Merge pull request elm#1031 from Skinney/fix-list-equality

Fixes runtime exception when comparing inequal lists with over 100 elements
ForgottenGensym · Nov 13, 2019 · d95e1f3 · d95e1f3
2 parents d90b7ae + 1eec0e1
commit d95e1f3
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Showing 2 changed files with 18 additions and 8 deletions.
diff --git a/src/Elm/Kernel/Utils.js b/src/Elm/Kernel/Utils.js
@@ -26,12 +26,6 @@ function _Utils_eq(x, y)
 
 function _Utils_eqHelp(x, y, depth, stack)
 {
-	if (depth > 100)
-	{
-		stack.push(_Utils_Tuple2(x,y));
-		return true;
-	}
-
 	if (x === y)
 	{
 		return true;
@@ -43,6 +37,12 @@ function _Utils_eqHelp(x, y, depth, stack)
 		return false;
 	}
 
+	if (depth > 100)
+	{
+		stack.push(_Utils_Tuple2(x,y));
+		return true;
+	}
+
 	/**__DEBUG/
 	if (x.$ === 'Set_elm_builtin')
 	{

diff --git a/tests/tests/Test/Equality.elm b/tests/tests/Test/Equality.elm
@@ -1,9 +1,10 @@
 module Test.Equality exposing (tests)
 
 import Basics exposing (..)
+import Expect
+import Fuzz
 import Maybe exposing (..)
 import Test exposing (..)
-import Expect
 
 
 type Different
@@ -30,5 +31,14 @@ tests =
                 , test "ctor diff" <| \() -> Expect.equal True ({ field = Just 3 } /= { field = Nothing })
                 , test "ctor diff, special case" <| \() -> Expect.equal True ({ ctor = Just 3 } /= { ctor = Nothing })
                 ]
+
+        listTests =
+            describe "List equality"
+                [ fuzz2 (Fuzz.intRange 100 10000) (Fuzz.intRange 100 10000) "Simple comparison" <|
+                    \size1 size2 ->
+                        Expect.equal
+                            (size1 == size2)
+                            (List.range 0 size1 == List.range 0 size2)
+                ]
     in
-        describe "Equality Tests" [ diffTests, recordTests ]
+        describe "Equality Tests" [ diffTests, recordTests, listTests ]