Implemented boolean literals

src/errors/Common.go

@@ -10,6 +10,7 @@ var (
 	ExpectedStructName         = &Base{"Expected struct name"}
 	ExpectedDLLName            = &Base{"Expected DLL name"}
 	InvalidNumber              = &Base{"Invalid number"}
+	InvalidCondition           = &Base{"Invalid condition"}
 	InvalidExpression          = &Base{"Invalid expression"}
 	InvalidRune                = &Base{"Invalid rune"}
 	MissingBlockStart          = &Base{"Missing '{'"}