Specialized errors for when colon and equals are mixed up (#7900)

* specialized errors for when colon and equals are mixed up in records, function arguments, and more

* changelog

Author: zth

CHANGELOG.md

@@ -32,6 +32,7 @@
 
 - Add (dev-)dependencies to build schema. https://github.com/rescript-lang/rescript/pull/7892
 - Dedicated error for dict literal spreads. https://github.com/rescript-lang/rescript/pull/7901
+- Dedicated error message for when mixing up `:` and `=` in various positions. https://github.com/rescript-lang/rescript/pull/7900
 
 #### :house: Internal
 

compiler/syntax/src/res_core.ml

@@ -99,6 +99,24 @@ module ErrorMessages = struct
 
   let dict_expr_spread = "Dict literals do not support spread (`...`) yet."
 
+  let record_field_missing_colon =
+    "Records use `:` when assigning fields. Example: `{field: value}`"
+
+  let record_pattern_field_missing_colon =
+    "Record patterns use `:` when matching fields. Example: `{field: value}`"
+
+  let record_type_field_missing_colon =
+    "Record fields in type declarations use `:`. Example: `{field: string}`"
+
+  let dict_field_missing_colon =
+    "Dict entries use `:` to separate keys from values. Example: `{\"k\": v}`"
+
+  let labelled_argument_missing_equal =
+    "Use `=` to pass a labelled argument. Example: `~label=value`"
+
+  let optional_labelled_argument_missing_equal =
+    "Optional labelled arguments use `=?`. Example: `~label=?value`"
+
   let variant_ident =
     "A polymorphic variant (e.g. #id) must start with an alphabetical letter \
      or be a number (e.g. #742)"
@@ -1414,6 +1432,13 @@ and parse_record_pattern_row_field ~attrs p =
       let optional = parse_optional_label p in
       let pat = parse_pattern p in
       (pat, optional)
+    | Equal ->
+      Parser.err ~start_pos:p.start_pos ~end_pos:p.end_pos p
+        (Diagnostics.message ErrorMessages.record_pattern_field_missing_colon);
+      Parser.next p;
+      let optional = parse_optional_label p in
+      let pat = parse_pattern p in
+      (pat, optional)
     | _ ->
       ( Ast_helper.Pat.var ~loc:label.loc ~attrs
           (Location.mkloc (Longident.last label.txt) label.loc),
@@ -3062,6 +3087,19 @@ and parse_braced_or_record_expr p =
       in
       Parser.expect Rbrace p;
       expr
+    | Equal ->
+      Parser.err ~start_pos:p.start_pos ~end_pos:p.end_pos p
+        (Diagnostics.message ErrorMessages.record_field_missing_colon);
+      Parser.next p;
+      let field_expr = parse_expr p in
+      Parser.optional p Comma |> ignore;
+      let expr =
+        parse_record_expr_with_string_keys ~start_pos
+          {Parsetree.lid = field; x = field_expr; opt = false}
+          p
+      in
+      Parser.expect Rbrace p;
+      expr
     | _ -> (
       let tag = if p.mode = ParseForTypeChecker then Some "js" else None in
       let constant =
@@ -3155,6 +3193,28 @@ and parse_braced_or_record_expr p =
           in
           Parser.expect Rbrace p;
           expr)
+      | Equal -> (
+        Parser.err ~start_pos:p.start_pos ~end_pos:p.end_pos p
+          (Diagnostics.message ErrorMessages.record_field_missing_colon);
+        Parser.next p;
+        let optional = parse_optional_label p in
+        let field_expr = parse_expr p in
+        match p.Parser.token with
+        | Rbrace ->
+          Parser.next p;
+          let loc = mk_loc start_pos p.prev_end_pos in
+          Ast_helper.Exp.record ~loc
+            [{lid = path_ident; x = field_expr; opt = optional}]
+            None
+        | _ ->
+          Parser.expect Comma p;
+          let expr =
+            parse_record_expr ~start_pos
+              [{lid = path_ident; x = field_expr; opt = optional}]
+              p
+          in
+          Parser.expect Rbrace p;
+          expr)
       (* error case *)
       | Lident _ ->
         if p.prev_end_pos.pos_lnum < p.start_pos.pos_lnum then (
@@ -3297,6 +3357,12 @@ and parse_record_expr_row_with_string_key p :
       Parser.next p;
       let field_expr = parse_expr p in
       Some {lid = field; x = field_expr; opt = false}
+    | Equal ->
+      Parser.err ~start_pos:p.start_pos ~end_pos:p.end_pos p
+        (Diagnostics.message ErrorMessages.record_field_missing_colon);
+      Parser.next p;
+      let field_expr = parse_expr p in
+      Some {lid = field; x = field_expr; opt = false}
     | _ ->
       Some
         {
@@ -3326,6 +3392,13 @@ and parse_record_expr_row p :
       let optional = parse_optional_label p in
       let field_expr = parse_expr p in
       Some {lid = field; x = field_expr; opt = optional}
+    | Equal ->
+      Parser.err ~start_pos:p.start_pos ~end_pos:p.end_pos p
+        (Diagnostics.message ErrorMessages.record_field_missing_colon);
+      Parser.next p;
+      let optional = parse_optional_label p in
+      let field_expr = parse_expr p in
+      Some {lid = field; x = field_expr; opt = optional}
     | _ ->
       let value = Ast_helper.Exp.ident ~loc:field.loc ~attrs field in
       let value =
@@ -3385,6 +3458,12 @@ and parse_dict_expr_row p =
       Parser.next p;
       let fieldExpr = parse_expr p in
       Some (field, fieldExpr)
+    | Equal ->
+      Parser.err ~start_pos:p.start_pos ~end_pos:p.end_pos p
+        (Diagnostics.message ErrorMessages.dict_field_missing_colon);
+      Parser.next p;
+      let fieldExpr = parse_expr p in
+      Some (field, fieldExpr)
     | _ -> Some (field, Ast_helper.Exp.ident ~loc:field.loc field))
   | _ -> None
 
