Infer multiple assignments

src/constrain.rs

@@ -53,15 +53,23 @@ pub fn constrain(
         Assign(assignments, ret_expr) => {
             let ret_con = constrain(bound_vars, subs, *ret_expr, expected);
 
-            if assignments.len() > 1 {
-                panic!("TODO can't handle multiple assignments yet");
-            }
+            if assignments.len() == 1 {
+                // Don't bother allocating a Vec of them if there's only one!
+                let (loc_pattern, loc_expr) = assignments.into_iter().next().unwrap();
+
+                constrain_def(loc_pattern, loc_expr, bound_vars, subs, ret_con)
+            } else {
+                let mut constraints = Vec::with_capacity(assignments.len());
 
                 for (loc_pattern, loc_expr) in assignments {
-                return constrain_def(loc_pattern, loc_expr, bound_vars, subs, ret_con);
+                    let constraint =
+                        constrain_def(loc_pattern, loc_expr, bound_vars, subs, ret_con.clone());
+
+                    constraints.push(constraint);
                 }
 
-            unreachable!();
+                And(constraints)
+            }
         }
         _ => { panic!("TODO constraints for {:?}", loc_expr.value) }
     }

src/types.rs

@@ -19,7 +19,7 @@ pub enum Type {
     Erroneous(Problem),
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub enum Expected<T> {
     NoExpectation(T),
     ForReason(Reason, T, Region),
@@ -34,7 +34,7 @@ impl<T> Expected<T> {
     }
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub enum Reason {
     OperatorLeftArg(Operator),
     OperatorRightArg(Operator),
@@ -43,7 +43,7 @@ pub enum Reason {
     ElemInList,
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub enum Constraint {
     Eq(Type, Expected<Type>, Region),
     Lookup(Symbol, Expected<Type>, Region),
@@ -52,7 +52,7 @@ pub enum Constraint {
     And(Vec<Constraint>)
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct LetConstraint {
     pub rigid_vars: Vec<Variable>,
     pub flex_vars: Vec<Variable>,

tests/test_infer.rs

@@ -357,7 +357,19 @@ mod test_infer {
         );
     }
 
+    #[test]
+    fn assign_multiple() {
+        infer_eq(
+            indoc!(r#"
+                a = \_ _ _ -> "test!"
 
+                b = a
+
+                b
+            "#),
+            "*, *, * -> String.String"
+        );
+    }
 
     // #[test]
     // fn int_thunk() {