rescript-lang · JonoPrest · May 20, 2026 · May 19, 2026 · May 19, 2026 · May 19, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -44,6 +44,7 @@
 - Remove `Primitive_option.toUndefined`; use `valFromOption` for optional ffi args. https://github.com/rescript-lang/rescript/pull/8380
 - Expand `super_errors` fixture coverage for warnings and errors. https://github.com/rescript-lang/rescript/pull/8429
 - Run `super_errors` fixtures in parallel (~2.4× faster locally). https://github.com/rescript-lang/rescript/pull/8430
+- Expand `super_errors` fixture coverage for the remaining reachable single-file error variants. https://github.com/rescript-lang/rescript/pull/8432
 
 
 # 13.0.0-alpha.4

diff --git a/tests/build_tests/super_errors/expected/access_functor_as_structure.res.expected b/tests/build_tests/super_errors/expected/access_functor_as_structure.res.expected
@@ -0,0 +1,10 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/access_functor_as_structure.res[0m:[2m9:8-10[0m
+
+   7 [2m│[0m }
+   8 [2m│[0m 
+   [1;31m9[0m [2m│[0m let _: [1;31mF.v[0m = 1
+  10 [2m│[0m 
+
+  The module F is a functor, not a structure
diff --git a/tests/build_tests/super_errors/expected/apply_generative.res.expected b/tests/build_tests/super_errors/expected/apply_generative.res.expected
@@ -0,0 +1,11 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/apply_generative.res[0m:[2m5:12[0m
+
+  3 [2m│[0m }
+  4 [2m│[0m 
+  [1;31m5[0m [2m│[0m module M = [1;31mF[0m({
+  6 [2m│[0m   let y = 2
+  7 [2m│[0m })
+
+  This is a generative functor. It can only be applied to ()
diff --git a/tests/build_tests/super_errors/expected/apply_non_function.res.expected b/tests/build_tests/super_errors/expected/apply_non_function.res.expected
@@ -0,0 +1,11 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/apply_non_function.res[0m:[2m3:9[0m
+
+  1 [2m│[0m let x = 1
+  2 [2m│[0m 
+  [1;31m3[0m [2m│[0m let y = [1;31mx[0m(2)
+  4 [2m│[0m 
+
+  This can't be called, it's not a function.
+  The function has type: int
diff --git a/tests/build_tests/super_errors/expected/bad_immediate_attribute.res.expected b/tests/build_tests/super_errors/expected/bad_immediate_attribute.res.expected
@@ -0,0 +1,10 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/bad_immediate_attribute.res[0m:[2m2:1-15[0m
+
+  1 [2m│[0m @immediate
+  [1;31m2[0m [2m│[0m [1;31mtype t = string[0m
+  3 [2m│[0m 
+
+  Types marked with the immediate attribute must be
+  non-pointer types like int or bool
diff --git a/tests/build_tests/super_errors/expected/bad_unboxed_attribute_abstract.res.expected b/tests/build_tests/super_errors/expected/bad_unboxed_attribute_abstract.res.expected
@@ -0,0 +1,8 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/bad_unboxed_attribute_abstract.res[0m:[2m1:10-15[0m
+
+  [1;31m1[0m [2m│[0m @unboxed [1;31mtype t[0m
+  2 [2m│[0m 
+
+  This type cannot be unboxed because it is abstract.
diff --git a/tests/build_tests/super_errors/expected/bad_unboxed_attribute_extensible.res.expected b/tests/build_tests/super_errors/expected/bad_unboxed_attribute_extensible.res.expected
@@ -0,0 +1,10 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/bad_unboxed_attribute_extensible.res[0m:[2m2:1-11[0m
+
+  1 [2m│[0m @unboxed
+  [1;31m2[0m [2m│[0m [1;31mtype t = ..[0m
+  3 [2m│[0m 
+
+  This type cannot be unboxed because
+  extensible variant types cannot be unboxed.
diff --git a/tests/build_tests/super_errors/expected/bad_unboxed_attribute_many_fields.res.expected b/tests/build_tests/super_errors/expected/bad_unboxed_attribute_many_fields.res.expected
@@ -0,0 +1,9 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/bad_unboxed_attribute_many_fields.res[0m:[2m2:1-25[0m
+
+  1 [2m│[0m @unboxed
+  [1;31m2[0m [2m│[0m [1;31mtype t = {a: int, b: int}[0m
+  3 [2m│[0m 
+
+  This type cannot be unboxed because it has more than one field.