@@ -3889,12 +3968,42 @@ and parse_argument2 p : argument option =
         in
         Some {label; expr}
       | Colon ->
+        let colon_start = p.start_pos in
         Parser.next p;
-        let typ = parse_typ_expr p in
-        let loc = mk_loc start_pos p.prev_end_pos in
-        let expr = Ast_helper.Exp.constraint_ ~loc ident_expr typ in
-        Some
-          {label = Asttypes.Labelled {txt = ident; loc = named_arg_loc}; expr}
+        let colon_end = p.prev_end_pos in
+        if Grammar.is_typ_expr_start p.Parser.token then
+          let typ = parse_typ_expr p in
+          let loc = mk_loc start_pos p.prev_end_pos in
+          let expr = Ast_helper.Exp.constraint_ ~loc ident_expr typ in
+          Some
+            {label = Asttypes.Labelled {txt = ident; loc = named_arg_loc}; expr}
+        else
+          let label, expr =
+            match p.Parser.token with
+            | Question ->
+              Parser.err ~start_pos:colon_start ~end_pos:colon_end p
+                (Diagnostics.message
+                   ErrorMessages.optional_labelled_argument_missing_equal);
+              Parser.next p;
+              let expr = parse_constrained_or_coerced_expr p in
+              (Asttypes.Optional {txt = ident; loc = named_arg_loc}, expr)
+            | _ ->
+              Parser.err ~start_pos:colon_start ~end_pos:colon_end p
+                (Diagnostics.message
+                   ErrorMessages.labelled_argument_missing_equal);
+              let expr =
+                match p.Parser.token with
+                | Underscore
+                  when not (is_es6_arrow_expression ~in_ternary:false p) ->
+                  let loc = mk_loc p.start_pos p.end_pos in
+                  Parser.next p;
+                  Ast_helper.Exp.ident ~loc
+                    (Location.mkloc (Longident.Lident "_") loc)
+                | _ -> parse_constrained_or_coerced_expr p
+              in
+              (Asttypes.Labelled {txt = ident; loc = named_arg_loc}, expr)
+          in
+          Some {label; expr}
       | _ ->
         Some
           {
@@ -4791,7 +4900,13 @@ and parse_string_field_declaration p =
     let name_end_pos = p.end_pos in
     Parser.next p;
     let field_name = Location.mkloc name (mk_loc name_start_pos name_end_pos) in
-    Parser.expect ~grammar:Grammar.TypeExpression Colon p;
+    (match p.Parser.token with
+    | Colon -> Parser.next p
+    | Equal ->
+      Parser.err ~start_pos:p.start_pos ~end_pos:p.end_pos p
+        (Diagnostics.message ErrorMessages.record_type_field_missing_colon);
+      Parser.next p
+    | _ -> Parser.expect ~grammar:Grammar.TypeExpression Colon p);
     let typ = parse_poly_type_expr p in
     Some (Parsetree.Otag (field_name, attrs, typ))
   | DotDotDot ->
@@ -4804,7 +4919,13 @@ and parse_string_field_declaration p =
       (Diagnostics.message (ErrorMessages.object_quoted_field_name name));
     Parser.next p;
     let field_name = Location.mkloc name name_loc in
-    Parser.expect ~grammar:Grammar.TypeExpression Colon p;
+    (match p.Parser.token with
+    | Colon -> Parser.next p
+    | Equal ->
+      Parser.err ~start_pos:p.start_pos ~end_pos:p.end_pos p
+        (Diagnostics.message ErrorMessages.record_type_field_missing_colon);
+      Parser.next p
+    | _ -> Parser.expect ~grammar:Grammar.TypeExpression Colon p);
     let typ = parse_poly_type_expr p in
     Some (Parsetree.Otag (field_name, attrs, typ))
   | _token -> None
@@ -4833,6 +4954,14 @@ and parse_field_declaration ?current_type_name_path ?inline_types_context p =
         extend_current_type_name_path current_type_name_path name.txt
       in
       parse_poly_type_expr ?current_type_name_path ?inline_types_context p
+    | Equal ->
+      Parser.err ~start_pos:p.start_pos ~end_pos:p.end_pos p
+        (Diagnostics.message ErrorMessages.record_type_field_missing_colon);
+      Parser.next p;
+      let current_type_name_path =
+        extend_current_type_name_path current_type_name_path name.txt
+      in
+      parse_poly_type_expr ?current_type_name_path ?inline_types_context p
     | _ ->
       Ast_helper.Typ.constr ~loc:name.loc {name with txt = Lident name.txt} []
   in
@@ -4874,6 +5003,11 @@ and parse_field_declaration_region ?current_type_name_path ?inline_types_context
       | Colon ->
         Parser.next p;
         parse_poly_type_expr ?current_type_name_path ?inline_types_context p
+      | Equal ->
+        Parser.err ~start_pos:p.start_pos ~end_pos:p.end_pos p
+          (Diagnostics.message ErrorMessages.record_type_field_missing_colon);
+        Parser.next p;
+        parse_poly_type_expr ?current_type_name_path ?inline_types_context p
       | _ ->
         Ast_helper.Typ.constr ~loc:name.loc ~attrs
           {name with txt = Lident name.txt}

