Better error message for anon records with missing fields

src/Compiler/Checking/ConstraintSolver.fs

@@ -1083,7 +1083,12 @@ and SolveAnonInfoEqualsAnonInfo (csenv: ConstraintSolverEnv) m2 (anonInfo1: Anon
         let message =
             match anonInfo1.SortedNames, anonInfo2.SortedNames with
             | Subset missingFields ->
-                FSComp.SR.tcAnonRecdFieldNameSubset(string missingFields)
+                match missingFields with
+                | [missingField] ->
+                    FSComp.SR.tcAnonRecdSingleFieldNameSubset(string missingField)
+                | _ ->
+                    let missingFields = String.concat ", " missingFields
+                    FSComp.SR.tcAnonRecdMultipleFieldsNameSubset(string missingFields)
             | Superset extraFields ->
                 FSComp.SR.tcAnonRecdFieldNameSuperset(string extraFields)
             | Overlap (missingFields, extraFields) ->

src/Compiler/FSComp.txt

@@ -1394,7 +1394,8 @@ tcGlobalsSystemTypeNotFound,"The system type '%s' was required but no referenced
 tcAnonRecdInvalid,"Invalid Anonymous Record type declaration."
 tcAnonRecdCcuMismatch,"Two anonymous record types are from different assemblies '%s' and '%s'"
 tcAnonRecdFieldNameMismatch,"This anonymous record does not exactly match the expected shape. Add the missing fields %s and remove the extra fields %s."
-tcAnonRecdFieldNameSubset,"This anonymous record does not have enough fields. Add the missing fields %s."
+tcAnonRecdSingleFieldNameSubset,"This anonymous record is missing field '%s'."
+tcAnonRecdMultipleFieldsNameSubset,"This anonymous record is missing fields '%s'."
 tcAnonRecdFieldNameSuperset,"This anonymous record has too many fields. Remove the extra fields %s."
 tcAnonRecdFieldNameDifferent,"This is the wrong anonymous record. It should have the fields %s."
 keywordDescriptionAbstract,"Indicates a method that either has no implementation in the type in which it is declared or that is virtual and has a default implementation."