synthdef indexing error

ERROR: Primitive '_BasicAt' failed.
Index not an Integer
RECEIVER:
Instance of Array {    (00000194ABF182B8, gc=8C, fmt=01, flg=10, set=02)
  indexed slots [4]
      0 : Integer 0
      1 : Integer 1
      2 : Integer 2
      3 : Integer 3
}

PROTECTED CALL STACK:
	Meta_MethodError:new	00000194A73E7180
		arg this = PrimitiveFailedError
		arg what = Index not an Integer
		arg receiver = [ 0, 1, 2, 3 ]
	Meta_PrimitiveFailedError:new	00000194A73ED740
		arg this = PrimitiveFailedError
		arg receiver = [ 0, 1, 2, 3 ]
	Object:primitiveFailed	00000194A6FE3B00
		arg this = [ 0, 1, 2, 3 ]
	a FunctionDef	00000194AAFFAD78
		sourceCode = "{
	arg int = 1;
	var array = #[0,1,2,3];
	array.at(int.asInteger).postln;
}"
		arg int = an OutputProxy
		var array = [ 0, 1, 2, 3 ]
	SynthDef:buildUgenGraph	00000194AABDCF40
		arg this = a SynthDef
		arg func = a Function
		arg rates = nil
		arg prependArgs = [  ]
		var result = nil
		var saveControlNames = nil
	a FunctionDef	00000194AABDB580
		sourceCode = "<an open Function>"
	Function:prTry	00000194A7660040
		arg this = a Function
		var result = nil
		var thread = a Thread
		var next = nil
		var wasInProtectedFunc = false

CALL STACK:
	MethodError:reportError
		arg this = <instance of PrimitiveFailedError>
	Nil:handleError
		arg this = nil
		arg error = <instance of PrimitiveFailedError>
	Thread:handleError
		arg this = <instance of Thread>
		arg error = <instance of PrimitiveFailedError>
	Object:throw
		arg this = <instance of PrimitiveFailedError>
	Function:protect
		arg this = <instance of Function>
		arg handler = <instance of Function>
		var result = <instance of PrimitiveFailedError>
	SynthDef:build
		arg this = <instance of SynthDef>
		arg ugenGraphFunc = <instance of Function>
		arg rates = nil
		arg prependArgs = nil
	Interpreter:interpretPrintCmdLine
		arg this = <instance of Interpreter>
		var res = nil
		var func = <instance of Function>
		var code = "SynthDef(\test, {
	arg int =..."
		var doc = nil
		var ideClass = <instance of Meta_ScIDE>
	Process:interpretPrintCmdLine
		arg this = <instance of Main>
^^ The preceding error dump is for ERROR: Primitive '_BasicAt' failed.
Index not an Integer
RECEIVER: [ 0, 1, 2, 3 ]