tests/syntax_tests/data/parsing/errors/expressions/expected/labelledArgumentMissingEqual.res.txt

@@ -0,0 +1,22 @@
+
+  Syntax error!
+  syntax_tests/data/parsing/errors/expressions/labelledArgumentMissingEqual.res:1:16
+
+  1 │ let _ = fn(~foo:1)
+  2 │ let _ = fn(~bar:?value)
+  3 │ 
+
+  Use `=` to pass a labelled argument. Example: `~label=value`
+
+
+  Syntax error!
+  syntax_tests/data/parsing/errors/expressions/labelledArgumentMissingEqual.res:2:16
+
+  1 │ let _ = fn(~foo:1)
+  2 │ let _ = fn(~bar:?value)
+  3 │ 
+
+  Optional labelled arguments use `=?`. Example: `~label=?value`
+
+let _ = fn ~foo:1
+let _ = fn ?bar:value

tests/syntax_tests/data/parsing/errors/expressions/labelledArgumentMissingEqual.res

@@ -0,0 +1,2 @@
+let _ = fn(~foo:1)
+let _ = fn(~bar:?value)

tests/syntax_tests/data/parsing/errors/pattern/expected/recordFieldWrongAssignment.res.txt

@@ -0,0 +1,10 @@
+
+  Syntax error!
+  syntax_tests/data/parsing/errors/pattern/recordFieldWrongAssignment.res:1:9
+
+  1 │ let {foo=bar} = record
+  2 │ 
+
+  Record patterns use `:` when matching fields. Example: `{field: value}`
+
+let { foo = bar } = record

tests/syntax_tests/data/parsing/errors/pattern/recordFieldWrongAssignment.res

@@ -0,0 +1 @@
+let {foo=bar} = record

tests/syntax_tests/data/parsing/errors/structure/expected/recordFieldWrongAssignment.res.txt

@@ -0,0 +1,10 @@
+
+  Syntax error!
+  syntax_tests/data/parsing/errors/structure/recordFieldWrongAssignment.res:1:13
+
+  1 │ let r = {foo=1}
+  2 │ 
+
+  Records use `:` when assigning fields. Example: `{field: value}`
+
+let r = { foo = 1 }

tests/syntax_tests/data/parsing/errors/structure/recordFieldWrongAssignment.res

@@ -0,0 +1 @@
+let r = {foo=1}

tests/syntax_tests/data/parsing/errors/typeDef/expected/recordFieldWrongAssignment.res.txt

@@ -0,0 +1,11 @@
+
+  Syntax error!
+  syntax_tests/data/parsing/errors/typeDef/recordFieldWrongAssignment.res:1:14
+
+  1 │ type t = {foo=string}
+  2 │ 
+
+  Record fields in type declarations use `:`. Example: `{field: string}`
+
+type nonrec t = {
+  foo: string }

tests/syntax_tests/data/parsing/errors/typeDef/recordFieldWrongAssignment.res

@@ -0,0 +1 @@
+type t = {foo=string}