rescript-lang · JonoPrest · May 18, 2026 · May 18, 2026 · May 18, 2026 · May 18, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -42,6 +42,7 @@
 #### :house: Internal
 
 - 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
 
 # 13.0.0-alpha.4
 

diff --git a/tests/build_tests/super_errors/expected/apply_wrong_label.res.expected b/tests/build_tests/super_errors/expected/apply_wrong_label.res.expected
@@ -0,0 +1,11 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/apply_wrong_label.res[0m:[2m3:22-28[0m
+
+  1 [2m│[0m let greet = (~name) => "Hello " ++ name
+  2 [2m│[0m 
+  [1;31m3[0m [2m│[0m let _ = greet(~names=[1;31m"world"[0m)
+  4 [2m│[0m 
+
+  This function does not take the argument [1;33m~names[0m.
+  This function has type: (~name: string) => string
diff --git a/tests/build_tests/super_errors/expected/conflicting_ffi_attributes.res.expected b/tests/build_tests/super_errors/expected/conflicting_ffi_attributes.res.expected
@@ -0,0 +1,10 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/conflicting_ffi_attributes.res[0m:[2m1:1-2:50[0m
+
+  [1;31m1[0m [2m│[0m [1;31m@val @send[0m
+  [1;31m2[0m [2m│[0m [1;31mexternal doThing: (string, int) => int = "doThing"[0m
+  3 [2m│[0m 
+  4 [2m│[0m let _ = doThing("x", 1)
+
+  Conflicting attributes: Attribute found that conflicts with %@val
diff --git a/tests/build_tests/super_errors/expected/duplicate_module_in_scope.res.expected b/tests/build_tests/super_errors/expected/duplicate_module_in_scope.res.expected
@@ -0,0 +1,13 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/duplicate_module_in_scope.res[0m:[2m5:8[0m
+
+  3 [2m│[0m }
+  4 [2m│[0m 
+  [1;31m5[0m [2m│[0m module [1;31mM[0m = {
+  6 [2m│[0m   let x = 2
+  7 [2m│[0m }
+
+  Multiple definition of the module name M 
+  at [1m[36m/.../fixtures/duplicate_module_in_scope.res[0m:[2m1:8[0m[0m
+   Names must be unique in a given structure or signature.
diff --git a/tests/build_tests/super_errors/expected/duplicate_variant_constructor.res.expected b/tests/build_tests/super_errors/expected/duplicate_variant_constructor.res.expected
@@ -0,0 +1,8 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/duplicate_variant_constructor.res[0m:[2m1:1-18[0m
+
+  [1;31m1[0m [2m│[0m [1;31mtype t = Foo | Foo[0m
+  2 [2m│[0m 
+
+  Two constructors are named Foo
diff --git a/tests/build_tests/super_errors/expected/duplicated_bs_deriving.res.expected b/tests/build_tests/super_errors/expected/duplicated_bs_deriving.res.expected
@@ -0,0 +1,9 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/duplicated_bs_deriving.res[0m:[2m1:22-30[0m
+
+  [1;31m1[0m [2m│[0m @deriving(accessors) [1;31m@deriving[0m(jsConverter)
+  2 [2m│[0m type t = One | Two
+  3 [2m│[0m 
+
+  duplicate @deriving attribute
diff --git a/tests/build_tests/super_errors/expected/exception_pattern_below_toplevel.res.expected b/tests/build_tests/super_errors/expected/exception_pattern_below_toplevel.res.expected
@@ -0,0 +1,11 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/exception_pattern_below_toplevel.res[0m:[2m3:10-28[0m
+
+  1 [2m│[0m let run = action =>
+  2 [2m│[0m   switch action() {
+  [1;31m3[0m [2m│[0m   | Some([1;31mexception Not_found[0m) => "nested exception pattern is invalid"
+  4 [2m│[0m   | _ => "ok"
+  5 [2m│[0m   }
+
+  Exception patterns must be at the top level of a match case.
