diff --git a/cli/tests/repl_eval.rs b/cli/tests/repl_eval.rs
index 029c7d913f..89aa02b7bb 100644
--- a/cli/tests/repl_eval.rs
+++ b/cli/tests/repl_eval.rs
@@ -54,12 +54,12 @@ mod repl_eval {
 
     #[test]
     fn literal_0x0() {
-        expect_success("0x0", "0 : Int");
+        expect_success("0x0", "0 : I64");
     }
 
     #[test]
     fn literal_0x42() {
-        expect_success("0x42", "66 : Int");
+        expect_success("0x42", "66 : I64");
     }
 
     #[test]
@@ -79,7 +79,7 @@ mod repl_eval {
 
     #[test]
     fn int_addition() {
-        expect_success("0x1 + 2", "3 : Int");
+        expect_success("0x1 + 2", "3 : I64");
     }
 
     #[test]
@@ -89,7 +89,7 @@ mod repl_eval {
 
     #[test]
     fn num_rem() {
-        expect_success("299 % 10", "Ok 9 : Result Int [ DivByZero ]*");
+        expect_success("299 % 10", "Ok 9 : Result I64 [ DivByZero ]*");
     }
 
     #[test]
@@ -191,7 +191,7 @@ mod repl_eval {
 
     #[test]
     fn str_count_graphemes() {
-        expect_success("Str.countGraphemes \"å🤔\"", "2 : Int");
+        expect_success("Str.countGraphemes \"å🤔\"", "2 : I64");
     }
 
     #[test]
@@ -206,7 +206,7 @@ mod repl_eval {
 
     #[test]
     fn literal_int_list() {
-        expect_success("[ 0x1, 0x2, 0x3 ]", "[ 1, 2, 3 ] : List Int");
+        expect_success("[ 0x1, 0x2, 0x3 ]", "[ 1, 2, 3 ] : List I64");
     }
 
     #[test]
@@ -239,7 +239,7 @@ mod repl_eval {
     fn nested_int_list() {
         expect_success(
             r#"[ [ [ 4, 3, 2 ], [ 1, 0x0 ] ], [ [] ], [] ]"#,
-            r#"[ [ [ 4, 3, 2 ], [ 1, 0 ] ], [ [] ], [] ] : List (List (List Int))"#,
+            r#"[ [ [ 4, 3, 2 ], [ 1, 0 ] ], [ [] ], [] ] : List (List (List I64))"#,
         );
     }
 
@@ -316,7 +316,7 @@ mod repl_eval {
     fn basic_2_field_i64_record() {
         expect_success(
             "{ foo: 0x4, bar: 0x2 }",
-            "{ bar: 2, foo: 4 } : { bar : Int, foo : Int }",
+            "{ bar: 2, foo: 4 } : { bar : I64, foo : I64 }",
         );
     }
 
@@ -340,7 +340,7 @@ mod repl_eval {
     fn basic_3_field_record() {
         expect_success(
             "{ foo: 4.1, bar: 2, baz: 0x5 }",
-            "{ bar: 2, baz: 5, foo: 4.1 } : { bar : Num *, baz : Int, foo : F64 }",
+            "{ bar: 2, baz: 5, foo: 4.1 } : { bar : Num *, baz : I64, foo : F64 }",
         );
     }
 
@@ -387,7 +387,7 @@ mod repl_eval {
     fn list_of_3_field_records() {
         expect_success(
             "[ { foo: 4.1, bar: 2, baz: 0x3 } ]",
-            "[ { bar: 2, baz: 3, foo: 4.1 } ] : List { bar : Num *, baz : Int, foo : F64 }",
+            "[ { bar: 2, baz: 3, foo: 4.1 } ] : List { bar : Num *, baz : I64, foo : F64 }",
         );
     }
 
diff --git a/compiler/builtins/src/unique.rs b/compiler/builtins/src/unique.rs
index 406f4d313f..43cddc7461 100644
--- a/compiler/builtins/src/unique.rs
+++ b/compiler/builtins/src/unique.rs
@@ -1207,7 +1207,7 @@ fn int_type(u: VarId) -> SolvedType {
         vec![
             flex(u),
             SolvedType::Alias(
-                Symbol::NUM_INT,
+                Symbol::NUM_I64,
                 Vec::new(),
                 Box::new(builtin_aliases::num_type(SolvedType::Apply(
                     Symbol::ATTR_ATTR,
diff --git a/compiler/can/tests/test_can.rs b/compiler/can/tests/test_can.rs
index a37252856c..b4aa3366f0 100644
--- a/compiler/can/tests/test_can.rs
+++ b/compiler/can/tests/test_can.rs
@@ -50,7 +50,7 @@ mod test_can {
                 assert_eq!(expected, actual);
             }
             actual => {
-                panic!("Expected an Int, but got: {:?}", actual);
+                panic!("Expected an I64, but got: {:?}", actual);
             }
         }
     }
@@ -249,7 +249,7 @@ mod test_can {
     fn correct_annotated_body() {
         let src = indoc!(
             r#"
-                f : Int -> Int
+                f : I64 -> I64
                 f = \ a -> a
 
                 f
@@ -265,7 +265,7 @@ mod test_can {
     fn correct_annotated_body_with_comments() {
         let src = indoc!(
             r#"
-                f : Int -> Int # comment
+                f : I64 -> I64 # comment
                 f = \ a -> a
 
                 f
@@ -281,7 +281,7 @@ mod test_can {
     fn name_mismatch_annotated_body() {
         let src = indoc!(
             r#"
-                f : Int -> Int
+                f : I64 -> I64
                 g = \ a -> a
 
                 g
@@ -307,7 +307,7 @@ mod test_can {
     fn name_mismatch_annotated_body_with_comment() {
         let src = indoc!(
             r#"
-                f : Int -> Int # comment
+                f : I64 -> I64 # comment
                 g = \ a -> a
 
                 g
@@ -333,7 +333,7 @@ mod test_can {
     fn separated_annotated_body() {
         let src = indoc!(
             r#"
-                f : Int -> Int
+                f : I64 -> I64
 
                 f = \ a -> a
 
@@ -354,7 +354,7 @@ mod test_can {
     fn separated_annotated_body_with_comment() {
         let src = indoc!(
             r#"
-                f : Int -> Int
+                f : I64 -> I64
                 # comment
                 f = \ a -> a
 
@@ -375,9 +375,9 @@ mod test_can {
     fn shadowed_annotation() {
         let src = indoc!(
             r#"
-                f : Int -> Int
+                f : I64 -> I64
 
-                f : Int -> Int
+                f : I64 -> I64
 
                 f
             "#
@@ -397,7 +397,7 @@ mod test_can {
     fn correct_nested_unannotated_body() {
         let src = indoc!(
             r#"
-                f : Int
+                f : I64
                 f =
                     g = 42
 
@@ -416,9 +416,9 @@ mod test_can {
     fn correct_nested_annotated_body() {
         let src = indoc!(
             r#"
-                f : Int
+                f : I64
                 f =
-                    g : Int
+                    g : I64
                     g = 42
 
                     g + 1
@@ -436,11 +436,11 @@ mod test_can {
     fn correct_nested_body_annotated_multiple_lines() {
         let src = indoc!(
             r#"
-                f : Int
+                f : I64
                 f =
-                    g : Int
+                    g : I64
                     g = 42
-                    h : Int
+                    h : I64
                     h = 5
                     z = 4
                     g + h + z
@@ -458,10 +458,10 @@ mod test_can {
     fn correct_nested_body_unannotated_multiple_lines() {
         let src = indoc!(
             r#"
-                f : Int
+                f : I64
                 f =
                     g = 42
-                    h : Int
+                    h : I64
                     h = 5
                     z = 4
                     g + h + z
@@ -478,7 +478,7 @@ mod test_can {
     fn correct_double_nested_body() {
         let src = indoc!(
             r#"
-                f : Int
+                f : I64
                 f =
                     g =
                         h = 42
@@ -499,7 +499,7 @@ mod test_can {
     fn annotation_followed_with_unrelated_affectation() {
         let src = indoc!(
             r#"
-                F : Int
+                F : I64
 
                 x = 1
 
@@ -520,9 +520,9 @@ mod test_can {
     fn two_annotations_followed_with_unrelated_affectation() {
         let src = indoc!(
             r#"
-                G : Int
+                G : I64
 
-                F : Int
+                F : I64
                 
                 x = 1
 
diff --git a/compiler/constrain/src/builtins.rs b/compiler/constrain/src/builtins.rs
index 36b19ec28e..9b57b9934a 100644
--- a/compiler/constrain/src/builtins.rs
+++ b/compiler/constrain/src/builtins.rs
@@ -92,7 +92,7 @@ pub fn num_floatingpoint() -> Type {
 
 #[inline(always)]
 pub fn num_int() -> Type {
-    Type::Alias(Symbol::NUM_INT, vec![], Box::new(num_num(num_integer())))
+    Type::Alias(Symbol::NUM_I64, vec![], Box::new(num_num(num_integer())))
 }
 
 #[inline(always)]
diff --git a/compiler/fmt/tests/test_fmt.rs b/compiler/fmt/tests/test_fmt.rs
index 1f25e0df89..5daac4b348 100644
--- a/compiler/fmt/tests/test_fmt.rs
+++ b/compiler/fmt/tests/test_fmt.rs
@@ -762,8 +762,8 @@ mod test_fmt {
         expr_formats_to(
             indoc!(
                 r#"
-                f: {                    y : Int,
-                                         x : Int ,
+                f: {                    y : I64,
+                                         x : I64 ,
                    }
                 
                 f"#
@@ -772,8 +772,8 @@ mod test_fmt {
                 r#"
                 f :
                     {
-                        y : Int,
-                        x : Int,
+                        y : I64,
+                        x : I64,
                     }
 
                 f"#
@@ -787,8 +787,8 @@ mod test_fmt {
             r#"
                 f :
                     {
-                        y : Int,
-                        x : Int,
+                        y : I64,
+                        x : I64,
                     }
 
                 f"#
@@ -800,7 +800,7 @@ mod test_fmt {
         expr_formats_same(indoc!(
             r#"
                 f :
-                    Int
+                    I64
 
                 f"#
         ));
@@ -880,7 +880,7 @@ mod test_fmt {
                 r#"
                 f :
                     { 
-                        x: Int # comment 1
+                        x: I64 # comment 1
                         ,
                         # comment 2
                     }
@@ -891,7 +891,7 @@ mod test_fmt {
                 r#"
                 f :
                     {
-                        x : Int,
+                        x : I64,
                         # comment 1
                         # comment 2
                     }
@@ -2458,7 +2458,7 @@ mod test_fmt {
     fn record_type() {
         expr_formats_same(indoc!(
             r#"
-            f : { foo : Int }
+            f : { foo : I64 }
             f = { foo: 1000 }
 
             a
@@ -2509,11 +2509,11 @@ mod test_fmt {
     //            r#"
     //            f :
     //                Result a
-    //                    { x : Int
+    //                    { x : I64
     //                    , y : Float
     //                    }
     //                    c
-    //                -> Int
+    //                -> I64
     //            f =
     //                \_ -> 4
     //            "#
diff --git a/compiler/gen/tests/gen_list.rs b/compiler/gen/tests/gen_list.rs
index 3322e1052b..599feb5f3f 100644
--- a/compiler/gen/tests/gen_list.rs
+++ b/compiler/gen/tests/gen_list.rs
@@ -162,7 +162,7 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                    initThrees : List Int
+                    initThrees : List I64
                     initThrees =
                         []
 
@@ -204,7 +204,7 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                    init : List Int
+                    init : List I64
                     init =
                         []
 
@@ -251,7 +251,7 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                empty : List Int
+                empty : List I64
                 empty =
                     []
 
@@ -330,7 +330,7 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                empty : List Int
+                empty : List I64
                 empty =
                     []
 
@@ -347,7 +347,7 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                alwaysTrue : Int -> Bool
+                alwaysTrue : I64 -> Bool
                 alwaysTrue = \_ ->
                     True
 
@@ -365,11 +365,11 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                alwaysTrue : Int -> Bool
+                alwaysTrue : I64 -> Bool
                 alwaysTrue = \_ ->
                     True
 
-                oneThroughEight : List Int
+                oneThroughEight : List I64
                 oneThroughEight =
                     [1,2,3,4,5,6,7,8]
 
@@ -386,7 +386,7 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                alwaysFalse : Int -> Bool
+                alwaysFalse : I64 -> Bool
                 alwaysFalse = \_ ->
                     False
 
@@ -403,7 +403,7 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                intIsLessThanThree : Int -> Bool
+                intIsLessThanThree : I64 -> Bool
                 intIsLessThanThree = \i ->
                     i < 3
 
@@ -440,7 +440,7 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                empty : List Int
+                empty : List I64
                 empty =
                     []
 
@@ -457,7 +457,7 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                nonEmpty : List Int
+                nonEmpty : List I64
                 nonEmpty =
                     [ 1 ]
 
@@ -474,7 +474,7 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                nonEmpty : List Int
+                nonEmpty : List I64
                 nonEmpty =
                     [ 1 ]
 
@@ -491,7 +491,7 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                nonEmpty : List Int
+                nonEmpty : List I64
                 nonEmpty =
                     [ 1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5 ]
 
@@ -510,7 +510,7 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                nonEmpty : List Int
+                nonEmpty : List I64
                 nonEmpty =
                     [ 1, 1, -4, 1, 2 ]
 
@@ -528,11 +528,11 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                 nonEmpty : List Int
+                 nonEmpty : List I64
                  nonEmpty =
                      [ 2, 2, -4, 2, 3 ]
 
-                 greaterThanOne : Int -> Bool
+                 greaterThanOne : I64 -> Bool
                  greaterThanOne = \i ->
                      i > 1
 
@@ -730,7 +730,7 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                    emptyList : List Int
+                    emptyList : List I64
                     emptyList =
                         []
 
@@ -752,11 +752,11 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                    firstList : List Int
+                    firstList : List I64
                     firstList =
                         []
 
-                    secondList : List Int
+                    secondList : List I64
                     secondList =
                         []
 
@@ -778,11 +778,11 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                    firstList : List Int
+                    firstList : List I64
                     firstList =
                         []
 
-                    secondList : List Int
+                    secondList : List I64
                     secondList =
                         []
 
@@ -1229,7 +1229,7 @@ mod gen_list {
                 app "quicksort" provides [ main ] to "./platform"
 