diff --git a/tests/build_tests/super_errors/expected/bad_unboxed_attribute_mutable.res.expected b/tests/build_tests/super_errors/expected/bad_unboxed_attribute_mutable.res.expected
@@ -0,0 +1,8 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/bad_unboxed_attribute_mutable.res[0m:[2m1:10-38[0m
+
+  [1;31m1[0m [2m│[0m @unboxed [1;31mtype t = {mutable value: int}[0m
+  2 [2m│[0m 
+
+  This type cannot be unboxed because it is mutable.
diff --git a/tests/build_tests/super_errors/expected/bad_variance.res.expected b/tests/build_tests/super_errors/expected/bad_variance.res.expected
@@ -0,0 +1,10 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/bad_variance.res[0m:[2m1:1-24[0m
+
+  [1;31m1[0m [2m│[0m [1;31mtype t<+'a> = 'a => unit[0m
+  2 [2m│[0m 
+
+  In this definition, expected parameter variances are not satisfied.
+  The 1st type parameter was expected to be covariant,
+  but it is injective contravariant.
diff --git a/tests/build_tests/super_errors/expected/bad_variance_contra.res.expected b/tests/build_tests/super_errors/expected/bad_variance_contra.res.expected
@@ -0,0 +1,10 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/bad_variance_contra.res[0m:[2m1:1-16[0m
+
+  [1;31m1[0m [2m│[0m [1;31mtype t<-'a> = 'a[0m
+  2 [2m│[0m 
+
+  In this definition, expected parameter variances are not satisfied.
+  The 1st type parameter was expected to be contravariant,
+  but it is injective covariant.
diff --git a/tests/build_tests/super_errors/expected/boxed_and_unboxed.res.expected b/tests/build_tests/super_errors/expected/boxed_and_unboxed.res.expected
@@ -0,0 +1,9 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/boxed_and_unboxed.res[0m:[2m2:1-17[0m
+
+  1 [2m│[0m @unboxed @boxed
+  [1;31m2[0m [2m│[0m [1;31mtype t = One(int)[0m
+  3 [2m│[0m 
+
+  A type cannot be boxed and unboxed at the same time.
diff --git a/tests/build_tests/super_errors/expected/bs_conflict_attributes.res.expected b/tests/build_tests/super_errors/expected/bs_conflict_attributes.res.expected
@@ -0,0 +1,9 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/bs_conflict_attributes.res[0m:[2m1:21-24[0m
+
+  [1;31m1[0m [2m│[0m external f: @string [1;31m@int[0m [#A | #B] => unit = "f"
+  2 [2m│[0m 
+  3 [2m│[0m let _ = f(#A)
+
+  conflicting attributes
diff --git a/tests/build_tests/super_errors/expected/bs_expect_int_literal.res.expected b/tests/build_tests/super_errors/expected/bs_expect_int_literal.res.expected
@@ -0,0 +1,9 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/bs_expect_int_literal.res[0m:[2m1:19-21[0m
+
+  [1;31m1[0m [2m│[0m external f: @int [[1;31m@as[0m("hello") #A | #B] => unit = "f"
+  2 [2m│[0m 
+  3 [2m│[0m let _ = f(#A)
+
+  expect int literal
diff --git a/tests/build_tests/super_errors/expected/bs_expect_opt_in_bs_return_to_opt.res.expected b/tests/build_tests/super_errors/expected/bs_expect_opt_in_bs_return_to_opt.res.expected
@@ -0,0 +1,11 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/bs_expect_opt_in_bs_return_to_opt.res[0m:[2m1:1-2:31[0m
+
+  [1;31m1[0m [2m│[0m [1;31m@return(null_to_opt)[0m
+  [1;31m2[0m [2m│[0m [1;31mexternal f: string => int = "f"[0m
+  3 [2m│[0m 
+  4 [2m│[0m let _ = f("x")
+
+  %@return directive *_to_opt expect return type to be 
+syntax wise `_ option` for safety
diff --git a/tests/build_tests/super_errors/expected/bs_expect_string_literal.res.expected b/tests/build_tests/super_errors/expected/bs_expect_string_literal.res.expected
@@ -0,0 +1,9 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/bs_expect_string_literal.res[0m:[2m1:22-24[0m
+
+  [1;31m1[0m [2m│[0m external f: @string [[1;31m@as[0m(1) #A | #B] => unit = "f"
+  2 [2m│[0m 
