2d alignments with plus operator

3 files changed, 25 insertions, 6 deletions

diff --git a/src/eval/mod.rs b/src/eval/mod.rs
index 1ff497e8..6b28e5ab 100644
--- a/src/eval/mod.rs
+++ b/src/eval/mod.rs
@@ -422,7 +422,7 @@ impl Eval for CallArgs {
                     }
                     v => {
                         if let Value::Dyn(dynamic) = &v {
-                            if let Some(args) = dynamic.downcast_ref::<Args>() {
+                            if let Some(args) = dynamic.downcast::<Args>() {
                                 items.extend(args.items.iter().cloned());
                                 continue;
                             }
diff --git a/src/eval/ops.rs b/src/eval/ops.rs
index e40fa78d..6fac354d 100644
--- a/src/eval/ops.rs
+++ b/src/eval/ops.rs
@@ -1,8 +1,9 @@
 use std::cmp::Ordering;
 use std::convert::TryFrom;
 
-use super::Value;
+use super::{Dynamic, Value};
 use crate::diag::StrResult;
+use crate::geom::{Align, Get, Spec};
 use crate::util::EcoString;
 use Value::*;
 
@@ -87,7 +88,25 @@ pub fn add(lhs: Value, rhs: Value) -> StrResult<Value> {
         (Template(a), Str(b)) => Template(a + b),
         (Str(a), Template(b)) => Template(a + b),
 
-        (a, b) => mismatch!("cannot add {} and {}", a, b),
+        (a, b) => {
+            if let (Dyn(a), Dyn(b)) = (&a, &b) {
+                // 1D alignments can be summed into 2D alignments.
+                if let (Some(&a), Some(&b)) =
+                    (a.downcast::<Align>(), b.downcast::<Align>())
+                {
+                    if a.axis() == b.axis() {
+                        return Err(format!("cannot add two {:?} alignments", a.axis()));
+                    }
+
+                    let mut aligns = Spec::default();
+                    aligns.set(a.axis(), Some(a));
+                    aligns.set(b.axis(), Some(b));
+                    return Ok(Dyn(Dynamic::new(aligns)));
+                }
+            }
+
+            mismatch!("cannot add {} and {}", a, b);
+        }
     })
 }
 
diff --git a/src/eval/value.rs b/src/eval/value.rs
index dec5c6c0..16e8b810 100644
--- a/src/eval/value.rs
+++ b/src/eval/value.rs
@@ -188,7 +188,7 @@ impl Dynamic {
     }
 
     /// Try to downcast to a reference to a specific type.
-    pub fn downcast_ref<T: 'static>(&self) -> Option<&T> {
+    pub fn downcast<T: 'static>(&self) -> Option<&T> {
         self.0.as_any().downcast_ref()
     }
 
@@ -225,7 +225,7 @@ where
     }
 
     fn dyn_eq(&self, other: &Dynamic) -> bool {
-        if let Some(other) = other.downcast_ref::<Self>() {
+        if let Some(other) = other.downcast::<Self>() {
             self == other
         } else {
             false
@@ -334,7 +334,7 @@ macro_rules! castable {
                 let found = match value {
                     $($pattern => return Ok($out),)*
                     $crate::eval::Value::Dyn(dynamic) => {
-                        $(if let Some($dyn_in) = dynamic.downcast_ref::<$dyn_type>() {
+                        $(if let Some($dyn_in) = dynamic.downcast::<$dyn_type>() {
                             return Ok($dyn_out);
                         })*
                         dynamic.type_name()