 
-                swap : Int, Int, List a -> List a
+                swap : I64, I64, List a -> List a
                 swap = \i, j, list ->
                     when Pair (List.get list i) (List.get list j) is
                         Pair (Ok atI) (Ok atJ) ->
@@ -1254,7 +1254,7 @@ mod gen_list {
     //        assert_evals_to!(
     //            indoc!(
     //                r#"
-    //                    swap : Int, Int, List a -> List a
+    //                    swap : I64, I64, List a -> List a
     //                    swap = \i, j, list ->
     //                        when Pair (List.get list i) (List.get list j) is
     //                            Pair (Ok atI) (Ok atJ) ->
@@ -1264,7 +1264,7 @@ mod gen_list {
     //
     //                            _ ->
     //                                []
-    //                    partition : Int, Int, List (Num a) -> [ Pair Int (List (Num a)) ]
+    //                    partition : I64, I64, List (Num a) -> [ Pair I64 (List (Num a)) ]
     //                    partition = \low, high, initialList ->
     //                        when List.get initialList high is
     //                            Ok pivot ->
@@ -1276,7 +1276,7 @@ mod gen_list {
     //                                Pair (low - 1) initialList
     //
     //
-    //                    partitionHelp : Int, Int, List (Num a), Int, Int -> [ Pair Int (List (Num a)) ]
+    //                    partitionHelp : I64, I64, List (Num a), I64, I64 -> [ Pair I64 (List (Num a)) ]
     //                    partitionHelp = \i, j, list, high, pivot ->
     //                        if j < high then
     //                            when List.get list j is
@@ -1306,7 +1306,7 @@ mod gen_list {
     //        assert_evals_to!(
     //            indoc!(
     //                r#"
-    //                    swap : Int, Int, List a -> List a
+    //                    swap : I64, I64, List a -> List a
     //                    swap = \i, j, list ->
     //                        when Pair (List.get list i) (List.get list j) is
     //                            Pair (Ok atI) (Ok atJ) ->
@@ -1316,7 +1316,7 @@ mod gen_list {
     //
     //                            _ ->
     //                                []
-    //                    partition : Int, Int, List (Num a) -> [ Pair Int (List (Num a)) ]
+    //                    partition : I64, I64, List (Num a) -> [ Pair I64 (List (Num a)) ]
     //                    partition = \low, high, initialList ->
     //                        when List.get initialList high is
     //                            Ok pivot ->
@@ -1328,7 +1328,7 @@ mod gen_list {
     //                                Pair (low - 1) initialList
     //
     //
-    //                    partitionHelp : Int, Int, List (Num a), Int, Int -> [ Pair Int (List (Num a)) ]
+    //                    partitionHelp : I64, I64, List (Num a), I64, I64 -> [ Pair I64 (List (Num a)) ]
     //
     //                    # when partition 0 0 [ 1,2,3,4,5 ] is
     //                    # Pair list _ -> list
@@ -1352,7 +1352,7 @@ mod gen_list {
                         quicksortHelp list 0 (n - 1)
 
 
-                    quicksortHelp : List (Num a), Int, Int -> List (Num a)
+                    quicksortHelp : List (Num a), I64, I64 -> List (Num a)
                     quicksortHelp = \list, low, high ->
                         if low < high then
                             when partition low high list is
@@ -1364,7 +1364,7 @@ mod gen_list {
                             list
 
 
-                    swap : Int, Int, List a -> List a
+                    swap : I64, I64, List a -> List a
                     swap = \i, j, list ->
                         when Pair (List.get list i) (List.get list j) is
                             Pair (Ok atI) (Ok atJ) ->
@@ -1375,7 +1375,7 @@ mod gen_list {
                             _ ->
                                 []
 
-                    partition : Int, Int, List (Num a) -> [ Pair Int (List (Num a)) ]
+                    partition : I64, I64, List (Num a) -> [ Pair I64 (List (Num a)) ]
                     partition = \low, high, initialList ->
                         when List.get initialList high is
                             Ok pivot ->
@@ -1387,7 +1387,7 @@ mod gen_list {
                                 Pair (low - 1) initialList
 
 
-                    partitionHelp : Int, Int, List (Num a), Int, (Num a) -> [ Pair Int (List (Num a)) ]
+                    partitionHelp : I64, I64, List (Num a), I64, (Num a) -> [ Pair I64 (List (Num a)) ]
                     partitionHelp = \i, j, list, high, pivot ->
                         if j < high then
                             when List.get list j is
@@ -1422,7 +1422,7 @@ mod gen_list {
                            quicksortHelp list 0 (List.len list - 1)
 
 
-                       quicksortHelp : List (Num a), Int, Int -> List (Num a)
+                       quicksortHelp : List (Num a), I64, I64 -> List (Num a)
                        quicksortHelp = \list, low, high ->
                            if low < high then
                                when partition low high list is
@@ -1434,7 +1434,7 @@ mod gen_list {
                                list
 
 
-                       swap : Int, Int, List a -> List a
+                       swap : I64, I64, List a -> List a
                        swap = \i, j, list ->
                            when Pair (List.get list i) (List.get list j) is
                                Pair (Ok atI) (Ok atJ) ->
@@ -1445,7 +1445,7 @@ mod gen_list {
                                _ ->
                                    []
 
-                       partition : Int, Int, List (Num a) -> [ Pair Int (List (Num a)) ]
+                       partition : I64, I64, List (Num a) -> [ Pair I64 (List (Num a)) ]
                        partition = \low, high, initialList ->
                            when List.get initialList high is
                                Ok pivot ->
@@ -1457,7 +1457,7 @@ mod gen_list {
                                    Pair (low - 1) initialList
 
 
-                       partitionHelp : Int, Int, List (Num a), Int, Num a -> [ Pair Int (List (Num a)) ]
+                       partitionHelp : I64, I64, List (Num a), I64, Num a -> [ Pair I64 (List (Num a)) ]
                        partitionHelp = \i, j, list, high, pivot ->
                            # if j < high then
                            if False then
@@ -1495,7 +1495,7 @@ mod gen_list {
                            quicksortHelp list 0 (List.len list - 1)
 
 
-                       quicksortHelp : List (Num a), Int, Int -> List (Num a)
+                       quicksortHelp : List (Num a), I64, I64 -> List (Num a)
                        quicksortHelp = \list, low, high ->
                            if low < high then
                                when partition low high list is
@@ -1507,7 +1507,7 @@ mod gen_list {
                                list
 
 
-                       swap : Int, Int, List a -> List a
+                       swap : I64, I64, List a -> List a
                        swap = \i, j, list ->
                            when Pair (List.get list i) (List.get list j) is
                                Pair (Ok atI) (Ok atJ) ->
@@ -1518,7 +1518,7 @@ mod gen_list {
                                _ ->
                                    []
 
-                       partition : Int, Int, List (Num a) -> [ Pair Int (List (Num a)) ]
+                       partition : I64, I64, List (Num a) -> [ Pair I64 (List (Num a)) ]
                        partition = \low, high, initialList ->
                            when List.get initialList high is
                                Ok pivot ->
@@ -1530,7 +1530,7 @@ mod gen_list {
                                    Pair (low - 1) initialList
 
 
-                       partitionHelp : Int, Int, List (Num a), Int, Num a -> [ Pair Int (List (Num a)) ]
+                       partitionHelp : I64, I64, List (Num a), I64, Num a -> [ Pair I64 (List (Num a)) ]
                        partitionHelp = \i, j, list, high, pivot ->
                            if j < high then
                                when List.get list j is
@@ -1562,7 +1562,7 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                x : List Int
+                x : List I64
                 x = []
 
                 List.len x + List.len x
@@ -1578,7 +1578,7 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                x : List Int
+                x : List I64
                 x = [1,2,3]
 
                 List.len x + List.len x
@@ -1594,10 +1594,10 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                x : List Int
+                x : List I64
                 x = [1,2,3]
 
-                id : List Int -> List Int
+                id : List I64 -> List I64
                 id = \y -> y
 
                 id x
@@ -1613,10 +1613,10 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                x : List Int
+                x : List I64
                 x = [1,2,3]
 
-                id : List Int -> List Int
+                id : List I64 -> List I64
                 id = \y -> List.set y 0 0
 
                 id x
@@ -1632,7 +1632,7 @@ mod gen_list {
         assert_evals_to!(
             indoc!(
                 r#"
-                id : List Int -> [ Pair (List Int) Int ]
+                id : List I64 -> [ Pair (List I64) I64 ]
                 id = \y -> Pair y 4
 
                 when id [1,2,3] is
diff --git a/compiler/gen/tests/gen_primitives.rs b/compiler/gen/tests/gen_primitives.rs
index a34fd94892..8660714182 100644
--- a/compiler/gen/tests/gen_primitives.rs
+++ b/compiler/gen/tests/gen_primitives.rs
@@ -135,7 +135,7 @@ mod gen_primitives {
         assert_evals_to!(
             indoc!(
                 r#"
-                x : [ Pair Int Int ]
+                x : [ Pair I64 I64 ]
                 x = Pair 0x2 0x3
 
                 when x is
@@ -152,7 +152,7 @@ mod gen_primitives {
         assert_evals_to!(
             indoc!(
                 r#"
-                x : [A Int, B Int]
+                x : [A I64, B I64]
                 x = A 0x2
 
                 when x is
@@ -170,7 +170,7 @@ mod gen_primitives {
         assert_evals_to!(
             indoc!(
                 r#"
-                x : [A Int, B Int]
+                x : [A I64, B I64]
                 x = B 0x3
 
                 when x is
@@ -293,7 +293,7 @@ mod gen_primitives {
             indoc!(
                 r#"
                 wrapper = \{} ->
-                    alwaysFloatIdentity : Int -> (F64 -> F64)
+                    alwaysFloatIdentity : I64 -> (F64 -> F64)
                     alwaysFloatIdentity = \_ ->
                         (\a -> a)
 
@@ -557,14 +557,14 @@ mod gen_primitives {
 
                 LinkedList a : [ Nil, Cons a (LinkedList a) ]
 
-                len : LinkedList a -> Int
+                len : LinkedList a -> I64
                 len = \list ->
                     when list is
                         Nil -> 0
                         Cons _ rest -> 1 + len rest
 
                 main =
-                    nil : LinkedList Int
+                    nil : LinkedList I64
                     nil = Nil
 
                     len nil
@@ -584,10 +584,10 @@ mod gen_primitives {
 
                 LinkedList a : [ Nil, Cons a (LinkedList a) ]
 
-                nil : LinkedList Int
+                nil : LinkedList I64
                 nil = Nil
 
-                length : LinkedList a -> Int
+                length : LinkedList a -> I64
                 length = \list ->
                     when list is
                         Nil -> 0
@@ -611,10 +611,10 @@ mod gen_primitives {
 
                 LinkedList a : [ Nil, Cons a (LinkedList a) ]
 
-                one : LinkedList Int
+                one : LinkedList I64
                 one = Cons 1 Nil
 
-                length : LinkedList a -> Int
+                length : LinkedList a -> I64
                 length = \list ->
                     when list is
                         Nil -> 0
@@ -638,10 +638,10 @@ mod gen_primitives {
 
                 LinkedList a : [ Nil, Cons a (LinkedList a) ]
 
-                one : LinkedList Int
+                one : LinkedList I64
                 one = Cons 1 Nil
 
-                length : LinkedList a -> Int
+                length : LinkedList a -> I64
                 length = \list ->
                     when list is
                         Nil -> 0
@@ -665,10 +665,10 @@ mod gen_primitives {
 
                 LinkedList a : [ Nil, Cons a (LinkedList a) ]
 
-                three : LinkedList Int
+                three : LinkedList I64
                 three = Cons 3 (Cons 2 (Cons 1 Nil))
 
-                length : LinkedList a -> Int
+                length : LinkedList a -> I64
                 length = \list ->
                     when list is
                         Nil -> 0
@@ -693,7 +693,7 @@ mod gen_primitives {
 
                 LinkedList a : [ Nil, Cons a (LinkedList a) ]
 
-                three : LinkedList Int
+                three : LinkedList I64
                 three = Cons 3 (Cons 2 (Cons 1 Nil))
 
 
@@ -721,10 +721,10 @@ mod gen_primitives {
 
                 LinkedList a : [ Nil, Cons a (LinkedList a) ]
 
-                zero : LinkedList Int
+                zero : LinkedList I64
                 zero = Nil
 
-                sum : LinkedList Int -> Int
+                sum : LinkedList I64 -> I64
                 sum = \list ->
                     when list is
                         Nil -> 0
@@ -748,7 +748,7 @@ mod gen_primitives {
 
                 LinkedList a : [ Nil, Cons a (LinkedList a) ]
 
-                three : LinkedList Int
+                three : LinkedList I64
                 three = Cons 3 (Cons 2 (Cons 1 Nil))
 
                 sum : LinkedList (Num a) -> Num a
@@ -779,7 +779,7 @@ mod gen_primitives {
                 r#"
                 Maybe a : [ Nothing, Just a ]
 
-                x : Maybe (Maybe Int)
+                x : Maybe (Maybe I64)
                 x = Just (Just 41)
 
                 when x is
@@ -796,7 +796,7 @@ mod gen_primitives {
                 r#"
                 Maybe a : [ Nothing, Just a ]
 
-                x : Maybe (Maybe Int)
+                x : Maybe (Maybe I64)
                 x = Just Nothing
 
                 when x is
@@ -814,7 +814,7 @@ mod gen_primitives {
                 r#"
                 Maybe a : [ Nothing, Just a ]
 
-                x : Maybe (Maybe Int)
+                x : Maybe (Maybe I64)
                 x = Nothing
 
                 when x is
@@ -1128,7 +1128,7 @@ mod gen_primitives {
 
                 main : Bool
                 main =
-                    myList : ConsList Int
+                    myList : ConsList I64
                     myList = empty
 
                     isEmpty myList
@@ -1159,7 +1159,7 @@ mod gen_primitives {
 
                 main : Bool
                 main =
-                    myList : ConsList Int
+                    myList : ConsList I64
                     myList = Cons 0x1 Nil
 
                     isEmpty myList
@@ -1177,16 +1177,16 @@ mod gen_primitives {
                 r#"
                 app "test" provides [ main ] to "./platform"
 
-                State a : { count : Int, x : a }
+                State a : { count : I64, x : a }
 
-                foo : State a -> Int
+                foo : State a -> I64
                 foo = \state ->
                     if state.count == 0 then
                         0
                     else
                         1 + foo { count: state.count - 1, x: state.x }
 
-                main : Int
+                main : I64
                 main =
                     foo { count: 3, x: {} }
                 "#
@@ -1267,7 +1267,7 @@ mod gen_primitives {
                         _ ->
                           Node color key value left right
 
-                main : Dict Int {}
+                main : Dict I64 {}
                 main =
                     insert 0 {} Empty
                 "#
@@ -1308,7 +1308,7 @@ mod gen_primitives {
                     _ ->
                         Empty
 
-                main : Dict Int
+                main : Dict I64
                 main =
                     balance Red 0 Empty Empty
                 "#
@@ -1331,7 +1331,7 @@ mod gen_primitives {
                 balance = \key, left ->
                     Node key left Empty
 
-                main : Dict Int
+                main : Dict I64
                 main =
                     balance 0 Empty
                 "#
@@ -1378,7 +1378,7 @@ mod gen_primitives {
                     _ ->
                         Empty
 
-                main : Dict Int Int
+                main : Dict I64 I64
                 main =
                     balance Red 0 0 Empty Empty
                 "#
@@ -1428,7 +1428,7 @@ mod gen_primitives {
                         _ ->
                           Node color key value left right
 
-                main : Dict Int Int
+                main : Dict I64 I64
                 main =
                     balance Red 0 0 Empty Empty
                 "#
@@ -1448,7 +1448,7 @@ mod gen_primitives {
 