+  3 [2m│[0m let _ = f(#A)
+
+  expect string literal
diff --git a/tests/build_tests/super_errors/expected/bs_illegal_attribute_scope.res.expected b/tests/build_tests/super_errors/expected/bs_illegal_attribute_scope.res.expected
@@ -0,0 +1,9 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/bs_illegal_attribute_scope.res[0m:[2m1:1-6[0m
+
+  [1;31m1[0m [2m│[0m [1;31m@scope[0m @val
+  2 [2m│[0m external x: int = "x"
+  3 [2m│[0m 
+
+  Illegal attributes
diff --git a/tests/build_tests/super_errors/expected/bs_invalid_bs_int_type.res.expected b/tests/build_tests/super_errors/expected/bs_invalid_bs_int_type.res.expected
@@ -0,0 +1,9 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/bs_invalid_bs_int_type.res[0m:[2m1:18-25[0m
+
+  [1;31m1[0m [2m│[0m external f: @int [1;31m[#A(int)[0m] => unit = "f"
+  2 [2m│[0m 
+  3 [2m│[0m let _ = f(#A(1))
+
+  Not a valid type for %@int
diff --git a/tests/build_tests/super_errors/expected/bs_invalid_bs_string_type.res.expected b/tests/build_tests/super_errors/expected/bs_invalid_bs_string_type.res.expected
@@ -0,0 +1,9 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/bs_invalid_bs_string_type.res[0m:[2m1:21-33[0m
+
+  [1;31m1[0m [2m│[0m external f: @string [1;31m[#A | #B(int)[0m] => unit = "f"
+  2 [2m│[0m 
+  3 [2m│[0m let _ = f(#A)
+
+  Not a valid type for %@string
diff --git a/tests/build_tests/super_errors/expected/bs_invalid_bs_unwrap_type.res.expected b/tests/build_tests/super_errors/expected/bs_invalid_bs_unwrap_type.res.expected
@@ -0,0 +1,10 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/bs_invalid_bs_unwrap_type.res[0m:[2m1:21-23[0m
+
+  [1;31m1[0m [2m│[0m external f: @unwrap [1;31mint[0m => unit = "f"
+  2 [2m│[0m 
+  3 [2m│[0m let _ = f(1)
+
+  Not a valid type for %@unwrap. Type must be an inline variant (closed), and
+each constructor must have an argument.
diff --git a/tests/build_tests/super_errors/expected/bs_not_supported_directive_in_bs_return.res.expected b/tests/build_tests/super_errors/expected/bs_not_supported_directive_in_bs_return.res.expected
@@ -0,0 +1,9 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/bs_not_supported_directive_in_bs_return.res[0m:[2m1:1-7[0m
+
+  [1;31m1[0m [2m│[0m [1;31m@return[0m(bogus)
+  2 [2m│[0m external f: string => int = "f"
+  3 [2m│[0m 
+
+  Not supported return directive
diff --git a/tests/build_tests/super_errors/expected/cannot_apply_non_functor.res.expected b/tests/build_tests/super_errors/expected/cannot_apply_non_functor.res.expected
@@ -0,0 +1,12 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/cannot_apply_non_functor.res[0m:[2m5:12[0m
+
+  3 [2m│[0m }
+  4 [2m│[0m 
+  [1;31m5[0m [2m│[0m module N = [1;31mM[0m()
+  6 [2m│[0m 
+
+  This module is not a functor; it has type {
+  let x: int
+}
diff --git a/tests/build_tests/super_errors/expected/cannot_extend_private_type.res.expected b/tests/build_tests/super_errors/expected/cannot_extend_private_type.res.expected
@@ -0,0 +1,10 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/cannot_extend_private_type.res[0m:[2m7:13[0m
+
+  5 [2m│[0m }
+  6 [2m│[0m 
+  [1;31m7[0m [2m│[0m type M.t += [1;31mC[0m
+  8 [2m│[0m 
+
+  Cannot extend private type definition M.t
diff --git a/tests/build_tests/super_errors/expected/cannot_infer_signature.res.expected b/tests/build_tests/super_errors/expected/cannot_infer_signature.res.expected
@@ -0,0 +1,10 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/cannot_infer_signature.res[0m:[2m2:14-22[0m
+
+  1 [2m│[0m let extract = m => {
+  [1;31m2[0m [2m│[0m   module M = [1;31munpack(m)[0m
+  3 [2m│[0m   M
+  4 [2m│[0m }
+
+  The signature for this packaged module couldn't be inferred.
