Add solve test

compiler/solve/tests/solve_expr.rs

@@ -154,7 +154,8 @@ mod solve_expr {
                 mut type_problems,
                 interns,
                 mut solved,
-                exposed_to_host,
+                mut exposed_to_host,
+                abilities_store,
                 ..
             },
             src,
@@ -172,6 +173,8 @@ mod solve_expr {
 
         let subs = solved.inner_mut();
 
+        exposed_to_host.retain(|s, _| !abilities_store.is_specialization_name(*s));
+
         debug_assert!(exposed_to_host.len() == 1);
         let (_symbol, variable) = exposed_to_host.into_iter().next().unwrap();
         let actual_str = name_and_print_var(variable, subs, home, &interns);
@@ -6426,4 +6429,30 @@ mod solve_expr {
             &["A#default : {} -> A"],
         )
     }
+
+    #[test]
+    fn stdlib_encode_json() {
+        infer_eq_without_problem(
+            indoc!(
+                r#"
+                app "test"
+                    imports [ Encode.{ toEncoder }, Json ]
+                    provides [ main ] to "./platform"
+
+                HelloWorld := {}
+
+                toEncoder = \@HelloWorld {} ->
+                    Encode.custom \bytes, fmt ->
+                        bytes
+                        |> Encode.appendWith (Encode.string "Hello, World!\n") fmt
+
+                main =
+                    when Str.fromUtf8 (Encode.toBytes (@HelloWorld {}) Json.format) is
+                        Ok s -> s
+                        _ -> "<bad>"
+                "#
+            ),
+            "Str",
+        )
+    }
 }