                 ConsList a : [ Cons a (ConsList a), Nil ]
 
-                balance : ConsList Int -> Int
+                balance : ConsList I64 -> I64
                 balance = \right ->
                   when right is
                     Cons 1 foo ->
@@ -1457,7 +1457,7 @@ mod gen_primitives {
                             _ -> 3
                     _ -> 3
 
-                main : Int
+                main : I64
                 main =
                     when balance Nil is
                         _ -> 3
@@ -1474,13 +1474,13 @@ mod gen_primitives {
 
                 ConsList a : [ Cons a (ConsList a), Nil ]
 
-                balance : ConsList Int -> Int
+                balance : ConsList I64 -> I64
                 balance = \right ->
                   when right is
                     Cons 1 (Cons 1 _) -> 3
                     _ -> 3
 
-                main : Int
+                main : I64
                 main =
                     when balance Nil is
                         _ -> 3
@@ -1502,7 +1502,7 @@ mod gen_primitives {
 
                 ConsList a : [ Cons a (ConsList a), Nil ]
 
-                balance : ConsList Int -> Int
+                balance : ConsList I64 -> I64
                 balance = \right ->
                   when right is
                     Cons 1 foo ->
@@ -1511,7 +1511,7 @@ mod gen_primitives {
                             _ -> 3
                     _ -> 3
 
-                main : Int
+                main : I64
                 main =
                     when balance Nil is
                         _ -> 3
@@ -1531,13 +1531,13 @@ mod gen_primitives {
 
                 ConsList a : [ Cons a (ConsList a), Nil ]
 
-                foo : ConsList Int -> Int
+                foo : ConsList I64 -> I64
                 foo = \list ->
                     when list is
                         Cons _ (Cons x _) -> x
                         _ -> 0
 
-                main : Int
+                main : I64
                 main =
                     foo (Cons 1 (Cons 32 Nil))
                 "#
@@ -1554,15 +1554,15 @@ mod gen_primitives {
                 r#"
                 app "test" provides [ main ] to "./platform"
 
-                BTree : [ Node BTree BTree, Leaf Int ]
+                BTree : [ Node BTree BTree, Leaf I64 ]
 
-                foo : BTree -> Int
+                foo : BTree -> I64
                 foo = \btree ->
                     when btree is
                         Node (Node (Leaf x) _) _ -> x
                         _ -> 0
 
-                main : Int
+                main : I64
                 main =
                     foo (Node (Node (Leaf 32) (Leaf 0)) (Leaf 0))
                 "#
diff --git a/compiler/gen/tests/gen_tags.rs b/compiler/gen/tests/gen_tags.rs
index 2b30ed5579..187bf7b01f 100644
--- a/compiler/gen/tests/gen_tags.rs
+++ b/compiler/gen/tests/gen_tags.rs
@@ -20,7 +20,7 @@ mod gen_tags {
                 r#"
                 Maybe a : [ Just a, Nothing ]
 
-                x : Maybe Int
+                x : Maybe I64
                 x = Nothing
 
                 x
@@ -39,7 +39,7 @@ mod gen_tags {
                 r#"
                 Maybe a : [ Just a, Nothing ]
 
-                x : Maybe Int
+                x : Maybe I64
                 x = Nothing
 
                 x
@@ -58,7 +58,7 @@ mod gen_tags {
                 r#"
                 Maybe a : [ Just a, Nothing ]
 
-                y : Maybe Int
+                y : Maybe I64
                 y = Just 0x4
 
                 y
@@ -76,7 +76,7 @@ mod gen_tags {
                 r#"
                 Maybe a : [ Just a, Nothing ]
 
-                y : Maybe Int
+                y : Maybe I64
                 y = Just 0x4
 
                 y
@@ -114,7 +114,7 @@ mod gen_tags {
     //     assert_evals_to!(
     //         indoc!(
     //             r#"
-    //             x : Result Int Int
+    //             x : Result I64 I64
     //             x = Err 41
 
     //             x
@@ -185,7 +185,7 @@ mod gen_tags {
     //                r#"
     //                LinkedList a : [ Cons a (LinkedList a), Nil ]
     //
-    //                empty : LinkedList Int
+    //                empty : LinkedList I64
     //                empty = Nil
     //
     //                1
@@ -203,7 +203,7 @@ mod gen_tags {
     //                r#"
     //                LinkedList a : [ Cons a (LinkedList a), Nil ]
     //
-    //                singleton : LinkedList Int
+    //                singleton : LinkedList I64
     //                singleton = Cons 0x1 Nil
     //
     //                1
@@ -290,7 +290,7 @@ mod gen_tags {
         assert_evals_to!(
             indoc!(
                 r#"
-                x : [ Nothing, Just Int ]
+                x : [ Nothing, Just I64 ]
                 x = Nothing
 
                 when x is
@@ -308,7 +308,7 @@ mod gen_tags {
         assert_evals_to!(
             indoc!(
                 r#"
-                x : [ Nothing, Just Int ]
+                x : [ Nothing, Just I64 ]
                 x = Just 41
 
                 when x is
@@ -326,7 +326,7 @@ mod gen_tags {
         assert_evals_to!(
             indoc!(
                 r#"
-                x : Result Int Int
+                x : Result I64 I64
                 x = Err 41
 
                 when x is
@@ -346,7 +346,7 @@ mod gen_tags {
                 r#"
                 These a b : [ This a, That b, These a b ]
 
-                x : These Int Int
+                x : These I64 I64
                 x = These 0x3 0x2
 
                 when x is
@@ -398,7 +398,7 @@ mod gen_tags {
         assert_evals_to!(
             indoc!(
                 r#"
-            x : Result Int Int
+            x : Result I64 I64
             x = Ok 2
 
             when x is
@@ -464,7 +464,7 @@ mod gen_tags {
                 r#"
                 Maybe a : [ Nothing, Just a ]
 
-                x : Maybe (Maybe Int)
+                x : Maybe (Maybe I64)
                 x = Just (Just 41)
 
                 when x is
@@ -558,7 +558,7 @@ mod gen_tags {
                 r#"
                 Unit : [ Unit ]
 
-                f : Unit -> Int
+                f : Unit -> I64
                 f = \Unit -> 42
 
                 f Unit
@@ -587,7 +587,7 @@ mod gen_tags {
         assert_evals_to!(
             indoc!(
                 r#"
-                f : {} -> Int
+                f : {} -> I64
                 f = \{} -> 42
 
                 f {}
@@ -614,7 +614,7 @@ mod gen_tags {
         assert_evals_to!(
             indoc!(
                 r#"
-                x : [ Pair Int ]
+                x : [ Pair I64 ]
                 x = Pair 2
 
                 x
@@ -634,7 +634,7 @@ mod gen_tags {
 
                 Maybe a : [ Nothing, Just a ]
 
-                x : Maybe (Maybe Int)
+                x : Maybe (Maybe I64)
                 x = Just (Just 41)
 
                 main =
@@ -806,7 +806,7 @@ mod gen_tags {
         assert_evals_to!(
             indoc!(
                 r"#
-                x : [ Three Bool Int, Empty ]
+                x : [ Three Bool I64, Empty ]
                 x = Three (1 == 1) 32
 
                 x
@@ -820,7 +820,7 @@ mod gen_tags {
         assert_evals_to!(
             indoc!(
                 r"#
-                x : [ Three Bool [ Red, Green, Blue ] Int, Empty ]
+                x : [ Three Bool [ Red, Green, Blue ] I64, Empty ]
                 x = Three (1 == 1) (if True then Red else if True then Green else Blue) 32
 
                 x
@@ -836,7 +836,7 @@ mod gen_tags {
         assert_evals_to!(
             indoc!(
                 r"#
-                x : [ Three Bool Int, Empty ]
+                x : [ Three Bool I64, Empty ]
                 x = Three (1 == 1) 32
 
                 when x is
@@ -854,7 +854,7 @@ mod gen_tags {
         assert_evals_to!(
             indoc!(
                 r"#
-                x : [ Three Bool [ Red, Green, Blue ] Int, Empty ]
+                x : [ Three Bool [ Red, Green, Blue ] I64, Empty ]
                 x = Three (1 == 1) (if True then Red else if True then Green else Blue) 32
 
                 when x is
diff --git a/compiler/load/tests/fixtures/build/app_with_deps/Quicksort.roc b/compiler/load/tests/fixtures/build/app_with_deps/Quicksort.roc
index af67b92f93..8ea4ef5b59 100644
--- a/compiler/load/tests/fixtures/build/app_with_deps/Quicksort.roc
+++ b/compiler/load/tests/fixtures/build/app_with_deps/Quicksort.roc
@@ -1,6 +1,6 @@
 app "quicksort" provides [ swap, partition, partitionHelp, quicksort ] to "./platform"
 
-quicksort : List (Num a), Int, Int -> List (Num a)
+quicksort : List (Num a), I64, I64 -> List (Num a)
 quicksort = \list, low, high ->
     when partition low high list is
         Pair partitionIndex partitioned ->
@@ -9,7 +9,7 @@ quicksort = \list, low, high ->
                 |> quicksort (partitionIndex + 1) high
 
 
-swap : Int, Int, List a -> List a
+swap : I64, I64, List a -> List a
 swap = \i, j, list ->
     when Pair (List.get list i) (List.get list j) is
         Pair (Ok atI) (Ok atJ) ->
@@ -21,7 +21,7 @@ swap = \i, j, list ->
             []
 
 
-partition : Int, Int, List (Num a) -> [ Pair Int (List (Num a)) ]
+partition : I64, I64, List (Num a) -> [ Pair I64 (List (Num a)) ]
 partition = \low, high, initialList ->
     when List.get initialList high is
         Ok pivot ->
@@ -33,7 +33,7 @@ partition = \low, high, initialList ->
             Pair (low - 1) initialList
 
 
-partitionHelp : Int, Int, List (Num a), Int, (Num a) -> [ Pair Int (List (Num a)) ]
+partitionHelp : I64, I64, List (Num a), I64, (Num a) -> [ Pair I64 (List (Num a)) ]
 partitionHelp = \i, j, list, high, pivot ->
     if j < high then
         when List.get list j is
diff --git a/compiler/load/tests/fixtures/build/app_with_deps/QuicksortOneDef.roc b/compiler/load/tests/fixtures/build/app_with_deps/QuicksortOneDef.roc
index f199f07272..602d82f511 100644
--- a/compiler/load/tests/fixtures/build/app_with_deps/QuicksortOneDef.roc
+++ b/compiler/load/tests/fixtures/build/app_with_deps/QuicksortOneDef.roc
@@ -1,7 +1,7 @@
 app "quicksort" provides [ quicksort ] to "./platform"
 
 quicksort = \originalList ->
-    quicksortHelp : List (Num a), Int, Int -> List (Num a)
+    quicksortHelp : List (Num a), I64, I64 -> List (Num a)
     quicksortHelp = \list, low, high ->
         if low < high then
             when partition low high list is
@@ -13,7 +13,7 @@ quicksort = \originalList ->
             list
 
 
-    swap : Int, Int, List a -> List a
+    swap : I64, I64, List a -> List a
     swap = \i, j, list ->
         when Pair (List.get list i) (List.get list j) is
             Pair (Ok atI) (Ok atJ) ->
@@ -24,7 +24,7 @@ quicksort = \originalList ->
             _ ->
                 []
 
-    partition : Int, Int, List (Num a) -> [ Pair Int (List (Num a)) ]
+    partition : I64, I64, List (Num a) -> [ Pair I64 (List (Num a)) ]
     partition = \low, high, initialList ->
         when List.get initialList high is
             Ok pivot ->
@@ -36,7 +36,7 @@ quicksort = \originalList ->
                 Pair (low - 1) initialList
 
 
-    partitionHelp : Int, Int, List (Num a), Int, (Num a) -> [ Pair Int (List (Num a)) ]
+    partitionHelp : I64, I64, List (Num a), I64, (Num a) -> [ Pair I64 (List (Num a)) ]
     partitionHelp = \i, j, list, high, pivot ->
         if j < high then
             when List.get list j is
diff --git a/compiler/load/tests/fixtures/build/interface_with_deps/Quicksort.roc b/compiler/load/tests/fixtures/build/interface_with_deps/Quicksort.roc
index d4e9b79490..341cf99126 100644
--- a/compiler/load/tests/fixtures/build/interface_with_deps/Quicksort.roc
+++ b/compiler/load/tests/fixtures/build/interface_with_deps/Quicksort.roc
@@ -2,7 +2,7 @@ interface Quicksort
     exposes [ swap, partition, quicksort ]
     imports []
 
-quicksort : List (Num a), Int, Int -> List (Num a)
+quicksort : List (Num a), I64, I64 -> List (Num a)
 quicksort = \list, low, high ->
     when partition low high list is
         Pair partitionIndex partitioned ->
@@ -11,7 +11,7 @@ quicksort = \list, low, high ->
                 |> quicksort (partitionIndex + 1) high
 
 
-swap : Int, Int, List a -> List a
+swap : I64, I64, List a -> List a
 swap = \i, j, list ->
     when Pair (List.get list i) (List.get list j) is
         Pair (Ok atI) (Ok atJ) ->
@@ -23,7 +23,7 @@ swap = \i, j, list ->
             []
 
 
-partition : Int, Int, List (Num a) -> [ Pair Int (List (Num a)) ]
+partition : I64, I64, List (Num a) -> [ Pair I64 (List (Num a)) ]
 partition = \low, high, initialList ->
     when List.get initialList high is
         Ok pivot ->
@@ -35,7 +35,7 @@ partition = \low, high, initialList ->
             Pair (low - 1) initialList
 
 
-partitionHelp : Int, Int, List (Num a), Int, (Num a) -> [ Pair Int (List (Num a)) ]
+partitionHelp : I64, I64, List (Num a), I64, (Num a) -> [ Pair I64 (List (Num a)) ]
 partitionHelp = \i, j, list, high, pivot ->
     if j < high then
         when List.get list j is
diff --git a/compiler/load/tests/test_load.rs b/compiler/load/tests/test_load.rs
index 0a960bdfe9..5d57bfa89a 100644
--- a/compiler/load/tests/test_load.rs
+++ b/compiler/load/tests/test_load.rs
@@ -265,7 +265,7 @@ mod test_load {
                             imports [ RBTree ] 
                             provides [ main ] to blah
 
-                        empty : RBTree.Dict Int Int
+                        empty : RBTree.Dict I64 I64
                         empty = RBTree.empty
 
