panic: Functions defined with calls in the argument list

[tsandall]

If a function is defined with a call in the argument list, the compiler panics. The compiler should be rewriting these args like it does with other terms that require evaluation (e.g., refs, comprehensions, etc.)

> g(x) = x
1 error occurred: 1:1: rego_type_error: undefined function g
> f(g(1)) { true }
panic: unreachable [recovered]
	panic: unreachable

goroutine 1 [running]:
github.com/open-policy-agent/opa/ast.(*Compiler).compile.func1()
	/src/ast/compile.go:846 +0x73
panic(0xe7f740, 0x1099990)
	/usr/local/go/src/runtime/panic.go:522 +0x1b5
github.com/open-policy-agent/opa/ast.(*TypeEnv).Get(0xc0002d2160, 0xf59fa0, 0xc0002d0de0, 0x0, 0x0)
	/src/ast/env.go:133 +0xff7
github.com/open-policy-agent/opa/ast.getArgTypes(0xc0002d2160, 0xc0002d0aa8, 0x2, 0x2, 0x0, 0x0, 0xfa5be9)
	/src/ast/check.go:980 +0x8b
github.com/open-policy-agent/opa/ast.(*typeChecker).checkExprEq(0xc0002d46c0, 0xc0002d2160, 0xc00018de00, 0x2)
	/src/ast/check.go:278 +0xa3
github.com/open-policy-agent/opa/ast.(*typeChecker).checkExpr(0xc0002d46c0, 0xc0002d2160, 0xc00018de00, 0x0)
	/src/ast/check.go:218 +0xc8
github.com/open-policy-agent/opa/ast.(*typeChecker).CheckBody.func1(0xc00018de00, 0x1)
	/src/ast/check.go:74 +0x34e
github.com/open-policy-agent/opa/ast.WalkExprs.func1(0xf7ca80, 0xc00018de00, 0x1)
	/src/ast/visit.go:205 +0x42
github.com/open-policy-agent/opa/ast.(*GenericVisitor).Walk(0xc000226f98, 0xf7ca80, 0xc00018de00)
	/src/ast/visit.go:270 +0x5b
github.com/open-policy-agent/opa/ast.(*GenericVisitor).Walk(0xc000226f98, 0xf5b620, 0xc0002d1120)
	/src/ast/visit.go:308 +0xb16
github.com/open-policy-agent/opa/ast.WalkExprs(0xf5b620, 0xc0002d1120, 0xc000227008)
	/src/ast/visit.go:209 +0x70
github.com/open-policy-agent/opa/ast.(*typeChecker).CheckBody(0xc0002d46c0, 0xc0002d2160, 0xc0002d2100, 0x2, 0x2, 0x203000, 0x203000, 0x203000, 0x203000)
	/src/ast/check.go:57 +0x188
github.com/open-policy-agent/opa/ast.(*typeChecker).checkRule(0xc0002d46c0, 0xc0002d2150, 0xc000293a40)
	/src/ast/check.go:149 +0x73
github.com/open-policy-agent/opa/ast.(*typeChecker).CheckTypes(0xc0002d46c0, 0xc0002d2150, 0xc0002d2120, 0x1, 0x1, 0x0, 0x0, 0x0, 0x6000103)
	/src/ast/check.go:101 +0x16a
github.com/open-policy-agent/opa/ast.(*Compiler).checkTypes(0xc0002c48f0)
	/src/ast/compile.go:811 +0x118
github.com/open-policy-agent/opa/ast.(*Compiler).runStage(0xc0002c48f0, 0xfb65eb, 0x19, 0xc0002c1ea0)
	/src/ast/compile.go:832 +0x43
github.com/open-policy-agent/opa/ast.(*Compiler).compile(0xc0002c48f0)
	/src/ast/compile.go:851 +0x115
github.com/open-policy-agent/opa/ast.(*Compiler).Compile(0xc0002c48f0, 0xc0002c6750)
	/src/ast/compile.go:345 +0x2a4
github.com/open-policy-agent/opa/repl.(*REPL).compileRule(0xc00022afc0, 0x10c1720, 0xc00009e018, 0xc000293740, 0x0, 0x0)
	/src/repl/repl.go:665 +0x381
github.com/open-policy-agent/opa/repl.(*REPL).evalStatement(0xc00022afc0, 0x10c1720, 0xc00009e018, 0xf41460, 0xc000293740, 0x1, 0x1)
	/src/repl/repl.go:826 +0xe1
github.com/open-policy-agent/opa/repl.(*REPL).evalBufferOne(0xc00022afc0, 0x10c1720, 0xc00009e018, 0x0, 0x1)
	/src/repl/repl.go:711 +0x2bf
github.com/open-policy-agent/opa/repl.(*REPL).OneShot(0xc00022afc0, 0x10c1720, 0xc00009e018, 0xc000186a00, 0x10, 0x0, 0x0)
	/src/repl/repl.go:253 +0x365
github.com/open-policy-agent/opa/repl.(*REPL).Loop(0xc00022afc0, 0x10c1720, 0xc00009e018)
	/src/repl/repl.go:152 +0x31b
github.com/open-policy-agent/opa/runtime.(*Runtime).StartREPL(0xc0001a6b00, 0x10c1720, 0xc00009e018)
	/src/runtime/runtime.go:375 +0x3c0
github.com/open-policy-agent/opa/cmd.init.7.func1(0xc00019c780, 0x16373f0, 0x0, 0x0)
	/src/cmd/run.go:138 +0x4e4
github.com/spf13/cobra.(*Command).execute(0xc00019c780, 0x16373f0, 0x0, 0x0, 0xc00019c780, 0x16373f0)
	/src/vendor/github.com/spf13/cobra/command.go:766 +0x2ae
github.com/spf13/cobra.(*Command).ExecuteC(0x15d7c60, 0x15d7c60, 0xc0000d1f88, 0x734d9f)
	/src/vendor/github.com/spf13/cobra/command.go:852 +0x2ec
github.com/spf13/cobra.(*Command).Execute(...)
	/src/vendor/github.com/spf13/cobra/command.go:800
main.main()
	/src/main.go:15 +0x32