Merge pull request #4127 from BZngr/UnreachableCaseInsp_Comments2

Unreachable Case inspection enhancements.

Author: retailcoder

Rubberduck.CodeAnalysis/Inspections/Concrete/UnreachableCaseInspection/ComparableDateValue.cs

@@ -0,0 +1,108 @@
+using Antlr4.Runtime;
+using Rubberduck.Parsing.PreProcessing;
+using System;
+using System.Collections.Generic;
+using System.Data;
+using System.Globalization;
+
+namespace Rubberduck.Inspections.Concrete.UnreachableCaseInspection
+{
+    public class ComparableDateValue : IValue, IComparable<ComparableDateValue>
+    {
+        private readonly DateValue _dateValue;
+        private readonly int _hashCode;
+
+        public ComparableDateValue(DateValue dateValue)
+        {
+            _dateValue = dateValue;
+            _hashCode = dateValue.AsDecimal.GetHashCode();
+        }
+
+        public Parsing.PreProcessing.ValueType ValueType => _dateValue.ValueType;
+
+        public bool AsBool => _dateValue.AsBool;
+
+        public byte AsByte => _dateValue.AsByte;
+
+        public decimal AsDecimal => _dateValue.AsDecimal;
+
+        public DateTime AsDate => _dateValue.AsDate;
+
+        public string AsString => _dateValue.AsString;
+
+        public IEnumerable<IToken> AsTokens => _dateValue.AsTokens;
+
+        public int CompareTo(ComparableDateValue dateValue)
+            => _dateValue.AsDecimal.CompareTo(dateValue._dateValue.AsDecimal);
+
+        public override int GetHashCode() => _hashCode;
+
+        public override bool Equals(object obj)
+        {
+            if (obj is ComparableDateValue decorator)
+            {
+                return decorator.CompareTo(this) == 0;
+            }
+
+            if (obj is DateValue dateValue)
+            {
+                return dateValue.AsDecimal == _dateValue.AsDecimal;
+            }
+
+            return false;
+        }
+
+        public override string ToString()
+        {
+            return _dateValue.ToString();
+        }
+
+        public string AsDateLiteral()
+        {
+            var asString = AsDate.ToString(CultureInfo.InvariantCulture);
+            var prePostPend = "#";
+            var result = asString.StartsWith(prePostPend) ? asString : $"{prePostPend}{asString}";
+            result = result.EndsWith(prePostPend) ? result : $"{result}{prePostPend}";
+            return result;
+        }
+
+        public static ComparableDateValue Parse(string valueText)
+        {
+                var literal = new DateLiteralExpression(new ConstantExpression(new StringValue(valueText)));
+                return new ComparableDateValue((DateValue)literal.Evaluate());
+        }
+
+        public static bool TryParse(string valueText, out ComparableDateValue value)
+        {
+            value = default;
+            if (!(valueText.StartsWith("#") && valueText.EndsWith("#")))
+            {
+                return false;
+            }
+
+            try
+            {
+                value = Parse(valueText);
+                return true;
+            }
+            catch (SyntaxErrorException)
+            {
+                return false;
+            }
+            catch (ArgumentOutOfRangeException)
+            {
+                return false;
+            }
+            catch (InputMismatchException)
+            {
+                return false;
+            }
+            catch (Exception e)
+            {
+                //even though a SyntaxErrorException/InputMismatchException is thrown, 
+                //this catch-all block seems to be needed(?)
+                return false;
+            }
+        }
+    }
+}