feat(compiler): Improve warning when omitting fields in record pattern (#2079)

Co-authored-by: Oscar Spencer <oscar.spen@gmail.com>

Author: spotandjake

compiler/src/utils/warnings.re

@@ -126,7 +126,9 @@ let message =
       msg,
     )
   | NonClosedRecordPattern(s) =>
-    "the following fields are missing from the record pattern: " ++ s
+    "the following fields are missing from the record pattern: "
+    ++ s
+    ++ "\nUse `_` to ignore unused fields."
   | FuncWasmUnsafe(func, f, m) =>
     "it looks like you are using "
     ++ func

compiler/test/suites/records.re

@@ -230,7 +230,6 @@ describe("records", ({test, testSkip}) => {
     "record Rec {foo: Number, bar: Number}; let a = {foo: 1, bar: 2}; let b = {...a, foo: 2, bar: 3}",
     Warnings.UselessRecordSpread,
   );
-
   assertWarning(
     "disambiguation_1",
     {|
@@ -256,4 +255,15 @@ describe("records", ({test, testSkip}) => {
       (x: B) => x.field
     |},
   );
+  // well_formedness field omission warning
+  assertWarning(
+    "record_field_omit_1",
+    "record Rec {foo: Number, bar: Number}; let a = {foo: 1, bar: 2}; match (a) { { foo } => void, _ => void }",
+    Warnings.NonClosedRecordPattern("bar"),
+  );
+  assertWarning(
+    "record_field_omit_2",
+    "record Rec {foo: Number, bar: Number, bar2: Number}; let a = {foo: 1, bar: 2, bar2: 3}; match (a) { { foo } => void, _ => void }",
+    Warnings.NonClosedRecordPattern("bar, bar2"),
+  );
 });