diff --git a/tests/build_tests/super_errors/expected/functor_apply_arg_mismatch.res.expected b/tests/build_tests/super_errors/expected/functor_apply_arg_mismatch.res.expected
@@ -0,0 +1,17 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/functor_apply_arg_mismatch.res[0m:[2m13:22-29[0m
+
+  11 [2m│[0m }
+  12 [2m│[0m 
+  [1;31m13[0m [2m│[0m module Result = Make([1;31mConcrete[0m)
+  14 [2m│[0m let _ = Result.bar
+  15 [2m│[0m 
+
+  Signature mismatch:
+  Modules do not match: {
+  let unrelated: string
+} is not included in HasFoo
+  The value `foo' is required but not provided
+  [36m/.../fixtures/functor_apply_arg_mismatch.res[0m:[2m2:3-14[0m:
+    Expected declaration
diff --git a/tests/build_tests/super_errors/expected/illegal_letrec_pat.res.expected b/tests/build_tests/super_errors/expected/illegal_letrec_pat.res.expected
@@ -0,0 +1,19 @@
+
+  [1;33mWarning number 39[0m
+  [36m/.../fixtures/illegal_letrec_pat.res[0m:[2m1:9-14[0m
+
+  [1;33m1[0m [2m│[0m let rec [1;33m(x, y)[0m = (1, 2)
+  2 [2m│[0m let _ = x + y
+  3 [2m│[0m 
+
+  unused rec flag.
+
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/illegal_letrec_pat.res[0m:[2m1:9-14[0m
+
+  [1;31m1[0m [2m│[0m let rec [1;31m(x, y)[0m = (1, 2)
+  2 [2m│[0m let _ = x + y
+  3 [2m│[0m 
+
+  Only variables are allowed as left-hand side of `let rec'
diff --git a/tests/build_tests/super_errors/expected/invalid_type_variable_name.res.expected b/tests/build_tests/super_errors/expected/invalid_type_variable_name.res.expected
@@ -0,0 +1,8 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/invalid_type_variable_name.res[0m:[2m1:9-16[0m
+
+  [1;31m1[0m [2m│[0m type t<'[1;31m_invalid[0m> = list<'_invalid>
+  2 [2m│[0m 
+
+  The type variable name '_invalid is not allowed in programs
diff --git a/tests/build_tests/super_errors/expected/label_multiply_defined_literal.res.expected b/tests/build_tests/super_errors/expected/label_multiply_defined_literal.res.expected
@@ -0,0 +1,11 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/label_multiply_defined_literal.res[0m:[2m3:19[0m
+
+  1 [2m│[0m type t = {a: int, b: int}
+  2 [2m│[0m 
+  [1;31m3[0m [2m│[0m let r: t = {a: 1, [1;31ma[0m: 2, b: 3}
+  4 [2m│[0m let _ = r
+  5 [2m│[0m 
+
+  The record field label a is defined several times
diff --git a/tests/build_tests/super_errors/expected/multiply_bound_variable.res.expected b/tests/build_tests/super_errors/expected/multiply_bound_variable.res.expected
@@ -0,0 +1,9 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/multiply_bound_variable.res[0m:[2m1:9[0m
+
+  [1;31m1[0m [2m│[0m let (x, [1;31mx[0m) = (1, 2)
+  2 [2m│[0m let _ = x
+  3 [2m│[0m 
+
+  Variable x is bound several times in this matching
diff --git a/tests/build_tests/super_errors/expected/or_pattern_type_clash.res.expected b/tests/build_tests/super_errors/expected/or_pattern_type_clash.res.expected
@@ -0,0 +1,12 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/or_pattern_type_clash.res[0m:[2m3:9-15[0m
