From 3cd76e21163edfda8b662d7071687180a4143ba2 Mon Sep 17 00:00:00 2001
From: Cristiano Calcagno <cristianoc@users.noreply.github.com>
Date: Sat, 4 Feb 2023 10:56:07 +0100
Subject: [PATCH] Fix issue with error messages for uncurried functions where
expected and given type were swapped
The logic for unification for `Function$`, which unifies with a generic uncurried type, was swapped.
The error message for arity mismatch was also swapped, so those errors were showing correctly.
However, in the case of expected curried function, when given a curried function whose type is begin inferred, the error message was swapped.
Also added a specialized error message when the uncurried type only contains a type variable, so `$function<'a, ...>` does not leak in the output. This happens as unification failt early, and the type of the function has not been determined yet.
---
CHANGELOG.md | 1 +
.../expected/curried_expected.res.expected | 10 ++++++++++
.../super_errors/fixtures/curried_expected.res | 3 +++
jscomp/ml/typecore.ml | 2 +-
jscomp/super_errors/super_typecore.ml | 9 +++++++--
5 files changed, 22 insertions(+), 3 deletions(-)
create mode 100644 jscomp/build_tests/super_errors/expected/curried_expected.res.expected
create mode 100644 jscomp/build_tests/super_errors/fixtures/curried_expected.res
diff --git a/CHANGELOG.md b/CHANGELOG.md
index d200abbc6b..3bdf0eb9a4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -54,6 +54,7 @@ These are only breaking changes for unformatted code.
- Fix issue where error messages related to non-existent props were displayed without location information https://github.com/rescript-lang/rescript-compiler/pull/5960
- Fix type inference issue with uncurried functions applied to a single unit argument. The issue was introduced in https://github.com/rescript-lang/rescript-compiler/pull/5907 when adding support to `foo()` when `foo` has only optional arguments. https://github.com/rescript-lang/rescript-compiler/pull/5970
- Fix issue where uncurried functions were incorrectly converting the type of a prop given as a default value to curried https://github.com/rescript-lang/rescript-compiler/pull/5971
+- Fix issue with error messages for uncurried functions where expected and given type were swapped https://github.com/rescript-lang/rescript-compiler/pull/5973
#### :nail_care: Polish
diff --git a/jscomp/build_tests/super_errors/expected/curried_expected.res.expected b/jscomp/build_tests/super_errors/expected/curried_expected.res.expected
new file mode 100644
index 0000000000..5b789c5abb
--- /dev/null
+++ b/jscomp/build_tests/super_errors/expected/curried_expected.res.expected
@@ -0,0 +1,10 @@
+
+ [1;31mWe've found a bug for you![0m
+ [36m/.../fixtures/curried_expected.res[0m:[2m3:24-38[0m
+
+ 1 [2m│[0m let expectCurried = f => f(1) + 2
+ 2 [2m│[0m
+ [1;31m3[0m [2m│[0m let z1 = expectCurried([1;31m(. x, y) => x+y[0m)
+ 4 [2m│[0m
+
+ This function is an uncurried function where a curried function is expected
\ No newline at end of file
diff --git a/jscomp/build_tests/super_errors/fixtures/curried_expected.res b/jscomp/build_tests/super_errors/fixtures/curried_expected.res
new file mode 100644
index 0000000000..224d432a15
--- /dev/null
+++ b/jscomp/build_tests/super_errors/fixtures/curried_expected.res
@@ -0,0 +1,3 @@
+let expectCurried = f => f(1) + 2
+
+let z1 = expectCurried((. x, y) => x+y)
diff --git a/jscomp/ml/typecore.ml b/jscomp/ml/typecore.ml
index 4dc62db56b..acdd846da4 100644
--- a/jscomp/ml/typecore.ml
+++ b/jscomp/ml/typecore.ml
@@ -2107,7 +2107,7 @@ and type_expect_ ?in_function ?(recarg=Rejected) env sexp ty_expected =
let state = Warnings.backup () in
let arity = Ast_uncurried.attributes_to_arity sexp.pexp_attributes in
let uncurried_typ = Ast_uncurried.make_uncurried_type ~env ~arity (newvar()) in
- unify_exp_types loc env ty_expected uncurried_typ;
+ unify_exp_types loc env uncurried_typ ty_expected;
(* Disable Unerasable_optional_argument for uncurried functions *)
let unerasable_optional_argument = Warnings.number Unerasable_optional_argument in
Warnings.parse_options false ("-" ^ string_of_int unerasable_optional_argument);
diff --git a/jscomp/super_errors/super_typecore.ml b/jscomp/super_errors/super_typecore.ml
index cef6a7ec0a..0f99ca1f0e 100644
--- a/jscomp/super_errors/super_typecore.ml
+++ b/jscomp/super_errors/super_typecore.ml
@@ -121,9 +121,9 @@ end
let reportArityMismatch ~arityA ~arityB ppf =
fprintf ppf "This function expected @{<info>%s@} %s, but got @{<error>%s@}"
- arityA
- (if arityA = "1" then "argument" else "arguments")
arityB
+ (if arityB = "1" then "argument" else "arguments")
+ arityA
(* Pasted from typecore.ml. Needed for some cases in report_error below *)
(* Records *)
@@ -169,6 +169,11 @@ let report_error env ppf = function
(_, {desc = Tconstr (Pident {name = "function$"},_,_)}) :: _
) ->
fprintf ppf "This function is a curried function where an uncurried function is expected"
+ | Expr_type_clash (
+ (_, {desc = Tconstr (Pident {name = "function$"}, [{desc=Tvar _}; _],_)}) ::
+ (_, {desc = Tarrow _}) :: _
+ ) ->
+ fprintf ppf "This function is an uncurried function where a curried function is expected"
| Expr_type_clash (
(_, {desc = Tconstr (Pident {name = "function$"},[_; tA],_)}) ::
(_, {desc = Tconstr (Pident {name = "function$"},[_; tB],_)}) :: _