                         main = empty
@@ -360,7 +360,7 @@ mod test_load {
                 "floatTest" => "F64",
                 "divisionFn" => "F64, F64 -> Result F64 [ DivByZero ]*",
                 "divisionTest" => "Result F64 [ DivByZero ]*",
-                "intTest" => "Int",
+                "intTest" => "I64",
                 "x" => "F64",
                 "constantNum" => "Num *",
                 "divDep1ByDep2" => "Result F64 [ DivByZero ]*",
@@ -377,10 +377,10 @@ mod test_load {
         expect_types(
             loaded_module,
             hashmap! {
-                "swap" => "Int, Int, List a -> List a",
-                "partition" => "Int, Int, List (Num a) -> [ Pair Int (List (Num a)) ]",
-                "partitionHelp" => "Int, Int, List (Num a), Int, Num a -> [ Pair Int (List (Num a)) ]",
-                "quicksort" => "List (Num a), Int, Int -> List (Num a)",
+                "swap" => "I64, I64, List a -> List a",
+                "partition" => "I64, I64, List (Num a) -> [ Pair I64 (List (Num a)) ]",
+                "partitionHelp" => "I64, I64, List (Num a), I64, Num a -> [ Pair I64 (List (Num a)) ]",
+                "quicksort" => "List (Num a), I64, I64 -> List (Num a)",
             },
         );
     }
@@ -406,10 +406,10 @@ mod test_load {
         expect_types(
             loaded_module,
             hashmap! {
-                "swap" => "Int, Int, List a -> List a",
-                "partition" => "Int, Int, List (Num a) -> [ Pair Int (List (Num a)) ]",
-                "partitionHelp" => "Int, Int, List (Num a), Int, Num a -> [ Pair Int (List (Num a)) ]",
-                "quicksort" => "List (Num a), Int, Int -> List (Num a)",
+                "swap" => "I64, I64, List a -> List a",
+                "partition" => "I64, I64, List (Num a) -> [ Pair I64 (List (Num a)) ]",
+                "partitionHelp" => "I64, I64, List (Num a), I64, Num a -> [ Pair I64 (List (Num a)) ]",
+                "quicksort" => "List (Num a), I64, I64 -> List (Num a)",
             },
         );
     }
diff --git a/compiler/load/tests/test_uniq_load.rs b/compiler/load/tests/test_uniq_load.rs
index 91fa1f304f..643bc1dd29 100644
--- a/compiler/load/tests/test_uniq_load.rs
+++ b/compiler/load/tests/test_uniq_load.rs
@@ -235,7 +235,7 @@ mod test_uniq_load {
                 "floatTest" => "Attr Shared F64",
                 "divisionFn" => "Attr Shared (Attr * F64, Attr * F64 -> Attr * (Result (Attr * F64) (Attr * [ DivByZero ]*)))",
                 "divisionTest" =>  "Attr * (Result (Attr * F64) (Attr * [ DivByZero ]*))",
-                "intTest" => "Attr * Int",
+                "intTest" => "Attr * I64",
                 "x" => "Attr * F64",
                 "constantNum" => "Attr * (Num (Attr * *))",
                 "divDep1ByDep2" => "Attr * (Result (Attr * F64) (Attr * [ DivByZero ]*))",
@@ -271,11 +271,11 @@ mod test_uniq_load {
         expect_types(
             loaded_module,
             hashmap! {
-                "swap" => "Attr * (Attr * Int, Attr * Int, Attr * (List (Attr Shared a)) -> Attr * (List (Attr Shared a)))",
-                "partition" => "Attr * (Attr Shared Int, Attr Shared Int, Attr b (List (Attr Shared (Num (Attr Shared a)))) -> Attr * [ Pair (Attr * Int) (Attr b (List (Attr Shared (Num (Attr Shared a))))) ])",
+                "swap" => "Attr * (Attr * I64, Attr * I64, Attr * (List (Attr Shared a)) -> Attr * (List (Attr Shared a)))",
+                "partition" => "Attr * (Attr Shared I64, Attr Shared I64, Attr b (List (Attr Shared (Num (Attr Shared a)))) -> Attr * [ Pair (Attr * I64) (Attr b (List (Attr Shared (Num (Attr Shared a))))) ])",
 
-                "partitionHelp" => "Attr Shared (Attr b Int, Attr Shared Int, Attr c (List (Attr Shared (Num (Attr Shared a)))), Attr Shared Int, Attr Shared (Num (Attr Shared a)) -> Attr * [ Pair (Attr b Int) (Attr c (List (Attr Shared (Num (Attr Shared a))))) ])",
-                "quicksort" => "Attr Shared (Attr b (List (Attr Shared (Num (Attr Shared a)))), Attr Shared Int, Attr Shared Int -> Attr b (List (Attr Shared (Num (Attr Shared a)))))",
+                "partitionHelp" => "Attr Shared (Attr b I64, Attr Shared I64, Attr c (List (Attr Shared (Num (Attr Shared a)))), Attr Shared I64, Attr Shared (Num (Attr Shared a)) -> Attr * [ Pair (Attr b I64) (Attr c (List (Attr Shared (Num (Attr Shared a))))) ])",
+                "quicksort" => "Attr Shared (Attr b (List (Attr Shared (Num (Attr Shared a)))), Attr Shared I64, Attr Shared I64 -> Attr b (List (Attr Shared (Num (Attr Shared a)))))",
             },
         );
     }
diff --git a/compiler/module/src/symbol.rs b/compiler/module/src/symbol.rs
index a3b3806f8e..d617b254a4 100644
--- a/compiler/module/src/symbol.rs
+++ b/compiler/module/src/symbol.rs
@@ -742,7 +742,7 @@ define_builtins! {
     1 NUM: "Num" => {
         0 NUM_NUM: "Num" imported // the Num.Num type alias
         1 NUM_AT_NUM: "@Num" // the Num.@Num private tag
-        2 NUM_INT: "Int" imported // the Int.Int type alias
+        2 NUM_I64: "I64" imported // the Num.I64 type alias
         3 NUM_INTEGER: "Integer" imported // Int : Num Integer
         4 NUM_AT_INTEGER: "@Integer" // the Int.@Integer private tag
         5 NUM_F64: "F64" imported // the Num.F64 type alias
diff --git a/compiler/mono/src/layout.rs b/compiler/mono/src/layout.rs
index 91b2e3986e..3b45f92b45 100644
--- a/compiler/mono/src/layout.rs
+++ b/compiler/mono/src/layout.rs
@@ -323,7 +323,7 @@ impl<'a> Layout<'a> {
             }
             Structure(flat_type) => layout_from_flat_type(env, flat_type),
 
-            Alias(Symbol::NUM_INT, args, _) => {
+            Alias(Symbol::NUM_I64, args, _) => {
                 debug_assert!(args.is_empty());
                 Ok(Layout::Builtin(Builtin::Int64))
             }
@@ -723,7 +723,7 @@ fn layout_from_flat_type<'a>(
     match flat_type {
         Apply(symbol, args) => {
             match symbol {
-                Symbol::NUM_INT => {
+                Symbol::NUM_I64 => {
                     debug_assert_eq!(args.len(), 0);
                     Ok(Layout::Builtin(Builtin::Int64))
                 }
diff --git a/compiler/mono/tests/test_mono.rs b/compiler/mono/tests/test_mono.rs
index 2f2f834362..a7a2842bb5 100644
--- a/compiler/mono/tests/test_mono.rs
+++ b/compiler/mono/tests/test_mono.rs
@@ -375,7 +375,7 @@ mod test_mono {
     fn ir_when_just() {
         compiles_to_ir(
             r#"
-            x : [ Nothing, Just Int ]
+            x : [ Nothing, Just I64 ]
             x = Just 41
 
             when x is
@@ -412,7 +412,7 @@ mod test_mono {
     fn one_element_tag() {
         compiles_to_ir(
             r#"
-            x : [ Pair Int ]
+            x : [ Pair I64 ]
             x = Pair 2
 
             x
@@ -502,7 +502,7 @@ mod test_mono {
             r#"
             Maybe a : [ Nothing, Just a ]
 
-            x : Maybe (Maybe Int)
+            x : Maybe (Maybe I64)
             x = Just (Just 41)
 
             when x is
@@ -795,7 +795,7 @@ mod test_mono {
         compiles_to_ir(
             r#"
             wrapper = \{} ->
-                x : Result Int Int
+                x : Result I64 I64
                 x = Ok 2
 
                 y =
@@ -1002,10 +1002,10 @@ mod test_mono {
         compiles_to_ir(
             indoc!(
                 r#"
-                x : List Int
+                x : List I64
                 x = [1,2,3]
 
-                id : List Int -> List Int
+                id : List I64 -> List I64
                 id = \y -> List.set y 0 0
 
                 id x
@@ -1185,7 +1185,7 @@ mod test_mono {
             compiles_to_ir(
                 indoc!(
                     r#"
-                quicksortHelp : List (Num a), Int, Int -> List (Num a)
+                quicksortHelp : List (Num a), I64, I64 -> List (Num a)
                 quicksortHelp = \list, low, high ->
                     if low < high then
                         (Pair partitionIndex partitioned) = Pair 0 []
@@ -1376,7 +1376,7 @@ mod test_mono {
                     r#"
                     app "test" provides [ main ] to "./platform"
 
-                    partitionHelp : Int, Int, List (Num a), Int, (Num a) -> [ Pair Int (List (Num a)) ]
+                    partitionHelp : I64, I64, List (Num a), I64, (Num a) -> [ Pair I64 (List (Num a)) ]
                     partitionHelp = \i, j, list, high, pivot ->
                         if j < high then
                             when List.get list j is
@@ -1412,7 +1412,7 @@ mod test_mono {
                     r#"
                     app "test" provides [ main ] to "./platform"
 
-                    quicksortHelp : List (Num a), Int, Int -> List (Num a)
+                    quicksortHelp : List (Num a), I64, I64 -> List (Num a)
                     quicksortHelp = \list, low, high ->
                         if low < high then
                             (Pair partitionIndex partitioned) = partition low high list
@@ -1424,7 +1424,7 @@ mod test_mono {
                             list
 
 
-                    swap : Int, Int, List a -> List a
+                    swap : I64, I64, List a -> List a
                     swap = \i, j, list ->
                         when Pair (List.get list i) (List.get list j) is
                             Pair (Ok atI) (Ok atJ) ->
@@ -1435,7 +1435,7 @@ mod test_mono {
                             _ ->
                                 []
 
-                    partition : Int, Int, List (Num a) -> [ Pair Int (List (Num a)) ]
+                    partition : I64, I64, List (Num a) -> [ Pair I64 (List (Num a)) ]
                     partition = \low, high, initialList ->
                         when List.get initialList high is
                             Ok pivot ->
@@ -1447,7 +1447,7 @@ mod test_mono {
                                 Pair (low - 1) initialList
 
 
-                    partitionHelp : Int, Int, List (Num a), Int, (Num a) -> [ Pair Int (List (Num a)) ]
+                    partitionHelp : I64, I64, List (Num a), I64, (Num a) -> [ Pair I64 (List (Num a)) ]
                     partitionHelp = \i, j, list, high, pivot ->
                         if j < high then
                             when List.get list j is
@@ -1690,10 +1690,10 @@ mod test_mono {
                 r#"
                 app "test" provides [ main ] to "./platform"
 
-                x : List Int
+                x : List I64
                 x = [1,2,3]
 
-                add : List Int -> List Int
+                add : List I64 -> List I64
                 add = \y -> List.set y 0 0
 
                 main =
@@ -1992,7 +1992,7 @@ mod test_mono {
                 r#"
                 Maybe a : [ Nothing, Just a ]
 
-                x : Maybe (Maybe Int)
+                x : Maybe (Maybe I64)
                 x = Just (Just 41)
 
                 when x is
@@ -2047,10 +2047,10 @@ mod test_mono {
                 r#"
                 LinkedList a : [ Nil, Cons a (LinkedList a) ]
 
-                nil : LinkedList Int
+                nil : LinkedList I64
                 nil = Nil
 
-                length : LinkedList a -> Int
+                length : LinkedList a -> I64
                 length = \list ->
                     when list is
                         Nil -> 0
@@ -2102,7 +2102,7 @@ mod test_mono {
                 r#"
                 app "test" provides [ main ] to "./platform"
 
-                swap : Int, Int, List a -> List a
+                swap : I64, I64, List a -> List a
                 swap = \i, j, list ->
                     when Pair (List.get list i) (List.get list j) is
                         Pair (Ok atI) (Ok atJ) ->
diff --git a/compiler/reporting/src/error/type.rs b/compiler/reporting/src/error/type.rs
index 8924d7870b..45e3d804ed 100644
--- a/compiler/reporting/src/error/type.rs
+++ b/compiler/reporting/src/error/type.rs
@@ -1608,8 +1608,8 @@ fn to_diff<'b>(
             let right = to_doc(alloc, Parens::Unnecessary, type2);
 
             let is_int = |t: &ErrorType| match t {
-                ErrorType::Type(Symbol::NUM_INT, _) => true,
-                ErrorType::Alias(Symbol::NUM_INT, _, _) => true,
+                ErrorType::Type(Symbol::NUM_I64, _) => true,
+                ErrorType::Alias(Symbol::NUM_I64, _, _) => true,
 
                 ErrorType::Type(Symbol::NUM_NUM, args) => match &args.get(0) {
                     Some(ErrorType::Type(Symbol::NUM_INTEGER, _)) => true,
diff --git a/compiler/reporting/tests/test_reporting.rs b/compiler/reporting/tests/test_reporting.rs
index ce47365af3..7855d5bd94 100644
--- a/compiler/reporting/tests/test_reporting.rs
+++ b/compiler/reporting/tests/test_reporting.rs
@@ -623,7 +623,7 @@ mod test_reporting {
                     Num
                     Set
                     Result
-                    Int
+                    F64
                 "#
             ),
         );
@@ -634,7 +634,7 @@ mod test_reporting {
     //        report_problem_as(
     //            indoc!(
     //                r#"
-    //                foo : Int as Int
+    //                foo : I64 as I64
     //                foo = 42
     //
     //                foo
@@ -657,7 +657,7 @@ mod test_reporting {
     //        report_problem_as(
     //            indoc!(
     //                r#"
-    //                foo : Int as a
+    //                foo : I64 as a
     //                foo = 42
     //
     //                foo
@@ -961,7 +961,7 @@ mod test_reporting {
                 r#"
                 bar = { bar : 0x3 }
 
-                f : { foo : Int } -> Bool
+                f : { foo : I64 } -> Bool
                 f = \_ -> True
 
                 f bar
@@ -978,11 +978,11 @@ mod test_reporting {
 
                 This `bar` value is a:
 
-                    { bar : Int }
+                    { bar : I64 }
 
                 But `f` needs the 1st argument to be:
 
-                    { foo : Int }
+                    { foo : I64 }
 
                 Tip: Seems like a record field typo. Maybe `bar` should be `foo`?
 
@@ -1037,7 +1037,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                f : [ Red Int, Green Bool ] -> Bool
+                f : [ Red I64, Green Bool ] -> Bool
                 f = \_ -> True
 
                 f (Blue 3.14)
@@ -1058,7 +1058,7 @@ mod test_reporting {
 
                 But `f` needs the 1st argument to be:
 
-                    [ Green Bool, Red Int ]
+                    [ Green Bool, Red I64 ]
 
                 Tip: Seems like a tag typo. Maybe `Blue` should be `Red`?
 
