Improve some messages on structure disambiguation

compiler/desugared/from_surface.ml

@@ -275,7 +275,7 @@ let rec translate_expr
             try Name_resolution.get_struct ctxt c
             with Not_found ->
               Errors.raise_spanned_error (Marked.get_mark c)
-                "Struct %s has not been defined before" (Marked.unmark c))
+                "Structure %s was not declared" (Marked.unmark c))
           c
       in
       Expr.edstructaccess e (Marked.unmark x) str emark)

compiler/shared_ast/definitions.ml

@@ -225,20 +225,20 @@ and ('a, 't) naked_gexpr =
       args : ('a, 't) gexpr ScopeVar.Map.t;
     }
       -> (([< desugared | scopelang ] as 'a), 't) naked_gexpr
-  (* [desugared] has ambiguous struct fields *)
   | EDStructAccess : {
       name_opt : StructName.t option;
       e : ('a, 't) gexpr;
       field : IdentName.t;
     }
       -> ((desugared as 'a), 't) naked_gexpr
-  (* Resolved struct/enums, after [desugared] *)
+      (** [desugared] has ambiguous struct fields *)
   | EStructAccess : {
       name : StructName.t;
       e : ('a, 't) gexpr;
       field : StructField.t;
     }
       -> (([< scopelang | dcalc | lcalc ] as 'a), 't) naked_gexpr
+      (** Resolved struct/enums, after [desugared] *)
   (* Lambda-like *)
   | EAssert : ('a, 't) gexpr -> (([< dcalc | lcalc ] as 'a), 't) naked_gexpr
   (* Default terms *)

compiler/shared_ast/typing.ml

@@ -464,13 +464,23 @@ and typecheck_expr_top_down :
             A.StructName.format_t name
       in
       let field =
-        try
-          A.StructName.Map.find name
-            (A.IdentName.Map.find field ctx.ctx_struct_fields)
+        let candidate_structs =
+          try A.IdentName.Map.find field ctx.ctx_struct_fields
+          with Not_found ->
+            Errors.raise_spanned_error context_mark.pos
+              "Field %s does not belong to structure %a (no structure defines \
+               it)"
+              field A.StructName.format_t name
+        in
+        try A.StructName.Map.find name candidate_structs
         with Not_found ->
           Errors.raise_spanned_error context_mark.pos
-            "Field %s does not belong to structure %a" field
+            "Field %s does not belong to structure %a, but to %a" field
             A.StructName.format_t name
+            (Format.pp_print_list
+               ~pp_sep:(fun ppf () -> Format.fprintf ppf "@ or@ ")
+               A.StructName.format_t)
+            (List.map fst (A.StructName.Map.bindings candidate_structs))
       in
       A.StructField.Map.find field str
     in

tests/test_struct/bad/wrong_qualified_field.catala_en

@@ -19,7 +19,7 @@ scope A:
 
 ```catala-test-inline
 $ catala Interpret -s A
-[ERROR] Field g does not belong to structure Foo
+[ERROR] Field g does not belong to structure Foo, but to Bar
 
 ┌─⯈ tests/test_struct/bad/wrong_qualified_field.catala_en:17.22-29:
 └──┐