5727500?, 0xc000348fc0?})
        /Users/stephan/Sources/open-policy-agent/opa/ast/visit.go:331 +0xb85
github.com/open-policy-agent/opa/ast.(*GenericVisitor).Walk(0xc0007fe1f8, {0x56ed420?, 0xc00026aac8?})
        /Users/stephan/Sources/open-policy-agent/opa/ast/visit.go:319 +0xac7
github.com/open-policy-agent/opa/ast.WalkExprs({0x56ed420?, 0xc00026aac8?}, 0x63b0a40?)
        /Users/stephan/Sources/open-policy-agent/opa/ast/visit.go:217 +0x58
github.com/open-policy-agent/opa/ast.checkUndefinedFuncs(0xc00011a738?, {0x56ed420?, 0xc00026aac8?}, 0x1?, 0xc00026a8d0?)
        /Users/stephan/Sources/open-policy-agent/opa/ast/compile.go:877 +0x78
github.com/open-policy-agent/opa/ast.(*queryCompiler).checkUndefinedFuncs(0xc000348f00, 0xc00025b380?, {0xc00011a738, 0x1, 0x1})
        /Users/stephan/Sources/open-policy-agent/opa/ast/compile.go:2476 +0x7e
github.com/open-policy-agent/opa/ast.(*queryCompiler).runStage(0x55e6720?, {0x577fe57?, 0x575dafe?}, 0x11?, {0xc00011a738?, 0x90?, 0x6d175b8?}, 0x90?)
        /Users/stephan/Sources/open-policy-agent/opa/ast/compile.go:2312 +0x173
github.com/open-policy-agent/opa/ast.(*queryCompiler).Compile(0xc000348f00, {0xc00011a430, 0x1, 0x5762f57?})
        /Users/stephan/Sources/open-policy-agent/opa/ast/compile.go:2356 +0x6bb
github.com/open-policy-agent/opa/rego.(*Rego).compileQuery(0xc00022a900, {0xc00011a430, 0x1, 0x1}, {0x0, 0x0, 0x0}, {0x0?, 0xc00011a430?}, {0xc0007feaa8, ...})
        /Users/stephan/Sources/open-policy-agent/opa/rego/rego.go:1886 +0x244
github.com/open-policy-agent/opa/rego.(*Rego).compileAndCacheQuery(0xc00022a900, 0xc000332c00?, {0xc00011a430, 0x1, 0x1}, {0x0, 0x0, 0x0}, {0x5ab4e48, 0xc000332c00}, ...)
        /Users/stephan/Sources/open-policy-agent/opa/rego/rego.go:1830 +0x265
github.com/open-policy-agent/opa/rego.(*Rego).prepare(0xc00022a900, {0x5ab0d20, 0xc0000360f0}, 0x0?, {0xc0007feaa8, 0x1, 0x1})
        /Users/stephan/Sources/open-policy-agent/opa/rego/rego.go:1625 +0x472
github.com/open-policy-agent/opa/rego.(*Rego).PrepareForEval(0xc00022a900, {0x5ab0d20, 0xc0000360f0}, {0x0, 0x0, 0x320004011387?})
        /Users/stephan/Sources/open-policy-agent/opa/rego/rego.go:1471 +0x518
github.com/open-policy-agent/opa/cmd.evalOnce({0x5ab0d20, 0xc0000360f0}, 0xc0000003c0)
        /Users/stephan/Sources/open-policy-agent/opa/cmd/eval.go:400 +0x272
github.com/open-policy-agent/opa/cmd.eval({_, _, _}, {0xc000239260, 0x0, 0x0, {0xc0000d7000, 0x1, 0x1}, {0x63ebd00, ...}, ...}, ...)
        /Users/stephan/Sources/open-policy-agent/opa/cmd/eval.go:328 +0x3ea
github.com/open-policy-agent/opa/cmd.init.5.func2(0xc0001ae500?, {0xc0000d7320?, 0x1?, 0x1?})
        /Users/stephan/Sources/open-policy-agent/opa/cmd/eval.go:253 +0x78
github.com/spf13/cobra.(*Command).execute(0xc0001ae500, {0xc0000d72f0, 0x1, 0x1})
        /Users/stephan/Sources/open-policy-agent/opa/vendor/github.com/spf13/cobra/command.go:860 +0x663
github.com/spf13/cobra.(*Command).ExecuteC(0x6394fc0)
        /Users/stephan/Sources/open-policy-agent/opa/vendor/github.com/spf13/cobra/command.go:974 +0x3b4
github.com/spf13/cobra.(*Command).Execute(...)
        /Users/stephan/Sources/open-policy-agent/opa/vendor/github.com/spf13/cobra/command.go:902
main.main()
        /Users/stephan/Sources/open-policy-agent/opa/main.go:15 +0x25

[johanfylling]

Duplicate of issue #4762.

[srenatus]

Yours is better. Thanks!