@@ -1075,7 +1075,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                x : Int
+                x : I64
                 x = if True then 3.14 else 4
 
                 x
@@ -1096,7 +1096,7 @@ mod test_reporting {
 
                 But the type annotation on `x` says it should be:
 
-                    Int
+                    I64
 
                 Tip: You can convert between Int and Float using functions like
                 `Num.toFloat` and `Num.round`.
@@ -1110,7 +1110,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                x : Int
+                x : I64
                 x =
                     when True is
                         _ -> 3.14
@@ -1124,7 +1124,7 @@ mod test_reporting {
 
                 Something is off with the body of the `x` definition:
 
-                1│   x : Int
+                1│   x : I64
                 2│   x =
                 3│>      when True is
                 4│>          _ -> 3.14
@@ -1135,7 +1135,7 @@ mod test_reporting {
 
                 But the type annotation on `x` says it should be:
 
-                    Int
+                    I64
 
                 Tip: You can convert between Int and Float using functions like
                 `Num.toFloat` and `Num.round`.
@@ -1149,7 +1149,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                x : Int -> Int
+                x : I64 -> I64
                 x = \_ -> 3.14
 
                 x
@@ -1161,7 +1161,7 @@ mod test_reporting {
 
                 Something is off with the body of the `x` definition:
 
-                1│  x : Int -> Int
+                1│  x : I64 -> I64
                 2│  x = \_ -> 3.14
                               ^^^^
 
@@ -1171,7 +1171,7 @@ mod test_reporting {
 
                 But the type annotation on `x` says it should be:
 
-                    Int
+                    I64
 
                 Tip: You can convert between Int and Float using functions like
                 `Num.toFloat` and `Num.round`.
@@ -1185,7 +1185,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                x : Int
+                x : I64
                 x = 42
 
                 x 3
@@ -1211,7 +1211,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                f : Int -> Int
+                f : I64 -> I64
                 f = \_ -> 42
 
                 f 1 2
@@ -1237,7 +1237,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                f : Int, Int -> Int
+                f : I64, I64 -> I64
                 f = \_, _ -> 42
 
                 f 1
@@ -1372,9 +1372,9 @@ mod test_reporting {
                 these names seem close though:
 
                     Bool
-                    Int
                     F64
                     Num
+                    Map
                 "#
             ),
         )
@@ -1483,7 +1483,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                { x } : { x : Int }
+                { x } : { x : I64 }
                 { x } = { x: 4.0 }
 
                 x
@@ -1495,7 +1495,7 @@ mod test_reporting {
 
                 Something is off with the body of this definition:
 
-                1│  { x } : { x : Int }
+                1│  { x } : { x : I64 }
                 2│  { x } = { x: 4.0 }
                             ^^^^^^^^^^
 
@@ -1505,7 +1505,7 @@ mod test_reporting {
 
                 But the type annotation says it should be:
 
-                    { x : Int }
+                    { x : I64 }
 
                 Tip: You can convert between Int and Float using functions like
                 `Num.toFloat` and `Num.round`.
@@ -1644,7 +1644,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                x : { a : Int, b : F64, c : Bool }
+                x : { a : I64, b : F64, c : Bool }
                 x = { b: 4.0 }
 
                 x
@@ -1656,7 +1656,7 @@ mod test_reporting {
 
                 Something is off with the body of the `x` definition:
 
-                1│  x : { a : Int, b : F64, c : Bool }
+                1│  x : { a : I64, b : F64, c : Bool }
                 2│  x = { b: 4.0 }
                         ^^^^^^^^^^
 
@@ -1666,7 +1666,7 @@ mod test_reporting {
 
                 But the type annotation on `x` says it should be:
 
-                    { a : Int, b : F64, c : Bool }
+                    { a : I64, b : F64, c : Bool }
 
                 Tip: Looks like the c and a fields are missing.
                 "#
@@ -1788,7 +1788,7 @@ mod test_reporting {
 
                 The body is an integer of type:
 
-                    Int
+                    I64
 
                 But the type annotation on `f` says it should be:
 
@@ -1796,7 +1796,7 @@ mod test_reporting {
 
                 Tip: The type annotation uses the type variable `msg` to say that this
                 definition can produce any type of value. But in the body I see that
-                it will only produce a `Int` value of a single specific type. Maybe
+                it will only produce a `I64` value of a single specific type. Maybe
                 change the type annotation to be more specific? Maybe change the code
                 to be more general?
                 "#
@@ -1810,7 +1810,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                f : Bool -> [ Ok Int, InvalidFoo ]
+                f : Bool -> [ Ok I64, InvalidFoo ]
                 f = \_ -> ok 4
 
                 f
@@ -1828,9 +1828,9 @@ mod test_reporting {
                 these names seem close though:
 
                     f
-                    Int
                     F64
                     Num
+                    Map
                "#
             ),
         )
@@ -1842,7 +1842,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                f : Bool -> Int
+                f : Bool -> I64
                 f = \_ ->
                     ok = 3
 
@@ -1867,7 +1867,7 @@ mod test_reporting {
 
                 Something is off with the body of the `f` definition:
 
-                1│  f : Bool -> Int
+                1│  f : Bool -> I64
                 2│  f = \_ ->
                 3│      ok = 3
                 4│
@@ -1880,7 +1880,7 @@ mod test_reporting {
 
                 But the type annotation on `f` says it should be:
 
-                    Int
+                    I64
                 "#
             ),
         )
@@ -2005,7 +2005,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                f : { fo: Int }ext -> Int
+                f : { fo: I64 }ext -> I64
                 f = \r ->
                     r2 = { r & foo: r.fo }
 
@@ -2026,7 +2026,7 @@ mod test_reporting {
 
                 This is usually a typo. Here are the `r` fields that are most similar:
 
-                    { fo : Int
+                    { fo : I64
                     }ext
 
                 So maybe `.foo` should be `.fo`?
@@ -2259,12 +2259,12 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                Either : [ Left Int, Right Bool ]
+                Either : [ Left I64, Right Bool ]
 
                 x : Either
                 x = Left 42
 
-                f : Either -> Int
+                f : Either -> I64
                 f = \Left v -> v
 
                 f x
@@ -2296,7 +2296,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                x : [ Left Int, Right Bool ]
+                x : [ Left I64, Right Bool ]
                 x = Left 42
 
 
@@ -2425,7 +2425,7 @@ mod test_reporting {
                 r#"
                 RemoteData e a :  [ NotAsked, Loading, Failure e, Success a ]
 
-                x : RemoteData Int Str
+                x : RemoteData I64 Str
 
                 when x is
                     NotAsked -> 3
@@ -2488,7 +2488,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                y : [ Nothing, Just Int ]
+                y : [ Nothing, Just I64 ]
                 y = Just 4
                 x = { a: y, b: 42}
 
@@ -2581,9 +2581,9 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                Foo : { x : Int }
+                Foo : { x : I64 }
 
-                f : Foo -> Int
+                f : Foo -> I64
                 f = \r -> r.x
 
                 f { y: 3.14 }
@@ -2605,7 +2605,7 @@ mod test_reporting {
 
                 But `f` needs the 1st argument to be:
 
-                    { x : Int }
+                    { x : I64 }
 
                 Tip: Seems like a record field typo. Maybe `y` should be `x`?
 
@@ -2835,7 +2835,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                a : { foo : Int, bar : F64, foo : Str }
+                a : { foo : I64, bar : F64, foo : Str }
                 a = { bar: 3.0, foo: "foo" }
 
                 a
@@ -2847,12 +2847,12 @@ mod test_reporting {
 
                 This record type defines the `.foo` field twice!
 
-                1│  a : { foo : Int, bar : F64, foo : Str }
+                1│  a : { foo : I64, bar : F64, foo : Str }
                           ^^^^^^^^^             ^^^^^^^^^
 
                 In the rest of the program, I will only use the latter definition:
 
-                1│  a : { foo : Int, bar : F64, foo : Str }
+                1│  a : { foo : I64, bar : F64, foo : Str }
                                                 ^^^^^^^^^
 
                 For clarity, remove the previous `.foo` definitions from this record
@@ -2867,7 +2867,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                a : [ Foo Int, Bar F64, Foo Str ]
+                a : [ Foo I64, Bar F64, Foo Str ]
                 a = Foo "foo"
 
                 a
@@ -2879,12 +2879,12 @@ mod test_reporting {
 
                 This tag union type defines the `Foo` tag twice!
 
-                1│  a : [ Foo Int, Bar F64, Foo Str ]
+                1│  a : [ Foo I64, Bar F64, Foo Str ]
                           ^^^^^^^           ^^^^^^^
 
                 In the rest of the program, I will only use the latter definition:
 
-                1│  a : [ Foo Int, Bar F64, Foo Str ]
+                1│  a : [ Foo I64, Bar F64, Foo Str ]
                                             ^^^^^^^
 
                 For clarity, remove the previous `Foo` definitions from this tag union
@@ -2899,7 +2899,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                bar : Int
+                bar : I64
                 foo = \x -> x
 
                 # NOTE: neither bar or foo are defined at this point
@@ -2913,7 +2913,7 @@ mod test_reporting {
                 This annotation does not match the definition immediately following
                 it:
 
-                1│>  bar : Int
+                1│>  bar : I64
                 2│>  foo = \x -> x
 
                 Is it a typo? If not, put either a newline or comment between them.
@@ -2927,7 +2927,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                bar : Int
+                bar : I64
 
                 foo = \x -> x
 
@@ -2943,7 +2943,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                MyAlias 1 : Int
+                MyAlias 1 : I64
 
                 4
                 "#
@@ -2954,7 +2954,7 @@ mod test_reporting {
 
                 This pattern in the definition of `MyAlias` is not what I expect:
 
-                1│  MyAlias 1 : Int
+                1│  MyAlias 1 : I64
                             ^
 
                 Only type variables like `a` or `value` can occur in this position.
@@ -2963,7 +2963,7 @@ mod test_reporting {
 
                 `MyAlias` is not used anywhere in your code.
 
-                1│  MyAlias 1 : Int
+                1│  MyAlias 1 : I64
                     ^^^^^^^^^^^^^^^
 
                 If you didn't intend on using `MyAlias` then remove it so future readers
@@ -2978,7 +2978,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                a : Num Int F64
+                a : Num I64 F64
                 a = 3
 
                 a
@@ -2990,7 +2990,7 @@ mod test_reporting {
 
                 The `Num` alias expects 1 type argument, but it got 2 instead:
 
-                1│  a : Num Int F64
+                1│  a : Num I64 F64
                         ^^^^^^^^^^^
 
                 Are there missing parentheses?
@@ -3004,7 +3004,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                f : Bool -> Num Int F64
+                f : Bool -> Num I64 F64
                 f = \_ -> 3
 
                 f
@@ -3016,7 +3016,7 @@ mod test_reporting {
 
                 The `Num` alias expects 1 type argument, but it got 2 instead:
 
-                1│  f : Bool -> Num Int F64
+                1│  f : Bool -> Num I64 F64
                                 ^^^^^^^^^^^
 
                 Are there missing parentheses?
@@ -3032,7 +3032,7 @@ mod test_reporting {
                 r#"
                 Pair a b : [ Pair a b ]
 
-                x : Pair Int
+                x : Pair I64
                 x = Pair 2 3
 
                 x
@@ -3044,7 +3044,7 @@ mod test_reporting {
 
                 The `Pair` alias expects 2 type arguments, but it got 1 instead:
 
-                3│  x : Pair Int
+                3│  x : Pair I64
                         ^^^^^^^^
 
                 Are there missing parentheses?
@@ -3060,7 +3060,7 @@ mod test_reporting {
                 r#"
                 Pair a b : [ Pair a b ]
 
-                x : Pair Int Int Int
+                x : Pair I64 I64 I64
                 x = 3
 
                 x
@@ -3072,7 +3072,7 @@ mod test_reporting {
 
                 The `Pair` alias expects 2 type arguments, but it got 3 instead:
 
-                3│  x : Pair Int Int Int
+                3│  x : Pair I64 I64 I64
                         ^^^^^^^^^^^^^^^^
 
                 Are there missing parentheses?
@@ -3088,7 +3088,7 @@ mod test_reporting {
                 r#"
                 Foo a : [ Foo ]
 
-                f : Foo Int
+                f : Foo I64
 
                 f
                 "#
@@ -3176,7 +3176,7 @@ mod test_reporting {
                 AList a b : [ ACons a (BList a b), ANil ]
                 BList a b : [ BCons a (AList a b), BNil ]
 
-                x : AList Int Int
+                x : AList I64 I64
                 x = ACons 0 (BCons 1 (ACons "foo" BNil ))
 
                 y : BList a a
@@ -3191,19 +3191,19 @@ mod test_reporting {
 
                 Something is off with the body of the `x` definition:
 
-                4│  x : AList Int Int
+                4│  x : AList I64 I64
                 5│  x = ACons 0 (BCons 1 (ACons "foo" BNil ))
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
                 This `ACons` global tag application has the type:
 
                     [ ACons (Num Integer) [ BCons (Num Integer) [ ACons Str [
-                    BCons Int [ ACons Int (BList Int Int), ANil ] as a, BNil ], ANil
+                    BCons I64 [ ACons I64 (BList I64 I64), ANil ] as a, BNil ], ANil
                     ], BNil ], ANil ]
 
                 But the type annotation on `x` says it should be:
 
-                    [ ACons Int (BList Int Int), ANil ] as a
+                    [ ACons I64 (BList I64 I64), ANil ] as a
                 "#
             ),
         )
@@ -3575,7 +3575,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                f : { x : Int, y ? Int } -> Int
+                f : { x : I64, y ? I64 } -> I64
                 f = \{ x, y ? "foo" } -> (\g, _ -> g) x y
 
                 f
@@ -3592,11 +3592,11 @@ mod test_reporting {
 
                 The argument is a pattern that matches record values of type:
 
-                    { x : Int, y ? Str }
+                    { x : I64, y ? Str }
 
                 But the annotation on `f` says the 1st argument should be:
 
-                    { x : Int, y ? Int }
+                    { x : I64, y ? I64 }
                 "#
             ),
         )
@@ -3608,7 +3608,7 @@ mod test_reporting {
             indoc!(
                 r#"
                 \rec ->
-                    { x, y } : { x : Int, y ? Bool }
+                    { x, y } : { x : I64, y ? Bool }
                     { x, y } = rec
 
                     { x, y }
@@ -3620,16 +3620,16 @@ mod test_reporting {
 
                 Something is off with the body of this definition:
 
-                2│>      { x, y } : { x : Int, y ? Bool }
+                2│>      { x, y } : { x : I64, y ? Bool }
                 3│>      { x, y } = rec
 
                 The body is a value of type:
 
-                    { x : Int, y : Bool }
+                    { x : I64, y : Bool }
 
                 But the type annotation says it should be:
 
-                    { x : Int, y ? Bool }
+                    { x : I64, y ? Bool }
 
                 Tip: To extract the `.y` field it must be non-optional, but the type
                 says this field is optional. Learn more about optional fields at TODO.
@@ -3643,7 +3643,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                f : { x : Int, y ? Int } -> Int
+                f : { x : I64, y ? I64 } -> I64
                 f = \{ x, y } -> x + y
 
                 f
@@ -3660,11 +3660,11 @@ mod test_reporting {
 
                 The argument is a pattern that matches record values of type:
 