+
+  1 [2m│[0m let f = (x: int) =>
+  2 [2m│[0m   switch x {
+  [1;31m3[0m [2m│[0m   | 1 | [1;31m"hello"[0m => "weird"
+  4 [2m│[0m   | _ => "other"
+  5 [2m│[0m   }
+
+  This pattern matches values of type [1;31mstring[0m
+  but a pattern was expected which matches values of type [1;33mint[0m
diff --git a/tests/build_tests/super_errors/expected/orpat_vars_unbalanced.res.expected b/tests/build_tests/super_errors/expected/orpat_vars_unbalanced.res.expected
@@ -0,0 +1,11 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/orpat_vars_unbalanced.res[0m:[2m3:5-18[0m
+
+  1 [2m│[0m let f = x =>
+  2 [2m│[0m   switch x {
+  [1;31m3[0m [2m│[0m   | [1;31mSome(n) | None[0m => n
+  4 [2m│[0m   | _ => 0
+  5 [2m│[0m   }
+
+  Variable n must occur on both sides of this | pattern
diff --git a/tests/build_tests/super_errors/expected/record_literal_missing_fields.res.expected b/tests/build_tests/super_errors/expected/record_literal_missing_fields.res.expected
@@ -0,0 +1,10 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/record_literal_missing_fields.res[0m:[2m3:12-13[0m
+
+  1 [2m│[0m type t = {a: int}
+  2 [2m│[0m 
+  [1;31m3[0m [2m│[0m let r: t = [1;31m{}[0m
+  4 [2m│[0m 
+
+  Some required record fields are missing: a.
diff --git a/tests/build_tests/super_errors/expected/recursive_type_abbrev_cycle.res.expected b/tests/build_tests/super_errors/expected/recursive_type_abbrev_cycle.res.expected
@@ -0,0 +1,8 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/recursive_type_abbrev_cycle.res[0m:[2m1:1-14[0m
+
+  [1;31m1[0m [2m│[0m [1;31mtype rec t = t[0m
+  2 [2m│[0m 
+
+  The type abbreviation t is cyclic
diff --git a/tests/build_tests/super_errors/expected/repeated_type_parameter.res.expected b/tests/build_tests/super_errors/expected/repeated_type_parameter.res.expected
@@ -0,0 +1,8 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/repeated_type_parameter.res[0m:[2m1:13[0m
+
+  [1;31m1[0m [2m│[0m type t<'a, '[1;31ma[0m> = ('a, 'a)
+  2 [2m│[0m 
+
+  A type parameter occurs several times
diff --git a/tests/build_tests/super_errors/expected/too_many_arguments.res.expected b/tests/build_tests/super_errors/expected/too_many_arguments.res.expected
@@ -0,0 +1,14 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/too_many_arguments.res[0m:[2m3:9-11[0m
+
+  1 [2m│[0m let add = (x, y) => x + y
+  2 [2m│[0m 
+  [1;31m3[0m [2m│[0m let _ = [1;31madd[0m(1, 2, 3)
+  4 [2m│[0m 
+
+  This function call is incorrect.
+  The function has type:
+  (int, int) => int
+
+  - The function takes [1;33mjust 2[0m unlabelled arguments, but is called with [1;31m3[0m
diff --git a/tests/build_tests/super_errors/expected/type_abbrev_missing_rec.res.expected b/tests/build_tests/super_errors/expected/type_abbrev_missing_rec.res.expected
@@ -0,0 +1,9 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/type_abbrev_missing_rec.res[0m:[2m1:10[0m
+
+  [1;31m1[0m [2m│[0m type t = [1;31mt[0m
+  2 [2m│[0m 
+
+  This type constructor, `t`, can't be found.
