clarify discussion of nil (#262)
* clarify discussion of nil
* fix typo
diff --git a/starlark/value.go b/starlark/value.go
index b5a8c12..267465f 100644
--- a/starlark/value.go
+++ b/starlark/value.go
@@ -42,9 +42,10 @@
// implementation of the Go function may use UnpackArgs to make sense of
// the positional and keyword arguments provided by the caller.
//
-// Starlark's None value is not equal to Go's nil, but nil may be
-// assigned to a Starlark Value. Be careful to avoid allowing Go nil
-// values to leak into Starlark data structures.
+// Starlark's None value is not equal to Go's nil. Go's nil is not a legal
+// Starlark value, but the compiler will not stop you from converting nil
+// to Value. Be careful to avoid allowing Go nil values to leak into
+// Starlark data structures.
//
// The Compare operation requires two arguments of the same
// type, but this constraint cannot be expressed in Go's type system.
@@ -58,7 +59,7 @@
// function evaluates a single expression. All evaluator functions
// require a Thread parameter which defines the "thread-local storage"
// of a Starlark thread and may be used to plumb application state
-// through Sklyark code and into callbacks. When evaluation fails it
+// through Starlark code and into callbacks. When evaluation fails it
// returns an EvalError from which the application may obtain a
// backtrace of active Starlark calls.
//