From 8b0433f9a80007b0f0befae2fb5450975f711fe3 Mon Sep 17 00:00:00 2001
From: Troels Henriksen <athas@sigkill.dk>
Date: Sun, 22 Dec 2024 21:48:24 +0100
Subject: [PATCH] Fix more error messages.

---
 src/Language/Futhark/TypeChecker/Constraints.hs | 9 +++++++++
 tests/sumtypes/sumtype46.fut                    | 2 +-
 tests/sumtypes/sumtype48.fut                    | 2 +-
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/Language/Futhark/TypeChecker/Constraints.hs b/src/Language/Futhark/TypeChecker/Constraints.hs
index 5a4586ce25..8b8355c12a 100644
--- a/src/Language/Futhark/TypeChecker/Constraints.hs
+++ b/src/Language/Futhark/TypeChecker/Constraints.hs
@@ -373,6 +373,14 @@ cannotUnify reason notes bcs t1 t2 = do
           "Latter:" <+> pretty latter'
         ]
 
+unsharedConstructorsMsg :: M.Map Name t -> M.Map Name t -> Doc a
+unsharedConstructorsMsg cs1 cs2 =
+  "Unshared constructors:" <+> commasep (map (("#" <>) . pretty) missing) <> "."
+  where
+    missing =
+      filter (`notElem` M.keys cs1) (M.keys cs2)
+        ++ filter (`notElem` M.keys cs2) (M.keys cs1)
+
 -- Precondition: 'v' is currently flexible.
 subTyVar :: Reason -> BreadCrumbs -> VName -> Type -> SolveM ()
 subTyVar reason bcs v t = do
@@ -412,6 +420,7 @@ subTyVar reason bcs v t = do
                 </> indent 2 (stack (map (("#" <>) . pretty) (M.keys cs1)))
                 </> "with type with constructors"
                 </> indent 2 (stack (map (("#" <>) . pretty) (M.keys cs2)))
+                </> unsharedConstructorsMsg cs1 cs2
     ( Just (Right (TyVarUnsol (TyVarSum _ cs1))),
       _
       ) ->
diff --git a/tests/sumtypes/sumtype46.fut b/tests/sumtypes/sumtype46.fut
index dac4e4671f..a56af88750 100644
--- a/tests/sumtypes/sumtype46.fut
+++ b/tests/sumtypes/sumtype46.fut
@@ -1,5 +1,5 @@
 -- ==
--- error: cannot match
+-- error: 0 constructor arguments
 
 type t = #foo f64
 
diff --git a/tests/sumtypes/sumtype48.fut b/tests/sumtypes/sumtype48.fut
index ad614f03cf..6c184e9239 100644
--- a/tests/sumtypes/sumtype48.fut
+++ b/tests/sumtypes/sumtype48.fut
@@ -3,4 +3,4 @@
 
 type t = #foo | #bar
 
-let f b : t = if b then #foo else #baar
+def f b : t = if b then #foo else #baar