diff --git a/Cargo.lock b/Cargo.lock
index 25e822d166..42b7c3f558 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3329,6 +3329,7 @@ dependencies = [
  "roc_collections",
  "roc_ident",
  "roc_region",
+ "static_assertions",
 ]
 
 [[package]]
@@ -3461,6 +3462,7 @@ dependencies = [
  "roc_collections",
  "roc_module",
  "roc_region",
+ "static_assertions",
  "ven_ena",
 ]
 
diff --git a/cli/cli_utils/src/helpers.rs b/cli/cli_utils/src/helpers.rs
index e5beddfecb..11a6a404f3 100644
--- a/cli/cli_utils/src/helpers.rs
+++ b/cli/cli_utils/src/helpers.rs
@@ -1,5 +1,4 @@
 extern crate bumpalo;
-extern crate inlinable_string;
 extern crate roc_collections;
 extern crate roc_load;
 extern crate roc_module;
diff --git a/cli/tests/cli_run.rs b/cli/tests/cli_run.rs
index 0494d35f41..0fb00a9e48 100644
--- a/cli/tests/cli_run.rs
+++ b/cli/tests/cli_run.rs
@@ -2,7 +2,6 @@
 extern crate pretty_assertions;
 
 extern crate bumpalo;
-extern crate inlinable_string;
 extern crate roc_collections;
 extern crate roc_load;
 extern crate roc_module;
diff --git a/compiler/load/tests/test_load.rs b/compiler/load/tests/test_load.rs
index d77e74ee38..7fbdae8ba7 100644
--- a/compiler/load/tests/test_load.rs
+++ b/compiler/load/tests/test_load.rs
@@ -6,7 +6,6 @@ extern crate pretty_assertions;
 extern crate maplit;
 
 extern crate bumpalo;
-extern crate inlinable_string;
 extern crate roc_collections;
 extern crate roc_load;
 extern crate roc_module;
diff --git a/compiler/module/Cargo.toml b/compiler/module/Cargo.toml
index c20acb533e..239468c8c6 100644
--- a/compiler/module/Cargo.toml
+++ b/compiler/module/Cargo.toml
@@ -11,6 +11,7 @@ roc_ident = { path = "../ident" }
 roc_collections = { path = "../collections" }
 bumpalo = { version = "3.6.1", features = ["collections"] }
 lazy_static = "1.4"
+static_assertions = "1.1.0"
 
 [dev-dependencies]
 pretty_assertions = "0.5.1"
diff --git a/compiler/module/src/ident.rs b/compiler/module/src/ident.rs
index 484ecfe785..0de36bd0bd 100644
--- a/compiler/module/src/ident.rs
+++ b/compiler/module/src/ident.rs
@@ -59,6 +59,8 @@ pub enum TagName {
     Closure(Symbol),
 }
 
+static_assertions::assert_eq_size!([u8; 24], TagName);
+
 impl TagName {
     pub fn as_ident_str(&self, interns: &Interns, home: ModuleId) -> IdentStr {
         match self {
diff --git a/compiler/solve/tests/solve_expr.rs b/compiler/solve/tests/solve_expr.rs
index e303608141..92907af3f7 100644
--- a/compiler/solve/tests/solve_expr.rs
+++ b/compiler/solve/tests/solve_expr.rs
@@ -4488,18 +4488,4 @@ mod solve_expr {
             "RBTree {}",
         );
     }
-
-    #[test]
-    fn sizes() {
-        let query = (
-            std::mem::size_of::<roc_module::ident::TagName>(),
-            std::mem::size_of::<roc_types::subs::Descriptor>(),
-            std::mem::size_of::<roc_types::subs::Content>(),
-            std::mem::size_of::<roc_types::subs::FlatType>(),
-            std::mem::size_of::<roc_types::types::Problem>(),
-        );
-
-        // without RecordFields in FlatType assert_eq!((40, 72, 56, 48, 64), query)
-        assert_eq!((24, 104, 88, 80, 48), query)
-    }
 }
diff --git a/compiler/types/Cargo.toml b/compiler/types/Cargo.toml
index de242bf348..512437bd66 100644
--- a/compiler/types/Cargo.toml
+++ b/compiler/types/Cargo.toml
@@ -10,6 +10,7 @@ roc_collections = { path = "../collections" }
 roc_region = { path = "../region" }
 roc_module = { path = "../module" }
 ven_ena = { path = "../../vendor/ena" }
+static_assertions = "1.1.0"
 
 [dev-dependencies]
 pretty_assertions = "0.5.1"
diff --git a/compiler/types/src/subs.rs b/compiler/types/src/subs.rs
index 67f3174ed8..23144a6c98 100644
--- a/compiler/types/src/subs.rs
+++ b/compiler/types/src/subs.rs
@@ -7,6 +7,13 @@ use std::fmt;
 use std::iter::{once, Extend, FromIterator, Iterator, Map, Zip};
 use ven_ena::unify::{InPlace, Snapshot, UnificationTable, UnifyKey};
 
+// if your changes cause this number to go down, great!
+// please change it to the lower number.
+// if it went up, maybe check that the change is really required
+static_assertions::assert_eq_size!([u8; 104], Descriptor);
+static_assertions::assert_eq_size!([u8; 88], Content);
+static_assertions::assert_eq_size!([u8; 80], FlatType);
+
 #[derive(Clone, Copy, Hash, PartialEq, Eq)]
 pub struct Mark(i32);
 
@@ -494,7 +501,7 @@ fn unnamed_flex_var() -> Content {
 }
 
 #[derive(Copy, Clone, Default, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct Rank(usize);
+pub struct Rank(u32);
 
 impl Rank {
     pub const NONE: Rank = Rank(0);
@@ -508,7 +515,7 @@ impl Rank {
     }
 
     pub fn into_usize(self) -> usize {
-        self.0
+        self.0 as usize
     }
 }
 
@@ -526,13 +533,13 @@ impl fmt::Debug for Rank {
 
 impl From<Rank> for usize {
     fn from(rank: Rank) -> Self {
-        rank.0
+        rank.0 as usize
     }
 }
 
 impl From<usize> for Rank {
     fn from(index: usize) -> Self {
-        Rank(index)
+        Rank(index as u32)
     }
 }