Reject to_mem on primitive types in storage

crates/analyzer/src/traversal/expressions.rs

@@ -1767,7 +1767,23 @@ fn expr_call_builtin_value_method(
                         vec![],
                     );
                 }
-                Location::Storage { .. } => {}
+                Location::Storage { .. } => {
+                    if value_attrs.typ.is_base(context.db())
+                        || matches!(value_attrs.typ.typ(context.db()), Type::Contract(_))
+                    {
+                        context.fancy_error(
+                            "`to_mem()` called on primitive type",
+                            vec![
+                                Label::primary(
+                                    value.span,
+                                    "this value does not need to be copied to memory",
+                                ),
+                                Label::secondary(method_name.span, "hint: remove `.to_mem()`"),
+                            ],
+                            vec![],
+                        );
+                    }
+                }
                 Location::Value => {
                     context.fancy_error(
                         "`to_mem()` called on primitive type",

crates/analyzer/tests/errors.rs

@@ -323,7 +323,7 @@ test_file! { abi_encode_from_storage }
 test_file! { assert_sto_msg_no_copy }
 test_file! { for_loop_sto_iter_no_copy }
 test_file! { revert_sto_error_no_copy }
-
+test_file! { call_to_mem_on_primitive }
 test_file! { call_to_mut_fn_without_self }
 test_file! { call_to_pure_fn_on_self }
 test_file! { call_to_pure_struct_fn_on_instance }

crates/analyzer/tests/snapshots/errors__call_to_mem_on_primitive.snap

@@ -0,0 +1,14 @@
+---
+source: crates/analyzer/tests/errors.rs
+expression: "error_string(&path, test_files::fixture(path))"
+
+---
+error: `to_mem()` called on primitive type
+  ┌─ compile_errors/call_to_mem_on_primitive.fe:5:16
+  │
+5 │         return self.bar.to_mem()
+  │                ^^^^^^^^ ------ hint: remove `.to_mem()`
+  │                │         
+  │                this value does not need to be copied to memory
+
+

crates/test-files/fixtures/compile_errors/call_to_mem_on_primitive.fe

@@ -0,0 +1,7 @@
+contract Foo {
+    bar: u256
+
+    fn call_me(self) -> u256 {
+        return self.bar.to_mem()
+    }
+}

newsfragments/801.bugfix.md

@@ -0,0 +1 @@
+Reject calling `to_mem()` on primitive types in storage