-                    { x : Int, y : Int }
+                    { x : I64, y : I64 }
 
                 But the annotation on `f` says the 1st argument should be:
 
-                    { x : Int, y ? Int }
+                    { x : I64, y ? I64 }
 
                 Tip: To extract the `.y` field it must be non-optional, but the type
                 says this field is optional. Learn more about optional fields at TODO.
@@ -3678,7 +3678,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                f : { x : Int, y ? Int } -> Int
+                f : { x : I64, y ? I64 } -> I64
                 f = \r ->
                         when r is
                             { x, y } -> x + y
@@ -3697,11 +3697,11 @@ mod test_reporting {
 
                 The first pattern is trying to match record values of type:
 
-                    { x : Int, y : Int }
+                    { x : I64, y : I64 }
 
                 But the expression between `when` and `is` has the type:
 
-                    { x : Int, y ? Int }
+                    { x : I64, y ? I64 }
 
                 Tip: To extract the `.y` field it must be non-optional, but the type
                 says this field is optional. Learn more about optional fields at TODO.
@@ -3715,7 +3715,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                f : { x : Int, y ? Int } -> Int
+                f : { x : I64, y ? I64 } -> I64
                 f = \r -> r.y
 
                 f
@@ -3732,11 +3732,11 @@ mod test_reporting {
 
                 This `r` value is a:
 
-                    { x : Int, y ? Int }
+                    { x : I64, y ? I64 }
 
                 But you are trying to use it as:
 
-                    { x : Int, y : Int }
+                    { x : I64, y : I64 }
 
                 Tip: To extract the `.y` field it must be non-optional, but the type
                 says this field is optional. Learn more about optional fields at TODO.
@@ -3750,7 +3750,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                    f : { x : Int, y ? Int } -> Int
+                    f : { x : I64, y ? I64 } -> I64
                     f = \r -> .y r
 
                     f
@@ -3767,11 +3767,11 @@ mod test_reporting {
 
                 This `r` value is a:
 
-                    { x : Int, y ? Int }
+                    { x : I64, y ? I64 }
 
                 But this function needs the 1st argument to be:
 
-                    { x : Int, y : Int }
+                    { x : I64, y : I64 }
 
                 Tip: To extract the `.y` field it must be non-optional, but the type
                 says this field is optional. Learn more about optional fields at TODO.
@@ -3785,7 +3785,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                f : { x : Int, y : Int } -> Int
+                f : { x : I64, y : I64 } -> I64
                 f = \r ->
                         when r is
                             { x, y : "foo" } -> x + 0
@@ -3805,11 +3805,11 @@ mod test_reporting {
 
                 The first pattern is trying to match record values of type:
 
-                    { x : Int, y : Str }
+                    { x : I64, y : Str }
 
                 But the expression between `when` and `is` has the type:
 
-                    { x : Int, y : Int }
+                    { x : I64, y : I64 }
                 "#
             ),
         )
@@ -3820,7 +3820,7 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                f : { x : Int, y ? Int } -> Int
+                f : { x : I64, y ? I64 } -> I64
                 f = \r ->
                         when r is
                             { x, y ? "foo" } -> (\g, _ -> g) x y
@@ -3840,11 +3840,11 @@ mod test_reporting {
 
                 The first pattern is trying to match record values of type:
 
-                    { x : Int, y ? Str }
+                    { x : I64, y ? Str }
 
                 But the expression between `when` and `is` has the type:
 
-                    { x : Int, y ? Int }
+                    { x : I64, y ? I64 }
                 "#
             ),
         )
diff --git a/compiler/solve/tests/solve_expr.rs b/compiler/solve/tests/solve_expr.rs
index b4b1fc2085..2b83b3cc6d 100644
--- a/compiler/solve/tests/solve_expr.rs
+++ b/compiler/solve/tests/solve_expr.rs
@@ -1326,12 +1326,12 @@ mod solve_expr {
         infer_eq(
             indoc!(
                 r#"
-                   int : Int
+                   int : I64
 
                    int
                 "#
             ),
-            "Int",
+            "I64",
         );
     }
 
@@ -1345,7 +1345,7 @@ mod solve_expr {
                    int
                 "#
             ),
-            "Int",
+            "I64",
         );
     }
 
@@ -1354,13 +1354,13 @@ mod solve_expr {
         infer_eq(
             indoc!(
                 r#"
-                   int : Int
+                   int : I64
                    int = 5
 
                    int
                 "#
             ),
-            "Int",
+            "I64",
         );
     }
 
@@ -1369,13 +1369,13 @@ mod solve_expr {
         infer_eq(
             indoc!(
                 r#"
-                   int : Num.Int
+                   int : Num.I64
                    int = 5
 
                    int
                 "#
             ),
-            "Int",
+            "I64",
         );
     }
 
@@ -1390,7 +1390,7 @@ mod solve_expr {
                    int
                 "#
             ),
-            "Int",
+            "I64",
         );
     }
 
@@ -1405,7 +1405,7 @@ mod solve_expr {
                    int
                 "#
             ),
-            "Int",
+            "I64",
         );
     }
 
@@ -1489,13 +1489,13 @@ mod solve_expr {
                 r#"
                     Res a e : [ Okay a, Error e ]
 
-                    ok : Res Int *
+                    ok : Res I64 *
                     ok = Okay 5
 
                     ok
                 "#
             ),
-            "Res Int *",
+            "Res I64 *",
         );
     }
 
@@ -1521,13 +1521,13 @@ mod solve_expr {
         infer_eq(
             indoc!(
                 r#"
-                    ok : Result Int *
+                    ok : Result I64 *
                     ok = Ok 5
 
                     ok
                 "#
             ),
-            "Result Int *",
+            "Result I64 *",
         );
     }
 
@@ -1551,7 +1551,7 @@ mod solve_expr {
         infer_eq(
             indoc!(
                 r#"
-                    ok : Result Int *
+                    ok : Result I64 *
                     ok = Ok 5
 
                     err : Result * Str
@@ -1563,7 +1563,7 @@ mod solve_expr {
                         err
                 "#
             ),
-            "Result Int Str",
+            "Result I64 Str",
         );
     }
 
@@ -1584,19 +1584,19 @@ mod solve_expr {
 
     // #[test]
     // fn annotation_using_num_used() {
-    //     // There was a problem where `Int`, because it is only an annotation
+    //     // There was a problem where `I64`, because it is only an annotation
     //     // wasn't added to the vars_by_symbol.
     //     infer_eq_without_problem(
     //         indoc!(
     //             r#"
-    //                int : Int
+    //                int : I64
 
     //                p = (\x -> x) int
 
     //                p
     //                "#
     //         ),
-    //         "Int",
+    //         "I64",
     //     );
     // }
 
@@ -1631,7 +1631,7 @@ mod solve_expr {
                     x
                 "#
             ),
-            "Int",
+            "I64",
         );
     }
 
@@ -1840,7 +1840,7 @@ mod solve_expr {
                 v
                 "#
             ),
-            "Foo Int",
+            "Foo I64",
         );
     }
 
@@ -1907,7 +1907,7 @@ mod solve_expr {
                     length
                        "#
             ),
-            "Peano -> Int",
+            "Peano -> I64",
         );
     }
 
@@ -2253,13 +2253,13 @@ mod solve_expr {
     //     infer_eq_without_problem(
     //         indoc!(
     //             r#"
-    //                 UserId x : [ UserId Int ]
+    //                 UserId x : [ UserId I64 ]
     //                 UserId x = UserId 42
 
     //                 x
     //             "#
     //         ),
-    //         "Int",
+    //         "I64",
     //     );
     // }
 
@@ -2340,13 +2340,13 @@ mod solve_expr {
                     ListB a : [ Cons a (ListC a) ]
                     ListC a : [ Cons a (ListA a), Nil ]
 
-                    val : ListC Num.Int
+                    val : ListC Num.I64
                     val = Cons 1 (Cons 2 (Cons 3 Nil))
 
                     val
                 "#
             ),
-            "ListC Int",
+            "ListC I64",
         );
     }
 
@@ -2388,7 +2388,7 @@ mod solve_expr {
         infer_eq_without_problem(
             indoc!(
                 r#"
-                partition : Int, Int, List Int -> [ Pair Int (List Int) ]
+                partition : I64, I64, List I64 -> [ Pair I64 (List I64) ]
                 partition = \low, high, initialList ->
                     when List.get initialList high is
                         Ok _ ->
@@ -2400,7 +2400,7 @@ mod solve_expr {
                 partition
                             "#
             ),
-            "Int, Int, List Int -> [ Pair Int (List Int) ]",
+            "I64, I64, List I64 -> [ Pair I64 (List I64) ]",
         );
     }
 
@@ -2410,7 +2410,7 @@ mod solve_expr {
             infer_eq_without_problem(
                 indoc!(
                     r#"
-                swap : Int, Int, List a -> List a
+                swap : I64, I64, List a -> List a
                 swap = \i, j, list ->
                     when Pair (List.get list i) (List.get list j) is
                         Pair (Ok atI) (Ok atJ) ->
@@ -2421,7 +2421,7 @@ mod solve_expr {
                         _ ->
                             list
 
-                partition : Int, Int, List Int -> [ Pair Int (List Int) ]
+                partition : I64, I64, List I64 -> [ Pair I64 (List I64) ]
                 partition = \low, high, initialList ->
                     when List.get initialList high is
                         Ok pivot ->
@@ -2449,7 +2449,7 @@ mod solve_expr {
                 partition
             "#
                 ),
-                "Int, Int, List Int -> [ Pair Int (List Int) ]",
+                "I64, I64, List I64 -> [ Pair I64 (List I64) ]",
             );
         });
     }
@@ -2462,14 +2462,14 @@ mod solve_expr {
                 idList : List a -> List a
                 idList = \list -> list
 
-                foo : List Int -> List Int
+                foo : List I64 -> List I64
                 foo = \initialList -> idList initialList
 
 
                 foo
             "#
             ),
-            "List Int -> List Int",
+            "List I64 -> List I64",
         );
     }
 
@@ -2547,7 +2547,7 @@ mod solve_expr {
                 Num.ceiling
                 "#
             ),
-            "F64 -> Int",
+            "F64 -> I64",
         );
     }
 
@@ -2559,7 +2559,7 @@ mod solve_expr {
                 Num.floor
                 "#
             ),
-            "F64 -> Int",
+            "F64 -> I64",
         );
     }
 
@@ -2571,7 +2571,7 @@ mod solve_expr {
                 Num.powInt
                 "#
             ),
-            "Int, Int -> Int",
+            "I64, I64 -> I64",
         );
     }
 
@@ -2789,15 +2789,15 @@ mod solve_expr {
     #[should_panic]
     fn rigid_record_quantification() {
         // the ext here is qualified on the outside (because we have rank 1 types, not rank 2).
-        // That means e.g. `f : { bar : String, foo : Int } -> Bool }` is a valid argument, but
-        // that function could not be applied to the `{ foo : Int }` list. Therefore, this function
+        // That means e.g. `f : { bar : String, foo : I64 } -> Bool }` is a valid argument, but
+        // that function could not be applied to the `{ foo : I64 }` list. Therefore, this function
         // is not allowed.
         //
         // should hit a debug_assert! in debug mode, and produce a type error in release mode
         infer_eq_without_problem(
             indoc!(
                 r#"
-                test : ({ foo : Int }ext -> Bool), { foo : Int } -> Bool
+                test : ({ foo : I64 }ext -> Bool), { foo : I64 } -> Bool
                 test = \fn, a -> fn a
 
                 test
@@ -2814,12 +2814,12 @@ mod solve_expr {
         infer_eq_without_problem(
             indoc!(
                 r#"
-                    negatePoint : { x : Int, y : Int, z ? Num c } -> { x : Int, y : Int, z : Num c }
+                    negatePoint : { x : I64, y : I64, z ? Num c } -> { x : I64, y : I64, z : Num c }
 
                     negatePoint { x: 1, y: 2 }
                 "#
             ),
-            "{ x : Int, y : Int, z : Num c }",
+            "{ x : I64, y : I64, z : Num c }",
         );
     }
 
@@ -2828,7 +2828,7 @@ mod solve_expr {
         infer_eq_without_problem(
             indoc!(
                 r#"
-                    negatePoint : { x : Int, y : Int, z ? Num c }r -> { x : Int, y : Int, z : Num c }r
+                    negatePoint : { x : I64, y : I64, z ? Num c }r -> { x : I64, y : I64, z : Num c }r
 
                     a = negatePoint { x: 1, y: 2 }
                     b = negatePoint { x: 1, y: 2, blah : "hi" }
@@ -2836,7 +2836,7 @@ mod solve_expr {
                     { a, b }
                 "#
             ),
-            "{ a : { x : Int, y : Int, z : Num c }, b : { blah : Str, x : Int, y : Int, z : Num c } }",
+            "{ a : { x : I64, y : I64, z : Num c }, b : { blah : Str, x : I64, y : I64, z : Num c } }",
         );
     }
 
@@ -2850,7 +2850,7 @@ mod solve_expr {
                     negatePoint { x: 1, y: 2.1, z: 0x3 }
                 "#
             ),
-            "{ x : Num a, y : F64, z : Int }",
+            "{ x : Num a, y : F64, z : I64 }",
         );
     }
 
@@ -2917,13 +2917,13 @@ mod solve_expr {
             indoc!(
                 r#"
                 \rec ->
-                    { x, y } : { x : Int, y ? Bool }*
+                    { x, y } : { x : I64, y ? Bool }*
                     { x, y ? False } = rec
 
                     { x, y }
                 "#
             ),
-            "{ x : Int, y ? Bool }* -> { x : Int, y : Bool }",
+            "{ x : I64, y ? Bool }* -> { x : I64, y : Bool }",
         );
     }
 
@@ -2944,14 +2944,14 @@ mod solve_expr {
         infer_eq_without_problem(
             indoc!(
                 r#"
-                empty : List Int
+                empty : List I64
                 empty =
                     []
 
                 List.walkBackwards empty (\a, b -> a + b) 0
                 "#
             ),
-            "Int",
+            "I64",
         );
     }
 
@@ -2970,7 +2970,7 @@ mod solve_expr {
                 g
                 "#
             ),
-            "Int",
+            "I64",
         );
     }
 
@@ -3023,7 +3023,7 @@ mod solve_expr {
                 app "test" provides [ main ] to "./platform"
 
                 Bar : [ Bar ]
-                Foo : [ Foo Bar Int, Empty ]
+                Foo : [ Foo Bar I64, Empty ]
 
                 foo : Foo
                 foo = Foo Bar 1
@@ -3037,7 +3037,7 @@ mod solve_expr {
                             x
                 "#
             ),
-            "[ Empty, Foo [ Bar ] Int ]",
+            "[ Empty, Foo [ Bar ] I64 ]",
         );
     }
 
@@ -3048,7 +3048,7 @@ mod solve_expr {
                 r#"
                 app "test" provides [ main ] to "./platform"
 
