Specials can check and accept/decline the signature of the call

...c/com/oracle/truffle/r/nodes/builtin/RBuiltinPackage.java

.../oracle/truffle/r/nodes/builtin/base/infix/Subscript.java

...com/oracle/truffle/r/nodes/builtin/base/infix/Subset.java

...e.r.nodes/src/com/oracle/truffle/r/nodes/RASTBuilder.java

...c/com/oracle/truffle/r/nodes/builtin/RBuiltinFactory.java

...com/oracle/truffle/r/nodes/function/RCallSpecialNode.java

...oracle/truffle/r/runtime/builtins/RBuiltinDescriptor.java

...om/oracle/truffle/r/runtime/builtins/RSpecialFactory.java