fix(compiler): Supply correct error for unbound record labels (#1200)

Author: ospencer

compiler/src/typed/env.re

@@ -2586,6 +2586,8 @@ let fold_modules = (f, lid, env, acc) =>
 let fold_values = f => find_all(env => env.values, sc => sc.comp_values, f)
 and fold_constructors = f =>
   find_all_simple_list(env => env.constructors, sc => sc.comp_constrs, f)
+and fold_labels = f =>
+  find_all_simple_list(env => env.labels, sc => sc.comp_labels, f)
 and fold_types = f => find_all(env => env.types, sc => sc.comp_types, f)
 and fold_modtypes = f =>
   find_all(env => env.modtypes, sc => sc.comp_modtypes, f);

compiler/src/typed/env.rei

@@ -275,6 +275,8 @@ let fold_types:
     'a
   ) =>
   'a;
+let fold_labels:
+  ((label_description, 'a) => 'a, option(Identifier.t), t, 'a) => 'a;
 /** Persistent structures are only traversed if they are already loaded. */
 
 let fold_constructors:

compiler/src/typed/typetexp.re

@@ -581,6 +581,7 @@ let fold_values = fold_simple(Env.fold_values);
 let fold_types = fold_simple(Env.fold_types);
 let fold_modules = fold_persistent(Env.fold_modules);
 let fold_constructors = fold_descr(Env.fold_constructors, d => d.cstr_name);
+let fold_labels = fold_descr(Env.fold_labels, l => l.lbl_name);
 let fold_modtypes = fold_simple(Env.fold_modtypes);
 
 let type_attributes = attrs => {
@@ -743,7 +744,10 @@ let report_error = (env, ppf) =>
       fprintf(ppf, "Unbound constructor %a", identifier, lid);
       spellcheck(ppf, fold_constructors, env, lid);
     }
-  | Unbound_label(_)
+  | Unbound_label(lid) => {
+      fprintf(ppf, "Unbound record label %a", identifier, lid);
+      spellcheck(ppf, fold_labels, env, lid);
+    }
   | Unbound_class(_)
   | Unbound_cltype(_) =>
     failwith("Impossible: deprecated error type in typetexp")

compiler/test/suites/records.re

@@ -46,6 +46,11 @@ describe("records", ({test, testSkip}) => {
     "record Rec {foo: Number}; {foo: 4, bar: 4}",
     "Unbound record label bar",
   );
+  assertCompileError(
+    "record_err_3",
+    "let foo = \"\"; foo.charAt(0)",
+    "Unbound record label charAt",
+  );
   assertRun(
     "record_get_1",
     "record Rec {foo: Number}; let bar = {foo: 4}; print(bar.foo)",