Fix #2124.

CHANGELOG.md

@@ -15,6 +15,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ### Fixed
 
+* Ignore type suffixes when unifying expressions (#2124).
+
 ## [0.25.14]
 
 ### Added

src/Language/Futhark/Prop.hs

@@ -1376,12 +1376,20 @@ similarSlices slice1 slice2
 
 -- | If these two expressions are structurally similar at top level as
 -- sizes, produce their subexpressions (which are not necessarily
--- similar, but you can check for that!).  This is the machinery
--- underlying expresssion unification.
+-- similar, but you can check for that!). This is the machinery
+-- underlying expresssion unification. We assume that the expressions
+-- have the same type.
 similarExps :: Exp -> Exp -> Maybe [(Exp, Exp)]
 similarExps e1 e2 | bareExp e1 == bareExp e2 = Just []
 similarExps e1 e2 | Just e1' <- stripExp e1 = similarExps e1' e2
 similarExps e1 e2 | Just e2' <- stripExp e2 = similarExps e1 e2'
+similarExps (IntLit x _ _) (Literal v _) =
+  case v of
+    SignedValue (Int8Value y) | x == toInteger y -> Just []
+    SignedValue (Int16Value y) | x == toInteger y -> Just []
+    SignedValue (Int32Value y) | x == toInteger y -> Just []
+    SignedValue (Int64Value y) | x == toInteger y -> Just []
+    _ -> Nothing
 similarExps
   (AppExp (BinOp (op1, _) _ (x1, _) (y1, _) _) _)
   (AppExp (BinOp (op2, _) _ (x2, _) (y2, _) _) _)

src/Language/Futhark/TypeChecker/Unify.hs

@@ -1152,8 +1152,10 @@ newDimOnMismatch loc t1 t2 = do
   pure (t, M.elems seen)
   where
     r = RigidCond t1 t2
+    same (e1, e2) =
+      maybe False (all same) $ similarExps e1 e2
     onDims _ d1 d2
-      | d1 == d2 = pure d1
+      | same (d1, d2) = pure d1
       | otherwise = do
           -- Remember mismatches we have seen before and reuse the
           -- same new size.

tests/issue2124.fut

@@ -0,0 +1,5 @@
+-- Ignore suffixes when computing differences when possible.
+
+def main b : [10]i64 =
+  if b then iota 10 : [10]i64
+  else iota 10i64 : [10]i64