Add checks for additional numeric literal syntax error edge cases

Assembler.cs

@@ -786,15 +786,24 @@ public static OperandType DetermineOperandType(string operand)
                         : Regex.Match(operand, @"[^0-9_\.](?<!^-)");
                     if (invalidMatch.Success)
                     {
-                        throw new SyntaxError(string.Format(Strings.Assembler_Error_Numeric_Invalid_Character, operand, new string(' ', invalidMatch.Index)));
+                        throw new SyntaxError(string.Format(Strings.Assembler_Error_Literal_Invalid_Character, operand, new string(' ', invalidMatch.Index)));
                     }
-                    if (operand[0] == '.' && operand.Length == 1)
+                    // Edge-case syntax errors not detected by invalid character regular expressions
+                    if ((operand[0] == '.' && operand.Length == 1) || operand == "-.")
                     {
-                        throw new SyntaxError(Strings.Assembler_Error_Floating_Point_Decimal_Only);
+                        throw new SyntaxError(Strings.Assembler_Error_Literal_Floating_Point_Decimal_Only);
+                    }
+                    if (operand[0] == '-' && operand.Length == 1)
+                    {
+                        throw new SyntaxError(Strings.Assembler_Error_Literal_Negative_Dash_Only);
                     }
                     if (operand.IndexOf('.') != operand.LastIndexOf('.'))
                     {
-                        throw new SyntaxError(string.Format(Strings.Assembler_Error_Numeric_Too_Many_Points, operand, new string(' ', operand.LastIndexOf('.'))));
+                        throw new SyntaxError(string.Format(Strings.Assembler_Error_Literal_Too_Many_Points, operand, new string(' ', operand.LastIndexOf('.'))));
+                    }
+                    if (operand is "0x" or "0b")
+                    {
+                        throw new SyntaxError(Strings.Assembler_Error_Literal_Base_Prefix_Only);
                     }
                     return OperandType.Literal;
                 }

Resources/Localization/Strings.resx

@@ -820,16 +820,16 @@ Consult the language reference for a list of all valid mnemonic/operand combinat
     {1}^
 Label names may not contain symbols other than underscores, and cannot start with a numeral.</value>
 	</data>
-	<data name="Assembler_Error_Numeric_Invalid_Character" xml:space="preserve">
+	<data name="Assembler_Error_Literal_Invalid_Character" xml:space="preserve">
 		<value>Invalid character in numeric literal:
     {0}
     {1}^
 Did you forget a '0x' prefix before a hexadecimal number or put a digit other than 1 or 0 in a binary number?</value>
 	</data>
-	<data name="Assembler_Error_Floating_Point_Decimal_Only" xml:space="preserve">
+	<data name="Assembler_Error_Literal_Floating_Point_Decimal_Only" xml:space="preserve">
 		<value>Floating point numeric literals must contain a digit on at least one side of the decimal point.</value>
 	</data>
-	<data name="Assembler_Error_Numeric_Too_Many_Points" xml:space="preserve">
+	<data name="Assembler_Error_Literal_Too_Many_Points" xml:space="preserve">
 		<value>Numeric literal contains more than one decimal point:
     {0}
     {1}^</value>
@@ -1018,4 +1018,10 @@ Press ENTER to continue, or type a command ('help' for command list): </value>
 	<data name="Assembler_Error_Label_Empty_Name" xml:space="preserve">
 		<value>Label names cannot be empty. Did you mean to include a colon here?</value>
 	</data>
+	<data name="Assembler_Error_Literal_Negative_Dash_Only" xml:space="preserve">
+		<value>Negative numeric literals must contain at least one digit.</value>
+	</data>
+	<data name="Assembler_Error_Literal_Base_Prefix_Only" xml:space="preserve">
+		<value>Numeric literals with a base prefix (0x or 0b) must contain at least one digit after the prefix.</value>
+	</data>
 </root>