+  If you wanted to write a recursive type, don't forget the `rec` in `type rec`
diff --git a/tests/build_tests/super_errors/expected/type_arity_mismatch.res.expected b/tests/build_tests/super_errors/expected/type_arity_mismatch.res.expected
@@ -0,0 +1,9 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/type_arity_mismatch.res[0m:[2m1:9-26[0m
+
+  [1;31m1[0m [2m│[0m let xs: [1;31marray<int, string>[0m = []
+  2 [2m│[0m 
+
+  The type constructor array expects 1 argument(s),
+  but is here applied to 2 argument(s)
diff --git a/tests/build_tests/super_errors/expected/typetexp_unbound_type_constructor.res.expected b/tests/build_tests/super_errors/expected/typetexp_unbound_type_constructor.res.expected
@@ -0,0 +1,9 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/typetexp_unbound_type_constructor.res[0m:[2m1:8-23[0m
+
+  [1;31m1[0m [2m│[0m let x: [1;31mnonexistent_type[0m = 1
+  2 [2m│[0m 
+
+  This type constructor, `nonexistent_type`, can't be found.
+  If you wanted to write a recursive type, don't forget the `rec` in `type rec`
diff --git a/tests/build_tests/super_errors/expected/unbound_type_var.res.expected b/tests/build_tests/super_errors/expected/unbound_type_var.res.expected
@@ -0,0 +1,8 @@
+
+  [1;31mWe've found a bug for you![0m
+  [36m/.../fixtures/unbound_type_var.res[0m:[2m1:12[0m
+
+  [1;31m1[0m [2m│[0m type t = ('[1;31ma[0m, int)
+  2 [2m│[0m 
+
+  Unbound type parameter 'a
diff --git a/tests/build_tests/super_errors/expected/warning_101_bs_unused_attribute.res.expected b/tests/build_tests/super_errors/expected/warning_101_bs_unused_attribute.res.expected
@@ -0,0 +1,11 @@
+
+  [1;31mWarning number 101[0m (configured as error) 
+  [36m/.../fixtures/warning_101_bs_unused_attribute.res[0m:[2m1:1-3[0m
+
+  [1;31m1[0m [2m│[0m [1;31m@as[0m("foo")
+  2 [2m│[0m let x = 1
+  3 [2m│[0m 
+
+  Unused attribute: @as
+This attribute has no effect here.
+For example, some attributes are only meaningful in externals.
diff --git a/tests/build_tests/super_errors/expected/warning_103_bs_ffi.res.expected b/tests/build_tests/super_errors/expected/warning_103_bs_ffi.res.expected
@@ -0,0 +1,9 @@
+
+  [1;33mWarning number 103[0m
+  [36m/.../fixtures/warning_103_bs_ffi.res[0m:[2m1:32-43[0m
+
+  [1;33m1[0m [2m│[0m @val external setMode: @string [1;33m[#Foo | #Bar[0m] => unit = "setMode"
+  2 [2m│[0m 
+  3 [2m│[0m let _ = setMode(#Foo)
+
+  FFI warning: @string is redundant here, you can safely remove it
diff --git a/tests/build_tests/super_errors/expected/warning_104_bs_derive.res.expected b/tests/build_tests/super_errors/expected/warning_104_bs_derive.res.expected
@@ -0,0 +1,19 @@
+
+  [1;33mWarning number 104[0m
+  [36m/.../fixtures/warning_104_bs_derive.res[0m:[2m2:1-12[0m
+
+  1 [2m│[0m @deriving(accessors)
+  [1;33m2[0m [2m│[0m [1;33mtype t = int[0m
+  3 [2m│[0m 
+
+  @deriving warning: accessors not applicable to this type
+
+
+  [1;33mWarning number 104[0m
+  [36m/.../fixtures/warning_104_bs_derive.res[0m:[2m2:1-12[0m
+
+  1 [2m│[0m @deriving(accessors)
+  [1;33m2[0m [2m│[0m [1;33mtype t = int[0m
+  3 [2m│[0m 
+
+  @deriving warning: accessors not applicable to this type
diff --git a/tests/build_tests/super_errors/expected/warning_12_unused_pat.res.expected b/tests/build_tests/super_errors/expected/warning_12_unused_pat.res.expected
@@ -0,0 +1,11 @@
+
+  [1;33mWarning number 12[0m
+  [36m/.../fixtures/warning_12_unused_pat.res[0m:[2m3:14[0m
+
+  1 [2m│[0m let describe = x =>
+  2 [2m│[0m   switch x {
+  [1;33m3[0m [2m│[0m   | Some(0 | [1;33m0[0m) => "zero"
+  4 [2m│[0m   | _ => "other"
+  5 [2m│[0m   }
+
+  this sub-pattern is unused.