-                Foo : [ @Foo [ @Bar ] Int, @Empty ]
+                Foo : [ @Foo [ @Bar ] I64, @Empty ]
 
                 foo : Foo
                 foo = @Foo @Bar 1
@@ -3062,7 +3062,7 @@ mod solve_expr {
                             x
                 "#
             ),
-            "[ @Empty, @Foo [ @Bar ] Int ]",
+            "[ @Empty, @Foo [ @Bar ] I64 ]",
         );
     }
 
@@ -3073,21 +3073,21 @@ mod solve_expr {
                 r#"
                 app "test" provides [ main ] to "./platform"
 
-                State a : { count : Int, x : a }
+                State a : { count : I64, x : a }
 
-                foo : State a -> Int
+                foo : State a -> I64
                 foo = \state ->
                     if state.count == 0 then
                         0
                     else
                         1 + foo { count: state.count - 1, x: state.x }
 
-                main : Int
+                main : I64
                 main =
                     foo { count: 3, x: {} }
                 "#
             ),
-            "Int",
+            "I64",
         );
     }
 
@@ -3108,15 +3108,15 @@ mod solve_expr {
                 empty =
                     Empty
 
-                foo : Dict Int Int
+                foo : Dict I64 I64
                 foo = empty
 
-                main : Dict Int Int
+                main : Dict I64 I64
                 main =
                     foo
                 "#
             ),
-            "Dict Int Int",
+            "Dict I64 I64",
         );
     }
 
@@ -3370,12 +3370,12 @@ mod solve_expr {
                         removeHelpEQGT targetKey (removeHelpPrepEQGT targetKey dict color key value left right)
 
 
-                main : Dict Int Int
+                main : Dict I64 I64
                 main =
                     removeHelp 1 Empty
                 "#
             ),
-            "Dict Int Int",
+            "Dict I64 I64",
         );
     }
 
@@ -3410,12 +3410,12 @@ mod solve_expr {
                         Empty
 
 
-                main : Dict Int
+                main : Dict I64
                 main =
                     removeHelp 1 Empty
                 "#
             ),
-            "Dict Int",
+            "Dict I64",
         );
     }
 
@@ -3486,12 +3486,12 @@ mod solve_expr {
 
                 removeMin : Dict k v -> Dict k v
 
-                main : Dict Int Int
+                main : Dict I64 I64
                 main =
                     removeHelp 1 Empty
                 "#
             ),
-            "Dict Int Int",
+            "Dict I64 I64",
         );
     }
 
@@ -3502,7 +3502,7 @@ mod solve_expr {
                 r#"
                 app "test" provides [ partitionHelp ] to "./platform"
 
-                swap : Int, Int, List a -> List a
+                swap : I64, I64, List a -> List a
                 swap = \i, j, list ->
                     when Pair (List.get list i) (List.get list j) is
                         Pair (Ok atI) (Ok atJ) ->
@@ -3513,7 +3513,7 @@ mod solve_expr {
                         _ ->
                             []
 
-                partitionHelp : Int, Int, List (Num a), Int, (Num a) -> [ Pair Int (List (Num a)) ]
+                partitionHelp : I64, I64, List (Num a), I64, (Num a) -> [ Pair I64 (List (Num a)) ]
                 partitionHelp = \i, j, list, high, pivot ->
                     if j < high then
                         when List.get list j is
@@ -3529,7 +3529,7 @@ mod solve_expr {
                         Pair i list
                 "#
             ),
-            "Int, Int, List (Num a), Int, Num a -> [ Pair Int (List (Num a)) ]",
+            "I64, I64, List (Num a), I64, Num a -> [ Pair I64 (List (Num a)) ]",
         );
     }
 
@@ -3546,12 +3546,12 @@ mod solve_expr {
                 balance = \key, left ->
                     Node key left Empty
 
-                main : Dict Int
+                main : Dict I64
                 main =
                     balance 0 Empty
                 "#
             ),
-            "Dict Int",
+            "Dict I64",
         );
     }
 
@@ -3570,12 +3570,12 @@ mod solve_expr {
                 balance = \key, left ->
                     node key left Empty
 
-                main : Dict Int
+                main : Dict I64
                 main =
                     balance 0 Empty
                 "#
             ),
-            "Dict Int",
+            "Dict I64",
         );
     }
 
@@ -3619,12 +3619,12 @@ mod solve_expr {
                         _ ->
                           Node color key value left right
 
-                main : Dict Int Int
+                main : Dict I64 I64
                 main =
                     balance Red 0 0 Empty Empty
                 "#
             ),
-            "Dict Int Int",
+            "Dict I64 I64",
         );
     }
 
@@ -3648,12 +3648,12 @@ mod solve_expr {
                             Empty
 
 
-                main : Dict Int
+                main : Dict I64
                 main =
                     balance 0 Empty
                 "#
             ),
-            "Dict Int",
+            "Dict I64",
         );
     }
 }
diff --git a/compiler/solve/tests/solve_uniq_expr.rs b/compiler/solve/tests/solve_uniq_expr.rs
index b2f107040a..cfc0ed1c7a 100644
--- a/compiler/solve/tests/solve_uniq_expr.rs
+++ b/compiler/solve/tests/solve_uniq_expr.rs
@@ -1124,7 +1124,7 @@ mod solve_uniq_expr {
                     x
                 "#
             ),
-            "Attr * Int",
+            "Attr * I64",
         );
     }
 
@@ -1377,7 +1377,7 @@ mod solve_uniq_expr {
                     x
                 "#
             ),
-            "Attr * Int",
+            "Attr * I64",
         );
     }
 
@@ -1405,7 +1405,7 @@ mod solve_uniq_expr {
         infer_eq(
             indoc!(
                 r#"
-                    swap : Int, Int, List a -> List a
+                    swap : I64, I64, List a -> List a
                     swap = \i, j, list ->
                         when Pair (List.get list i) (List.get list j) is
                             Pair (Ok atI) (Ok atJ) ->
@@ -1418,7 +1418,7 @@ mod solve_uniq_expr {
                     swap
                 "#
             ),
-            "Attr * (Attr * Int, Attr * Int, Attr * (List (Attr Shared a)) -> Attr * (List (Attr Shared a)))"
+            "Attr * (Attr * I64, Attr * I64, Attr * (List (Attr Shared a)) -> Attr * (List (Attr Shared a)))"
         );
     }
 
@@ -1431,7 +1431,7 @@ mod solve_uniq_expr {
             infer_eq(
             indoc!(
                 r#"
-                quicksort : List (Num a), Int, Int -> List (Num a)
+                quicksort : List (Num a), I64, I64 -> List (Num a)
                 quicksort = \list, low, high ->
                     when partition low high list is
                         Pair partitionIndex partitioned ->
@@ -1440,7 +1440,7 @@ mod solve_uniq_expr {
                                 |> quicksort (partitionIndex + 1) high
 
 
-                swap : Int, Int, List a -> List a
+                swap : I64, I64, List a -> List a
                 swap = \i, j, list ->
                     when Pair (List.get list i) (List.get list j) is
                         Pair (Ok atI) (Ok atJ) ->
@@ -1452,7 +1452,7 @@ mod solve_uniq_expr {
                             []
 
 
-                partition : Int, Int, List (Num a) -> [ Pair Int (List (Num a)) ]
+                partition : I64, I64, List (Num a) -> [ Pair I64 (List (Num a)) ]
                 partition = \low, high, initialList ->
                     when List.get initialList high is
                         Ok pivot ->
@@ -1480,7 +1480,7 @@ mod solve_uniq_expr {
                 quicksort
                    "#
             ),
-            "Attr Shared (Attr b (List (Attr Shared (Num (Attr Shared a)))), Attr Shared Int, Attr Shared Int -> Attr b (List (Attr Shared (Num (Attr Shared a)))))"
+            "Attr Shared (Attr b (List (Attr Shared (Num (Attr Shared a)))), Attr Shared I64, Attr Shared I64 -> Attr b (List (Attr Shared (Num (Attr Shared a)))))"
         );
         })
     }
@@ -2149,7 +2149,7 @@ mod solve_uniq_expr {
                     Num.maxInt // Num.maxInt
                 "#
             ),
-            "Attr * (Result (Attr * Int) (Attr * [ DivByZero ]*))",
+            "Attr * (Result (Attr * I64) (Attr * [ DivByZero ]*))",
         );
     }
 
@@ -2161,7 +2161,7 @@ mod solve_uniq_expr {
                     3 // 4
                 "#
             ),
-            "Attr * (Result (Attr * Int) (Attr * [ DivByZero ]*))",
+            "Attr * (Result (Attr * I64) (Attr * [ DivByZero ]*))",
         );
     }
 
@@ -2173,7 +2173,7 @@ mod solve_uniq_expr {
                     3 // Num.maxInt
                 "#
             ),
-            "Attr * (Result (Attr * Int) (Attr * [ DivByZero ]*))",
+            "Attr * (Result (Attr * I64) (Attr * [ DivByZero ]*))",
         );
     }
 
@@ -2264,17 +2264,17 @@ mod solve_uniq_expr {
 
     #[test]
     fn list_len() {
-        infer_eq("List.len", "Attr * (Attr * (List *) -> Attr * Int)");
+        infer_eq("List.len", "Attr * (Attr * (List *) -> Attr * I64)");
     }
 
     #[test]
     fn list_get() {
-        infer_eq("List.get", "Attr * (Attr (* | b) (List (Attr b a)), Attr * Int -> Attr * (Result (Attr b a) (Attr * [ OutOfBounds ]*)))");
+        infer_eq("List.get", "Attr * (Attr (* | b) (List (Attr b a)), Attr * I64 -> Attr * (Result (Attr b a) (Attr * [ OutOfBounds ]*)))");
     }
 
     #[test]
     fn list_set() {
-        infer_eq("List.set", "Attr * (Attr (* | b | c) (List (Attr b a)), Attr * Int, Attr (b | c) a -> Attr * (List (Attr b a)))");
+        infer_eq("List.set", "Attr * (Attr (* | b | c) (List (Attr b a)), Attr * I64, Attr (b | c) a -> Attr * (List (Attr b a)))");
     }
 
     #[test]
@@ -2286,7 +2286,7 @@ mod solve_uniq_expr {
     fn list_repeat() {
         infer_eq(
             "List.repeat",
-            "Attr * (Attr * Int, Attr Shared a -> Attr * (List (Attr Shared a)))",
+            "Attr * (Attr * I64, Attr Shared a -> Attr * (List (Attr Shared a)))",
         );
     }
 
@@ -2487,15 +2487,15 @@ mod solve_uniq_expr {
         infer_eq(
             indoc!(
                 r#"
-                Model : { foo : Int }
+                Model : { foo : I64 }
 
-                extract : Model -> Int
+                extract : Model -> I64
                 extract = \{ foo } -> foo
 
                 extract
                 "#
             ),
-            "Attr * (Attr (* | a) Model -> Attr a Int)",
+            "Attr * (Attr (* | a) Model -> Attr a I64)",
         );
     }
 
@@ -2504,15 +2504,15 @@ mod solve_uniq_expr {
         infer_eq(
             indoc!(
                 r#"
-                Model : { foo : Int, bar : Int  }
+                Model : { foo : I64, bar : I64  }
 
-                extract : Model -> Int
+                extract : Model -> I64
                 extract = \{ foo } -> foo
 
                 extract
                 "#
             ),
-            "Attr * (Attr (* | a) Model -> Attr a Int)",
+            "Attr * (Attr (* | a) Model -> Attr a I64)",
         );
     }
 
@@ -2521,15 +2521,15 @@ mod solve_uniq_expr {
         infer_eq(
             indoc!(
                 r#"
-                Model : { foo : Int, bar : Int }
+                Model : { foo : I64, bar : I64 }
 
-                extract : Model -> Int
+                extract : Model -> I64
                 extract = \{foo, bar} -> foo + bar
 
                 extract
                 "#
             ),
-            "Attr * (Attr (* | * | *) Model -> Attr * Int)",
+            "Attr * (Attr (* | * | *) Model -> Attr * I64)",
         );
     }
 
@@ -2627,13 +2627,13 @@ mod solve_uniq_expr {
         infer_eq(
             indoc!(
                 r#"
-                f : Int, Int -> Int
+                f : I64, I64 -> I64
                 f = \a, b -> a + b
 
                 f
                 "#
             ),
-            "Attr * (Attr * Int, Attr * Int -> Attr * Int)",
+            "Attr * (Attr * I64, Attr * I64 -> Attr * I64)",
         );
     }
 
@@ -2642,13 +2642,13 @@ mod solve_uniq_expr {
         infer_eq(
             indoc!(
                 r#"
-                foobar : Int -> Int
+                foobar : I64 -> I64
                 foobar = \x -> Num.abs x
 
                 foobar
                 "#
             ),
-            "Attr * (Attr * Int -> Attr * Int)",
+            "Attr * (Attr * I64 -> Attr * I64)",
         );
     }
 
@@ -2662,7 +2662,7 @@ mod solve_uniq_expr {
                 f
                 "#
             ),
-            "Attr * (Attr a Int, Attr b Int -> Attr c Int)",
+            "Attr * (Attr a I64, Attr b I64 -> Attr c I64)",
         );
     }
 
@@ -3001,13 +3001,13 @@ mod solve_uniq_expr {
                 Model a : { foo : Set a }
 
 
-                initialModel : position -> Model Int
+                initialModel : position -> Model I64
                 initialModel = \_ -> { foo : Set.empty }
 
                 initialModel
                 "#
             ),
-            "Attr * (Attr * position -> Attr * (Model (Attr * Int)))",
+            "Attr * (Attr * position -> Attr * (Model (Attr * I64)))",
         );
     }
 
@@ -3035,12 +3035,12 @@ mod solve_uniq_expr {
         infer_eq(
             indoc!(
                 r#"
-                    negatePoint : { x : Int, y : Int, z ? Num c } -> { x : Int, y : Int, z : Num c }
+                    negatePoint : { x : I64, y : I64, z ? Num c } -> { x : I64, y : I64, z : Num c }
 
                     negatePoint { x: 1, y: 2 }
                 "#
             ),
-            "Attr * { x : Attr * Int, y : Attr * Int, z : Attr * (Num (Attr * c)) }",
+            "Attr * { x : Attr * I64, y : Attr * I64, z : Attr * (Num (Attr * c)) }",
         );
     }
 
@@ -3049,7 +3049,7 @@ mod solve_uniq_expr {
         infer_eq(
             indoc!(
                 r#"
-                    negatePoint : { x : Int, y : Int, z ? Num c }r -> { x : Int, y : Int, z : Num c }r
+                    negatePoint : { x : I64, y : I64, z ? Num c }r -> { x : I64, y : I64, z : Num c }r
 
                     a = negatePoint { x: 1, y: 2 }
                     b = negatePoint { x: 1, y: 2, blah : "hi" }
@@ -3057,7 +3057,7 @@ mod solve_uniq_expr {
                     { a, b }
                 "#
             ),
-            "Attr * { a : Attr * { x : Attr * Int, y : Attr * Int, z : Attr * (Num (Attr * c)) }, b : Attr * { blah : Attr * Str, x : Attr * Int, y : Attr * Int, z : Attr * (Num (Attr * c)) } }"
+            "Attr * { a : Attr * { x : Attr * I64, y : Attr * I64, z : Attr * (Num (Attr * c)) }, b : Attr * { blah : Attr * Str, x : Attr * I64, y : Attr * I64, z : Attr * (Num (Attr * c)) } }"
         );
     }
 
