When introducing user-callable functions, we want to make a break with the past and not support some of the modes that the current builtin function calls support (like, for example, we want a clear distinction between functions and validators). In order to do that, the plan is to introduce a new `adt.Func` type to implement the new semantics rather than complicate the already complex `adt.Builtin` logic. That means that we want the `CallExpr` logic to be independent of the `Builtin` logic, but they are both somewhat intertwined currently. Factor out `Builtin.rawCall` from `CallExpr.evaluate` in order to separate the two some more, and also rename `CallContext` to `BuiltinCallContext` make it clear that the type is about Builtin calls - we will use a different API for `adt.Func`. This should have no semantic effect at all. Signed-off-by: Roger Peppe <rogpeppe@gmail.com> Change-Id: I2d33b14a8cf5c431dd70cc7a9e14930ba43d807f Reviewed-on: https://cue.gerrithub.io/c/cue-lang/cue/+/1232332 Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com> TryBot-Result: CUEcueckoo <cueckoo@cuelang.org> Reviewed-by: Daniel Martí <mvdan@mvdan.cc>