Feature fields: a type for each role (Expr, BodyName, FacePick…) (#1273)

Thanks @jijinbei.

crates/doc/src/assembly.rs

@@ -176,7 +176,7 @@ fn map_geo_ref(m: &Mat, g: &mut crate::construct::GeoRef) {
 /// Map a point given as expressions by `m`: numbers stay numbers; a coordinate that is an
 /// expression stays one (`m · (x, y, z) + t`, written out), so it still follows its parameters.
 pub fn map_point_expr(m: &Mat, p: &mut crate::PointExpr) {
-    let num = |e: &String| e.trim().parse::<f64>().ok().filter(|v| v.is_finite());
+    let num = |e: &crate::Expr| e.trim().parse::<f64>().ok().filter(|v| v.is_finite());
     if let [Some(x), Some(y), Some(z)] = [num(&p[0]), num(&p[1]), num(&p[2])] {
         *p = crate::point_expr(apply_point(m, Vec3::new(x, y, z)));
         return;
@@ -202,7 +202,7 @@ pub fn map_point_expr(m: &Mat, p: &mut crate::PointExpr) {
         } else if constant.abs() >= 1e-12 {
             e = format!("{e} {} {} mm", if constant < 0.0 { '-' } else { '+' }, constant.abs());
         }
-        *out = e;
+        *out = e.into();
     }
 }