Improve diagnostics for malformed anonymous record types

src/Compiler/Checking/CheckExpressions.fs

@@ -4353,8 +4353,9 @@ and TcTypeOrMeasure kindOpt (cenv: cenv) newOk checkConstraints occ (iwsam: Warn
     | SynType.Tuple(isStruct, segments, m) ->
         TcTupleType kindOpt cenv newOk checkConstraints occ env tpenv isStruct segments m
 
-    | SynType.AnonRecd(_, [],m) ->
-        error(Error((FSComp.SR.tcAnonymousTypeInvalidInDeclaration()), m))
+    | SynType.AnonRecd(fields = []) ->
+        // The parser takes care of error messages
+        NewErrorType(), tpenv
 
     | SynType.AnonRecd(isStruct, args, m) ->
         TcAnonRecdType cenv newOk checkConstraints occ env tpenv isStruct args m

tests/FSharp.Compiler.ComponentTests/Conformance/Types/RecordTypes/AnonymousRecords.fs

@@ -42,4 +42,26 @@ module AnonRecd =
 """
         |> compile
         |> shouldFail
-        |> withErrorCode 3523
+        |> withErrorCode 3523
+
+    [<Fact>]
+    let ``Anonymous record types with parser errors or no fields do not produce overlapping diagnostics`` () =
+        FSharp """
+module AnonRecd
+
+type ContactMethod =
+    | Address of {| Line1 : string; Line 2 : string; Postcode : string |}
+
+let (x: {| |}) = ()
+
+type ErrorResponse =
+    { error: {| type : string
+                message : string |} }
+"""
+        |> typecheck
+        |> shouldFail
+        |> withDiagnostics [
+            Error 10, Line 5, Col 42, Line 5, Col 43, "Unexpected integer literal in field declaration. Expected ':' or other token."
+            Error 10, Line 7, Col 12, Line 7, Col 14, "Unexpected symbol '|}' in field declaration. Expected identifier or other token."
+            Error 10, Line 10, Col 17, Line 10, Col 21, "Incomplete structured construct at or before this point in field declaration. Expected identifier or other token."
+        ]