diff --git a/tests/build_tests/super_errors/expected/warning_23_useless_record_with.res.expected b/tests/build_tests/super_errors/expected/warning_23_useless_record_with.res.expected
@@ -0,0 +1,11 @@
+
+  [1;33mWarning number 23[0m
+  [36m/.../fixtures/warning_23_useless_record_with.res[0m:[2m4:10-27[0m
+
+  2 [2m│[0m 
+  3 [2m│[0m let r = {a: 1, b: 2}
+  [1;33m4[0m [2m│[0m let r2 = [1;33m{...r, a: 3, b: 4}[0m
+  5 [2m│[0m 
+  6 [2m│[0m let _ = r2
+
+  All the fields are already explicitly listed in this record. You can remove the `...` spread.
diff --git a/...build_tests/super_errors/expected/warning_28_wildcard_arg_to_constant_constr.res.expected b/...build_tests/super_errors/expected/warning_28_wildcard_arg_to_constant_constr.res.expected
@@ -0,0 +1,11 @@
+
+  [1;33mWarning number 28[0m
+  [36m/.../fixtures/warning_28_wildcard_arg_to_constant_constr.res[0m:[2m5:9[0m
+
+  3 [2m│[0m let f = x =>
+  4 [2m│[0m   switch x {
+  [1;33m5[0m [2m│[0m   | Foo([1;33m_[0m) => 0
+  6 [2m│[0m   | Bar(_) => 1
+  7 [2m│[0m   }
+
+  wildcard pattern given as argument to a constant constructor
diff --git a/tests/build_tests/super_errors/expected/warning_30_duplicate_definitions.res.expected b/tests/build_tests/super_errors/expected/warning_30_duplicate_definitions.res.expected
@@ -0,0 +1,9 @@
+
+  [1;33mWarning number 30[0m
+  [36m/.../fixtures/warning_30_duplicate_definitions.res[0m:[2m2:9-11[0m
+
+  1 [2m│[0m type a = Foo
+  [1;33m2[0m [2m│[0m and b = [1;33mFoo[0m
+  3 [2m│[0m 
+
+  the constructor Foo is defined in both types a and b.
diff --git a/tests/build_tests/super_errors/expected/warning_33_unused_open.res.expected b/tests/build_tests/super_errors/expected/warning_33_unused_open.res.expected
@@ -0,0 +1,9 @@
+
+  [1;33mWarning number 33[0m
+  [36m/.../fixtures/warning_33_unused_open.res[0m:[2m1:1-17[0m
+
+  [1;33m1[0m [2m│[0m [1;33mopen Stdlib_Array[0m
+  2 [2m│[0m 
+  3 [2m│[0m let x = 1
+
+  unused open Stdlib_Array.
diff --git a/tests/build_tests/super_errors/expected/warning_34_unused_type.res.expected b/tests/build_tests/super_errors/expected/warning_34_unused_type.res.expected
@@ -0,0 +1,11 @@
+
+  [1;33mWarning number 34[0m
+  [36m/.../fixtures/warning_34_unused_type.res[0m:[2m4:3-23[0m
+
+  2 [2m│[0m   let v: int
+  3 [2m│[0m } = {
+  [1;33m4[0m [2m│[0m   [1;33mtype unusedType = int[0m
+  5 [2m│[0m   let v = 1
+  6 [2m│[0m }
+
+  unused type unusedType.