diff --git a/tests/build_tests/super_errors/expected/constraint_failed.res.expected b/tests/build_tests/super_errors/expected/constraint_failed.res.expected
@@ -0,0 +1,10 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/constraint_failed.res[0m:[2m3:14-19[0m
+
+  1 [2m│[0m type t<'a> = 'a constraint 'a = int
+  2 [2m│[0m 
+  [1;31m3[0m [2m│[0m type bad = t<[1;31mstring[0m>
+  4 [2m│[0m 
+
+  This type string should be an instance of type int
diff --git a/tests/build_tests/super_errors/expected/constructor_arity_mismatch.res.expected b/tests/build_tests/super_errors/expected/constructor_arity_mismatch.res.expected
@@ -0,0 +1,11 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/constructor_arity_mismatch.res[0m:[2m5:9-15[0m
+
+  3 [2m│[0m   | Single(string)
+  4 [2m│[0m 
+  [1;31m5[0m [2m│[0m let x = [1;31mPair(1)[0m
+  6 [2m│[0m 
+  7 [2m│[0m let y = Single(1, 2)
+
+  This variant constructor [1;33mPair[0m expects 2 arguments, but it's only being passed 1.
diff --git a/tests/build_tests/super_errors/expected/constructor_arity_mismatch_pattern.res.expected b/tests/build_tests/super_errors/expected/constructor_arity_mismatch_pattern.res.expected
@@ -0,0 +1,11 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/constructor_arity_mismatch_pattern.res[0m:[2m5:5-11[0m
+
+  3 [2m│[0m let f = x =>
+  4 [2m│[0m   switch x {
+  [1;31m5[0m [2m│[0m   | [1;31mPair(a)[0m => a
+  6 [2m│[0m   }
+  7 [2m│[0m 
+
+  This variant constructor [1;33mPair[0m expects 2 arguments, but it's only being passed 1.
diff --git a/tests/build_tests/super_errors/expected/definition_mismatch.res.expected b/tests/build_tests/super_errors/expected/definition_mismatch.res.expected
@@ -0,0 +1,9 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/definition_mismatch.res[0m:[2m1:1-26[0m
+
+  [1;31m1[0m [2m│[0m [1;31mtype t = list<int> = Empty[0m
+  2 [2m│[0m 
+
+  This variant or record definition does not match that of type list<int>
+  They have different arities.
diff --git a/tests/build_tests/super_errors/expected/field_access_on_dict_type.res.expected b/tests/build_tests/super_errors/expected/field_access_on_dict_type.res.expected
@@ -0,0 +1,10 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/field_access_on_dict_type.res[0m:[2m3:11[0m
+
+  1 [2m│[0m let d: dict<int> = dict{"a": 1}
+  2 [2m│[0m 
+  [1;31m3[0m [2m│[0m let v = d.[1;31ma[0m
+  4 [2m│[0m 
+
+  Direct field access on a dict is not supported. Use Dict.get instead.
diff --git a/tests/build_tests/super_errors/expected/fragile_pattern_toplevel.res.expected b/tests/build_tests/super_errors/expected/fragile_pattern_toplevel.res.expected
@@ -0,0 +1,20 @@
+
+  [1;33mWarning number 8[0m
+  [36m/.../fixtures/fragile_pattern_toplevel.res[0m:[2m1:5-11[0m
+
+  [1;33m1[0m [2m│[0m let [1;33mSome(x)[0m = Some(1)
+  2 [2m│[0m 
+  3 [2m│[0m let _ = x
+
+  You forgot to handle a possible case here, for example: 
+  | None
+
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/fragile_pattern_toplevel.res[0m:[2m1:5-11[0m
+
+  [1;31m1[0m [2m│[0m let [1;31mSome(x)[0m = Some(1)
+  2 [2m│[0m 
+  3 [2m│[0m let _ = x
+
+  Such fragile pattern not allowed in the toplevel
diff --git a/tests/build_tests/super_errors/expected/illegal_letrec_expr.res.expected b/tests/build_tests/super_errors/expected/illegal_letrec_expr.res.expected
@@ -0,0 +1,8 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/illegal_letrec_expr.res[0m:[2m1:13-17[0m
+
+  [1;31m1[0m [2m│[0m let rec x = [1;31mx + 1[0m
+  2 [2m│[0m 
+
+  This kind of expression is not allowed as right-hand side of `let rec'