Add `BuildSolid`

crates/fj-kernel/src/operations/build/mod.rs

@@ -2,6 +2,7 @@ mod cycle;
 mod edge;
 mod face;
 mod shell;
+mod solid;
 mod surface;
 
 pub use self::{
@@ -9,5 +10,6 @@ pub use self::{
     edge::BuildHalfEdge,
     face::{BuildFace, Polygon},
     shell::{BuildShell, TetrahedronShell},
+    solid::BuildSolid,
     surface::BuildSurface,
 };

crates/fj-kernel/src/operations/build/solid.rs

@@ -0,0 +1,11 @@
+use crate::objects::Solid;
+
+/// Build a [`Solid`]
+pub trait BuildSolid {
+    /// Build an empty solid
+    fn empty() -> Solid {
+        Solid::new([])
+    }
+}
+
+impl BuildSolid for Solid {}

crates/fj-kernel/src/operations/mod.rs

@@ -7,8 +7,8 @@ mod update;
 
 pub use self::{
     build::{
-        BuildCycle, BuildFace, BuildHalfEdge, BuildShell, BuildSurface,
-        Polygon, TetrahedronShell,
+        BuildCycle, BuildFace, BuildHalfEdge, BuildShell, BuildSolid,
+        BuildSurface, Polygon, TetrahedronShell,
     },
     insert::{Insert, IsInserted, IsInsertedNo, IsInsertedYes},
     join::JoinCycle,