From 12a7cbf8ef911f0cbfcbd13d1c888025fa411de4 Mon Sep 17 00:00:00 2001
From: Joel Kronqvist <joel.kronqvist@iki.fi>
Date: Fri, 22 Aug 2025 23:48:35 +0300
Subject: fix: added missing conversions and generic inferring for coproducts

---
 src/type/check.rs      |  8 ++++++++
 src/type/conversion.rs | 15 ++++++++++++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/type/check.rs b/src/type/check.rs
index 5ccd0e7..bb88efb 100644
--- a/src/type/check.rs
+++ b/src/type/check.rs
@@ -510,6 +510,14 @@ impl Type {
                 Ok(r1)
             },
 
+            (SumType(a1, a2), SumType(b1, b2)) => {
+                let mut r1 = a1.infer_generics_ctx(b1, ctx.clone())?;
+                let r2 = a2.infer_generics_ctx(b2, ctx.clone())?;
+                r1.extend_from_slice(&r2);
+                r1.extend_from_slice(&ctx);
+                Ok(r1)
+            },
+
             (List(v1), List(v2)) => {
                 let mut res = ctx.clone();
                 for (t1, t2) in v1.into_iter().zip(v2.into_iter()) {
diff --git a/src/type/conversion.rs b/src/type/conversion.rs
index ab858e6..54fc59d 100644
--- a/src/type/conversion.rs
+++ b/src/type/conversion.rs
@@ -11,7 +11,7 @@ impl Type {
     /// 0. self == other => self
     /// 1. (T T ... T T) -> (T ...)
     /// 2. self = concrete and other = variable type => self,
-    /// 3. arrow types and lists are mapped
+    /// 3. arrow types and lists and sums are mapped
     /// 4. makes [self] self if self == other
     pub fn convert(self, other: &Type) -> Result<Type, ()> {
 	let (ty, ctx) = self.convert_ctx(other)?;
@@ -62,6 +62,14 @@ impl Type {
 		Ok((arr(t1, t2), ctx))
 	    },
 
+	    (SumType(a1, a2), SumType(b1, b2)) => {
+		let (t1, newctx) = a1.convert_ctx(b1)?;
+		ctx.extend(newctx);
+		let (t2, newctx) = a2.convert_ctx(b2)?;
+		ctx.extend(newctx);
+		Ok((sumtype(t1, t2), ctx))
+	    },
+
 	    (List(v), VecOf(ty)) => match v.get(0) {
 		Some(t) => {
 		    let (convt, newctx) = t.clone().convert_ctx(ty)?;
@@ -163,6 +171,11 @@ mod tests {
 		.convert(&arr(vt("T"), vt("T"))),
 	    Ok(arr(arr(vecof(Integer), Integer), arr(vecof(Integer), Integer)))
 	);
+	assert_eq!(
+	    sumtype(sumtype(vecof(Integer), Integer), sumtype(vecof(Integer), Integer))
+		.convert(&sumtype(vt("T"), vt("T"))),
+	    Ok(sumtype(sumtype(vecof(Integer), Integer), sumtype(vecof(Integer), Integer)))
+	);
 
 	assert!(
 	    List(vec![Integer, Boolean])
-- 
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