From b9deeb5bd7fb07267f4cec849b4a06c3f03ae8b7 Mon Sep 17 00:00:00 2001
From: Pat Hickey <phickey@fastly.com>
Date: Tue, 17 Dec 2019 16:41:51 -0800
Subject: [PATCH] add module for calculating C ABI layout of datatypes

---
 tools/witx/src/layout.rs | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/tools/witx/src/layout.rs b/tools/witx/src/layout.rs
index 626ac67b..9aa1df68 100644
--- a/tools/witx/src/layout.rs
+++ b/tools/witx/src/layout.rs
@@ -125,7 +125,22 @@ mod test {
 
 impl UnionDatatype {
     pub fn layout(&self, cache: &mut HashMap<TypeRef, SizeAlign>) -> SizeAlign {
-        unimplemented!()
+        let sas = self
+            .variants
+            .iter()
+            .map(|v| v.tref.layout(cache))
+            .collect::<Vec<SizeAlign>>();
+        let size = sas
+            .iter()
+            .map(|sa| sa.size)
+            .max()
+            .expect("nonzero variants");
+        let align = sas
+            .iter()
+            .map(|sa| sa.align)
+            .max()
+            .expect("nonzero variants");
+        SizeAlign { size, align }
     }
 }