Type check and coerce arguments to user functions and return values from std Rust functions (#6958)

* Shuffle around function call code

Signed-off-by: Nick Cameron <nrc@ncameron.org>

* Refactor function calls to share more code

Signed-off-by: Nick Cameron <nrc@ncameron.org>

* Hack to leave the result of revolve as a singleton rather than array

Signed-off-by: Nick Cameron <nrc@ncameron.org>

---------

Signed-off-by: Nick Cameron <nrc@ncameron.org>

rust/kcl-lib/src/std/mod.rs

@@ -328,14 +328,14 @@ impl StdLib {
         self.fns.get(name).cloned()
     }
 
-    pub fn get_either(&self, name: &Name) -> FunctionKind {
+    pub fn get_rust_function(&self, name: &Name) -> Option<Box<dyn StdLibFn>> {
         if let Some(name) = name.local_ident() {
             if let Some(f) = self.get(name.inner) {
-                return FunctionKind::Core(f);
+                return Some(f);
             }
         }
 
-        FunctionKind::UserDefined
+        None
     }
 
     pub fn contains_key(&self, key: &str) -> bool {
@@ -349,11 +349,5 @@ impl Default for StdLib {
     }
 }
 
-#[derive(Debug)]
-pub enum FunctionKind {
-    Core(Box<dyn StdLibFn>),
-    UserDefined,
-}
-
 /// The default tolerance for modeling commands in [`kittycad_modeling_cmds::length_unit::LengthUnit`].
 const DEFAULT_TOLERANCE: f64 = 0.0000001;