@@ -3071,7 +3071,7 @@ mod solve_uniq_expr {
                     negatePoint { x: 1, y: 2.1, z: 0x3 }
                 "#
             ),
-            "Attr * { x : Attr * (Num (Attr * a)), y : Attr * F64, z : Attr * Int }",
+            "Attr * { x : Attr * (Num (Attr * a)), y : Attr * F64, z : Attr * I64 }",
         );
     }
 
@@ -3149,14 +3149,14 @@ mod solve_uniq_expr {
         infer_eq(
             indoc!(
                 r#"
-                empty : List Int
+                empty : List I64
                 empty = 
                     []
 
                 List.walkBackwards empty (\a, b -> a + b) 0
                 "#
             ),
-            "Attr a Int",
+            "Attr a I64",
         );
     }
 }
diff --git a/compiler/types/src/builtin_aliases.rs b/compiler/types/src/builtin_aliases.rs
index 981c1b4a58..d5aca18c38 100644
--- a/compiler/types/src/builtin_aliases.rs
+++ b/compiler/types/src/builtin_aliases.rs
@@ -50,7 +50,7 @@ pub fn aliases() -> MutMap<Symbol, BuiltinAlias> {
 
     // Int : Num Integer
     add_alias(
-        Symbol::NUM_INT,
+        Symbol::NUM_I64,
         BuiltinAlias {
             region: Region::zero(),
             vars: Vec::new(),
@@ -155,7 +155,7 @@ fn float_alias_content() -> SolvedType {
 
 #[inline(always)]
 pub fn int_type() -> SolvedType {
-    SolvedType::Alias(Symbol::NUM_INT, Vec::new(), Box::new(int_alias_content()))
+    SolvedType::Alias(Symbol::NUM_I64, Vec::new(), Box::new(int_alias_content()))
 }
 
 #[inline(always)]
diff --git a/compiler/types/src/pretty_print.rs b/compiler/types/src/pretty_print.rs
index e26ba69b8f..d2dd43db1c 100644
--- a/compiler/types/src/pretty_print.rs
+++ b/compiler/types/src/pretty_print.rs
@@ -19,8 +19,8 @@ static EMPTY_TAG_UNION: &str = "[]";
 ///
 /// Separately, if we're inside a type parameter, we may need to use parens:
 ///
-/// List Int
-/// List (List Int)
+/// List I64
+/// List (List I64)
 ///
 /// Otherwise, parens are unnecessary.
 #[derive(Clone, Copy, Debug, PartialEq)]
@@ -330,7 +330,7 @@ fn write_content(env: &Env, content: Content, subs: &Subs, buf: &mut String, par
 
                     match &content {
                         Alias(nested, _, _) => match *nested {
-                            Symbol::NUM_INTEGER => buf.push_str("Int"),
+                            Symbol::NUM_INTEGER => buf.push_str("I64"),
                             Symbol::NUM_FLOATINGPOINT => buf.push_str("F64"),
 
                             _ => write_parens!(write_parens, buf, {
@@ -343,7 +343,7 @@ fn write_content(env: &Env, content: Content, subs: &Subs, buf: &mut String, par
                             let attr_content = subs.get_without_compacting(nested_args[1]).content;
                             match &attr_content {
                                 Alias(nested, _, _) => match *nested {
-                                    Symbol::NUM_INTEGER => buf.push_str("Int"),
+                                    Symbol::NUM_INTEGER => buf.push_str("I64"),
                                     Symbol::NUM_FLOATINGPOINT => buf.push_str("F64"),
                                     _ => write_parens!(write_parens, buf, {
                                         buf.push_str("Num ");
@@ -403,7 +403,7 @@ fn write_flat_type(env: &Env, flat_type: FlatType, subs: &Subs, buf: &mut String
         Record(fields, ext_var) => {
             use crate::types::{gather_fields, RecordStructure};
 
-            // If the `ext` has concrete fields (e.g. { foo : Int}{ bar : Bool }), merge them
+            // If the `ext` has concrete fields (e.g. { foo : I64}{ bar : Bool }), merge them
             let RecordStructure { fields, ext } = gather_fields(subs, fields, ext_var);
             let ext_var = ext;
 
@@ -465,8 +465,8 @@ fn write_flat_type(env: &Env, flat_type: FlatType, subs: &Subs, buf: &mut String
                     // This is an open record, so print the variable
                     // right after the '}'
                     //
-                    // e.g. the "*" at the end of `{ x: Int }*`
-                    // or the "r" at the end of `{ x: Int }r`
+                    // e.g. the "*" at the end of `{ x: I64 }*`
+                    // or the "r" at the end of `{ x: I64 }r`
                     write_content(env, content, subs, buf, parens)
                 }
             }
@@ -523,8 +523,8 @@ fn write_flat_type(env: &Env, flat_type: FlatType, subs: &Subs, buf: &mut String
                 // This is an open tag union, so print the variable
                 // right after the ']'
                 //
-                // e.g. the "*" at the end of `{ x: Int }*`
-                // or the "r" at the end of `{ x: Int }r`
+                // e.g. the "*" at the end of `{ x: I64 }*`
+                // or the "r" at the end of `{ x: I64 }r`
                 write_content(env, content, subs, buf, parens)
             }
         }
@@ -576,8 +576,8 @@ fn write_flat_type(env: &Env, flat_type: FlatType, subs: &Subs, buf: &mut String
                 // This is an open tag union, so print the variable
                 // right after the ']'
                 //
-                // e.g. the "*" at the end of `{ x: Int }*`
-                // or the "r" at the end of `{ x: Int }r`
+                // e.g. the "*" at the end of `{ x: I64 }*`
+                // or the "r" at the end of `{ x: I64 }r`
                 write_content(env, content, subs, buf, parens)
             }
 
@@ -754,7 +754,7 @@ fn write_apply(
             match &arg_content {
                 Content::Structure(FlatType::Apply(symbol, nested_args)) => match *symbol {
                     Symbol::NUM_INTEGER if nested_args.is_empty() => {
-                        buf.push_str("Int");
+                        buf.push_str("I64");
                     }
                     Symbol::NUM_FLOATINGPOINT if nested_args.is_empty() => {
                         buf.push_str("F64");
@@ -768,7 +768,7 @@ fn write_apply(
                             double_nested_args,
                         ))) => match double_nested_symbol {
                             Symbol::NUM_INTEGER if double_nested_args.is_empty() => {
-                                buf.push_str("Int");
+                                buf.push_str("I64");
                             }
                             Symbol::NUM_FLOATINGPOINT if double_nested_args.is_empty() => {
                                 buf.push_str("F64");
diff --git a/compiler/uniq/src/builtins.rs b/compiler/uniq/src/builtins.rs
index 3c7069e587..f15ec9f7ec 100644
--- a/compiler/uniq/src/builtins.rs
+++ b/compiler/uniq/src/builtins.rs
@@ -14,7 +14,7 @@ use roc_types::types::Type::{self, *};
 pub fn int_literal(num_var: Variable, expected: Expected<Type>, region: Region) -> Constraint {
     let num_type = Variable(num_var);
     let reason = Reason::IntLiteral;
-    let int_type = builtin_type(Symbol::NUM_INT, vec![]);
+    let int_type = builtin_type(Symbol::NUM_I64, vec![]);
     let expected_literal = ForReason(reason, int_type, region);
 
     exists(
diff --git a/examples/closure/Closure.roc b/examples/closure/Closure.roc
index fcd157f768..329cc8ff25 100644
--- a/examples/closure/Closure.roc
+++ b/examples/closure/Closure.roc
@@ -1,6 +1,6 @@
 app "closure" provides [ makeClosure ] to "./platform/"
 
-makeClosure : ({} -> Int) as MyClosure
+makeClosure : ({} -> I64) as MyClosure
 makeClosure =
     x = 42
     y = 42
diff --git a/examples/effect/ConsList.roc b/examples/effect/ConsList.roc
index 8c0b9eda4f..a86281ca5f 100644
--- a/examples/effect/ConsList.roc
+++ b/examples/effect/ConsList.roc
@@ -5,7 +5,7 @@ ConsList a : [ Cons a (ConsList a), Nil ]
 empty : ConsList a
 empty = Nil
 
-len : ConsList a -> Int
+len : ConsList a -> I64
 len = \list ->
     when list is
         Cons _ rest -> 1 + len rest
diff --git a/examples/effect/RBTree.roc b/examples/effect/RBTree.roc
index 1c792e5125..71c35f8f9b 100644
--- a/examples/effect/RBTree.roc
+++ b/examples/effect/RBTree.roc
@@ -21,11 +21,11 @@ singleton = \key, value ->
   Node Black key value Empty Empty
 
 # {-| Determine the number of key-value pairs in the dictionary. -}
-size : Dict k v -> Int
+size : Dict k v -> I64
 size = \dict ->
     sizeHelp 0 dict
 
-sizeHelp : Int, Dict k v -> Int
+sizeHelp : I64, Dict k v -> I64
 sizeHelp = \n, dict ->
   when dict is
     Empty ->
diff --git a/examples/multi-module/Quicksort.roc b/examples/multi-module/Quicksort.roc
index 549d964954..5b60dae312 100644
--- a/examples/multi-module/Quicksort.roc
+++ b/examples/multi-module/Quicksort.roc
@@ -1,9 +1,9 @@
 app "quicksort" imports [ Utils.{ swap } ] provides [ quicksort ] to "./platform"
 
 
-quicksort : List Int -> List Int
+quicksort : List I64 -> List I64
 quicksort = \originalList ->
-    quicksortHelp : List (Num a), Int, Int -> List (Num a)
+    quicksortHelp : List (Num a), I64, I64 -> List (Num a)
     quicksortHelp = \list, low, high ->
         if low < high then
             when partition low high list is
@@ -14,7 +14,7 @@ quicksort = \originalList ->
         else
             list
 
-    partition : Int, Int, List (Num a) -> [ Pair Int (List (Num a)) ]
+    partition : I64, I64, List (Num a) -> [ Pair I64 (List (Num a)) ]
     partition = \low, high, initialList ->
         when List.get initialList high is
             Ok pivot ->
@@ -26,7 +26,7 @@ quicksort = \originalList ->
                 Pair (low - 1) initialList
 
 
-    partitionHelp : Int, Int, List (Num a), Int, (Num a) -> [ Pair Int (List (Num a)) ]
+    partitionHelp : I64, I64, List (Num a), I64, (Num a) -> [ Pair I64 (List (Num a)) ]
     partitionHelp = \i, j, list, high, pivot ->
         if j < high then
             when List.get list j is
diff --git a/examples/multi-module/Utils.roc b/examples/multi-module/Utils.roc
index bad64dcab9..156a3c51c8 100644
--- a/examples/multi-module/Utils.roc
+++ b/examples/multi-module/Utils.roc
@@ -1,6 +1,6 @@
 interface Utils exposes [ swap ] imports []
 
-swap : Int, Int, List a -> List a
+swap : I64, I64, List a -> List a
 swap = \i, j, list ->
     when Pair (List.get list i) (List.get list j) is
         Pair (Ok atI) (Ok atJ) ->
diff --git a/examples/quicksort/Quicksort.roc b/examples/quicksort/Quicksort.roc
index d2e3cfd31b..0092b7b527 100644
--- a/examples/quicksort/Quicksort.roc
+++ b/examples/quicksort/Quicksort.roc
@@ -2,7 +2,7 @@ app "quicksort" provides [ quicksort ] to "./platform"
 
 quicksort = \originalList ->
 
-    quicksortHelp : List (Num a), Int, Int -> List (Num a)
+    quicksortHelp : List (Num a), I64, I64 -> List (Num a)
     quicksortHelp = \list, low, high ->
         if low < high then
             when partition low high list is
@@ -14,7 +14,7 @@ quicksort = \originalList ->
             list
 
 
-    partition : Int, Int, List (Num a) -> [ Pair Int (List (Num a)) ]
+    partition : I64, I64, List (Num a) -> [ Pair I64 (List (Num a)) ]
     partition = \low, high, initialList ->
         when List.get initialList high is
             Ok pivot ->
@@ -25,7 +25,7 @@ quicksort = \originalList ->
             Err _ ->
                 Pair (low - 1) initialList
 
-    partitionHelp : Int, Int, List (Num a), Int, (Num a) -> [ Pair Int (List (Num a)) ]
+    partitionHelp : I64, I64, List (Num a), I64, (Num a) -> [ Pair I64 (List (Num a)) ]
     partitionHelp = \i, j, list, high, pivot ->
         if j < high then
             when List.get list j is
@@ -41,7 +41,7 @@ quicksort = \originalList ->
             Pair i list
 
 
-    swap : Int, Int, List a -> List a
+    swap : I64, I64, List a -> List a
     swap = \i, j, list ->
         when Pair (List.get list i) (List.get list j) is
             Pair (Ok atI) (Ok atJ) ->
diff --git a/examples/shared-quicksort/Quicksort.roc b/examples/shared-quicksort/Quicksort.roc
index b75781e673..63e395bcd6 100644
--- a/examples/shared-quicksort/Quicksort.roc
+++ b/examples/shared-quicksort/Quicksort.roc
@@ -1,12 +1,12 @@
 app "quicksort" packages { base: "./platform" } provides [ quicksort ] to base
 
-quicksort : List Int -> List Int
+quicksort : List I64 -> List I64
 quicksort = \originalList -> helper originalList
 
-helper : List Int -> List Int
+helper : List I64 -> List I64
 helper = \originalList ->
 
-    quicksortHelp : List (Num a), Int, Int -> List (Num a)
+    quicksortHelp : List (Num a), I64, I64 -> List (Num a)
     quicksortHelp = \list, low, high ->
         if low < high then
             when partition low high list is
@@ -18,7 +18,7 @@ helper = \originalList ->
             list
 
 
-    swap : Int, Int, List a -> List a
+    swap : I64, I64, List a -> List a
     swap = \i, j, list ->
         when Pair (List.get list i) (List.get list j) is
             Pair (Ok atI) (Ok atJ) ->
@@ -29,7 +29,7 @@ helper = \originalList ->
             _ ->
                 []
 
-    partition : Int, Int, List (Num a) -> [ Pair Int (List (Num a)) ]
+    partition : I64, I64, List (Num a) -> [ Pair I64 (List (Num a)) ]
     partition = \low, high, initialList ->
         when List.get initialList high is
             Ok pivot ->
@@ -41,7 +41,7 @@ helper = \originalList ->
                 Pair (low - 1) initialList
 
 
-    partitionHelp : Int, Int, List (Num a), Int, (Num a) -> [ Pair Int (List (Num a)) ]
+    partitionHelp : I64, I64, List (Num a), I64, (Num a) -> [ Pair I64 (List (Num a)) ]
     partitionHelp = \i, j, list, high, pivot ->
         if j < high then
             when List.get list j is